Apple Inc.

Denis M Chen

Darya Amin-Shahidi

Hari Vasudevan

Juil Lee

Disclosed herein are reluctance actuators and methods for feedback control of their applied force. Embodiments of the reluctance actuators include an electromagnet positioned to deflect a metallic plate to provide a haptic output. The control of the force is provided without force sensors (sensorless control) by monitoring voltage and/or current (V/I) applied during an actuation. For a given intended force output, an electrical parameter value (flux, current, or other parameter) is read from a look up table (LUT). The LUT may store a present value of the inductance of the reluctance actuator. The feedback control may be a quasi-static control in which the LUT is updated after actuation based on the monitored V/I. The feedback control may be real-time, with a controller comparing an estimated electrical parameter value based on the measured V/I with the value from the LUT.

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San Jose, CA, United States of America

Denis M Chen