Gait and Trajectory Rolling Planning for Hexapod Robot in Complex Environment
Hexapod robots have stronger adaptability to dynamic unknown environment than wheeled or trucked ones due to their flexibility. In this paper, a control strategy based on rolling gait and trajectory planning that enables a hexapod robot to walk in dynamic
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Abstract Hexapod robots have stronger adaptability to dynamic unknown environment than wheeled or trucked ones due to their flexibility. In this paper, a control strategy based on rolling gait and trajectory planning that enables a hexapod robot to walk in dynamic environment is proposed. The core content of the control strategy is to constantly change the gait and trajectory according to the dynamic environment and predicted stability margin of robot. Kalman filter is employed to compute predicted zero moment point (ZMP) monitoring the stability of robot in order to keep balance with adjusting gait and trajectory. A hierarchical control architecture consisting of high-level gait planner, low-level trajectory planner, joint servo controller and compliance controller is presented. The control strategy is applied to a hexapod robot engaging to disaster rescue. Experiment results show the efficiency of our control strategy over challenging terrain. Keywords Rolling planning
Hexapod robot Stability control Kalman filter
G. Xin (&) H. Deng G. Zhong H. Wang School of Mechanical and Electrical Engineering, Central South Universiy, Changsha 410083, Hunan, China e-mail: [email protected] H. Deng e-mail: [email protected] G. Zhong e-mail: [email protected] H. Wang e-mail: [email protected] G. Xin H. Deng G. Zhong H. Wang State Key Laboratory of High-Performance Complex Manufacturing, Central South University, Changsha 410083, Hunan, China © Springer Nature Singapore Pte Ltd. 2017 X. Zhang et al. (eds.), Mechanism and Machine Science, Lecture Notes in Electrical Engineering 408, DOI 10.1007/978-981-10-2875-5_3
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1 Introduction Hexapod robots have attracted the attention of researchers because of their superior adaptability to complex environments than their wheeled counterparts. The leg mechanisms of most existing hexapod robot prototypes are 3-DOF serial mechanism including 3 links and 3 revolute joints, which is based on bionics principle. However, in the past works [1–3], we proposed a novel hexapod robot called as PH-Robot, as shown in Fig. 1, with parallel leg mechanism so as to bring the advantage of parallel mechanisms to legged robots. In order to implement rolling planning of gait according to different missions and environmental conditions, different types of gait should be generated. Many studies have focused on the gait generation. As far as we know, it’s hard for hexapod robots to execute dynamic gaits, such as trot or gallop which belongs to mammal gaits. The static gaits including tripod, quadruped, one-by-one types of gait as in [4] and other free gait in [5, 6] are widely used in hexapod robots. Wang et al. [7] discussed three different gaits, i.e., insect-wave gait, mammal-kick gait and mixed gait. They still belong to static gaits. Asif et al. [8] proposed a method that is to increase the number of supporting legs according to the roughness of terrain in order to increase stability. Other researchers [9–12] focused on the analysis of fault tolerant gait as
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