HAPTIC CONTROL AND
OPERATOR-GUIDED GAIT COORDINATION OF A
PNEUMATIC HEXAPEDAL RESCUE ROBOT
A Master’s Thesis Presentation
By
Brian A. Guerriero
Georgia Institute of Technology
George W. Woodruff School of ME
Intelligent Machine Dynamics Lab
NSF Center for Compact and Efficient Fluid Power
Dr. Wayne Book
CCEFP TB4 Brian Guerriero
Introduction
NSF CCEFP




Paving the way in improving the
compactness, efficiency, and
effectiveness of fluid power
7 member universities
3 thrusts
4 testbeds
CCEFP TB4 Brian Guerriero
Introduction
Testbed 4: Compact Rescue Crawler




Develop testbed for man-machine
multimodal interface research
Research bilateral teleoperation
and coordinated pneumatic control
Research methods of enabling a
single operator to control an 18
DoF mobile robot
Use PHANToM haptic devices to
wield control over two robot legs
CCEFP TB4 Brian Guerriero
Introduction
CCEFP Collaborator Roles

Vanderbilt University

Develop chemofluidic monopropellant
fuel source and components
 Develop high-level automatic gait
coordination

NCAT

Evaluate human factors issues
regarding operator interface
 Evaluate optimum methods for feeding
large amounts of data effectively to
operator
CCEFP TB4 Brian Guerriero
Acknowledgements
Dr. Wayne Book
Dr. Harvey Lipkin
Dr. Chris Paredis
JD Huggins
Others:
Dr. Matt Kontz
IMDL Labmates
Friends & Colleagues
Dr. Haihong Zhu
CCEFP TB4 Brian Guerriero
Acknowledgements
Industry Support and Sponsors
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
Background Research
Pneumatic Servo Control


Wang, Pu, Moore: acceleration
feedback instead of pressure
Chillari, Guccione, Muscato: Survey
of pneumatic control schemes
 Differential pressure gain scheduling
 Fuzzy, Neuro-Fuzzy, Sliding mode


Guvenc: Discrete time model
regulation with model inversion
Korondi and Gyeviki: robust sliding
mode control
CCEFP TB4 Brian Guerriero
Background Research
Chemofluidic Monopropellant
Research


Goldfarb, Barth, Fite, Mitchell,
Shields, Gogola, Wehrmeyer:
Control, characterization and
implementation techniques
Al-Dakkan, Goldfarb, Barth:
Energy saving techniques reusing
high-pressure exhaust gasses
CCEFP TB4 Brian Guerriero
Background Research
High Level Gait Coordination



Cruse: Stick insect cauausius
morosus gait analysis, developed
WALKNET
Wait and Goldfarb: Further WALKNET
development, application to a
legged robot and simulations
Torige, Noguchi, Ishizawa:
Centipede style gaits moving feet
in waves based on previous foot
positions
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
CRC V1.0
Developed from Vanderbilt
design

7/8” Airpel/Sentrinsic Actuators

3 DoF, Good Range of Motion
CCEFP TB4 Brian Guerriero
CRC V1.0
Dec. 06 – Apr. 07


Mounted to table
Simple PID Control
CCEFP TB4 Brian Guerriero
CRC V1.0
Problems and Issues

No-stiction cylinders proved
difficult to control, 100 psi MAX
Weak shoulder joint design

Mechanical interferences

CCEFP TB4 Brian Guerriero
CRC V1.0
V1.0 In Action
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
CRC V2.0
4-07 - Present

Complete and thorough two-legged
redesign
Designed for 300 psi actuation

New prototype Sentrinsic cylinders

CCEFP TB4 Brian Guerriero
CRC V2.0
Design Benefits
Shoulder Joints

Clevis system eliminates slop and
wear
CCEFP TB4 Brian Guerriero
CRC V2.0
Design Benefits
Larger Actuators


1.5” pneumatic cylinders: 530 lbf
at 300psi operating pressure
Valves mounted on or as close as
possible to cylinders
CCEFP TB4 Brian Guerriero
CRC V2.0
Design Challenges
Range of Motion


Decreased due to larger cylinders
Prevent mechanical interferences
Safety

Robots Hurt!
Integration

Sensors, valves and actuators
packaged together
CCEFP TB4 Brian Guerriero
CRC V2.0
Fabrication
Aluminum Leg Profiles

Waterjet cut at GTRI and finished
at ME shop
CCEFP TB4 Brian Guerriero
CRC V2.0
Fabrication
Senrinsic Cylinders


Designed and built by Sentinsic
at GT
Custom rod ends and base clevises

NFPA tie-rod design and fiberwound barrel construction

Months of development, fabrication,
debugging and revisions
CCEFP TB4 Brian Guerriero
CRC V2.0
Fabrication
Senrinsic Cylinders

0-10V position output

Integrated pressure sensors
CCEFP TB4 Brian Guerriero
CRC V2.0
Sensors
Position
CCRS integrated into cylinders
Pressure


Measurement Specialties 250 psi
MEMS sensors
CCEFP TB4 Brian Guerriero
CRC V2.0
Sensors
Pressure

Tested for linearity

Custom housings integrated into
ends of cylinders
CCEFP TB4 Brian Guerriero
CRC V2.0
Sensors
Sensor Integration


Op-amp board developed for 12x
pressure sensors
Custom PCB routes all power,
sensors and valve commands
CCEFP TB4 Brian Guerriero
CRC V2.0
System Integration
Onboard Computing




PC-104+ stack runs real-time
control via xPC Target
802.11n wireless data transfer
32 16-bit Analog inputs
16 12-bit Analog outputs
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
Control
Transformations
 PHANToM/operator Cartesian space

Joint Space (θ1, θ2, θ3)

Cylinder Space
CCEFP TB4 Brian Guerriero
Control
Stroke Control


Cylinder stroke length command
converted into 0-10V command
Festo Proportional Valves control
flow into each cylinder
CCEFP TB4 Brian Guerriero
Control
Goals

Stability
 Pneumatic systems are high-order and
traditionally difficult to control

Tracking performance
 Each cylinder under highly varying
loading conditions
 Target: 10%

Robust to disturbances
 Noise and debris impacts
CCEFP TB4 Brian Guerriero
Control
Original PD Control


Control effort based on position
error only
Stable, worked well in original
configuration
yPD   k p e  kd e 
Vvalve  yPD  5
CCEFP TB4 Brian Guerriero
Control
Two-Legged PD Control (Mounted)
CCEFP TB4 Brian Guerriero
Control
Critical Flaw

When weight applied to legs,
control effort not high enough

Large position errors

Crawler could not actually crawl
CCEFP TB4 Brian Guerriero
Control
Cylinder L1
Tracking
Response
1
0.5
0
90
95
100
105
110
105
110
105
110
Stroke Length (in.)
Cylinder L2
1
0.5
0
90
95
100
Cylinder L3
1
0.5
CCEFP TB4 Brian Guerriero
0
90
95
100
Time (s)
Control
Two-Legged PD Control (Struggling)
CCEFP TB4 Brian Guerriero
Control
Improvements

Addition of velocity feed-forward
command

Velocity damping term

Differential pressure gain
scheduler
 p  kdp1 : p  0, e  0

yPD  k p  xref  xact   kd xact  kvff xref
CCEFP TB4 Brian Guerriero

p  k : p  0, e  0

dp 2
ydp  
 p  kdp 3 : p  0, e  0
 p  kdp 4 : p  0, e  0
Vvalve  yPD  ydp  5
Control
Results

Supplementary force control
improved tracking

Crawler developed a ‘hopping’
syndrome, decreasing stability
Vvalve  yPD  ydp  5
CCEFP TB4 Brian Guerriero
Control
Hopping syndrome
CCEFP TB4 Brian Guerriero
Control
Results

Hopping caused by instantaneous
gain change from position error
sign change
 p  kdp1 : p  0, e  0
p  k : p  0, e  0

dp 2
ydp  
 p  kdp 3 : p  0, e  0
 p  kdp 4 : p  0, e  0
Vvalve  yPD  ydp  5
CCEFP TB4 Brian Guerriero
Control
Cylinder L1
1
0.5
Stroke Length (in.)
0
60
65
70
Cylinder L2
75
80
65
70
Cylinder L3
75
80
75
80
1
0.5
0
60
xref
x actual
1
0.5
0
60
CCEFP TB4 Brian Guerriero
65
70
Time (s)
Control
Solution

Scale force supplement by
position error and differential
force
 p  kdp1 : p  0, e  0
p  k : p  0, e  0

dp 2
ydp  
 p  kdp 3 : p  0, e  0
 p  kdp 4 : p  0, e  0
Vvalve  yPD  ydp  5
CCEFP TB4 Brian Guerriero
 F  kdfe1  e  ke : F  0, e  0
F  k  e  k : F  0, e  0

dfe 2
e
ydfe  
 F  kdfe3  e  ke : F  0, e  0
 F  kdfe 4  e  ke : F  0, e  0
Vvalve  yPD  ydfe  5
Cylinder L1
Control
1
xref
xact
0.5
Stroke Length (in.)
0
45
50
55
60
65
60
65
60
65
Cylinder L2
1
0.5
0
45
50
55
Cylinder L3
1
0.5
0
45
CCEFP TB4 Brian Guerriero
50
55
Time (s)
Control
Improved force-based position control
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
User Interface
Operator Workstation

Reconfigurable task-space

Initial Augmented Reality (AR)
setup
CCEFP TB4 Brian Guerriero
User Interface
Operator Tasks

Feel environment and obstacles
 PHANToM haptic devices

See and hear environment
 Head-mounted display
 PTZ camera onboard robot

Ancillary functions
 Tactile switches on PHANToMs
 Voice recognition
CCEFP TB4 Brian Guerriero
User Interface
Haptic Interface

PHANToM force output
Directional
Proportional to position error
Haptic Force, Y-axis, Full controller
Spring force 4
3
Force (y-axis) (N)
2
1
0
-1
-2
-3
CCEFP TB4 Brian Guerriero
-4
80
85
90
95
Time (s)
100
105
110
User Interface
Immersive Environment

Head-mounted display of feeds
operator robot’s-eye-view

Motion tracker translates head
movements into camera movement
CCEFP TB4 Brian Guerriero
User Interface
Head-Camera Interface
CCEFP TB4 Brian Guerriero
User Interface
Ancillary Functions

Operator communications with
high-level gait controller

Voice and tactile methods

Visual robot status feedback
 Fuel
 Leg positions
 Noise alerts
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
High Level Control

Operator must wield control over
18 degrees of freedom

WALKNET coordination ideal for
smooth flat terrain and simple
commands
WALKNET coordination not
sufficient for maneuvering
through debris

CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
Tiers of CRC Control
1. WALKNET Gait Coordination
Simple operator commands i.e.
‘Forward’ or ‘Left’
2. Guided-Gait Coordination
Operator haptically places front
legs, rear pairs follow
3. Complete Control
Operator haptically controls any leg
(Extreme maneuvering)
CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
Guided-Gait
Outline
L1
R1
L2
R2
R3
L3
CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
Trajectory Recording

Record foot trajectories made
haptically

Smooth trajectory with a spline
PHANToM x
200
300
0
0
2
4
6
8
10
PHANToM y
12
8
10
PHANToM z
12
14
16
18
200
300
y (mm)
PHANToM input (mm)
-200
Raw Trajectory
Splined Trajectory
200
100
0
100
0
2
4
6
14
16
18
50
100
0
0
-150
-50
-100
0
2
4
6
8
10
Time (s)
CCEFP TB4 Brian Guerriero
12
14
16
0
-50
50
18
x (mm)
-100
150
-200
z (mm)
Guided-Gait
Coordination
Stepping Stones

Each trajectory Ti is a map
between two known safe points
Coordinate transforms
relate robot position
to inertial reference
frame
 W pr updated each cycle
(distance from origin)

CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
Successive Leg Pairs

Recorded trajectories played
through rear legs

Master list of
stepping stones and
trajectories
CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
Conditions and Goals

Maintain forward progress
 “Move rear legs to the most anterior
reachable stepping stone”
 “Advance body until one leg reaches
its posterior extreme point”


Operator must tell coordinator
when to move a set of legs
Operator gives cue to the
controller to begin body
advancement
CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
Body Advancement

Body advances by moving all six
feet rearward at the same rates

Advancement stops when one leg is
at its posterior extreme position
CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
CCEFP TB4 Brian Guerriero
Guided-Gait
Coordination
CCEFP TB4 Brian Guerriero
Presentation
Outline
Background Research


Pneumatic Control
High Level Gait Coordination
CRC V1.0
CRC V2.0



Design
Sensors
System Configuration
Control


Classical Methods
Revised Force-based Position Controller
User Interface


Haptic Feedback
Operator Workstation
Guided-Gait Coordination
Conclusions & Next Steps
CCEFP TB4 Brian Guerriero
Conclusions & Next
Steps
Robot Construction

Two legged robot design is
robust, easy to maintain, and
reliable
Future Work



Stiffen spine
Package computers & PSUs
Integrate VU H2O2 technology
CCEFP TB4 Brian Guerriero
Conclusions & Next
Steps
Control

Foot position tracks operator
commands to within 10% under all
normal load conditions
Future Work


Improve tracking to 5%
Improve haptic feedback so that
operator applies no more than 1/6
robot weight to an obstacle
before detection
CCEFP TB4 Brian Guerriero
Conclusions & Next
Steps
User Interface

Operator workstation in place and
operational
Future Work



Improve AR overlays
Integrate work from NCAT
collaborators optimizing data
feed to operator
Implement sensors and tools
necessary for mission success
CCEFP TB4 Brian Guerriero
Conclusions & Next
Steps
Guided-Gait Coordination


Trajectory recording in place
Overall algorithm ready for
implementation
Future Work



Develop software of gait
controller
Develop simulation of rear four
legs
Integrate functions of controller
CCEFP TB4 Brian Guerriero
Thank You
Questions?
CCEFP TB4 Brian Guerriero