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Research Papers

Robust Impedance Control of Manipulators Carrying a Heavy Payload

[+] Author and Article Information
Farhad Aghili

Space Technologies, Canadian Space Agency, Saint-Hubert, QC, J3Y 8Y9, Canadafarhad.aghili@asc-csa.gc.ca

Also known as the spacial purpose dexterous manipulator (SPDM)

If the z-axis of the coordinate frame {W} is perfectly parallel to the earth’s gravity vector, then k=col(0,0,1).

J. Dyn. Sys., Meas., Control 132(5), 051011 (Aug 24, 2010) (8 pages) doi:10.1115/1.4001898 History: Received June 11, 2009; Revised April 26, 2010; Published August 24, 2010; Online August 24, 2010

A heavy payload attached to the wrist force/moment (F/M) sensor of a manipulator can cause the conventional impedance controller to fail in establishing the desired impedance due to the noncontact components of the force measurement, i.e., the inertial and gravitational forces of the payload. This paper proposes an impedance control scheme for such a manipulator to accurately shape its force-response without needing any acceleration measurement. Therefore, no wrist accelerometer or a dynamic estimator for compensating the inertial load forces is required. The impedance controller is further developed using an inner/outer loop feedback approach that not only overcomes the robot dynamics uncertainty, but also allows the specification of the target impedance model in a general form, e.g., a nonlinear model. The stability and convergence of the impedance controller are analytically investigated, and the results show that the control input remains bounded provided that the desired inertia is selected to be different from the payload inertia. Experimental results demonstrate that the proposed impedance controller is able to accurately shape the impedance of a manipulator carrying a relatively heavy load according to the desired impedance model.

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Copyright © 2010 by Canadian Government
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References

Figures

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Figure 1

A manipulator carrying a heavy payload

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Figure 2

The manipulator carrying a payload

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Figure 3

Dynamics force and moment

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Figure 4

Trajectories of the linear and angular velocities

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Figure 5

The z-axis position of the payload

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Figure 6

Contact force and moment

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Figure 7

Trajectories of the linear and angular velocities

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