Contactless position sensing and control of pneumatic cylinders using a hall effect sensor array

This paper proposes an accurate position sensing method and subsequent positional control for pneumatic actuators. An array of hall effect sensors is used to allow contactless sensing of the flux field produced by a magnet located inside most pneumatic cylinders. The hard-ware functions conjointly with the proposed algorithm that fuses the sensor data and deter- mines the piston position through predefined mathematical functions produced by data analyses and careful sensor calibration. The hall effect sensors used have a high sensitive dependence on initial conditions, due to the fundamental non-linearity of the equations describing their response, therefore careful system identification and numerical model validation was per- formed. Preliminary solenoid valve controllers are proposed, allowing for full positional control of pneumatic pistons and location stabilization. This extends the uses of such actuators further than currently accustomed, and allows a cylinder to act as a linear actuator that exhibits compliant behaviour due to the underlying compressibility of air