Patent ID: 11934595
Assignee: LOGITECH EUROPE S.A.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 0:
1. A user input device, comprising:
a rotary input control, comprising:
a wheel; and
an electropermanent magnet assembly, comprising:
a magnetizing coil, and
a permanent magnet coupled to the magnetizing coil and emitting a magnetic field; and

a control system configured to modulate an amount of electrical current supplied to the magnetizing coil to change a resistance profile within a linear torque region of the electropermanent magnet assembly for the rotary input control, the modulation switching the permanent magnet from a first state with a first resistance profile for freewheeling in which the magnetic field has a first magnetic flux and operates within the linear torque region to a second state with a second resistance profile in which the magnetic field has a second magnetic flux greater than the first magnetic flux and operates within the linear torque region, the magnetic field having a same polarity in both the first and second states,
wherein the control system modulates the amount of current supplied to the magnetizing coil based on a generated error signal corresponding to a difference measurement between a current supplied to the magnetizing coil and a new current setting corresponding to the second state; and
wherein the control system recalibrates an amount of current supplied to the magnetizing coil in the first state by measuring a rate of decay of an RPM of the wheel and using the rate of decay to establish a new baseline resistance.