Linear resonant actuators (LRAs) create tactile feedback in consumer devices by generating vibrations. LRA characteristics can change with time due to environmental conditions, thereby degrading the performance of the LRA. Variations in LRA performance can be compensated during operation by using techniques of parameter detection, measurement, and correction, which themselves rely on accurate back EMF measurement. A back EMF test is accurate so long as the LRA is stationary, the device is lying on a flat, vibration-free surface, and is free of external movement. This disclosure describes techniques that ensure accurate measurement of LRA parameters by performing back EMF measurements when onboard motion sensors indicate zero or low device motion.
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Anac, Ozan; Mukherjee, Debanjan; and Wang, Jianxun, "Field Tuning of Linear Resonant Actuators Using Motion Sensor Feedback", Technical Disclosure Commons, (March 10, 2020)