Digital control loop to solve instability of electrostatic drives beyond 1/3 gap limit

A circuit to create a drive voltage that is linearly proportional to a position of a movable member of an electrostatic actuator device that is positioned by a voltage applied thereto, comprising:

• a sensor to sense a position of said movable member from a reference position to provide an analog position indicating signal;
• an analog-to-digital converter (ADC) for receiving the analog position indicating signal to convert said analog position indicating signal to a digital position indicating signal;
• a digital signal processor (DSP) for receiving said digital position indicating signal, said DSP being programmed to convert the digital position indicating signal into a digital signal that is linearly proportional to the position of said movable member;
• a digital-to-analog converter (DAC) for receiving said digital signal that is linearly proportional to the position of said movable member for producing a linear analog positioning command;
• and
• a voltage amplifier for receiving said linear analog positioning command to produce a position voltage and for application to said movable member.

A method for operating an electrostatic actuator of the type having a first member that is positionable with respect to a reference position in response to a drive voltage applied therebetween, comprising:

• sensing a position of said first element with respect to said reference location;
• generating an analog position indicating signal in response to said sensing a position;
• linearizing said analog position indicating signal to generate a position drive signal in response thereto;
• generating said drive voltage in response to said position drive signal;
• and
• applying said drive voltage to said first member to modify a position of said member.

An electrostatic actuator having a first member that is positionable with respect to a reference location in response to a drive voltage applied between said first member and a second member, comprising:

• means for sensing a position of said first element with respect to said reference location;
• means for generating an analog position indicating signal in response to an output of said means for sensing a position;
• means for linearizing said analog position indicating signal and for generating a position drive signal in response thereto;
• means for generating said drive voltage in response to said position drive signal;
• and
• means for applying said drive voltage to said first member to modify a position of said first member.