Catalogue of Artificial Intelligence Techniques


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Sensory Feedback and Compliance

Keywords: Control Theory

Categories: Robotics

Author(s): W.F. Clocksin

A common problem in robotics is to bring a tool to a certain spatial relationship to a workpiece, or to bring two or more components together into a certain spatial relationship. However, owing to accumulation of dimensional variation and tolerances that cannot be minimised at their source, errors can occur, making it unexpectedly difficult or impossible to solve this problem by dead reckoning. Thus, in many cases, a robot must be able to detect that components are poorly positioned, and it must have the ability to make small incremental changes in position to minimise the error. `Sensing', or the measurement of physical properties (optical, acoustic, tactile, etc.) can be used actively to detect displacements from the correct position; the resulting error signal is fed back to steer the robot in the direction to minimise the error. This is known as closed-loop control, which is formalised by control theory. Compliance is a passive control technique, where springs and other mechanical devices are used to produce corrective displacements in reaction to forces in the tool.



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