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Research Papers

Robust Tracking Control of a Prosthesis Test Robot

[+] Author and Article Information
Hanz Richter

Associate Professor
Mechanical Engineering Department,
Cleveland State University,
Cleveland, OH 44115
e-mail: h.richter@csuohio.edu

Dan Simon

Professor
Electrical and Computer Engineering Department,
Cleveland State University,
Cleveland, OH 44115
e-mail: d.j.simon@csuohio.edu

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received February 1, 2013; final manuscript received December 1, 2013; published online February 19, 2014. Assoc. Editor: Won-jong Kim.

J. Dyn. Sys., Meas., Control 136(3), 031011 (Feb 19, 2014) (12 pages) Paper No: DS-13-1052; doi: 10.1115/1.4026342 History: Received February 01, 2013; Revised December 01, 2013

This paper develops a passivity-based robust motion controller for a robot used in prosthetic leg performance studies. The mathematical model of the robot and passive prosthesis corresponds to a three degree-of-freedom, underactuated rigid manipulator. A form of robotic testing of prostheses involves tracking reference trajectories obtained from human gait studies. The robot presented in this paper emulates hip vertical displacement and thigh swing, and we consider a prosthesis with a passive knee for control development. The control objectives are to track commanded hip displacements and thigh angles accurately, even in the presence of parametric uncertainties and large disturbance forces arising from ground contact during the stance phase. We develop a passivity-based controller suitable for an underactuated system and compare it with a simple independent-joint sliding mode controller (IJ-SMC). This paper describes the mathematical model and nominal parameters, derives the passivity-based controller using Lyapunov techniques and reports success in real-time implementation of both controllers, whose advantages and drawbacks are compared.

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References

Figures

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Fig. 1

Machine schematic and overall robot installation

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Fig. 2

Denavit–Hartenberg coordinate frame assignments

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Fig. 3

Damping cylinder and knee geometry. The indicated direction for q3 is positive (flexion), the opposite is extension. The cylinder has separate adjustment rings for the damping coefficient during flexion and extension.

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Fig. 4

Simulation of the RPBC in motion reference tracking with 50% parameter perturbation

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Fig. 5

Simulation of IJ-SMC

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Fig. 6

RPBC: hip displacement and thigh angle tracking performance and control voltages (nominal)

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Fig. 11

IJ-SMC hip displacement and thigh angle tracking performance and control voltages (off-nominal)

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Fig. 10

IJ-SMC: knee angle and vertical ground reaction force (nominal)

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Fig. 8

RPBC: hip displacement and thigh angle tracking performance and control voltages (off-nominal)

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Fig. 7

RPBC: knee angle and vertical ground reaction force (nominal)

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Fig. 12

Simulation of backlash effects: RPBC versus IJ-SMC

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Fig. 9

IJ-SMC: hip displacement and thigh angle tracking performance and control voltages (nominal)

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