Real-Time Disturbance Compensation with Accelerometers & Piezoelectric-Driven Mechanism

Disturbance / vibration reduction is critical in many applications. One example is disk drive industry. With the advance in optical disk drive technology, the off-track or off-focusing error caused by disturbance is limiting the performance. Instead of going with the more familiar approach like vibration absorber, a real-time disturbance compensation without much phase lag is proposed. In this paper, to illustrate the idea of real-time compensation, a one dof cancellation of tremor is performed. Instantaneous motion due to the disturbance is sensed by an accelerometer inertial measurement unit (IMU). Modeling of the accelerometer is done to provide better readings. The compensation motion is provided by manipulating a piezoelectric-driven flexure-based mechanism. Due to the existence of backslash in revolute joints, flexure-based mechanism is proposed to achieve better result. Piezoelectric actuator is proposed because of its high frequency and precision. The hysteretic non-linearity of the piezoelectric actuator is modeled using Prandtl-Ishlinskii operator. Based on this model, an open-loop inverse feed-forward controller is implemented to accurately provide the required motion.