• 한국소음진동공학회논문집
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• 제18권7호
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• pp.756-763
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• 2008

This paper presents an inchworm with three piezoelectric actuators. The dynamic stiffness of the inchworm is generally low compared to its driving condition, so mechanical vibration may degenerate the motion accuracy of the inchworm. The dynamic model of inchworm is identified by curve fitting technique based on the experimental frequency response function. For the precision motion control and low residual vibration of inchworm, driving input signal is designed by using cycloid step input and LQG control technique. Experimental result shows that proposed input shaping method is applicable effectively to the inchworm.

• 한국공작기계학회논문집
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• 제17권2호
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• pp.83-89
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• 2008

This paper presents the dynamic analysis and input shaping control of a positioning stage. Vibration characteristics of the positioning stage are affected not only by the structural dynamics but also by the servo actuators that consist of the mechanism; driving motor and controller. This paper proposes an integrated dynamic model to accommodate both the structural dynamics and the servo actuators. Theoretical modal analysis with a commercial finite element code is carried out to investigate the dynamic characteristics of the experimental positioning stage. Experiments are performed to validate the theoretical modal analysis and estimate the equivalent stiffness due to the servo actuators. This paper deals with an input shaping scheme to suppress vibration of the positioning stage. Input shapers are systematically implemented for the positioning stage in consideration of its dynamics. The effects of servo control gain are also investigated. The experiments show that input shaping effectively removes residual vibrations and then improves the performance of positioning stage.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.877-880
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• 2001

This paper presents the new linear motion device so called "inch-worm" which gets large displacement by incrementally summing small displacements of PZT actuators. Dynamics stiffness of inch-worm is generally low compared to its driving condition due to the requirement of inch-worm like small size and light weight. This low stiffness may degenerate the positional precision of inch-worm. An inch-worm is realized using three PZT actuators, a monolithic moving device and a guide way frame. Driving input signal is shaped to reduce the residual vibration of inch-worm by LQG controller and cycloid step input. The practical feasibility of inch-worm is also examined by running test.ning test.

• 한국정밀공학회지
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• 제18권8호
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• pp.157-163
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• 2001

This paper presents the new linear notion device so called \"inch-werm\" which gets large displacement by incrementally summing small displacements of PZT actuators. Dynamic stiffness of inch-worm is generally low compared to its driving condition due to the requirement of inch-worm like small size and light weight. This low stiffness may degenerate the positional precision of inch-worm. An inch-worm is realized using three PZT actuators, a monolithic moving device and a guide way frame. Finite element method and experimental approach are used to analyse the static and dynamic motion of the designed inch-worm. Command reference input is shaped to reduce the residual vibration of inch-worm. The practical feasibility of inch-worm is also examined by running tests.ing tests.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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• pp.24-34
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• 2000

In this paper we propose a controller design method, called Quasi-LQG/$H_{\infty}$/LTR for nonlinear servo systems with hard nonlinearities such as Coulomb friction, dead-zone. Introducing the RIDF method to model Coulomb friction and dead-zone, the statistically linearized system is built. Then, we consider $H_{\infty}$ performance constraint for the optimization of statistically linearized systems, by replacing a covariance Lyapunov equation into a modified Riccati equation of which solution leads to an upper bound of the LQG performance. As a result, the nonlinear correction term is included in coupled Riccati equation, which is generally very difficult to thave a numerical solution. To solve this problem, we use the modified loop shaping technique and show some analytic proofs on LTR condition. Finally, the Quasi-LQG/$H_{\infty}$/LTR controller for a nonlinear system is synthesized by inverse random input describing function techniques (ITIDF). It is shown that the proposed design method has a better performance robustness to the hard nonlinearity than LQG/$H_{\infty}$/LTR method via simulations and experiments for the timing-belt driving servo system that contains the Coulomb friction and dead-zone.

• 대한전자공학회논문지
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• 제8권2호
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• pp.24-33
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• 1971

부성특성회로로서 쌍트랜지스터 회가의 양에미터단자사이에 용량 C와 저항 R의 병렬회로를 삽입하고, 표준화주파수의 단형파전류원를 에미터·바이어스전류원으로 하여 쌍회로를 구동하면, RC병렬회로는 정부변조회로의 적분회로로서 동작시킬 수 있다. 이 적분회로와 직렬로 신호파전압원을 접속시키면 쌍회로가 구동전원의 표준화펄스에 의하여 구동될 때 마다, RC 적분회로의 적분전압과 신호파전압이 서로 비교되기 때문에 그들의 차전압에 의하여 쌍회로의 트랜지스터들 중의 어느 한 쪽이 ON되기 때문에 그 베이스결합저항단자에는 one bit의 펄스가 송출된다. 본실험에서는 극히 간소한 회로구성을 갖는 쌍트랜지스터회로에 의한 정착변조회로를 제시하고 그들의 특성을 부기하였다. 정착변조파의 품질 혹은 S/N비의 향상을 위하여 고려하여야 할 문제로서, 적분회로의 회로정수 및 양자화전압의 구동펄스의 파고와 파폭의 관계를 검토한다.