Author_Institution :
Dept. of Electr. & Comput. Eng., Michigan State Univ., East Lansing, MI, USA
Abstract :
Atomic force microscopy (AFM) is a powerful measurement instrument, which has been widely implemented in various fields. To enhance the maneuverability, an AFM can be modified and its cantilever can be controlled as a robotic end-effector. To precisely control the nanorobots, their scanners inherent hysteresis, which is the main disadvantage, should be compensated sufficiently. Mostly, hysteresis compensators used in AFM control system only employ the symmetric models, which cannot well represent the asymmetric hysteresis phenomena of piezo-scanners. However, under many cases, the smart material based scanners possess asymmetric hysteresis slightly or seriously, which is far more complex than the regular symmetric case; in addition, for commercial or customized AFMs, the scanners are usually controlled without feedback. These drawbacks tackle further improvement of positioning accuracy of AFM systems. To effectively describe and further reduce the hysteresis of general cases, we propose a new type of generalized Prandtl-Ishlinskii (PI) operator based superposition model, named unparallel PI (UPI) model. The flexible edge of the UPI operator can be tilted freely within a defined range, which enables it to capture asymmetric hysteresis efficiently. To cancel the hysteresis effect in an open-loop system, three inverse compensation approaches are proposed, compared, and the corresponding stability is analyzed. Experiments with AFM based nanorobot verified the proposed approaches with convincing performance.
Keywords :
atomic force microscopy; cantilevers; compensation; end effectors; hysteresis; microrobots; motion control; open loop systems; position control; stability; AFM based nanorobot; AFM control system; UPI model; UPI operator; asymmetric hysteresis; asymmetric hysteresis phenomena; atomic force microscopy; cantilever; customized AFMs; generalized Prandtl-Ishlinskii operator based superposition model; hysteresis compensators; inverse compensation approach; measurement instrument; nanorobot motion control; open-loop system; piezoscanners; robotic end-effector; smart material based scanners; symmetric models; unparallel PI model; Analytical models; Data models; Hysteresis; Inverse problems; Polynomials; Predictive models; Stability analysis;