Force/position control algorithms for industrial manipulators: theory and experiments.
Starting from a simple control scheme, extensively simulated during
the degree thesis work of P.Rocco and experimented on a research
manipulator during his stage at Tecnospazio, the research has
now come to new and interesting results and in particular
to the application of a force/position control scheme to a real
industrial robot. This control scheme closes a force control loop
around the industrial position controllers. A lot of theoretical work
is being done to support the proposal of a control law
particularly suitable for stiff environment: in particular the elasticity
of the transmission systems at the joints of the robot has been found
to play a critical role in the performance of the control systems.
Various methods for the identification of the elastic parameters have
thus been studied. New techniques for the improvement of the performances of
elastic servo drives have been studied as well.
The adoption of linear control laws in the motion control of
industrial robots raises the problem of the stability analysis of the
resulting nonlinear control system. P. Rocco has proposed a
new stability proof for the PID control of robot arms, which leads to
a simple stability condition relating the exponential stability degree
of the nominally linear system to the bounds on the nonlinear
dynamics. A design choice of the control parameters has been
proposed too, which proves to be consistent with the classical design
choices.
Paolo Rocco
rocco@euler.marc.gatech.edu
Last Revised: May 12, 1995