Ref. Ares(2016)7165820 - 23/12/2016
MRI and Ultrasound Robotic Assisted Biopsy
D5.1 Robot flange
Project: MURAB
Project Number: 688188
Title: D5.1. Robot flange
Version: 1.0
Confidential
Authors: Klaus Miller, Johannes Lachner, Vincent Groenhuis and Françoise J. Siepel
Date: 19 December 2016
This project has received funding from the European Union’s Horizon 2020 research and innovation
programme under grant agreement No 688188.
Executive Summary
The MURAB project has the ambition to revolutionise breast cancer and muscle diseases diagnosis and has the
potential to save lives by early detection and treatment. The project intends to create a new paradigm in which
the medical imaging modalities MRI and Ultrasound are combined and supplemented by the precision of robotics
in order to target the right place in the body for taking biopsies in breast cancer and muscle diseases.
The end effector or robotic head of the robotic arm is specifically designed for the MURAB project and contains
a needle holder, ultrasound probe and a camera. The endeffector will be attached to the robotic arm with help
of a robotic flange. This robotic flange was designed and is part of the hardware integration. Besides the
mechanical connection, the flange facilitates the communication interfaces for the data to the robotic head.
A demonstration of the robotic flange is given (video) and flange specifications were described. The media flange
provides an ergonomic interface for hand guiding, manual tool change mechanism, internal guiding of cables,
safety switches for hand guiding, defined direction of tool mount.
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Document Details
Version
Author(s)
Date
1.0
Klaus Miller, Johannes Lachner,
Vincent Groenhuis, and Françoise J.
Siepel
21 December 2016
Document history
Draft/Version
Author(s)
Date
Changes
D.1
Klaus Miller, Johannes
Lachner, and Françoise J.
Siepel
Klaus Miller, Johannes
Lachner, Vincent
Groenhuis and Françoise J.
Siepel
Klaus Miller, Johannes
Lachner, and Françoise J.
Siepel
October 2016
First draft
November 2016
Revision
December 2016
Comments by other partners
D.2
V.1
Internal review history
Internal Reviewer
Date
Comments
Stefano Stramigioli
8 December 2016
various
Uwe Zimmermann
13 December 2016
various
All project partners
22 December 2016
various
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Table of Contents
1
2
3
Introduction .......................................................................................................................... 4
Flange specifications .............................................................................................................. 4
2.1 Mechanical and Electrical Requirements ............................................................................4
2.2 Power supply and signals ....................................................................................................6
2.2.1 KUKA Lightweight Robot...........................................................................................6
2.2.2 Needle holder ...........................................................................................................7
2.2.3 Camera .....................................................................................................................7
2.2.4 Force sensor .............................................................................................................8
2.2.5 Ultrasound probe .....................................................................................................8
Mechanical and Electrical Realisation .................................................................................... 9
3.1 Mechanical Structure of the Robotic Flange.......................................................................9
3.2 Wiring Scheme ..................................................................................................................10
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1
Introduction
The MURAB project has the ambition to revolutionise breast cancer and muscle diseases diagnosis and has the
potential to save lives by early detection and treatment. The project intends to create a new paradigm in which
the medical imaging modalities MRI and Ultrasound are combined and supplemented by the precision of robotics
in order to target the right place in the body for taking biopsies. This will be achieved by identifying a target using
Magnetic Resonance Imaging (MRI) and then use a robot with an ultrasound (US) probe to match the images and
navigate to the right location. The emphasis will be on reaching the tumor tissue that represents the target point
for the MURAB robotic biopsy system. The same approach will be performed with regard to the muscle tissue.
For this, two prototypes of end effectors to be attached on the robot arm were designed. An optimization step
to the third design of an end effector will be further implemented. The connection between the end effector and
the robot arm, the robotic flange, was designed specifically for the MURAB project, and is the main topic of
deliverable 5.1.
Deliverable 5.1 includes:
§ Demonstrator: demonstration video of the robot flange mounted between the KUKA arm and the end
effector (link: https://youtu.be/7E2wyzAFa8o)
§ Documentation of the flange specifications as described in this document.
In the next chapter we will describe the flange specifications.
2
Flange specifications
The hardware integration concerns the design of a robotic flange that the instrumented robotic head can be
attached to. Besides the mechanical connection, the flange features the communication interfaces for the data
generated at the robotic head level. Internal connections to the robotic head were made including the camera,
force sensor, ultrasound probe and needle holder.
As the KUKA lightweight arm LBR iiwa 7 kg comes with a standard flange called KUKA media flange inside electric,
illustrated in figure 1, which serves as a clean interface for standard endeffectors like actuated grippers or other
tools, in the wake of the MURAB project the flange has to offer even more sophisticated features to meet the
requirements of the overall application. In the following chapters it has to be distinguished between the standard
flange (media flange or KUKA KUKA media flange inside electric) and the newly developed additional robotic
flange.
2.1
Mechanical and Electrical Requirements
Distance to robotic head
The design of the LBR iiwa prevents a human to be clamped in the structure of the manipulator during its movement. Nevertheless a wrong layout of the robotic tool may produce new clamping points and e.g. the hand of
the surgeon can be pinched during the robot movement (Figure 1).
Figure 1: Obstacle contours
Hence the intermedia flange enables a certain distance between robot flange and the tool to counter these effects. Furthermore the design of the intermedia flange should take into account that the US probe has to be
normal to the breast and needle. For a dexterous workspace the mounting direction of the tool may be declined.
In this case the design of the tool has to be adapted. A straight layout without declination was chosen for the
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intermedia flange.
Handguiding
For intervention by the medical staff handguiding of the robot should be possible. The surgeon has the possibility
to engage in the application whenever wanted. Therefore it is more comfortable to have a handle to steer the
robot manually with both hands. The handle should be located in a ergonomic reasonable way. For cleaning
purposes, the tool should be removable. Therefore it can be graped at the handle.
Interference with environment
A rounded design of the intermedia flange is important, since sharp edges and exposed parts may harm the
surgeon and the patient during movement. Moreover, the hand holder should be as small as possible to not
collide with the patient table during scanning/insertion phase. The handle was designed as small as possible but
can be changed if test setups show new awarenesses.
Positioning accuracy
The intermedia flange will be mounted on the robot flange. Therefore the according hole pattern of the robot
has to be taken into account (Figure 2).
Figure 2: Hole pattern of robotic flange
On the other side of the intermedia flange the tool will be mounted. Suitable hole pattern between intermedia
flange and tool have to be chosen. Positioning accuracy is significant for a successful biopsy process. Lesions may
be as small as 4 mm, hence the positioning accuracy during the intervention phase has to be as accurate as
possible. Therefore the mechanical interface between all parts of the endeffector (intermedia flange and robotic
tool) should be very precise. By use of aligning pins an positioning accuracy of less than 1mm should be reached
(with respect to the TCP of the tool). The workspace of the endeffector should cover the whole surface of the
breast, while taking into account that the insertion of the needle must not perforate the chest wall. In addition,
the thickness of the table could limit the reachable workspace.
Due to the highly constrained environment task space control is a suitable way of controlling the robot in MURAB.
One possibility is to implement force control. For an exact algorithm calculation the centre of mass has to be
determined as accurate as possible. Pressure of the robot towards the skin should be limited. A minimal pressure
on the breast is necessary in order to keep contact with the breast and to acquire the ultrasound images. The
maximal pressure should be adjusted and controlled. In case of movement of patient or radiologist the robotic
arm should anticipate. An option would be to move the robotic arm in line with the movement of the patient/radiologist. The robotic flange must kept as stable as possible in those safety actions during intervention. Motion
artefacts should be reduced and therefore, movements such as breathing and other small movements should be
taken into account.
Material requirements
All subcomponent’s choice of material has to meet the clinical requirements. The flange must be sterilizable for
the MURAB procedure, to prevent contamination between patients.
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Safety Switches and other input devices on flange
Background information: Intentiously the MURAB application will be performed autonomously. Nevertheless the
medical staff proposed to have the possibility to intervene at any time via multiple mechanisms. That includes
grabbing the robot at its structure or the intermediate robotic flange and move the robot manually. For safety
reasons the ongoing application has to be stopped, a safe mode has to be activated and the handguiding application has to be initiated. This sequence can be started with one single safety switch. At least one input device
is needed. Necessity for additional input devices is unknown yet, but might be revealed during development of
the application.
Three safety switches were integrated into the handle of the herein documented version of the MURAB robotic
flange.
Optical Features
Background information: Lot of industrial applications as well as service robotic applications are equipped with
an optical indicator that gives rough information about the application’s status. Well known are amples (redyellow-green) or LED-strips. More sophisticated instruments are LC-Displays. Similar devices could be implemented in the MURAB intermediate robotic flange. An immediate necessity for this requirement was not given
at the date of the first flange realisation, as the medical staff will usually interact just to insert the biopsy needle
and will be focused on medical imaging visualizations. Respectively to the above-named requirement of space,
any additional inside electronics should be avoided. Nevertheless a pre-clinical test phase on ergonomic and
intuitive operating performances might change the necessity again. The needed space was reserved in the herein
documented version of the MURAB robotic flange.
Interface requirements
Background information: The MURAB robotic flange has to provide hardware interfaces at its top level, where
components of the MURAB robotic head (extra motors and drives, vision systems etc.) can source their electrical
power or other signals. If possible these interfaces have to be aligned with the given interfaces of the robotic
head components. If this is not possible, a generic alternative has to be implemented and a detailed documentation (wiring scheme) has to be drawn.
Internal wiring requirements
Background information: The MURAB robotic flange has to provide enough internal space for internal wiring. At
least the internal wiring that comes with a standard KUKA LBR iiwa 7 kg has to be led through the flange to the
components of the MURAB robotic tool / head. For medical and cleaning purposes the intention is to hide as
much of the cabling as possible inside the robot/ MURAB robotic flange. Detailed requirements on component’s
wiring are described in the following chapter 2.2.
2.2
Power supply and signals
A main functionality is providing power supply at the flange top for additional components as well as providing
channels for sensor data of these components back to corresponding components at the foot level of the robot.
Following subchapters describe components of the MURAB demonstrator, that will have influence on the design
of the robotic flange.
2.2.1 KUKA Lightweight Robot
To move the robotic head to and around the patient KUKA’s lightweight robot LBR iiwa will be put into service.
In a standard configuration this robot offers several power and signal cords internally: 3 x twisted-pair wires
(AWG28), 4 x electric (1.0 mm²) and 1 x Ethernet-compliant cabling. A total of 18 wires are available, of which
four are suitable for high power transfer and the others are meant as signal cables.
Figure 3 and 4 show the standard configuration of available interfaces of the KUKA LBR iiwa 7 kg with its media
flange inside electric.
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Figure 3. Scheme with input and output of the robotic flange.
Figure 4. Media flange and control unit
2.2.2 Needle holder
The 2016 version needle holder is driven by three stepper motors. The Arduino-based controller is in the white
box near the base of the KUKA arm on Figure 6. Each motor is connected to the white box by four wires. The
wires need to be rated at 24V, 1.2A. So, three motors times four wires equals twelve wires which are all rated at
24V, 1.2A each. The power for all three stepper motors will be bundled in one pair of high-current electric cables,
and the stepper motor drivers will be built inside the end-effector, controlled over a single communication link
(serial or USB).
2.2.3 Camera
A camera is attached to the end-effector. The camera, Intel® RealSense™ Camera SR300 (see figure 5), consists
of infrared projector, infrared camera, and a conventional camera which will be used for marker detection and
enables depth sensing. Main features are Depth Capture from 0.2 to 1.5m (1) , an Infrared (IR) Laser Projector
System as well as Synchronized Depth, Colour, Infrared Video.
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Figure 5. Front and rear view of the camera (Specifications: Intel® RealSense™ Camera SR300)
The current camera uses the USB 3.0 protocol, which uses 9 wires (4 from USB 2.0 (VCC, GND, D+, D-) + 5 new
for super (2 shielded pair wires for data, and one ground wire: SSTX+/-, SSRX+/-, GND)). The voltage is 5V, the
current 0.6A, and the signal cables require appropriate shielding according to USB 2.0 specifications.
As mentioned above, the signal and power cables will be conducted outside the robot and its flanges. The following illustration shows the cable specification.
2.2.4 Force sensor
A more precise force sensor than KUKA’s internal one will be implemented for accurate force measurements. A
Schunk FTN-Mini40 will be used, and this sensor communicates over a CAN bus or RS485 bus; in the default setup
it is connected to a NetBox which in turn communicates to the computer over an Ethernet connection. The NetBox is too large to install on the end-effector itself; the cable from sensor to NetBox is 3mm thick and 1.8 m long
and has eight wires.
2.2.5 Ultrasound probe
The end-effector contains an Siemens VL12-4 ultrasound probe. The probe is compatible with a high end systems
of Siemens such as Acuson X600 and X700. The cable with a diameter of 8 mm will be attached to the side of
several joints of the KUKA arm.
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Figure 6. The 2016 version of the MURAB end-effector
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Mechanical and Electrical Realisation
3.1
Mechanical Structure of the Robotic Flange
The robotic flange is designed with a robot side (on the left side in figure 8) and a tool side (on the right side in
figure 8) where the robottool is mounted on. The connection of the robot-side to the tool-side allows rotation of
the tool relative to the robot.
The overview of the subparts of the intermedia flange is shown in figure 8 and details in Figure 7. The robot side
is mounted on the robot using screws. A corresponding hole pattern of the tool will be inserted on top of the
flange. The orange electrical connection is mounted in the flange. The hole enables the electrical connection to
the tool. All cables are guided internally and there is the option to put cables externally. There is a manual (un)lock mechanism, when pressing the green lever, you are able to fix or unfix it. There are some safety switches
so that the robot can be hand guided. Data and power supply are guided through the connector of the media
flange inside (orange). The handle of the robotic flange was designed to facilitate movement of the flange while
having the robot in hand mode. In addition, a mechanism was developed to fix and remove the intermedia flange
by hand.
The following functions were realized:
• Ergonomic interface for hand guiding
• Manual tool change mechanism
• Internal guiding of cables
• Safety switches for hand guiding
• Defined direction of tool mount (only in one direction)
The connector, flange and robot are attached to each other. The connector of media flange inside is mounted in
the rotating part by four screws, and cables are guided through the housing. This connector is held in position
(for fixation in robot flange), and is not allowed to rotate. When you rotate the tool the connector has to stay in
one fixed direction. With the mechanism of springs the orange connector is guaranteed to be in one position,
while the rest of the tool is rotating. The safety switch enables demounting of the tool, and assures safety. This
is an extra safety in case a failure will occur for example a rotation by the surgeon. A spring forces the pin to lock
the flange. Data and power supply cables will be guided through the hole in the centre up to the connection to
the tool. Thus, cables will be guided from the bottom, via connector through the inside, and then to the outside.
External connection to the tool is realized via M8 and M12 connection plugs.
Mounting steps:
1. Robot-sided part is mounted to the robot via seven M6 screws, enabling fast change of robotic tool
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2.
3.
4.
5.
6.
7.
Electrical connection plug is inserted and fixed in the flange counterpart by four M2 screws
Rotating part is inserted into the flanges clutch plate. Two springs are inlayed to give the part a defined
position
Security pin with spring is mounted into the clutch plate
Three nuts are inserted into the corresponding cavities
Three M6 screws are used to fix the pre-assembled parts
Three additional M6 screws are used to fix the upper part of the intermedia flange
Figure 7. Featured highlights of the MURAB robotic flange
Figure 8. Parts of the MURAB robotic flange
3.2
Wiring Scheme
The newly designed robotic flange is equipped with a so called tool connector, an electrical inlay which is counterpart to the pins of the standard flange. Through this electrical connection the said interfaces will be conducted
through the robotic flange directly to the components. During mounting and demounting processes this part
stays in place until the complete robotic flange is lifted from the top of the robot (see Figure 9).
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Figure 9. Electrical interfaces of standard flange and MURAB robotic flange
From the tool connector internal wires are leading to three hardware interfaces on the very top side. Two M8
and one M12 sensor connector can be used to plug in components of the robotic head, as shown in Figure 10.
Figure 10. Outer electrical hardware interfaces of MURAB robotic flange
The complete wiring scheme from the robot’s foot to the top level of the robotic flange is documented in an
electric wiring plan. An excerpt shows Figure 11. Herein the available wiring inside the robot and inside the flange
is depicted.
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The internal wires will likely be used for the drives and motors of the biopsy needle holder as well as for the serial
bus of the force torque sensor. A final electronic construction is not part of this deliverable, but it will aim at a
concept which hides as many of the cables inside the system.
The Level of detail of this document might seem too high for a research demonstrator on the first glance, but
production, realization and maintenance purposes demand a gapless manual in which every single pin can be
traced back to its functionality.
Figure 11.Wiring scheme and electrical interfaces of the MURAB robotic flange
Available space inside the robot is very limited and internal running cables have to fulfill certain robustness criteria. Thus not all cables will fit into the robot or meet the criteria and several bypass connections, which lead
outside the robot, have to be installed. Especially sensor cables for key components as the US transducer and
the vision system need to be shielded to hold up signal quality. Figure 12 shows a schematic overview of the
inside and outside conducted cables used in the MURAB demonstrator.
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Figure 12. Schematic overview of cable conducting within the MURAB demonstrator
As the described internal wiring also the bypass wiring will be likewise documented with an electric wiring plan.
Herein after shown in Figure 12 and 13 is an example for external wiring: power and sensor signals of the used
vision system. The complete wiring schemes were attached at the end of this document.
Figure 13.Wiring of vision system
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