Closed-loop control of linear resonant actuator using back emf and inertial compensation
AssigneeApple Inc.
InventorsHari Vasudevan, Eileen A. Mazzochette, Arman Hajati, Shingo Yoneoka
Life of this patent
Estimating the term…
Abstract
A system for providing closed-loop control of a linear resonant actuator using Back Electromotive Force (EMF) and inertial compensation is disclosed. In an embodiment, one or more inertial sensors are used to estimate low frequency motion of a haptic engine moving mass and compensate for the motion using a feedforward model, thus providing a more robust closed-loop control system for controlling the moving mass when subjected to low frequency disturbances by a user, for example, shaking or swinging the device.
Claims20
A system for providing closed-loop control of a linear resonant actuator, the system comprising:
- a linear resonant actuator (LRA) including a frame, one or more coils mounted to the frame and operable to generate a magnetic field, and a mass including magnetic portions positioned within the frame and configured to move within the frame along a movement axis;
- drive electronics coupled to the linear resonant actuator (LRA) and to the one or more coils;
- one or more inertial sensors;
- a closed-loop controller coupled to the one or more inertial sensors and the drive electronics, the controller configured to:
- estimate a coil resistance of the one or more coils;
- compute an estimated linear acceleration of the moving mass based on signals from the one or more inertial sensors;
- compute a disturbance rejection feedforward compensation signal based on the estimated linear acceleration, the estimated coil resistance and a motor constant;
- compute a position feedforward compensation signal based on a reference position of the mass;
- compute an estimated velocity of the moving mass based on output signals of the drive electronics and the estimated coil resistance;
- compute an actuator control signal based on a difference between the estimated mass velocity and a reference mass velocity;
- compute a compensated actuator control signal by compensating the actuator control signal with the disturbance rejection feedforward compensation signal and the position feedforward compensation signal;
- and
- provide the compensated actuator control signal to the drive electronics, the compensated actuator signal causing the drive electronics to adjust coil current in the one or more coils.
A method of providing closed-loop control of a linear resonant actuator, the method comprising:
- estimating, by a closed-loop controller, a coil resistance for one or more coils of a linear resonant actuator (LRA);
- computing, by the closed-loop controller, an estimated linear acceleration of a moving mass in the LRA based on signals from the one or more inertial sensors;
- computing, by the closed-loop controller, a disturbance rejection feedforward compensation signal based on the estimated linear acceleration, the estimated coil resistance and a motor constant;
- computing, by the closed-loop controller, a position feedforward compensation signal based on a reference position of the mass;
- computing, by the closed-loop controller, an estimated velocity of the moving mass based on output signals of drive electronics coupled to the one or more coils, and the estimated coil resistance;
- computing, by the closed-loop controller, an actuator control signal based on a difference between the estimated mass velocity and a reference mass velocity;
- computing, by the closed-loop controller, a compensated actuator control signal by compensating the actuator control signal with the disturbance rejection feedforward compensation signal and the position feedforward compensation signal;
- and
- providing, by the closed-loop controller, the compensated actuator control signal to the drive electronics, the compensated actuator signal causing the drive electronics to adjust coil current in the one or more coils.
Dependencies are inferred from the claim text.