1 glauco garcia scandaroli, geovany araújo borges, adson ferreira da rocha, and francisco assis de...

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Glauco Garcia Scandaroli, Geovany Araújo Borges, Adson Ferreira da Rocha, and

Francisco Assis de Oliveira Nascimentoe-mails: glaucoscn@gmail.com, gaborges@ene.unb.br,

adson@ene.unb.br, assis@ene.unb.br.

Adaptive Knee Joint Control for anActive Amputee Prosthesis

5th Latin American Robotics Symposium – LARS 2008Salvador, October 29 – 30, 2008

Laboratório de Robótica e Automação (LARA)Grupo de Robótica, Automação e Visão Computacional (GRAV)Departamento de Eng. Elétrica - Universidade de Brasília (UnB)

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Outline of the presentation Introduction;

Prosthesis Description;

System Modeling;

Control Strategies;

Conclusions & Ongoing Work.

Introduction Rehabilitation robotics:

Restoring lost motor functions; Supporting treatment.

Importance of knee in locomotion. Active or Passive knee?

Three DOF Prosthesis: More similar to human leg.

Prosthesis Description Thee DOF:

Knee (3R15 Otto Bock): Sagittal Plane.

Foot: Sagittal Plane; Frontal Plane.

Actuators: Servo-Amplifiers +

DC Motors. Movements:

EMG Signals – Knee; Predictive Model – Foot:

Gyrometers + IR.

System Modeling Simplified Model based on Free Body Diagram.

Discrete non-linear model:

Variable change:

Finally:

System Modeling Parameter Identification:

Batch Least Squares. Second order approach:

First order approach:

System Modeling Parameter Identification:

Batch Least Squares. Second order approach:

First order approach:

Control Strategies

ia,kcontroller ν (φk)

ADC potentiometer

φref

PID Control: Root-Locus Tuned; Experimentally Tuned.

Model Reference Adaptive Control (MRAC).

DAC .ia plantφ

Control Strategies PID – Root Locus Tuned:

Kp = 0.0624, Ki = 0.06, Kd = 0.0024, CL Poles:

s1 = -4.89, s2 = -0.9917. Rise time: 650 ms.

Control Strategies PID – Root Locus Tuned:

Kp = 0.0624, Ki = 0.06, Kd = 0.0024, CL Poles:

s1 = -4.89, s2 = -0.9917.

Control Strategies PID – Experimentally Tuned:

Kp = 0.1, Ki = 0.111, Kd = 0.0011,

Control Strategies PID – Experimentally Tuned:

Kp = 0.1, Ki = 0.111, Kd = 0.0011,

Control Strategies MRAC:

Characteristics of reference model: First order; Rise time: 300 ms, Null steady-state error.

Parameters: θ1 = 0.099481; θ2 = 0.089133; γ = 1/3.

Control Strategies MRAC:

Characteristics of reference model: First order; Rise time: 300 ms, Null steady-state error.

Parameters: θ1 = 0.099481; θ2 = 0.089133; γ = 1/3.

Control Strategies MRAC:

Characteristics of reference model: First order; Rise time: 300 ms, Null steady-state error.

Parameters: θ1 = 0.099481; θ2 = 0.089133; γ = 1/3.

Conclusions & ongoing work System Modeling:

First order approximation → No transitory losses.

Control Strategies: PID Root-Locus → Steady-state error; PID Experimental → Oscillation, MRAC → Small oscillation.

Ongoing work: Control of foot joints; EMG Integration.

Questions?

Thank you for your attention!