| Volume 26 Issue 3 - Publication Date: 1 March 2007 |
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| The Low-Stiffness Teleoperator
Slave – a Trade-off between Stability and Performance |
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| G. A. V. Christiansson
and F. C. T. van der Helm Delft Haptics Laboratory, Delft University
of Technology, The Netherlands |
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| Stability is essential for
teleoperation and a prerequisite for performance. This paper analyzes the
the stability/performance trade-off of a teleoperator where the slave device
has a built-in passive intrinsic stiffness. Stability is quantified as time
delay robustness and performance is expressed using teleoperator damping
and teleoperator stiffness, the boundaries of the Colgate Z-width. |
| Two classic control schemes,
position error and Lawrence 4-channel, are used along with a novel 5-channel
scheme where the slave stiffness deflection is measured, and compensated
for, to improve the performance. |
| The teleoperator system was
analyzed theoretically using a linear model and the findings were experimentally
validated on a one degree of freedom teleoperation setup. |
| It was found that: |
- A lower slave stiffness improves stability for all three teleoperator architectures.
- The stability boundary of the three controllers is similar.
- The performance of the controllers increases from: (poor) position error, 4-Channel to (excellent) 5-channel.
- A classical linear analysis method can accurately predict the stability characteristics of the teleoperator system.
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| Therefore it can be concluded
that a compliant slave device offers a stability advantage for a range of
teleoperation situations and that the loss of performance can be partly
compensated. |
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