Adaptive Servo Controller Design In An Optical Trap

Optical traps are an important tool in biophysics, which are capable of measuring forces on the the order of piconewtons and displacements on the order of nanometers. When being used as a probe, objects confined in optical traps are subjected to a broad-band thermal noise source known as Brownian motion. Closed loop control offers a method for reducing the magnitude of these disturbances, but controller design is a difficult and time consuming process. Even after a controller has been constructed, changes in the trapping power or changes between particles will change the plant dynamics and ultimately affect how well the controller performs For these reasons, presented here is a method of designing an adaptive controller which automatically identifies the plant and actuator dynamics and designs a cor responding controller for disturbance rejection. The controller design is easily implemented on any digital control system.