Showing papers by "Jingyan Song published in 2012"

A new hybrid navigation algorithm for mobile robots in environments with incomplete knowledge

Abstract: Focusing on the navigation problem of mobile robots in environments with incomplete knowledge, a new hybrid navigation algorithm is proposed. The novel system architecture in the proposed algorithm is the main contribution of this paper. Unlike most existing hybrid navigation systems whose deliberative layers usually play the dominant role while the reactive layers are only simple executors, a more independent reactive layer that can guarantee convergence without the assistance of a deliberative layer is pursued in the proposed architecture, which brings two benefits. First, the burden of the deliberative layer is released, which is beneficial to guaranteeing real-time property and decreasing resource requirement. Second, some possible layer conflicts in the traditional architecture can be resolved, which improves the system stability. The convergence of the new algorithm has been proved. The simulation results show that compared with three traditional algorithms based on different architectures, the new hybrid navigation algorithm proposed in this paper performs more reliable in terms of escaping from traps, resolving conflicts between layers and decreasing the computational time for avoiding time out of the control cycle. The experiments on a real robot further verify the validity and applicability of the new algorithm.

A new bug‐type navigation algorithm for mobile robots in unknown environments containing moving obstacles

Abstract: – The purpose of this paper is to improve the traditional bug algorithms for the navigation of mobile robots in unknown environments by considering the limitations in previous works such as generating long path, limited to static environments as well as ignoring implementation issues. With this purpose, a new bug‐type algorithm termed Distance Histogram Bug (DH‐Bug) is proposed for overcoming these limitations., – DH‐Bug redefines the traditional motion modes and switching criteria to shorten the path length. In order to extend the framework of the traditional bug algorithms to tackle the navigation problem in dynamic environments, a new mode and the related switching conditions are designed for dealing with moving obstacles. Moreover, a realization method termed the Distance Histogram (DH) method which takes many implementation issues into full account is proposed for implementing DH‐Bug on real robots., – DH‐Bug is convergent in static environments and it also guarantees “approximate” convergence based on several reasonable assumptions when there are moving obstacles. Simulations results show that DH‐Bug generates shorter average path length than some classical Bug algorithms in static environments and it also performs well in most simulations that contain moving obstacles except for some extremely adverse scenarios which have been discussed in the paper. Experiments on real robots further verify its applicability in both static environments and dynamic environments containing moving obstacles., – Compared with previous works, DH‐Bug has three main contributions. First, in static environments, it can shorten the average path length than many classical bug algorithms in the premise of guaranteeing convergence. Second, it can be applied in dynamic environments containing moving obstacles. Third, unlike the previous bug algorithms that always ignore the practical implementation issues, DH‐Bug presents not only an abstract concept, but also a realization approach for realizing this concept on real robots.

A new method for mobile robots to avoid collision with moving obstacle

Abstract: A new method for helping mobile robots to avoid collisions with moving obstacles is proposed. This method adopts the concept of safe sectors in the vector field histogram (VFH) method, but simplifies its description. Moreover, the new method takes the threat of moving obstacles into account when selecting the direction of motion, and a new speed control law that considers more factors is designed. Hence, it is better at avoiding moving obstacles than the VFH method. Simulation results indicate that the new method also shows many advantages over the dynamic potential field (DPF) method, which is a representative approach for avoiding moving obstacles. Experiments have further verified its applicability.

Improved model‐based control of a six‐degree‐of‐freedom Stewart platform driven by permanent magnet synchronous motors

Abstract: – The precise control and dynamic analysis of the electrical Stewart platform have not been so well treated in the literature. This paper aims to design a novel model‐based controller to improve the tracing performance of the electrical Stewart platform. Moreover, the simulations under uncertain environments are used to verify the robustness of the controller., – In the electrical Stewart platform, there exist two special movements of the motor systems: motor systems' movement with the actuators and meanwhile the rotors and snails' rotation around their axis. The Kane equation is used to compute the driven torque of the movements of motor systems, actuators and movable platform. The improved dynamic models of the electrical Stewart platform which consider the motor systems and actuators' influences are used to design the novel controller. The PID controller and the simple model‐based controller are also developed to compare with the novel one. Moreover, the robustness of the controller is verified by the platform friction and the parameters uncertainty., – Simulation results show that the novel model‐based controller can gain a better tracing performance than the PID controller and even the simple model‐based controller. Under the environments of the platform with friction and 5% parameters variety, the tracing performance of the novel controller is also satisfactory, which verifies the robustness of the controller. Most importantly, the novel model‐based controller can be used in a higher precision control demand and a more complicated environment., – The main contribution of this paper is to derive a novel model‐based controller considering the motor systems' influence, which enhances the robustness of the controller. To the authors' best knowledge, such a framework for the improved model based controller has not been well treated in the past literature. The conventional PID controller and a simple model‐based controller are also built to verify the advantages of the improved model‐based controller.

Robust control oriented identification of errors-in-variables models based on normalised coprime factors

Abstract: A robust control oriented identification approach is proposed to deal with the identification of errors-in-variables models EIVMs, which are corrupted with input and output noises. Based on normalised coprime factor model NCFM representations, a frequency-domain perturbed NCFM for an EIVM is derived according to a geometrical explanation for the v-gap metric. As a result, identification of the EIVM is converted into that of the NCFM. Besides an identified nominal NCFM, its worst case error has to be quantified. Unlike other traditional control-oriented identification methods, the v-gap metric is employed to measure the uncertainties including a priori information on the disturbing noises and the worst case error for the resulting nominal NCFM. Since this metric is also used as an optimisation criterion, the associate parameter estimation problem can be effectively solved by linear matrix inequalities. Finally, a numerical simulation shows the effectiveness of the proposed method.