In this paper, we study an image-based PID control of a redundant planar parallel robot using a fixed camera
configuration. The control objective is to move the robot end effector to the desired image reference position. The
control law has a PD term plus an integral term with a nonlinear function of the position error. The proportional and
integral actions use image loop information whereas the derivative action adds task space damping using joint level
measurements. The Lyapunov method and the LaSalle invariance principle allow assessing asymptotic closed loop
stability. Experiments show the feasibility of the proposed approach.
This paper presents a comparative study of two
task space control approaches. The first approach, similar
to most of task space controllers, makes use of an inner
velocity loop. The second proposed approach employs an inner
proportional derivative (PD) joint position-velocity loop. A
stability proof for the second apprach is provided together
with experiments using a visual servoed robot. It is shown
that the proposed control law needs less gain at the task
space level then precluding amplification of the measurement
noise; moreover, it is shown that the first approach produces
uncontrolled movements when the task space sensor fails
whereas the proposed controller avoids uncontrolled behavior
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