Homepage: http://seniordesign.engr.uidaho.edu/2007_2008/moonavators/index.html
email:moonavators@uidaho.edu
Address: University of Idaho Moscow, ID 83844
Date: April 15, 2020 phone: 208-885-2202
Vytas SunSpiral
NASA Ames Research Center
Moffett Field, Mountain View, CA
94035
(650) 604-5000
Dave Atkinson/Becky Highfill
Idaho Space Grant Consortium
College of Engineering, JEB B40
University of Idaho
P.O. Box 441011
Moscow, ID 83844-101
Dear associated parties:
The Moonavators is a University of Idaho senior design team comprised of Mechanical and Electrical Engineering students. Our project consists of designing, fabricating, and testing a non-prehensile manipulation device the M-08 that will be cable of manipulating earth’s soil. The project has been provided by NASA Ames Research Center and sponsored by the Idaho Space Consortium through the University of Idaho. This report describes the design, operation, and capabilities of the manipulator.
This is a second iteration project that was started last year. The manipulator was improved in its structural strength and design. Improvements were also made in the electronic control systems; this provides the capability for standalone operation. Motors that drive the manipulator were improved to increase capabilities.
This manipulator can now be used during the summer of 2008 for testing.
Recommendations have been made in this report to improve the operation of the manipulator.
Sincerely,
Moonavators: Caitlin Flynn, Craig Craviotto, Hans Leidenfrost, Shane Duff, Jacob
Conn, and Michael Mahlum

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The primary purpose of this project is to provide NASA Ames, the Idaho Space
Grant Consortium, and any other persons involved in this project a non-prehensile robotic manipulator capable of breaking hard soil. The project began during the 2006-2007 year when the first model, the L-07, was built. Since then, new design possibilities have been implemented to improve its ability to manipulate soil. The new design is called the M-
08. This report provides an analysis of the L-07, a detailed description of each design and component in the M-08 and an analysis of the new design’s effectiveness. This includes an assessment of the actual designs chosen for the M-08 as well as alternative designs for various components that the team considered. The documentation and analysis in this report may be used to assist the RLEP team at NASA Ames in future robotics.
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Abstract…………...………………………………………………………………….pg. 2
1.0 Introduction………………………………………………………..…………....pg. 4
1.1 Executive Summary…………………………………………………..…..….pg. 4
1.2 Purpose………………………………………………………………..……...pg.4
1.3 Background…………………………………………………………..………pg. 5
1.4 Problem Definition………………………………..………………………….pg. 6
2.0 Improvements to the L-07……………………………………………………….pg. 6
3.0 Mechanical Design of the M-08…………………………………………………pg. 9
3.1 Percussive Poker..…………………………………………………..........…pg. 10
3.2 Wrist Joint…………………………………………………………………..pg. 12
3.3 Elbow Joint…………………………………………………………………pg. 14
3.4 Shoulder Joint…………………………………..…………………………...pg.16
3.5 Base Joint………………………………………...…………………………pg. 18
4.0 Control System…….……………………………………………………………pg. 20
4.1 User Interface – Playstation One Controller (PSX)…………….…….…… pg. 21
4.2 RABBIT 4110 Microprocessor……………………………….…………… pg. 24
4.3 Motor Controllers…….………………………………….…………………pg. 26
5.0 Power System……………………….…………………….…………………….pg. 32
5.1 XP-08S Power Management……………………..…………………………pg. 33
5.2 DC1HV DC-DC Converter……………………….………………………..pg. 34
5.3 DC123S DC-DC Converter…………………….………..…………………pg. 34
5.4 HD4RX Wireless Kill Switch……………………...……………………….pg. 35
6.0 Design Evaluation…………………………………………………………...…pg. 36
7.0 Works Cited…………………………………………….………………...……pg. 40
8.0 Appendices…………………………………………...…………………………pg. 41
A. Control Flow Diagram………………………………………………………pg. 41
B. Moonavators Schedule……………….……..……………………………….pg. 42
C. Bill of Materials……………………..…..…………………………………...pg. 44
D. Poker Math Model………………….………………………………………..pg. 47
E. DFMEA………………………………..…………………………………….pg. 49
F. Drawing Package……………………….……………………………………pg. 52
G. Resumes……………………………………………………….…………….pg. 98
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1.1
Executive Summary
The goal of this project is to design and build a non-prehensile robotic Earth soil manipulator capable of performing tasks related to setting up a human habitat on the moon. The manipulator will eventually interface with a lunar rover that would allow the arm to operate autonomously. The project began last year when the first model, the L-07, was built. This year, an evaluation of the L-07 concluded that the design required more powerful motors, a stronger frame, and a more capable end effecter to break rock. The first semester of the project was dedicated to improving the performance of last year’s model to better understand what components needed redesign. There were two main shortcomings of the L-07: first, it could not break hard, moonlike soil and second, the user interface was complicated and cumbersome. Therefore, the primary objective of the new design was to construct a robust robotic arm based on the L-07 design with an easy to operate interface and a new end effecter that would be capable of producing enough force to break rock. The team designed a simple, cam driven percussive poker to replace the linear actuator for chipping rock. A Playstation One controller was connected to replace the cumbersome Labview computer operations to control the robot. The new arm design, the M-08, operates similarly to a backhoe consisting of a two link arm with two selectable end effectors at the wrist joint: at the one end of the joint, a backhoe bucket and at the other, the percussive poker. Various other design possibilities were implemented into the final arm such as a direct-drive, brushless motor for the base and a
RABBIT 4100 microprocessor to control the motor controllers. All of these designs were implemented with the intent of analyzing the effectiveness of various robotic options for the NASA RLEP team to consider in future endeavors.
1.2
Purpose
The NASA Ames Research Center assigned our team the task of designing and constructing a robotic mechanism for excavation and soil manipulation. The device should be capable of managing soil in as many different ways as possible with easy to fix, interchangeable parts. The purpose of this paper is to present a complete assessment
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of the final design. The M-08 will then be considered for future tests in the deserts of
California. Later, the design ideas used in the M-08 may be implemented in a more sophisticated mechanism more suitable for the harsh conditions of space. Astronauts can then use the mechanism to aid them in performing tasks on the lunar surface.
1.3 Background of RLEP
Lunar exploration, from its early stages in 1950 to the culmination of the Apollo missions in 1972, has contributed much to our understanding of the Moon’s history and its relationship with the earth. Since then, humans have explored the idea of returning to the Moon to investigate the possibilities of excavating natural resources, examining another celestial body for future inhabitation, and creating commercial development in space. The moon could serve as a permanent habitat or potentially be used as a pit stop for more extended tasks, such as the missions to Mars. The next step in outer space research is building a lunar habitat for astronauts to live for longer missions. It could also be used as a refueling station for ships as well as other missions in the future. Robotic exploration will pave the way for manned missions, by exploring and building this infrastructure.
In order to prepare for manned missions to the moon, lunar rovers will prepare sites for use. These lunar rovers will survey the landscape for optimal sites and prepare as much of the site as possible autonomously. The NASA Ames Research Center ( ARC) develops the technology, control algorithms and operational concepts for the autonomous rovers, by testing them in earth’s environment.
Currently, there are no small scale excavation device that are capable of breaking hard regolith and rocks needed for lunar excavation. Regolith is a layer of loose soil covering solid rock on the lunar surface. Furthermore, there is no operational concept or algorithm that describes the best method for an autonomous rover to conduct surveying in this environment. Once the ARC has developed this technology, the Jet Propulsion
Laboratory (JPL) may use it to construct rovers that are able to deal with the harsh environments of space.
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1.4
Problem Definition
The goal of this project is to design an arm with the ability to break hard soil, chip rock and excavate the material. This arm will eventually interface with the K-10 rovers of NASA enabling it to be controlled autonomously. At this point, a human operator must close the feedback control loop for arm manipulation.
During the first semester, the team evaluated the mechanical and electrical design of last year’s model, the L-07. The goal of this semester was to assess problem areas of the old design, fix and improve the design, and research possible design solutions for the next generation model, the M-08 ( see Ошибка! Источник ссылки не найден. ). The main areas for improvement were broken down into three areas of design: the base, the arm, and the linear actuator (
see Figure 1 ).
Task Percent Work
This Semester
Repair L07
A. Base
Section total : 70%
Machined new baseplate
Added guide gears
12%
8%
B. Arm
New square arms replace helical gear elbow shaft mountings
5%
15%
13%
C. Linear Actuator
Replaced ball bearings with bushings
Replace drive motor
Instal extra driving gear
2nd Semester Planning
A. Ideas & Brainstorming
B. Motor selection
Discussions/meetings
Concept drawings general research motor research
5%
2%
10%
Section total : 30%
12%
5%
5%
Total 100%
8%
Table 1 - First Semester Goals
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Figure 1 – (Left) Original L-07 and (Right) the Improved L-07
Base
The L-07 base was sloppy and provided inaccurate feedback. The slop was the result of inaccurate machining of alignment holes and a Lazy Susan used as the support for the arm rotation. The inaccurate machining required a weak assembly of washers and spacers used to make the base motor attach correctly to the base mounting plate. The
Lazy Susan supported the base plate with an internal gear attached to the bottom. The base plate was allowed to rotate with the help of a drive gear on a right angle motor coming up from underneath the base plate support. The Lazy Susan allowed a 1/8” of horizontal movement causing the drive gear to occasionally disengage. A potentiometer, opposite the drive gear inside the internal gear, was installed to stabilize the setup.
However, it was not strong enough to keep the assembly centered and the movement created stress on the axle. The potentiometer was also loosely pressed into the frame plate and remained in place by friction alone. Most of these problems were fixed when the original base was replaced with a new base machined to the correct tolerances. Two additional gears were also added to the base constricting the horizontal movement from
the Lazy Susan( Figure 2)
.
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Additional gears added
Figure 2 - Free spinning gears added to base design for stability
Nevertheless, the Lazy Susan did not provide accurate rotation for the base. The new design incorporates a direct drive motor for the base to replace the clumsy design of the Lazy Susan.
Arms
The flimsy arm design machined from very thin aluminum (Figure 3) allowed for an exceptional amount of undesired tensional movement. This movement occurred because the thin aluminum arms could not adequately support the uneven load induced by the linear actuator and the helical gearing used to rotate the actuator. The twisting movement caused the elbow gearing to slip.
Figure 3 – (Left) Original Arm of L-07 and (Right) New Arm of L-07
The original arm design was replaced with square aluminum stock, 3/4”x 3/4,”
and bent to match the geometry of the original design ( Figure 3). New upper and lower
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arm couplers were machined that could slide into square arms. This effectively improved the robustness of the arm design, allowing it to withstand substantial stress from both the linear actuator and the arm joint motors.
Linear Actuator
The linear actuator roller bearings provided inconsistent motion, frequently jammed, and produced a significant amount of slop during operation. Most of the slop was the result of inadequate surface contact between the rack and pinion of the linear actuator. The small contact surface allowed the rack to twist almost 180 degrees within the bearings. Finally, the drive motor we received for the actuator was broken which made the entire assembly completely inoperable.
The roller bearings were replaced by sleeve bushings that would supply more surface support for the linear actuator. A motor was purchased with a much lower gear ratio to improve the torque for scooping. Finally, the drive gear was replaced with a two gears to increase the contact area with the rack to reduce rotation.
After evaluating last year’s model, the L-07, the Moonavators designed a new arm called the M-08 based on the L-07 design improvements made during the first semester
(Section 2.0). The linear actuator was replaced with a much more effective percussive poker. The wrist was redesigned with significantly more torque and a more robust support arm that would connect the backhoe bucket on one end and the poker on the other. The arm was redesigned to have a joint supplying the robot with an extra degree of freedom that it lost when the motion of the linear actuator was removed. The new design was renamed the elbow joint and was also supplied a much larger amount of torque. The arms were built with a robust, rectangular aluminum tubing frame similar to the modified
L-07. The Lazy Susan was replaced to test the effectiveness of the much more efficient
direct-drive brushless DC motor. Figure 4 shows the final design.
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Figure 4 - Final Design - The M-08
3.1 Percussive Poker
Purpose
To break up soil and chip hard rock using a percussive, hammering action mechanically driven by a cam.
Main Components
1.
Twin lobe cam
2.
Poker Follower
3.
Spring
Twin Lobe
Cam
Cam
Housing
Figure 5 – (Left) Percussive Poker on the M-08 and on the (right) Percussive Poker Components
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(Optional
Single Lobe
Cam)
Poker
Follower
Spring

Capabilities

Chip hard rock

Break up soil for easier scooping
Percussive Poker Design Description
The percussive poker uses a cam driven follower to produce the continuous hammering effect. A high speed motor spins the cam which drives the poker shaft down.
A spring was placed on the shaft to return the poker shaft up as the cam rotates. Roller bearings were mounted on both sides to stabilize the cam during rotation to minimize the friction between the cam and the poker housing. Bushings were placed in the poker shaft to give the poker a smooth linear motion. Finally, the poker tip was threaded to allow for different tips to be tested.
Percussive Poker Design Analysis
The main purpose of the arm was to be capable of delivering the necessary force to break rock without compromising the arm or the K-10 Rover. Since the moon experiences only a sixth of the gravity that earth experiences, a force strong enough to break the rock with a single impact might launch the robot off the ground. Although a spring induced impact force was considered and built, a smaller force delivered repeatedly at high speeds that did not require as much compliance in the system was determined to be the most effective method of chipping rock.
The team considered two percussive designs: a three-bar slider crank mechanism and a cam-follower mechanism. The three-bar linkage, inspired by the design of a sewing machine, was driven by a circular cam. Attached to the cam was a connector linkage that rotated with the cam. Attached at the other end of the connector linkage was the poker (the slider crank) which moved up and down as the cam spun. The poker was constrained to a linear motion by bushings. The first problem with this design was the connector linkage would experience very high stresses when the poker struck a rock.
This could lead to very rapid wear in the mechanism. The next problem was that the design, although simple in theory, required a complicated design of the cam and connections between the cam and connector linkage with high tolerances to work
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effectively. Thus, due to the necessity for complexity to make the design work coupled with the prospect of wear instilled in the design that would quickly diminish the effectiveness of the design, this mechanism was not chosen.
The cam-follower mechanism, however, provided a much simpler design solution.
The cam size was optimized using a cycloidal profile and the cam rise was minimized to reduce the poker shaft’s acceleration as the poker moved up. It was important to keep the return velocity and acceleration small to keep the poker shaft from completely separating from the cam while in motion. Also, the smaller the return velocity, the less force required by the spring to hold the poker against the cam. Thus, less torque was required to compress the spring and more force, as well as higher speeds, could be produced. To reduce wear a roller was used instead of a friction surface for contact from the cam to the poker shaft. To increase durability, both the cam and poker shaft were made of tool grade steel instead of aluminum, and heat treated to increase strength. These design decisions were made because of excessive wear that developed in an initial prototype.
3.2 Wrist Joint
Purpose
To alternate between the scoop and the poker and provide torque for scooping
Main Components
1.
3x3 scoop for digging and trenching
2.
Rino gear box with a 120:1 gear ratio
3.
Anaheim motor
4.
Slip ring for continuous rotation without tangled wires
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Motor
Scoop
Figure 6 - Wrist Assembly
Capabilities

Alternate between the scoop and the poker to allow digging or chipping rock without the need to physically remove components
 Help adjust the angle of the poker to allow it to be positioned at the most effective angle

To be used in conjunction with the elbow to dig and manipulate soil
Wrist Design Description
The goal of this design was simple, to provide the M-08 a degree of freedom that allowed it to alternate between digging and breaking rock. Therefore, the design includes an Anaheim motor that provides 46oz-in of torque and a powerful gear box with 120:1 gear ratio. A slip ring was also recommended by the 2006-2007 team to allow the end effectors continuous 360 degrees of rotation, eliminate the burden of wires and improve the appearance of the machine.
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Wrist Design Analysis
The 2006-2007 team realized they needed a powerful motor for the scoop to be capable of lifting rocks and soil. Originally, a more powerful Dynetic motor-gearbox was purchased for the wrist. However, due to shipping delays, the assembly was redesigned to incorporate either the Anaheim motor with a gearbox or the above mentioned combination motor gearbox. The Anaheim motor with gearbox works well, but the
Dynetic should be installed for increased torque and control.
3.3 Elbow Joint
Purpose
To increase the precision of linear positioning of the percussive poker and scooper mechanism
Main Components
1. Rino Mechanical P20-60 60:1 worm and wheel gearbox
2. Rino Mechanical P20-DX Keyed output shaft coupled to the P20-60 gearbox
3. Rino Mechanical 5mm x 6mm Oldham shaft coupler
4. Anaheim Automation 12V DC 5.5oz-in rated torque Brushed Spur Gear Motor
Gearbox
Output
Shaft
Shaft
Coupler
Figure 7 - Elbow Assembly
Motor
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Capabilities

Provides a constant torque rated at 333 oz-in

At the 1.5A stall current, provides an upward of 2499 oz-in of peak torque to assist in the wrist scooping

The Anaheim motor and Rino P20 gearbox combination weighs .9lbs
Elbow Design Description
The elbow joint was designed to supply high levels of torque for scooping with relatively low weight. The design combines an Anaheim Automation 12V DC motor and a Rino Mechanical P20-60 with a 60:1 gear ratio worm and wheel gearbox. A single output shaft connects the arms to the output bore of the gearbox. This motor-gearbox combination gives the elbow joint a constant rated 333oz-in of torque to the drive shaft and, at the 1.5A stall current, an upward of 2499oz-in of peak torque.
Elbow Design Analysis
The original elbow design for the M-08 included an HG62 gear motor from robotmarketplace.com. This motor had very impressive stats on paper, but after working with it in person, we decided the Anaheim motor was much more capable. The HG62 motor has a very high stall current of 32A and was easy to stall at a supplied 1A using only our hands holding onto the shaft. The motor is twice as large physically and weighs three times as much as the Anaheim Automation motor. Due to these limitations, our team deemed the Anaheim BDSG motor much more suitable for our application.
At the 9.7A stall current, the motor driving the linear actuator design on the L-07 produced 1465oz-in of peak torque. The motor was coupled to a right angle gearbox, but was a 1:1 zero gear reduction gearbox therefore not increasing the torque supplied to the linear actuator. The previous elbow joint design for the L-07 weighed 2 lbs, and currently, the Anaheim motor and Rino P20 gearbox combination weighs .9lbs. The motor for the M-08 is approximately one third of the physical size of the L-07 elbow motor, and produces up to 10 times the rated torque using a miniature internal worm wheel gearbox. The L-07 used a heavy and large external worm gear and shaft combination to translate the rotational motor motion ninety degrees into the elbow joint
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to rotate the linear actuator setup. Not only was this setup bulky, but also allowed for dirt and dust to enter the gearing and after time could produce problems with the meshing.
This new elbow design effectively increases the supplied torque twofold from last year’s design while dropping the stall current down to a manageable 1.5A which is easily handled by the HB-25 motor controller from Parallax Inc. The team also ordered the
R100 and R200 series motors which would increase the peak torque tenfold from the L-
07 design, and bolt straight into the current M-08 mounting brackets without any modifications. Going with Anaheim Automation motors allowed us to order three different motors while maintaining the same mounting brackets, position and size constraints with each one mounted to the Rino gearbox.
3.4 Shoulder Joint
Purpose –
To move the entire arm assembly for positioning purposes.
Main Components
1.
Oriental Motor BLH450KC-200FR
2.
Shoulder Plate
3.
(2) Front motor brackets
4.
Back motor bracket (2 parts)
5.
Drive Shaft and key
6.
Couplers
7.
Low Clearance C-clamps (on shaft behind arms)
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5
3
6
Figure 8 - Shoulder Design
Capabilities
 Move arm up and down to position end of arm
Base Design Description
The shoulder was designed to move and position the whole arm assembly. The shoulder sits on the shoulder plate which mounts to the rotor mount in the base assembly.
The brackets that hold up the Oriental BLH450KC-200FR Brushless DC Speed Control
System are designed to keep the motor setup from moving even when the arm is extended and therefore supplying a large moment to the shoulder. The shoulder motor is also held up so the arm wiring can go under the shoulder motor and through the hole in the middle of the base to keep the wiring organized.
Base Design Analysis
The shoulder motor was able to handle all the loads from the weight of the arm and the forces from soil manipulation throughout testing. The only problem that developed in the shoulder was due to a lack of speed control and a lack of a brake. When the shoulder motor was told to lower the arm, the weight of the arm made the arms lower too fast and required a user restart of the motor controller. When the shoulder was not
4
2
1
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directed to raise the arms, the weight of the arms would pull the whole arm down as there was no brake to hold the arms up.
3.4 Base Joint
Purpose
To turn arm assembly for positioning needs
Main Components
1.
Direct Drive Motor
2.
Stator Mount
3.
Rotor Mount
4.
Angular Contact Bearing
5.
Bearing Cap
6.
Motor Clamps
Figure 9 - Base Design
Capabilities

Rotate base without spinning the direct drive motor’s wires

Rotor rotates suspended in stator without contact.

Direct Drive allows for frictionless rotation
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Base Design Description
The base was designed around the direct drive motor purchased by the summer
RLEP team. The motor consists of a stator with magnetic poles and a rotor that has to float concentrically in the middle of the stator. The copper windings on the stator poles have to be at least 6 mm from any meta. Because of this, the stator mount needed to have a lip for the stator to clamp onto. The stator mount also has a cylinder concentric with the stator lip to attach the rest of the motor onto. The center cylinder also has a small lip on the bottom top hold the rotating part of the motor off of the bottom of the stator mount.
An angular contact bearing sits on this lip and is held concentric by the above mentioned cylinder. The angular contact bearing was chosen because it can take loads in two directions. The weight of the shoulder can sit on the top of the bearing and the rotational forces can be supported by the outside of the bearing. The bearing is held onto the stator mount with a bearing cap that bolts onto the center cylinder, clamping the bearing down.
The rotor mount presses onto the bearing to translate the rotational force from the motor.
There is a lip on the rotor mount for the motor rotor to rest on. This lip holds the rotor at the same height as the stator and keeps the rotor concentric to the stator all around. The shoulder plate bolts to the rotor mount, but the rotor mount doesn’t actually hold the shoulder plate. The shoulder plate actually helps keep the rotor up as the shoulder plate sits on the bearing. Both the stator mount and the rotor mounts have slots cut in them for the motor clamps. These slots are slightly below the tops of the stator and rotor. This height difference allows for small metal pieces to bolt down and clamp the motor into place.
Base Design Analysis
The Direct Drive motor was selected for this year’s robot by the summer team to replace the original L-07 Lazy Susan design. The implementation of the motor was an experiment to study the attributes of a brushless direct drive motor. The angular contact bearing were chosen to be able to support the vertical weight of the arm as well as the rotational force of motor. The rotor was positioned concentric to the stator so that a small space of about 3-4 mm would remain between the stator and rotor.
Finally, clamps were made to keep both parts of the motor firmly fixed to their mounts.
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The primary change to the control system was the introduction of the Playstation
One Controller which allowed more responsive control of the robot than the previous
LabView user interface. The avionics box, used to house all electrical control components, was simplified with the introduction of the Rabbbit 4110 Microprocessor.
The Rabbit processor can control all motor controllers, as well as take in the data from the Playstation controller. Finally, the original motor controllers called motor minds in the L-07 were replaced with more powerful motor controllers that could handle the
higher amperage required to sustain the high torques in the joints. Figure shows the new
Avionics Box.
Figure 10 - M-08 Avionics Box
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4.1 User Interface - Playstation One Controller (PSX)
M-08 Playstation One Controller Interface
The Playstation One (PSX) controller allows the user to easily control the speed and direction of each joint simultaneously and in real time. This interface option is desirable because there is less hardware to use and the cost of replacement controllers is relatively low. The twin analog control sticks allow operation similar to that of a standard backhoe. The controller has ten other buttons that can control additional items like the poker motor and disable switches for motors if desired.
Figure 9 Playstation controller
The PSX controller was chosen because there was an open source code already written to communicate with it via a Basic Stamp 2 microprocessor. This code in was modified by decreasing its poll time, and outputting a character string to the Rabbit via the serial port when the status of the controller changes. The poll time was decreased to 17mS to ensure it remains below 200mS, the visual reaction time of a person. (Kosinski) The serial port also allows the manipulator to be controlled by another device, as long as it sends the
same type of character string. Figure shows how the Playstation controllers buttons and
joysticks move the M-08.
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Figure 10 - Playstation Controller Layout
Alternative User Interfaces
The initial controlling device used for the L-07 robotic arm was an LCD touchscreen. The screen ran from an onboard Mini-ITX computer with the Windows operating system implementing an executable file that was created in LabView.
Figure 13 - LabView generated control file for touch-screen
As seen in Figure , the file contains four separate sliders. Each slider controls a
joint on the arm by either position or direction and speed. The slider is set to a position and then the speed is set as positive for one direction and negative for the other direction.
It was simple to turn on or off the motors individually and change the direction of motion, but proved difficult to do quickly and accurately. An effort to get the end of the robot arm to a specific point in space and at a specific angle required a skilled operator
22

controlling the touch-screen and an ample amount of time. Since control of the robot must be maintained at all times, this device does not meet necessary requirements for this project. Furthermore, the use of Mini-ITX system required the use of a USB mouse and keyboard to navigate the operating system. This process called for even more electrical hardware and consumed more power. However, the onboard computer system did allow for the robot to be synced with other robots easily if needed in the future.
Figure 11 Laser 6 radio transmitter by Hitec
A radio transmitter was tested for the M-08 (Figure 14). Radio controllers, primarily used for airplanes, helicopters and cars, were considered due to their simplicity.
They are designed to be used with servo motors and they output a pulse-width modulation (PWM) signal.
Figure 12 PWM signal at 50% duty cycle and 20% duty cycle
PWM is a series of pulses at a pre-determined frequency at a specific duty cycle.
The period (T) is the inverse of the frequency (f) and remains constant. At 0% duty cycle, the output is all logic low and at 100% duty cycle, the output is all logic high.
23

Figure shows two signals, 50% and 20%, for two periods. For some servo motors, the
minimum pulse is about 1ms and the maximum pulse is about 2ms, with 1.5ms being the center, or off, position (may differ depending on manufacturer).
The team bench-tested the Laser 6 radio transmitter ( Figure ) and Supreme 8
Channel Dual Conversion 75MHz Receiver (not shown) to test for compatibility with the
M-08 microcontroller, Rabbit 4100. The transmitter sends a signal to the receiver at
75MHz and the receiver converts that to a 50Hz PWM output. In order to use this transmitter/receiver combination, the PWM signal from the receiver output would have to be converted to an analog signal with an RC filter. The voltage buffer is then passed to the microcontroller. The 50Hz output is a relatively low frequency and would require a significantly large capacitor in the RC filter to reduce voltage ripple in the analog signal.
The necessity to design and build additional electronic hardware made this interface option less desirable because it would cost more money, draw more power, and increase the number of parts that could potentially fail. Therefore, this device was thrown out as an option for controlling the robot.
4.2 RABBIT 4110 Microprocessor
Operation
The Rabbit 4110 Rabbit Core ( Figure ) controls all the motor controllers on the
M-08. It is the brains of the M-08. It reads an input character string from serial port C and then takes this data and performs the programmed logic to operate the motor controllers accordingly. The motor controllers then provide the high voltage and current needed to operate the motors under load.
Figure 13 Rabbit 4110 RabbitCore by Rabbit Semiconductor
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The Rabbit has 4 PWM (PWM 0-4) outputs, 8 analog inputs, 6 serial ports, and 29 parallel digital I/O lines available on board. This number of I/O in addition to 512kB of onboard memory allow for connection of multiple controllers. The processor operates at about 60MHz, which supports fast run-time for controlling the robot arm joints by cooperative multitasking. Cooperative multitasking allows the Rabbit to execute other tasks while it is waiting for an event to occur.
The Rabbit 4110 was chosen for this project primarily because of its sufficient number of inputs and outputs to interface with the motor controllers, multitasking capabilities and the team’s familiarity with its operation. The Rabbit is also programmed in C programming language which is desirable.
C Programming code
The input character string consists of 8 characters. The first two characters indicate that the PSX controller is returning data and that it is in the proper mode of operation. The variable names in the C code are “psxstatus” and “psxid”. If the values of these variables are 0x5a-returning data and 0x73-analog mode respectively then the PSX is in the correct mode of operation. The next five characters are the status of the buttons and control sticks on the PSX, the C variables “thumbL”, “thumbR”, “joyRX”, “joyRY”,
“joyLX” and “joyLY”. The “thumb##” variables are active low meaning the bit corresponding to each button in the character will be 0 when the button is pressed. The
“joy##” variables are integer values ranging from 0 to 255, and are 128 when the PSX joystick is centered on the respective axis. Lines of code from 76 to 105 read the character string and assign the input variables.
4.3 Motor Controllers
25

Shoulder Motor Controller – Oriental Motor BLHD50K
Operation
The BLHD50K ( Figure ) motor controller was chosen because it is designed to
control the BLH450 motor used at the shoulder joint. The controller has many features to control the speed and direction of the motor. The speed stability reads the value of the motor speed and adjusts the current to hold the set speed for different loading on the motor. There are four events that may trigger the alarm setting: (1) an overload occurring for more than 5 seconds, (2) a disconnected motor, (3) the motor speed exceeding 3500
RPM, or (4) the input voltage to the controller reaching 25% below or 15% above
24VDC. These safety precautions are beneficial because when the arm is under high loading, the shoulder joint receives the majority of the torque.
Figure 14 BLHD50K motor controller by Oriental Motor Co.
The control signals are in a parallel, meaning that a control line is either pulled high or low to change the operation of the corresponding control line. This increases the number of output pins needed to control the motor. The control signals are:

START/STOP

RUN/BRAKE

CW/CCW

INT.VR/EXT

ALARM-RESET
The input to the BLHD50K is inverted, meaning a low voltage will result in a logical high. This is done because each input line has an internal pull up resistor. This setup
26

type is commonly used because if a failure occurs, it occurs in a failsafe mode which stops the motion. The speed control of this BLHD50K was set to the internal potentiometer (POT#1) instead of external speed control by an analog voltage because the Rabbit does not have an analog voltage output. This speed control was not considered a necessity as the BLHD50K also has POT#2 for acceleration and deceleration rate, allowing the motor to speed up and slow down at a rate slower than full speed.
Rabbit Interface
The BLHD50K requires 5V for operation. This is problematic because the Rabbit can only output 3.3V for a high voltage. To overcome this problem a PCF 8574A I
2
C expansion chip was used. I
2
C is a serial protocol that uses pull up resistors on the signal lines. The master and slave devices can toggle the line as desired by effectively grounding the signal line, by using an open drain output on the control line. This choice was made because the signal lines can be 5V as the Rabbit I/O pins are 5V tolerant. This is why I
2
C is commonly used to interface two different voltage based devices. This also reduced the number of I/O pins used from 5 to 2, because the Rabbit uses serial communication to the PCF 8574A and it then controls each of the parallel control lines to the BLHD50K.
C programming code
The C code used to control this device was easy to implement because Rabbit has an I 2 C library in its development environment. The only adaptation needed was to change the output pins to those connected to the PCF 8574A and change the identification value to the one specified by the device. Once communication to the PCF
8574A was established and the output pins could be toggled as desired, the control logic was implemented. There is a minimum of a 10mS delay between changing any two control lines. (Oriental Motor Corporation) The BLHD50K to PCF 8574A pin out is
START/STOP-Pin7, RUN/BRAKE-Pin6, CW/CCW-Pin5, INT.VR/EXT-Pin4 and
ALARM-RESET-Pin3. The variable used to control the shoulder is the “joyLY”. This variable functions as a switch because the speed is set by the BLHD50K POT#1. This
27

switch is not equally proportional on the control stick because the manipulator moves downward more quickly than it raises due to its weight. The motor naturally moves downward when the control stick is in the center position because the brake cannot be applied constantly. The manipulator can gain enough speed while being driven downward that it over accelerates the motor, causing it to go into a reset mode. The only time the shoulder motor should be driven down is when the poker motor is being used. The shoulder provides significant downward force to help keep the poker at its desired position while in operation. A software brake was attempted in the code from lines 115 to 134 but was not successful. Lines 98 to 171 show the control operation of the shoulder motor.
Elbow, Wrist and Poker Motor Controller – Parallax HB-25
Operation
The HB-25 motor controllers were chosen because they have a high output current, low cost and are designed for use with DC motors, the motors used to move the
elbow, wrist and poker. The HB-25 motor controller ( Figure ) can handle 25 amps (35
amps peak). This feature made the HB-25 ideal for controlling the percussive poker and the joints under high loading, which draw large amounts of current. The HB-25 uses a servo motor pulse-width modulation signal to control the speed and direction of the motor. The time period when the pulse is high is considered the pulse width. The servo pulses vary from 1mS to 2mS with 1.5mS indicating stop or no movement. Any increase or decrease in pulse width will turn the motor in the indicated direction and will increase in speed as the pulses become closer to the limits of 1mS or 2mS. If the pulse widths go outside the range of 0.8mS-2.2mS, the HB-25 will shut off the motor until it receives a valid pulse width. (Parallax Inc.) Therefore, the pulse widths are limited to 1mS and 2mS to install a safety margin. This ensures that the motors always stay in operation. The
HB-25 also requires a 5mS delay between pulses. (Parallax Inc.)
28

Figure 15 HB-25 motor controller by Parallax
The original L-07 robot used a Motor Mind motor controller for each of its joints.
This controller allowed 3.5 amps peak current and 2 amps running current. However, it could not support a high enough current that the motors needed to produce the maximum torque under high loads. Although the Motor Mind has features such as brakes, tachometer, and pulse counter, which require more coding, these features were not necessary for operation on the M-08. Therefore, the Motor Minds were removed from the robot and replaced with the HB-25 motor controllers
Rabbit Interface
Each of the HB-25’s is controlled by one of four Pulse Width Modulation (PWM) pins on the Rabbit. The Rabbit can only set one base PWM frequency for all of its PWM outputs. (Rabbit Semiconductor) This frequency is based on the Rabbits internal timer
A6. Once the base frequency is set, the pulse width can be changed based on an integer number. Using this integer, the duty cycle can vary from 0-1024 with 0 being a no pulse and 1024 a max pulse of the entire cycle. The Rabbit can suppress 7 out of 8 and 3 out of
4 pulses from any of its PWM outputs. This allows the base PWM frequency to be increased from 50Hz with no suppression to 505Hz.
C Programming Code
The use of Rabbits PWM library made the set up and control of the HB-25’s easier. The limiting factor is 2mS high pulse width for the HB-25. This corresponds to a frequency of 500Hz because at a full PWM duty cycle of 1024 while the proper delay is
29

achieved by suppressing 7 out of 8 pulses. Therefore the “PWMFREQ” variable is set to
505Hz because this is the closest frequency that the Rabbit can produce with its internal timers. The C variables that control the DC motors are: “joyRX”-elbow motor, “joyRY”wrist motor, “thumbR” bits 4 and 5- poker motor (O on and ▲off on the PSX). The poker motor was set to be either max speed when on or off. The “joy##” variable is also mapped into the desired PWM duty cycle, from an integer value of 0-255 to a duty cycle of 512-1024. The lower PWM duty cycle of 512 is found from the equation below.
Eq. 1
The desired time and PWM base frequency is 1mS and 505Hz, respectively. This will result in a pulse width of 1mS. Therefore the mapping function is shown below.
Eq. 2
Lines 172 to 202 and 230 to 266 control the operation of the elbow, wrist and poker motors.
Base Motor Controller – Advanced Motion Control B12A6N (AMC)
Operation
The AMC motor controller was chosen because it is a direct drive motor controller and the base motor is a direct drive motor. The direct drive motor uses tertiary windings and has Hall Effect sensors. The Hall Effect sensors are connected to the AMC controller providing it with feedback data. The AMC has three modes of operation: current, tachometer and open loop mode. The open loop mode was chosen because there is no tachometer on the base motor. Current mode is intended for use if the motor is operating at a constant speed with a variable load. In motors, current is proportional to torque and voltage is proportional to speed. Therefore, it is desirable to adjust the speed rather than torque for position control. In open loop mode the output voltage to the windings is proportional to the input signal. This was chosen because the user can close
30

the control loop. Thus, the user, by controlling the voltage, will control the speed of the motor. The AMC is controlled by a differential analog voltage which can range from
+10V to -10V. At 0V, there is no movement. A positive or negative voltage controls the direction and magnitude of the voltage by increasing or decreasing the speed. This device also has an inhibit motor input pin that is used to ensure the motor moves only when desired.
Figure 16 B15A8 Brushless motor controller by Advanced Motion Controls
Rabbit Interface
The Rabbit was very limited in controlling the AMC as it cannot directly output an analog voltage. To overcome this, two devices were needed to produce a differential analog voltage: an RS-232 driver and a low pass filter. To create an analog voltage, the
PWM 2 output is connected to the RS-232 driver chip, a UA9636AP. This converts the
PWM signal to a signal that is +10V when the PWM is high and -10V when the signal is low. The output of the driver chip is then low pass filtered. This creates a DC voltage that is then sent to the AMC as the signal input. The driver chip uses the ±10V outputs from the AMC as its power source because this voltage is not available on the Rabbit board. This voltage increases or decreases as the PWM changes. For a 0V signal, the
PWM duty cycle is 512. Therefore, the PWM is high and low for an equal amount of time.
C Programming
31

The maximum allowable PWM base frequency is set to 505 for the BH-25 motor controllers with 7/8 th
suppression. This created problems for the filter design of the low pass filter. By using the Rabbits PWM spread ability, this base frequency was increased to 2020Hz for the output pin PWM2 controlling the AMC. This resulted in an increase in capacitor size from 1μF to 22μF because the size of the capacitor is dependent on frequency to reduce ripple voltage. A ripple of 8mV was obtained. The “joyLX” variable is used to control the base motor. Similar to the HB-25, the “joyLX” variable needed to be mapped to a PWM duty cycle. This was done by simply multiplying
“joyLX” by 4. The inhibit line for the AMC was controlled by the “thumbR” variable bits 6 and 7, on and X off. The inhibit line is connected to the Rabbit pin PB3. It needs 0 or 5V to enable or disable the inhibit pin on the AMC. This was accomplished by setting
PB3 as an input pin for enable, and setting PB3 as an output pin in open drain mode.
This output pin required an open drain mode because the Rabbit can only drive a voltage up to 3.3V.
This section contains basic information regarding the electronics required to supply power to the robot. The components used offer high output power and have builtin over-current protection relays. No other power management schemes were researched for this project because these boards meet the requirements for power on the robot.
Many of the components on the M-08 require different voltage inputs. In order to do this, there are four main modules incorporated into the avionics box: (1) XP-08S power management, (2) DC1HV DC-DC converter, (3) DC123S DC-DC converter, and
(4) HD4RX wireless kill switch. These components were incorporated into the robot at
Ames Research Center. Figure shows how the power is distributed throughout the
system.
32

Figure 20 - Power Systems Flowchart
5.1 XP-08S Power Management
The XP-08S power management ( Figure ) is designed to operate from either an
18VDC (external of M-08) or Smart Li-Ion battery packs (internal of M-08). However, the external 18VDC supply requires a 120VAC source. The XP-08S outputs a clean
(low-noise and steady) 18VDC to the DC1HV DC-DC converter to ensure the rest of the system is maintained with a constant power. This board also charges the Smart Li-Ion battery packs when the external 18VDC is connected.
33

Figure 17 - XP-08S Power Management by Oceanserver
5.2 DC1HV DC-DC Converter
Figure
shows the DC1HV DC-DC converter. This board takes power from the
XP-08S and is capable of supplying 350 Watts of power at 18VDC and 24VDC. This component powers the DC123S DC-DC converter, the B15A8 motor controller and the
BLH-450 motor controller.
Figure 18- DC1HV DC-DC converter by Oceanserver
5.3 DC123S DC-DC Converter
The DC123S DC-DC converter ( Figure ) is powered by the DC1HV DC-DC
converter. It provides up to 144 Watts of power at 3.3VDC, 5VDC, and 12VDC. It is supplying power to the three HB-25 motor controllers, the Rabbit microcontroller, the
BasicStamp Homework board, the HD4RX wireless kill switch, and the avionics box fans.
34

Figure 19 - DC123S DC-DC Converter by Oceanserver
3.4 HD4RX Wireless Kill Switch
The HD4RX wireless kill switch ( Figure ) is integrated to the M-08 as a safety
precaution. It simply acts as a quick on/off switch for the motor controllers.
Figure 20 - HD4RX Wireless Kill Switch [Transmitter (Left)/Receiver (Right)]
If any of the motors cannot be stopped by software with the PSX controller, then this device will completely kill the power to any of the four motor controllers.
Kill Switch
Button
Motor
Controller
M-08
Joint
1
2
3
3
4
B15A8 Base
BLH-450 Shoulder
HB-25_E
HB-25_W
HB-25_P
Elbow
Wrist
Poker
Table 2 - HD4RX Wireless Kill Switch button assignment
The transmitter in Figure has four buttons numbered 1 through 4, arranged as
seen in Table 2 (Note: Button 3 is connected to the elbow and wrist joints).
35

The M-08 performed very well during testing. The percussive poker was capable of chipping rock, the motors supplied ample torque for digging, and the Playstation controller functioned significantly better than the previous user interface, LabView. This section provides a detailed evaluation of the performance of each design.
Percussive Poker Assessment
As this component was the primary objective of this project, the percussive poker was definitely a success. The poker managed to break through several hard rocks during testing. While testing, however, the poker managed to bury itself into the rock making a small hole rather than chip away at the rock and break it. This effect could be in part due to the use of the poker in conjunction with the very powerful elbow and shoulder motors.
These motors helped to wedge the sharp poker straight into the rock rather than allow it to slowly chip the rock. This extra force may also have given significantly more wear to the inside of the poker than it was designed to withstand. Several times during testing, the roller on the poker shaft was forced off of the cam and needed to be taken apart and reassembled. The poker motor also burnt out because the 12V supplied to the motor was higher than the motor was made to handle, which was 7.2V.
Percussive Poker Improvements

The motor used during testing was exceptionally cheap so it is recommended that another motor is used that can handle the 12 V requirement.

The poker tip was shaped as a short point but it can easily be removed and replaced with a new tip with the tapped end on the poker. A longer tip with a flat edge like a flathead screwdriver or a jackhammer might chip rock without burying itself in the rock.

A larger roller on the end of the poker in contact with the cam may allow more force to be applied through the shoulder to the poker without disconnecting the roller.
36

Wrist Assessment
The wrist assembly easily performed its major tasks. The motor and gearbox provided the necessary torque to dig through dirt as well as rotate between the shovel and the percussive poker. The slip ring was also a success in effectively minimizing the wires outside the machine and allowing for continuous rotation. The most obvious drawback however, is the exceptionally slow speed of rotation. This became painfully obvious when switching between the poker and the shovel. Another problem with this particular gearbox is its small keyways. These 2 mm wide keyways support all of the torque induced in the assembly making it by far one of the most extreme areas for failure. The support arm that held the percussive poker and backhoe bucket and the flange couplers that connect the wrist to the arms are also quite bulky and heavy.
Wrist Improvements

These components could be redesigned significantly smaller without sacrificing worry of failure under load and therefore reducing weight at the end of the arm.

A new gear box with higher speed and less torque and output shafts with a larger keyway. It is very likely that the increase in speed will cause a substantial reduction in performance of the wrist in digging. However, if a more powerful gearbox is placed in the elbow, then that joint could replace the wrist as the primary source of torque for digging. (Note: it is important to verify that the motor and gearbox can lock under the load supplied by the torque of the elbow. Also, digging was never done using only the wrist but rather the wrist, elbow and shoulder motors in conjunction with one another.
37

Elbow Assessment
The elbow joint was not only very effective at positioning the percussive poker and shovel, but also proved to be a valuable asset in digging. Similar to a backhoe, every joint, including the elbow, was required to make a controlled scoop and move the dirt and rocks. The elbow joint used the same gearbox as the wrist joint with a slightly smaller gear reduction. Therefore, the gearbox had a very small keyway that supported all of the torque. If the elbow were to fail, that would be the most likely place for failure. The elbow also has relatively small diameter flange couplers connecting the two sets of arms.
These might also be a potential failure point if more torque is added to the joint.
Elbow Improvements

A new gear box with a larger output shaft and larger keyway to support the high stresses and loads.

Larger flange couplers for a more robust connection between the arms providing less chance for failure under load.
Shoulder Joint
The shoulder motor worked very well in positioning the percussive poker and the shovel with the elbow joint. This particular motor really excelled in assisting the other joints digging by providing an extraordinary amount of torque. As the shoulder had no brake, it would allow the whole arm to slowly fall when not being directed to lift the arm.
Shoulder Joint Improvements

A brake to hold the shoulder motor in place when not in motion.
Base Joint
The direct drive brushless DC motor had no problem rotating the arm from left to right. The motor provided a more power efficient, frictionless method of performing this task. However, it was discovered to be not the most advantageous option for the base joint. The motor runs best at high velocities, around 2000 rpm. The base, on the other hand, rarely makes a full revolution. The primary function was to rotate within a 180
38

degree spectrum. This functional limitation, combined with the frictionless rotation, made the base very difficult to control. During testing, the base controls had to be operated with, meticulous precision in order to perform basic positioning; otherwise, it would jerk too far. The frictionless attribute proved to be more of a problem than a benefit since more control had to be used to bring the arm to a halt where desired and would float rotationally once stopped. In the end, the direct drive base was a very good learning experience but it did not provide the necessary control needed for the task.
Base Joint Improvements

A new motor to replace the direct drive motor in the base is strongly recommended. A stepper motor is an effective alternative to increase control and stopping while still retaining the brushless efficiency.

A brake to hold the base in place after positioned.
39

Kosinski, Robert J. A Literature Review. September 2006. 5 April 2008
<http://biae.clemson.edu/bpc/bp/Lab/110/reaction.htm#Type%20of%20Stimulus>.
Oriental Motor Corporation. "BLH Series Operating Manual." 2007.
Parallax Inc. "HB-25 Motor Controller." April 2007. www.parallax.com. 15 May 2008
<www.parallax.com>.
Rabbit Semiconductor. "Rabbit 4000 Microprocessor User's Manual." 2007. www.rabbit.com. 10
February 2008
<http://www.rabbit.com/documentation/docs/manuals/Rabbit4000/UsersManual/R4000UM.p
df>.
40

Appendix A
41

Appendix B – Moonavators Schedule
Month
Aug-07
Sep-07
2007-2008 Moonavators Scheduling
Task
Research robotic technologies
Read through L-07 end of year report
Contact Client to better understand expectations
Oct-07
Research Symposium Presentation at Commons
Create block diagram for understanding L-07
Initial ideas and design sketches
Microsoft Project Timeline
Nov-07
Decide on specs wanted for M-08
Teleconference with Vytas
Break into teams for L-07 redesign - Focus on joint improvements
Redesign problem areas on L-07
Begin machining and manufacturing of parts for L-07 redesign
Dec-07
Team trip to AMES
Meeting with Vytas - tours, design review presentation
Tweak future design around what Vytas is looking for
Begin initial sketches and ideas for M-08
Interim Report
Initial cost expectations for second semester
Initial M-08 design sketches CD
Christmas Break - sketch ideas, explore current advanced robotic technologies CD
P
P
CD
CD
P
CD
Classification
Problem Definition (PD)
PD
PD
Presentations (P)
Concept Design (CD)
CD
CD
CD
P
CD
Detail Design (DD)
Fabrication (F)
Jan-08
Feb-08
Break into separate joints to better focus our time and efforts
Begin research for improved motors and gearboxes
Create sketches and solidworks drawings for new design
Include Base, Shoulder, Elbow, Wrist, and Poker in new designs
CD
CD
DD
DD
Mar-08
Nail down scheduling and goals for rest of semester
Teleconference with Vytas - Update with new ideas and progress
Plan to remove ITX board from avionics box
Switch to Rabbit Controller
Order all motors and gearboxes
Begin base machining
Research and source slip wrings for wrist
CD
P
P
DD
F
CD
42

Apr-08
Final solidworks drawings for M-08
Spring Snapshot
Merge Shoulder, Elbow and Wrist designs together
Begin manufacturing on rest of M-08
Final touches on machining
Troubleshoot control issues
Fix small machining mistakes
Begin final paper, poster, presentation
EXPO
DD
P
DD
F
F
Testing/Delivery (T+D)
T+D
T+D
P
43

Appendix C – Bill of Materials (M-08)
Sub assembly Part name Part Number
Bought /
Machined Qty. Cost Supplier
Elbow joint
Elbow joint
Elbow joint
Elbow joint
Elbow joint
Elbow joint
Elbow joint
Elbow joint
Shoulder joint
(3/3/2008)
Shoulder joint
Shoulder joint
Shoulder joint
Wrist
Wrist
Wrist
Wrist
Wrist
Wrist
Wrist
Wrist
Wrist
Wrist
Wrist
Poker
Poker
Poker
Wrist (2/29/08) Motor/gearbox
Wrist Gearbox
Wrist
Poker
Poker
Poker
Poker
Poker
Poker
Poker
GYW-17
P20-120
Motor
4-conductor Slip
Ring w/ boot kit scoop support upper gearbox clamp lower gearbox clamp slip ring shaft
MS-15 motor
#8-32x1"
#8-32x2"
#6-40x2" motor bolt plate standard shaft caseblock right half caseblock left half bushings flanged roller bearings poker shaft spring pin spring pin cam keyed shaft motor bolt plate
BDSG-37-30
430
MS-15
Gearbox
Motor keyed shaft arm mounts
Arms
Motor Mount
Gearbox Mount
Bushings shoulder plate shoulder motor/gearhead shoulder motor
P20-60
BDSG-37-30
P20
BLHM450KC-
GFS/GFS4G-FR
Dynetic (Not Currently
Installed 5/08)
Rinomechanical.com
Anaheimautomation.com
Mercotac
Dynetic
McMaster
McMaster
Tri-State
Tri-State
Mc-Master
Rinomechanical.com
Anaheimautomation.com
Anaheimautomation.com
Mcmaster.com oriental motor oriental motor
8
2
2
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
2
2
2
2
2
B
B
M
B
M
B
M
B
B m b b
B
M
M
M
M
B
B
B
B
M
M
M m m m m
B
M
M
B
B
M m
44

Shoulder joint
Shoulder joint
Shoulder joint
Shoulder joint
Shoulder joint
Base joint
(3/3/2008)
Base joint
Base joint
Base joint
Base joint
Base joint
Base joint
Electrical box
(2/29/08)
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box
Electrical box key shoulder front bracket shoulder back bracket shoulder back bracket2 shoulder driveshaft arm mounts
Direct Drive motor stator/rotor angular contact bearing stator mount frame frame holders (8) bearing rotor mount bearing cap
165-a-12
5207 sealed
RCM4100
RabbitCore
Development Kit
CONN RECEPT
8POS 3MM
SINGLE ROW
STANDOFF M/F
HEX 4-40 NYL 0.5"
STANDOFF M/F
HEX 4-40 NYL
0.25"
SCREW MACH
PHIL 4-40X1/4 NYL
CONN PLUG 8POS
3MM SINGLE
ROW
CONN TERM
FEMALE 20-
24AWG TIN
CONN TERM
MALE 20-24AWG
TIN
CONN RECEPT
2POS DUAL,
FEMALE
CONN RECEPT
4POS DUAL,
FEMALE
CONN RECEPT
6POS DUAL,
FEMALE
CONN RECEPT
8POS DUAL,
101-1157
43645-0800
4802K-ND
4800K-ND
H542-ND
43640-0801
43030-0007
43031-0007
WM3700-ND
WM3701-ND
WM3702-ND
WM3703-ND
B
B
B
B
B
B
B
B
B
B
B
B m m m b m b b m m m m
Applimotion
Applied Industries (SKF
Bearing)
1 229.00 Rabbit Semiconductor
3
50
0.77 Digikey Corp.
0.44 Digikey Corp.
50 0.42 Digikey Corp.
100 0.09 Digikey Corp.
3
30
30
6
4
14
14
0.77
0.15
0.47
0.52
Digikey Corp.
Digikey Corp.
0.15 Digikey Corp.
0.37 Digikey Corp.
0.42 Digikey Corp.
Digikey Corp.
Digikey Corp.
45

Electrical box
Electrical box
Electrical box
Electrical box
Platform
(2/29/08)
FEMALE
CONN RECEPT
20POS DUAL,
FEMALE
CONN PLUG
20POS PANEL
MOUNT, MALE
CONN TERM
FEMALE 18-
24AWG TIN
CONN TERM
MALE 18-24AWG
TIN
Hitec Laser-6
75MHz
Transmitter
WM3709-ND
WM1028-ND
WM2501-ND
WM2500-ND
157751 Platform
B
B
B
B
B
1 1.27 Digikey Corp.
1 1.54 Digikey Corp.
100 0.10 Digikey Corp.
30 0.14 Digikey Corp.
1 142.98 Amazon.com
46

Appendix D – Poker Math Model
"Position Variables" r2 = .5 [in] "primary radius" t2 = phi "driver angle" t3 = pi "angle of hammer (it stays 90 degrees)" r3 = r2 + S "position of the hammer"
L = .25 [in] "maximum length of the cam stroke"
B = pi/2 t1_degrees = t1*180 [degrees] /pi t2_degrees = phi *180 [degrees]/pi "driver angle in units of degrees"
"Velocity Variables" rd2 = 0 [in/s] "linear velocity of vector 2 is zero because the primary radius is constant at .5 in" w2 = 62.8 [rad/s] "driver angular velocity of vector 2" w3 = 0 [rad/s] "angular velocity of vector 3 is zero because the hammer motion is constrained linearly" rd3 = V*w2 "linear velocity of the hammer"
"Acceleration Variables" rdd2 = 0 [in/s^2] "linear acceleration of vector 2 is zero because the primary radius is constant at .5 in" a2 = 0 [rad/s^2] "angular acceleration of vector 2 is zero because the angular velocity is assumed constant" a3 = 0 [rad/s^2] "angular acceleration of vector 3 is zero because the hammer motion is constrained linearly" rdd3 = A*w2^2 "linear acceleration of the hammer"
"Force Variables" k = 12 [lbf/in] "spring constant for the spring used to keep the hammer in contact with the cam" m_poker = .000593 [slug] "mass of the poker (aluminum)" m_cam = .001338 [slug] "mass of the cam (aluminum)" g = 32.2 [ft/s^2] "gravity" x_h = .0833 [ft] " vertical distance from the center of mass of the poker to the end of the poker" x_b1 = (.75 [in] - S)/12 [in/ft] " vertical distance from the center of mass of the poker to the top of the bearing that constrains the hammer linearly - distance changes as hammer moves - converted from in to ft" x_b2 = (.5 [in] - S)/12 [in/ft] " vertical distance from the center of mass of the poker to the bottom of the bearing that constrains the hammer linearly - distance changes as hammer moves - converted from in to ft"
"Position Vector Loop" r1*cos(t1) = r2*cos(t2) + r3*cos(t3) r1*sin(t1) = r2*sin(t2) + r3*sin(t3)
S=L*(phi/B-1/(2*pi)*sin(2*pi*phi/B))
"Velocity Vector Loop" rd1*cos(t1) - r1*w1*sin(t1) = rd2*cos(t2) - r2*w2*sin(t2) + rd3*cos(t3) - r3*w3*sin(t3) rd1*sin(t1) + r1*w1*cos(t1) = rd2*sin(t2) + r2*w2*cos(t2) + rd3*sin(t3) + r3*w3*cos(t3)
V=L/B*(1-cos(2*pi*phi/B))
"Acceleration Vector Loop" rdd1*cos(t1) - 2*rd1*w1*sin(t1) - r1*w1^2*cos(t1) - r1*a1*sin(t1) = rdd2*cos(t2) - 2*rd2*w2*sin(t2) - r2*w2^2*cos(t2) - r2*a2*sin(t2) + rdd3*cos(t3) - 2*rd3*w3*sin(t3) - r3*w3^2*cos(t3) - r3*a3*sin(t3) rdd1*sin(t1) + 2*rd1*w1*cos(t1) - r1*w1^2*sin(t1) + r1*a1*cos(t1) = rdd2*sin(t2) + 2*rd2*w2*cos(t2) - r2*w2^2*sin(t2) + r2*a2*cos(t2) + rdd3*sin(t3) + 2*rd3*w3*cos(t3) - r3*w3^2*sin(t3) + r3*a3*cos(t3)
A=2*pi*L/B^2*(sin(2*pi*phi/B))
47

"Pressure Angle between the Cam and the Hammer" tan(p_rad) = V/(r2 + S) "pressure angle (angle at which the contact force between the cam and the hammer acts, this angle changes as the cam revolves)" p = p_rad*180[degrees]/pi "pressure angle in degrees"
F_cy = F_contact*cos(p_rad) "contact force between the cam and the hammer in the y direction"
F_cx = F_contact*sin(p_rad) "contact force between the cam and the hammer in the x direction"
"Cam Force Equations"
W_c = m_cam*g "weight of cam" r3_ft = r3/12 [in/ft] "convert r3 from inches to ft"
-W_c - F_1y + F_cy = 0 "sum of the forces in the y direction (cam)"
-F_1x + F_cx = 0 "sum of the forces in the x direction (cam)"
T - F_cx*r3_ft = 0 "sum of the moments (cam)"
"Hammer Force Equations"
W_p = m_poker*g "weight of the poker"
F_s = k*S "force exerted by the spring through the hammer"
Fr = 170 [lbf] "driving force to test limits of motor and determine max force the hammer can apply (units are lbs)"
Fr = c*(pi/2)^3 "solve for constant to relate quadratic equation of the force exerted by the rock when the hammer hits it to the position of the cam - peak 200 lbs acts at the end of the cycle at pi/2"
F_r = c*(phi)^3 "quadratic equation that relates the force exerted by the rock when the hammer hits it to the position of the cam with a unit change from lbs to N for calculations" rdd3_ftss = rdd3/12 [in/ft]
-W_p - F_cy+F_s +F_r= m_poker*rdd3_ftss "sum of the forces in the y direction (hammer)"
-F_cx + F_b1 -F_b2 = 0 "sum of the forces in the x direction (hammer)"
F_cx*x_h - F_b1*x_b1 - F_b2*x_b2 = 0 "sum of the moments (hammer)"
T_oz_in = T*16[oz/lbf]*12[in/ft]
48

Appendix E – DFMEA
Revision
Date 5/1/2008
Base
DESIGN FAILURE MODE AND EFFECT ANALYSIS
(DFMEA)
Project
Year
Lunar Soil Manipulator
2007-2008
Team Members Jake Conn, Craig Craviotto, Shane Duff, Caitlin Flynn, Hans Leidenfrost, Mike Mahlum
ITEM AND
FUNCTION
Direct Drive
Motor Fails
POTENTIAL
FAILURE
MODE(S)
POTENTIAL
EFFECT(S) OF
FAILURE
S
E
V
POTENTIAL
CAUSE(S) OF
FAILURE
O
C
C
U
R
CURRENT
DESIGN
CONTROLS
D
E
T
E
C
T
R
P
N
RECOMMENDE
D ACTIONS
S
E
V
Action Results
O
C
D
E
R
P
N C
U
R C
T
T
E electrical
1=inconvenience, up to 10=injury, broken fingers loss of control 7 dead power supply 4 none 8 check wiring 4 7 8 224 no power- free spinning 6 stop arm motion with hand 6 5 6 180 mechanical overload
6 bad wiring arm stuck, force on arm stronger
7 than force of motor
5 remote on-off switch
9 none 5 turn off power 7 9 5 315 programming loss of control: no braking capabilities bearing breaksjoint stops turning motor continually runsspins arm around
8 no brake has been designed
4 overuse, faulty bearing
6 endless loop
9
2 none
3 remote on-off switch arm hits the frame
8
6
7 stop arm with hand turn off power turn off power
8
4
6
10
2
3
8 640
6 48
7 126
Shoulder Joint
Shoulder Motor electrical loss of control, erratic motion no power- free spinning
10 dead power supply 4 none
2 bad wiring arm stuck, force on arm stronger
7 than force of motor
5 none
7 remote on-off switch
Shoulder Joint mechanical programming mechanical overload bearing breaksjoint stops turning motor continually runsspins arm around fracture and failure of mechanical structure
5 overuse, faulty bearing
10 endless loop
10 break in joint or arm- material fails
8 none
4 remote on-off switch
6 none stuck- no more use of joint 2 jam 9 none
8
9
6
8
5
3
8 check wiring let the arm fall by itself
10
2
4
5
8 320
9 90 turn off power turn off power
7 7 6 294
5 8 8 320 turn off power 10 4 5 200 turn off power, remove loads kill power, remove loads
10 6 3 180
2 9 8 144
49

Elbow Joint
Motor
Structure
Gearbox electrical
Lubrication loss of control, erratic motion no power- free spinning
10 dead power supply no power- free spinning erratic arm motion
Seizes
4 none
2 bad wiring
10
Wires
Disconnected/C ut
10 Programming
2 Oil Issues
5 none
6 none
5 remote on-off switch
2 none
Mechanical
Connections Screws shear
Bending
Keyways shear arms deflect
Stops moving Seizes gearbox does not work
9
Over/under torque screws/bolts, torque overload 4 none
8 torque overload 9 none
4 force overload 1 none
2 Lubrication
3
Bad from factory
2 none
1 none
8
9
8
9
5
#
#
4
7
1 check wiring let the arm fall by itself kill power kill power lubricate kill power kill power remove load lubricate
10
2
10
10
2
9
8
4
2
3
4
5
8 320
9 90
6
5
2
4
2
1
8 480
9 450
5 20
10
7
1
360
9 10 720
1 4 16
28
3
Wrist Wrist Motor
Gearbox shafts scoop support electrical mechanical mechanical bending breaking loss of control no power, no motion overload dirt inside gearbox
Keyways shear
4 broken wires
4 arm stuck, motor stalled
7 wrist joint breaks
5 gearbox runs rough
3 wrist joint breaks arm strikes the ground too hard fasteners shear off
7 wrist joint breaks
5 scoop is not usuable bending scoop support bends under load 6 scoop is not usuable
5 none
9 none
6 none
3 none
9 none
8 none
6 none
#
4
6
#
6
#
# check wiring remove load, restart motor kill power kill power kill power move arm up kill power
7
5
4
4
3
5 6 120
9 10 360
6
3
4 168
6 90
9 10 270
7
5
8 10 560
6 10 300
50

Poker
Electronics poker motor
Software
Hardware electrical infinite loop
Code error
Corrupt memory
Component failure no motion
Loss of control
Loss of control
Loss of control
Loss of control
3 bad wiring 3 none
Test code
Test code none
Bypass Caps
Limiting electronics on controllers
Protect sensitive parts
6 mechanical current overload, motor breaks camshaft shears cam keyway or key shears high friction
4 motor draws too much current, too high force load
4 force overload
4 force overload
4 shaft roller siezes up
9 remote on-off switch
7 none
7 none lubrication 4 no lube
8 none
6 none cam seizes up roller bearings sieze poker shaft siezes up
4 no lube
4 no lube
5 none
6 none
#
#
7
5
8
6
7
Screws poker roller screw unscrews 2 motion in general 9 none 7
Improper code design
Improper code design
Hardware memory failure
Transient voltages
Current overload
Structural damage check wiring 3 3 6 54 cry cry install new cam dissasemble poker dissasemble poker dissasemble poker dissasemble poker put screw back on
4
4
4
4
4 10 10 400
4
4
7
7
7
10
196
280
8
6
5
6
5 160
8 192
6 120
7 168
2 10 7 140
51