Browsing by Author "Tzen, JJ"

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Analysis of two-dimensional fixture clamping with friction
(1999-06-01)
Tzen, JJ
;
Jeng, SL
;
Cheing, WH
;
機械工程學系
;
Department of Mechanical Engineering
Fixtures that constrain the unwanted motion of a workpiece are important tools in automated manufacturing today. In this paper, we analyze the stability of clamping with passive friction force. The concept of the instant center of rotation is applied to transform the stability analysis into a search for a static equilibrium state. Many properties related to the stability analysis are studied. According to these properties, we design an efficient algorithm for searching the static equilibrium state. The maximum allowable cutting force or the minimum normal stress, which are key concerns in automated design of fixtures, can be calculated precisely by using the search operation. The algorithm can also be extended to the case of multiply distributed friction forces with differently configured clamping areas. Several examples are provided to illustrate cutting force design for different fixture conditions.
Modeling of piezoelectric actuator for compensation and controller design
(2003-01-01)
Tzen, JJ
;
Jeng, SL
;
Chieng, WH
;
機械工程學系
;
Department of Mechanical Engineering
This work proposes a novel method for describing the hysteretic non-linearity of a piezoelectric actuator. The hysteresis behavior of piezoelectric actuators, including the minor loop trajectory and the residual displacement near zero input, are modeled by a set of hysteresis operators, including a gain and an input-dependent lag, as well as the parameter scheduling method. A hysteresis model, using the identified parameters, and containing only the dominant hysteresis operator, is presented herein. Based upon a simplified hysteresis model, tracking is-controlled to reduce the non-linear effects in the characteristics of the piezoelectric actuator. A proportional-integral (PI) controller, with inverse model feed-forward, suppresses the tracking error to within +/-1% full span range (FSR) of the actuator, noticeably improving the tracking performance of the piezoelectric actuator. (C) 2002 Elsevier Science Inc. All rights reserved.