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Model Algorithm Control for Path Tracking of Wheeled Mobile Robots
Zhang, Yuanliang,Park, Jong-Ho,Chong, Kil-To 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.5
This paper proposes a model algorithm control (MAC) method for the path tracking control of differentially steered wheeled mobile robots (WMRs) subject to nonholonomic constraints. The continuous dynamic model of the wheeled mobile robot is presented and used as the model to be controlled. The MAC controller is designed based on the sampled-data representation of the system. In this paper the case that there exists time delay in the control input is also considered. A time discretization method using the Taylor series and the zero-order-hold (ZOH) assumption is proposed to discretize the continuous dynamic model of the WMR. This time discretization method is especially useful in the case of the time delayed system. It can provide finite dimensional and more accurate discretized form model of the mobile robot with input time delay and convert it into a general nonlinear time discretizedform to which the MAC controller can be applied. Simulations are conducted to show the performance and feasibility of the proposed control strategy. In these simulations the WMR is controlled to track two difference reference paths such as the "8" shape path and the circular path. The bounded inertial parameters uncertainties and some disturbance are also considered in the model of the control system.
Hybrid discretization method for time-delay nonlinear systems
Zhang, Zheng,Kostyukova, Olga,Zhang, Yuanliang,Chong, Kil-To 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3
A hybrid discretization scheme that combines the virtues of the Taylor series and Matrix exponential integration methods is proposed. In the algorithm, each sampling time interval is divided into two subintervals to be considered according to the time delay and sampling period. The algorithm is not too expensive computationally and lends itself to be easily inserted into large simulation packages. The mathematical structure of the new discretization scheme is explored and described in detail. The performance of the proposed discretization procedure is evaluated by employing case studies. Various input signals, sampling rates, and time-delay values are considered to test the proposed method. The results demonstrate that the proposed discretization scheme is better than previous Taylor series method for nonlinear time-delay systems, especially when a large sampling period is inevitable.
Yuanliang Zhang,Kil To Chong 대한전기학회 2006 International Journal of Control, Automation, and Vol.4 No.3
A new discretization method for calculating a sampled-data representation of a nonlinear continuous-time system is proposed. The proposed method is based on the well¬known Taylor series expansion and zero-order hold (ZOH) assumption. The mathematical structure of the new discretization method is analyzed. On the basis of this structure, a sampled-data representation of a nonlinear system with a time-delayed input is derived. This method is applied to obtain a sampled-data representation of a non-affine nonlinear system, with a constant input time delay. In particular, the effect of the time discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. 'Hybrid' discretization schemes that result from a combination of the 'scaling and squaring' technique with the Taylor method are also proposed, especially under conditions of very low sampling rates. Practical issues associated with the selection of the method parameters to meet CPU time and accuracy requirements are examined as well. The performance of the proposed method is evaluated using a nonlinear system with a time-delayed non-affine input.
An GPS/DR Navigation System Using Neural Network for Mobile Robot
Yuanliang Zhang,정길도 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.12
Dead reckoning (DR) is frequently used for mobile robot navigation as it can provide precise short term navigation information butthe errors of a DR system can accumulate over time. A global positioning system (GPS) can be used for outside navigation andlocalization but the error of a single GPS receiver is still big even though an error intentionally introduced into the system called theselective availability policy (SA) was already removed. Standard differential GPS (DGPS) can provide an accuracy of less than onemeter but it is too expensive for the mass market aside from the need of having a base station to provide differential data. This paperproposes a new GPS/DR fusion method based on the data characteristics of a cheap single GPS receiver and use neural networkto estimate the output of the GPS receiver to provide precise navigation information to the mobile robot. Simulation results validatedthe performance of the proposed method and showed its potential use in outdoor mobile robot navigation.
A GPS/DR Data Fusion Method Based on the GPS Characteristics for Mobile Robot Navigation
Yuanliang Zhang,Kil To Chong 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.10
In this paper we have considered the problem of outdoor mobile robot navigation using dead reckoning (DR) system and single GPS receiver. DR is a very simple and practical positioning technique. It is used in various positioning and navigation applications, especially for the mobile robot. DR can provide short term precise navigation information. But its errors will generally accumulate as the mobile robot continues to travel, and the calculated position of the mobile robot will become less and less accurate. For outdoor navigation application, GPS exhibit lots of advantages. It can provide real time and relatively accurate position data in spite of bad weather or other negative factors. But the big errors of civilian used single GPS receiver prevent it from applying to navigation for mobile robot alone. Differential GPS (DGPS) can be used to achieve an error of less than one meter but the costs are prohibitive in terms of commercializing it into the mass market. In this study, a cheap single GPS receiver cooperated with a DR system was used for the navigation system of a outdoors mobile robot in which a new GPS/DR data fusion method was utilized. This proposed fusion algorithm was based on the characteristics of the chosen single GPS receiver. The presented fusion algorithm does not bring much calculation burden and can provide accurate and robust navigation information for the mobile robot by adaptively switching between GPS/DR and DR when GPS lost the satellite signals. Simulation and experiment were performed to validate the effectiveness of the proposed fusion method and the good results showed its potential for outdoors mobile robot navigation.
Time-Discretization of Nonlinear Systems with Time Delayed Output via Taylor Series
Yuanliang Zhang,Chong Kil-To The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.7
An output time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via a digital computer. A new method for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed in this paper. This method is applied to the sampled-data representation of a nonlinear system with a constant output time-delay. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. In addition, 'hybrid' discretization schemes resulting from a combination of the 'scaling and squaring' technique with the Taylor method are also proposed, especially under conditions of very low sampling rates. A performance of the proposed method is evaluated using two nonlinear systems with time-delay output.