Control structure for oscillators with nonlinear frequency response

A method for controlling an oscillator structure configured to oscillate about an axis according to a driving signal, wherein an angle amplitude and a frequency of the oscillator structure have a non-linear dependency, the method comprising:

• measuring the angle amplitude of the oscillator structure;
• measuring a phase error of the of the oscillator structure;
• generating a reference oscillator period based on the measured angle amplitude;
• determining an estimated oscillator period of the oscillator structure;
• determining an oscillator period error as a difference between the estimated oscillator period and the reference oscillator period;
• generating at least one control parameter of the driving signal based on the oscillator period error and the measured phase error, including adapting the at least one control parameter of the driving signal to compensate for the measured phase error;
• determining a driving period of the driving signal based on the oscillator period error and the measured phase error, including adapting the driving period to compensate for the measured phase error;
• and
• generating the driving signal based on the at least one control parameter of the driving signal and the driving period.

A Light Detection and Ranging (LIDAR) control system, comprising:

• a microelectromechanical system (MEMS) mirror configured to oscillate about an axis, wherein an angle amplitude and a frequency of the MEMS mirror have a non-linear dependency;
• a driver circuit configured to generate a driving signal to drive an oscillation of the MEMS mirror;
• a detection circuit configured to measure the angle amplitude and a phase error of the MEMS mirror;
• an outer control loop comprising an amplitude controller configured to generate a reference mirror period based on the measured angle amplitude;
• and
• an inner control loop comprising a period and phase controller configured to receive the reference mirror period from the outer control loop and the measured phase error from the detection circuit, generate at least one control parameter of the driving signal based on the reference mirror period and the measured phase error, and determine a driving period of the driving signal based on the reference mirror period and the measured phase error,
• wherein the period and phase controller is configured to:
• determine an estimated oscillator period of the MEMS mirror,
• determine an oscillator period error as a difference between the estimated oscillator period and a reference oscillator period,
• generate the at least one control parameter of the driving signal based on the determined oscillator period error and the measured phase error, and
• determine the driving period of the driving signal based on the determined oscillator period error and the measured phase error, and
• wherein the driver circuit is configured to generate the driving signal based on the at least one control parameter of the driving signal and the driving period.