Position Controller for Voice Coil Motors Using Nonlinear Friction Compensation

Voice Coil Motor(VCM) has many advantages such as no mechanical backlash, fast response, low power driving and small size, etc. This motor is widely used in fields that require high precision position control, so high performance position control is essentially required. This paper suggested a new method of designing PID feedback position controller gains. But, there is a limit to improving the position control precision with only feedback controller, so feedforward control is essential. Feedforward terms required in a VCM include inertial force, frictional force and spring force. Among the three terms, frictional force in particular is a nonlinear element that hinders the precise position control of a VCM. Therefore, this paper proposed a new friction model that considers nonlinear characteristics based on friction data obtained through experiments. By applying the designed PID position controller gains and a proposed model, in experiments, position precision improvement will be demonstrated through position error.