• 제어로봇시스템학회논문지
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• 제18권9호
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• pp.845-853
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• 2012

We propose time-optimal cornering motion trajectory planning and control algorithms for differential wheeled mobile robot with motor actuating voltage constraint, under piecewise constant control input condition. For time-optimal cornering trajectory generation, 1) we considered mobile robot's dynamics including actuator motors, 2) divided the cornering trajectory into one liner section, followed by two cornering section with angular acceleration and deceleration, and finally one liner section, and 3) formulated an efficient trajectory generation algorithm satisfying the bang-bang control principle. Also we proposed an efficient trajectory control algorithm and implemented with an X-bot to prove the performance.

• 한국지능시스템학회논문지
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• 제27권2호
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• pp.89-98
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• 2017

외바퀴 로봇 제어에 있어 필수적인 균형 안정화 제어를 위해 제어 모멘트 자이로스코프(CMG)를 이용할 수 있다. 단일 짐벌 CMG는 단순한 구조를 가지면서 외란에 대해 강력한 복원 토크를 로봇에게 전달할 수 있다. 그러나 CMG는 복원 토크 외에 원치 않는 방향의 토크도 발생시킨다. 원치 않는 방향 토크는 회전 자유도가 높은 외바퀴 로봇 시스템에서 불안정성 문제를 야기한다. 본 논문에서는 원치 않는 방향 토크를 제거하기 위해 CMG 가위쌍을 이용한 외바퀴 이동 로봇 제어 시스템을 제시한다. 외바퀴 로봇 동역학식에 있어서의 모델 오차에 강인한 특성을 갖는 LQR 제어 알고리즘을 설계하였다. 3D 비선형 동역학 컴퓨터 시뮬레이션을 통해 CMG 가위쌍과 LQR 제어 알고리즘을 갖는 외바퀴 로봇 제어 시스템을 검증하였다.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1094-1106
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• 2004

In this paper, a nonlinear controller based on sliding mode control is applied to a two-wheeled Welding Mobile Robot (WMR) to track a smooth curved welding path at a constant velocity of the welding point. The mobile robot is considered in terms of dynamics model in Cartesian coordinates under the presence of external disturbance, and its parameters are exactly known. It is assumed that the disturbance satisfies the matching condition with a known boundary. To obtain the controller, the tracking errors are defined, and the two sliding surfaces are chosen to guarantee that the errors converge to zero asymptotically. Two cases are to be considered: fixed torch and controllable torch. In addition, a simple way of measuring the errors is introduced using two potentiometers. The simulation and experiment on a two-wheeled welding mobile robot are provided to show the effectiveness of the proposed controller.

• 전자공학회논문지SC
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• 제48권6호
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• pp.1-7
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• 2011

본 논문에서는 역진자 시스템과 이동로봇 시스템의 두 시스템으로 구성된 두 바퀴 구동 이동로봇의 구현 및 제어에 대해 논한다. 제어 목적은 균형을 유지하며 이동하는 것이다. 밸런싱 로봇은 한 점에서 회전이 가능하고 바닥으로 부터의 외란에 강건한 균형을 유지한다. 국부 및 전역 좌표계에서의 제어방식의 시뮬레이션을 수행하였다. 로봇이 대칭을 이루도록 만들어졌기 때문에 균형과 주행제어에 간단한 선형 제어기를 사용하였다. 기울어진 각도를 추출하기 위해 자이로와 기울기 센서를 융합하여 사용하였다. 주어진 원형 경로를 주행하는 실험을 수행하였다.

• 전기학회논문지
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• 제60권8호
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• pp.1577-1585
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• 2011

This paper proposes a posture stabilization control algorithm for a wheeled mobile robot using hybrid visual servo control method with a position based and an image based visual servoing (PBVS and IBVS). To overcome chattering phenomena which were shown in the previous researches using a simple switching function based on a threshold, the proposed hybrid visual servo control law introduces the fusion function based on a blending function. Then, the chattering problem and rapid motion of the mobile robot can be eliminated. Also, we consider the nonlinearity of the wheeled mobile robot unlike the previous visual servo control laws using linear control methods to improve the performances of the visual servo control law. The proposed posture stabilization control law using hybrid visual servoing is verified by a theoretical analysis and simulation and experimental results.

• 한국정밀공학회지
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• 제17권5호
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• pp.145-153
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• 2000

This paper discusses the dynamic modeling and robust control development for a differentially steered mobile robot subject to wheel slip according to high load. Consideration of wheel slip is crucial for high load applications such as construction automation tasks because wheel slip acts as a severe disturbance to the system. It is shown that the uncertainty terms due to the wheel slip satisfy the matching condition for the sliding mode control design. From the full dynamic model of the mobile robot, a reduced ideal model is extracted to facilitate the control design. The sliding mode control method ensures the dynamic tracking performance for such a mobile robot. Numerical simulation shows the promise of the developed algorithm.

• 제어로봇시스템학회논문지
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• 제11권10호
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• pp.888-894
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• 2005

In this paper, experimental studies of balancing a pendulum mounted on a wheeled drive mobile robot and its position control are presented. Main PID controllers are compensated by a neural network. Neural network learning algorithm is embedded on a DSP board and neural network controls the angle of the pendulum and the position of the mobile robot along with PID controllers. Uncertainties in system dynamics are compensated by a neural network in on-line fashion. Experimental results show that the performance of balancing of the pendulum and position tracking of the mobile robot is good.

• 제어로봇시스템학회논문지
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• 제17권10호
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• pp.1037-1043
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• 2011

Two-wheeled balancing mobile robots are currently controlled in terms of linear control methods without considering the nonlinear dynamical characteristics. However, in the high maneuvering situations such as fast turn and abrupt start and stop, such neglected terms become dominant and greatly influence the overall driving performance. This paper addresses the SDRE nonlinear optimal control method to take advantage of the exact nonlinear dynamics of the balancing robot. Simulation results indicate that the SDRE control outperforms LQR in the respect of transient performance and required wheel torques. A design example is suggested for the state matrix that provides design flexibility in the SDRE control. It is shown that a well-planned state matrix by reflecting the physics of a balancing robot greatly contributes to the driving performance and stability.

• 제어로봇시스템학회논문지
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• 제20권1호
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• pp.87-93
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• 2014

Conventional two-wheeled balancing robots are limited in terms of turning speed because they lack the lateral motion to compensate for the centrifugal force needed to stop rollover. In order to improve lateral stability, this paper suggests a two-wheeled balancing mobile platform equipped with a tilting mechanism to generate roll motions. In terms of static force analysis, it is shown that the two-body sliding type tilting method is more suitable for small-size mobile robots than the single-body type. For the mathematical modeling, the tilting-balancing platform is assumed as a 3D inverted pendulum and the four-degrees-of-freedom equation of motion is derived. In the velocity/posture control loop, the desired tilting angle is naturally determined according to the changes of forward velocity and steering yaw rate. The efficiency of the developed tilting type balancing mobile platform is validated through experimental results.

• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1241-1248
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• 2004

A controller of wheeled mobile robot(WMR) based on Lyapunov theory is designed and a Fuzzy-Neural Network algorithm is applied to this system to adjust controller gain. In conventional controller of WMR that adopts fixed controller gain, controller can not pursuit trajectory perfectly when initial condition of system is changed. Moreover, acquisition of optimal value of controller gain due to variation of initial condition is not easy because it can be get through lots of try and error process. To solve such problem, a Fuzzy-Neural Network algorithm is proposed. The Fuzzy logic adjusts gains to act up to position error and position error rate. And, the Neural Network algorithm optimizes gains according to initial position and initial direction. Computer simulation shows that the proposed Fuzzy-Neural Network controller is effective.