• Tribology and Lubricants
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• 제24권5호
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• pp.241-249
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• 2008

This paper describes the tribological effects on the nonlinear behavior of a spur gear pair with one-way clutch according to the direct contact elastic deformation model over a wide range of speeds, considering the hydrodynamic effects. The effects of various lubrication parameters, such as viscosity, film width, and friction, on the nonlinear dynamic behavior were analyzed. Forces due to the entraining velocity and the hydrodynamic friction were about two orders smaller than normal forces over the whole speed range. While the viscosity has a strong effect on the behavior of gear pair systems, friction has very little effect on torsional behavior. The inclusion of the hydrodynamic effect facilitates nonlinearity by increasing the overlap and damping, as well as decreasing elastic deformation and tooth reaction forces.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2555-2559
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• 2003

In this study, we develop an automatic sorting system, which is mostly affected by frictional forces between a veneer and friction-generating device. So we will make a suitable dynamic model and mechanism to control friction force using a AC servo-motor. We suggest Stick friction and Column friction model, which is occurred between roller and veneer and within veneers as well. A kind of sensor can get the velocity of roller and movement of roller vertical direction. We assume that the several things to simplify the complicate and difficult nonlinear friction phenomenon. And to create an optimal normal force, which can generate a suitable friction force, we control the movement of sorting roller and supporter as well. We introduce several results about a friction character and suggest the value of calibration of sorting roller movement and supporters as well.

• 한국항행학회논문지
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• 제14권5호
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• pp.760-766
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• 2010

본 논문에서는 유압 비례 제어 밸브로 구동되는 유압모터 부하계에 존재하는 정지마찰토크와 점성마찰토크를 해석하였다. 이에 기초 실험으로 유압시스템의 에너지인 압력과 유량에 대한 특성실험을 수행하였고, 공압브레이크 시스템을 이용하여 브레이크 압력의 변화를 인가하여 마찰토크의 변화를 실험하였다. 비선형마찰과 선형마찰에 대한 해석은 유압 시스템의 마찰특성에 대하여 수행하였다.

• 한국항행학회논문지
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• 제13권5호
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• pp.756-762
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• 2009

비선형 마찰인 유압 작동기의 스틱-슬립 마찰은 정확성과 응답성에 문제가 된다. 그러므로 마찰보상은 다양한 제어알고리즘을 통하여 연구되어 왔다. 적응이산시간 슬라이딩 추종제어기는 유압작동기 내의 비선형 마찰 특성을 보상하기 위하여 적용하였다. 다오판틴 방정식을 기초로 하여 새로운 이산시간 슬라이딩 함수는 마찰과 모델링 오차를 포함하여 제어법칙을 정의하였다. 비선형 파라미터의 추종성을 기초로 슬라이딩 함수와 프로젝션 항수를 이용하여 강인성을 높였다. 시뮬레이션과 실험결과는 좋은 추종성능을 얻었다.

• 대한기계학회논문집A
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• 제24권4호
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• pp.1065-1074
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• 2000

A robust nonlinear $H_2$/$H_{\infty}$ control method for a parallel inverted pendulum with structured perturbation and dry friction is proposed. By the random input describing function techniques, the nonlinear dry friction is approximated into the quasi-linear system. Introducing the quadratic robustness theorem, the robust $H_2$/$H_{\infty}$ control system is constructed for the quasi-linear perturbed system. But it is difficult to design a controller due to the nonlinear correction term in Riccati equation. With some transformations on the Riccati equation containing nonlinear correction term, the design of the robust nonlinear controller can be done easily. Hence when the stiffness and mass of the parallel inverted pendulum vary in certain ranges, the proposed control scheme has the robustness for both the structured perturbation and dry friction. The results of computer simulation show the effectiveness of our proposed control method.

• 동력기계공학회지
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• 제12권1호
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• pp.80-86
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• 2008

A motor cylinder apparatus is used to transfer a load in industrial applications. The apparatus is composed of a motor and power transmission elements such as worm gear and screw. In this case, the nonlinear friction of the transmission elements has a bad influence on the position control performance. To overcome this problem, the position control system consists of a feedback controller to achieve nominal control performance and a disturbance observer to compensate nonlinear friction. Especially the filter of a disturbance observer is designed from viewpoint of robust stability. Finally, the simulation result shows that the proposed control system is effective for the disturbance elimination as well as the friction compensation.

• 한국정밀공학회지
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• 제17권1호
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• pp.110-119
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• 2000

This paper presents simple and effective nonlinear friction compensation methods. When the direction of position command reverses, the integrator output of the PID controller does not change the sign of its output instantaneously, due to friction at zero velocity, i.e. stiction resulting tracking errors, that results in continuous push even though the command direction has been changed. To overcome this problem, we attempt to reverse the sign of the integrator output as the sign of velocity changes. The effectiveness of this approach is demonstrated by experiments on a 3-PRPS (Prismatic-Revolute-Prismatic-Shperical joints) in-parallel 6-D.O.F manipulator. The control strategy has been analyzed for stability. Also discussed are disturbance observer and velocity observer approaches for friction compensation.

• 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.

• 한국산학기술학회논문지
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• 제12권11호
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• pp.5194-5201
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• 2011

본 논문에서는 부분적으로 알고 있는 비선형 마찰력이 있는 2차 기계시스템에 대한 강인한 적응제어 기법을 제시한다. 제시하는 적응제어 방법은 잡음이나 모델링 에러가 없는 경우에는 위치 및 속도 추적 오차는 점근적으로 영으로 수렴함을 보장하며, 잡음이나 모델링 에러가 있는 경우에는 그동안 발표된 다른 논문의 결과와 달리 디자인 변수를 적절하게 선택하면 위치 및 속도 추적 오차를 원하는 범위까지 줄일 수 있음을 보였으며 이는 시뮬레이션 결과를 통해 입증하였다.

• 한국공작기계학회논문집
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• 제12권6호
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• pp.77-83
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• 2003

This paper deals with a position control problem of a hydraulic proportional position control system using a nonlinear friction compensation control. As nonlinear friction, stiction and coulomb friction forces are considered and modeled as deadzone and external disturbance respectively. In order to compensate this nonlinearities, we designed the controller which is the adaptive friction compensator using discrete time Model Reference Adaptive Control method in this paper. Digital Signal Processing board is employed for data acquisition and manipulation. The experimental results show that response is slow and steady-state error cannot be compensated properly without friction compensation but this compensator is effective to obtain fast response and good steady-state response.