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

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

PD p d

valve PD

y k e k e

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

Cylinder L1

90 95 100 105 1100

Cylinder L2

90 95 100 105 1100

Time (s)

Cylinder L3

Control

Two-Legged PD Control (Struggling)

Control

Improvements

Velocity damping term

Differential pressure gain scheduler

: 0, 0

valve PD dp

p k p e

p k p ey

p k p e

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

: 0, 0

valve PD dp

p k p e

p k p ey

p k p e

Control

60 65 70 75 800

Cylinder L1

60 65 70 75 800

in.) Cylinder L2

60 65 70 75 800

Time (s)

Cylinder L3

x actual

Control

Solution Scale force supplement by position error and differential force

: 0, 0

valve PD dp

p k p e

p k p ey

p k p e

: 0, 0

dfedfe e

valve PD dfe

F k e k F e

F k e k F ey

F k e k F e

Control

45 50 55 60 650

Cylinder L1

45 50 55 60 650

Cylinder L2

45 50 55 60 650

Time (s)

Cylinder L3

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

Time (s)

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

Trajectory Recording Record foot trajectories made haptically

Smooth trajectory with a spline

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

200PHANToM x

0 2 4 6 8 10 12 14 16 180

m) PHANToM y

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

Time (s)

PHANToM z

Raw Trajectory

Splined Trajectory

-150-50

50150 -200

z (mm)x (mm)

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?

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

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