HAPTIC CONTROL AND OPERATOR-GUIDED GAIT COORDINATION OF A PNEUMATIC HEXAPEDAL RESCUE ROBOT

CCEFP TB4 Brian Guerriero

HAPTIC CONTROL AND OPERATOR-GUIDED GAIT COORDINATION OF A

PNEUMATIC HEXAPEDAL RESCUE ROBOTA Master’s Thesis Presentation

By

Brian A. GuerrieroGeorgia Institute of TechnologyGeorge W. Woodruff School of MEIntelligent Machine Dynamics Lab

NSF Center for Compact and Efficient Fluid Power

Dr. Wayne Book


Introduction

NSF CCEFP Paving the way in improving

the compactness, efficiency, and effectiveness of fluid power

7 member universities 3 thrusts 4 testbeds


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


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


Acknowledgements

Dr. Wayne Book

Dr. Chris Paredis

Dr. Harvey Lipkin

JD HugginsOthers:

Dr. Matt Kontz

IMDL Labmates

Friends & Colleagues

Dr. Haihong Zhu


Acknowledgements

Industry Support and Sponsors


PresentationOutline

Background Research Pneumatic Control High Level Gait Coordination

CRC V1.0CRC V2.0

Design Sensors System Configuration

Control Classical Methods Revised Force-based Position Controller

User Interface Haptic Feedback Operator Workstation

Guided-Gait CoordinationConclusions & Next Steps


PresentationOutline


CRC V1.0CRC V2.0






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


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


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


PresentationOutline


CRC V1.0CRC V2.0






CRC V1.0

Developed from Vanderbilt design

7/8” Airpel/Sentrinsic Actuators

3 DoF, Good Range of Motion


CRC V1.0

Dec. 06 – Apr. 07 Mounted to table Simple PID Control


CRC V1.0

Problems and Issues No-stiction cylinders proved difficult to control, 100 psi MAX

Weak shoulder joint design Mechanical interferences


CRC V1.0

V1.0 In Action


PresentationOutline


CRC V1.0CRC V2.0






CRC V2.0

4-07 - Present Complete and thorough two-legged redesign

Designed for 300 psi actuation

New prototype Sentrinsic cylinders


CRC V2.0Design Benefits

Shoulder Joints Clevis system eliminates slop and wear


CRC V2.0Design Benefits

Larger Actuators 1.5” pneumatic cylinders: 530 lbf at 300psi operating pressure

Valves mounted on or as close as possible to cylinders


CRC V2.0Design Challenges

Range of Motion Decreased due to larger cylinders Prevent mechanical interferences

Safety Robots Hurt!

Integration Sensors, valves and actuators packaged together


CRC V2.0Fabrication

Aluminum Leg Profiles Waterjet cut at GTRI and finished at ME shop


CRC V2.0Fabrication

Senrinsic Cylinders Designed and built by Sentinsic at GT

Custom rod ends and base clevises NFPA tie-rod design and fiber-wound barrel construction

Months of development, fabrication, debugging and revisions


CRC V2.0Fabrication

Senrinsic Cylinders 0-10V position output Integrated pressure sensors


CRC V2.0Sensors

Position CCRS integrated into cylinders

Pressure Measurement Specialties 250 psi MEMS sensors


CRC V2.0Sensors

Pressure Tested for linearity

Custom housings integrated into ends of cylinders


CRC V2.0Sensors

Sensor Integration Op-amp board developed for 12x pressure sensors

Custom PCB routes all power, sensors and valve commands


CRC V2.0System 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


PresentationOutline


CRC V1.0CRC V2.0






Control

Transformations

Joint Space (θ1, θ2, θ3)

PHANToM/operator Cartesian space

Cylinder Space


Control

Stroke Control Cylinder stroke length command converted into 0-10V command

Festo Proportional Valves control flow into each cylinder


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 disturbancesNoise and debris impacts


Control

Original PD Control Control effort based on position error only

Stable, worked well in original configuration

5

PD p d

valve PD

y k e k e

V y


Control

Two-Legged PD Control (Mounted)


Control

Critical Flaw When weight applied to legs, control effort not high enough

Large position errors

Crawler could not actually crawl


Control

Tracking

Response

90 95 100 105 1100

0.5

1

Cylinder L1

90 95 100 105 1100

0.5

1

Str

oke

Leng

th (

in.)

Cylinder L2

90 95 100 105 1100

0.5

1

Time (s)

Cylinder L3


Control

Two-Legged PD Control (Struggling)


Control

Improvements

Velocity damping term

Differential pressure gain scheduler

1

2

3

4

: 0, 0

: 0, 0

: 0, 0

: 0, 0

5

dp

dp

dpdp

dp

valve PD dp

p k p e

p k p ey

p k p e

p k p e

V y y

Addition of velocity feed-forward command

PD p ref act d act vff refy k x x k x k x


Control

Results Supplementary force control improved tracking

Crawler developed a ‘hopping’ syndrome, decreasing stability

5valve PD dpV y y


Control

Hopping syndrome


Control

Results Hopping caused by instantaneous gain change from position error sign change

1

2

3

4

: 0, 0

: 0, 0

: 0, 0

: 0, 0

5

dp

dp

dpdp

dp

valve PD dp

p k p e

p k p ey

p k p e

p k p e

V y y


Control

60 65 70 75 800

0.5

1

Cylinder L1

60 65 70 75 800

0.5

1

Str

oke

Leng

th (

in.) Cylinder L2

60 65 70 75 800

0.5

1

Time (s)

Cylinder L3

xref

x actual


Control

Solution Scale force supplement by position error and differential force

1

2

3

4

: 0, 0

: 0, 0

: 0, 0

: 0, 0

5

dp

dp

dpdp

dp

valve PD dp

p k p e

p k p ey

p k p e

p k p e

V y y

1

2

3

4

: 0, 0

: 0, 0

: 0, 0

: 0, 0

5

dfe e

dfe e

dfedfe e

dfe e

valve PD dfe

F k e k F e

F k e k F ey

F k e k F e

F k e k F e

V y y


Control

45 50 55 60 650

0.5

1

Cylinder L1

45 50 55 60 650

0.5

1

Str

oke

Leng

th (

in.)

Cylinder L2

45 50 55 60 650

0.5

1

Time (s)

Cylinder L3

xref

xact


Control

Improved force-based position control


PresentationOutline


CRC V1.0CRC V2.0






User Interface

Operator Workstation Reconfigurable task-space

Initial Augmented Reality (AR) setup


User Interface

Operator Tasks Feel environment and obstacles

PHANToM haptic devices

See and hear environmentHead-mounted displayPTZ camera onboard robot

Ancillary functions Tactile switches on PHANToMsVoice recognition


User Interface

Haptic Interface PHANToM force output

Directional

Proportional to position error

Spring force

80 85 90 95 100 105 110-4

-3

-2

-1

0

1

2

3

4

Time (s)

For

ce (

y-ax

is)

(N)

Haptic Force, Y-axis, Full controller


User Interface

Immersive Environment Head-mounted display of feeds operator robot’s-eye-view

Motion tracker translates head movements into camera movement


User Interface

Head-Camera Interface


User Interface

Ancillary Functions Operator communications with high-level gait controller

Voice and tactile methods Visual robot status feedback

FuelLeg positionsNoise alerts


PresentationOutline


CRC V1.0CRC V2.0






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



Tiers of CRC Control1.WALKNET Gait Coordination

Simple operator commands i.e. ‘Forward’ or ‘Left’

2.Guided-Gait CoordinationOperator haptically places front legs, rear pairs follow

3.Complete ControlOperator haptically controls any leg (Extreme maneuvering)



Guided-Gait

Outline

L1 R1

R2

R3

L3

L2



Trajectory Recording Record foot trajectories made haptically

Smooth trajectory with a spline

0 2 4 6 8 10 12 14 16 18-200

0

200PHANToM x

0 2 4 6 8 10 12 14 16 180

100

200

300

PH

AN

ToM

inpu

t (m

m) PHANToM y

0 2 4 6 8 10 12 14 16 18-100

-50

0

50

Time (s)

PHANToM z

Raw Trajectory

Splined Trajectory

-150-50

50150 -200

-100

0

1000

100

200

300

z (mm)x (mm)

y (m

m)



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)



Successive Leg Pairs Recorded trajectories played through rear legs

Master list of stepping stones and trajectories



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



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






PresentationOutline


CRC V1.0CRC V2.0






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



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



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



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


Thank YouQuestions?

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HAPTIC CONTROL AND OPERATOR-GUIDED GAIT COORDINATION OF A PNEUMATIC HEXAPEDAL RESCUE ROBOT