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160 Robot Dynamics

Figure 3.6.3: Step response of motor with very flexible shaft.

of approximately 0.1 s due to the flexibility in the shaft.
It is extremely interesting to note that the shaft flexibility has the effect of
speeding up the slowest motor real pole [compare (8) and (9)], so that w L
approaches its steady-state value more quickly than in the rigid-shaft case.
This is due to the “whipping” action of the flexible shaft.
The shaft dynamics make the control of θ L, which corresponds in a robot
arm to the joint angle q i, very difficult without some sort of specially designed
controller.

Copyright © 2004 by Marcel Dekker, Inc.