Integrated strain and force feedback for high-performance control of piezoelectric actuators

This paper presents a new sensor arrangement and feedback controller for hysteresis, creep and vibration in piezoelectric actuators. A piezoelectric force sensor is combined with a resistive strain gage to provide both extremely low noise and high stability. The use of a force sensor also results in a system transfer function that exhibits zero-pole ordering. Such systems allow a simple integral controller to provide excellent tracking and damping performance with guaranteed stability.The proposed technique is demonstrated on a nanopositioning platform with a range of 10 μm and a resonance frequency of 2.4 kHz. In closed-loop, the controller damps the resonance by 33 dB and provides a tracking bandwidth of 1.8 kHz. Excellent tracking of a 130 Hz triangular reference and reduction of hysteresis to 0.46% at 10 Hz is also demonstrated. The closed-loop positioning noise, predicted from the sensor noise density, was approximately 0.67 nm peak-to-peak, or 0.0067% of the 10 μm range.