Control system for high precision positioning applications based on piezo motors

Abstract

In this paper implementation of a control system for high precision applications is presented. The control system is developed for a Piezo LEGS motor, which is a walking piezo motor that can be employed in nanometric precision applications. In the control system structure, two main components are digital signal controller which executes control algorithm and power driver that is generating driving voltages for the motor. The waveforms of the driving voltages are designed using a recently presented coordinate transformation. This transformation enables synthesis of driving waveforms according to design requirements regarding force imposed to the motor's rod and rod's x-direction trajectory profile. In this work, the waveforms are selected to ensure no relative motion between the motor's legs and rod, and constant velocity of the rod within one step. Control algorithm is named as virtual time control. Despite its simplicity, the algorithm allows high precision positioning which is very close to theoretically achievable one.

Force control of piezoelectric walker

“…This motor is capable of very precise positioning and has high force/volume ratio which makes it ideal for precise positioning application where size and weight constraints play dominant role in design [19], [23], [26]. This work additionally demonstrates the force control capabilities of such motor.…”

“…The displacements of the legs from each pair can be described, according to the relations given in our previous publications [22], [23], [26], in the following form…”

“…In this way, the force control can be executed using the position control algorithm, that has been already proposed in previous papers [23], [26]. The mentioned position control algorithm was named virtual time control, since it is changing the argument of the moving vector components.…”

“…A Insect-inspired drive mechanism for the Piezo LEGS motor is introduced in [21], and the authors showed that it truly improves performance of the motor when generating force capabilities and maximal drive velocity are analyzed. Lately, implementation of the FPGA-based and DSC-based control systems for the Piezo LEGS motor were reported in [22] and [23]. The Piezo LEGS motor used in this research was utilized to perform force control in [24] and [25].…”

Commutation-Angle Iterative Learning Control for Intermittent Data: Enhancing Piezo-Stepper Actuator Waveforms

“…Applications, such as nano-motion stages (Merry et al (2011)) and scanning probe microscopy (Den Heijer et al (2014)), require the high resolution, high stiffness, and fast response of the piezoelectric elements as well as a large mover stroke which is provided by a motion that resembles walking. There are various ways to implement this walking motion, for example by walking drives (Shamoto and Moriwaki (1997)) or bi-morph legs (Uzunovic et al (2015)).…”