Most available actuators and transmissions exhibit nonlinear characteristics which impair precision and speed of response. This research addresses the problem of reducing the hysteresis found in the actuation of most smart materials. The concept of phaser is introduced, an operator which shifts the phase of a periodic signal but keeps its magnitude unchanged. Since it is possible to approximate phasers with linear filters, it is possible to design practical compensators. The design requires the knowledge of one parameter, easily identified from experimental transfer function estimates. For the system with saturating hysteresis, two phasers are used in a tandem connection. This compensation reduces the hysteresis to a memoryless single saturation. The method is applied to an SMA and piezo actuators.
Piezo actuation test bed with optical microdisplacement measurements