Article Summary

Motion control requires feedback. Without feedback, there is no controlled motion. Position sensors are a key element of a motion control system, regardless of whether the primary power is hydraulic, pneumatic or electrical. There are a multitude of position feedback sensor options that reflect a very broad range of technologies—from electromechanical to electronic to optoelectronic to state-of-the-art fiber optics. Design decisions are usually based on a multitude of factors—including environmental, reliability, redundancy, safety and reliability. These applications can also reflect a preponderance of conservatism versus state-of-the-art in a spirited clash of the old school versus new school of engineering.

This paper provides an overview of the more common position sensor options and references actual case studies to illustrate the diverse solutions available and the reasons behind some of the decisions. Three cases are used to illustrate the needs of different applications leading to the choice of a particular type of position sensor. The cases reviewed include a gantry crane, wind turbine and aerial cable car.