Self sensing: closed-loop estimation for a linear electromagnetic actuator

Self-sensing is a valuable technique that allows information about position and/or force to be obtained directly from the actuator, without separate sensors. This technique has been applied to piezoceramic actuators and electromagnets for vibration control applications. This paper reports on the development of a rheometer to quantify viscoelastic bone cement; this measurement task requires a more powerful, longer stroke actuator. A new type of electromagnetic linear actuator is analytically modelled and configured as a self-sensor. Tests confirm that displacement estimation using the new actuator is accurate to 0.2mm with the actuator oscillating with a magnitude of 32mm (peak-peak). Further testing reveals that the actuator can estimate the size of an added mass to within 0.0025kg, with a load of up to 0.15kg