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The product You were Looking for was moved Click Here for new Address Fundamentals ... (cont.) Methods to Improve Piezo Dynamics The dynamic behavior of a piezo positioning system depends on the system's resonant frequency, any position sensor, and the controller properties. Simple controller designs limit the usable closed-loop tracking bandwidth of a piezoelectric system to 1/10 of the system's resonant frequency. PI has developed controllers featuring a variety of techniques for increased system dynamics (see table). Two of the methods are described below; additional information is available on request. InputShaping™ Stops Structural Ringing Caused by High-Throughput Motions Rapid actuation of nanomechanisms can cause recoil-generated ringing of their loads and any adjacent components. This ringing can take hundreds of milliseconds to damp out. The problem obviously grows more serious as motion throughputs increase and resolution requirements tighten. Conventional wisdom suggests that there is nothing that can be done about these resonant reactions, since they occur outside the servo loop and cannot be observed by the controls. A patented real-time feedforward technology called InputShaping™ nullifies resonances before they start, rather than waiting for them to damp out (turn into heat). The result: the fastest possible motion, with virtually instant settling, as shown in actual vibrometer testing. InputShaping™ was developed based on research at the Massachusetts Institute of Technology and commercialized by Convolve, Inc., (http://www.convolve.com). It is a (built-in) option in several PI digital piezo controllers, is easy to set up for a particular OEM application and robust against dynamic changes in the setup. It requires no change to the system software, application, physical setup or servo parameters. InputShaping™ eliminates unwanted motion-driven resonances and ringing in step-mode and continuous-motion (scanning) applications, and it greatly improves throughput and resolution in high-speed applications. Fig. 33. InputShaping™ eliminates the recoil-driven resonant reaction of loads and neighboring components due to rapid NanoPositioner actuation. Top: Laser Vibrometer reveals the resonant behavior of an undamped fixture when the nanomechanism is stepped. Bottom: Same fixture, same step, with InputShaping ™. The structural ringing is eliminated.

Various Methods to Improve Piezo Dynamics

Method	Goals
Feedforward	Reduce phase difference between output and input (tracking error)
Signal preshaping (software)	Increase operating frequency of the system, correct amplitude and phase response. Two learning phases required; only for periodic signals.
Adaptive preshaping (hardware)	Increase operating frequency of the system, correct amplitude and phase response. No learning phase, but settling phase required; only for periodic signals.
Linearization (analog, in power amplifier)	Compensate for piezo hysteresis
Linearization (digital, in DSP)	Compensate for piezo hysteresis and creep effects
InputShaping™	Cancel recoil-generated ringing of load and any adjacent components. Reduce the settling time. Closed and open-loop.
Learning control	Increase operating frequency of the system, correct amplitude and phase response in scanning processes. Online learning phase and trigger for start of period required. Only periodic signals