Implementation of Caterpillar Inspired Rolling Gait and Nonlinear Control Strategy in a Spherical Robot
This paper presents a novel Central Pattern Generator (CPG) based rolling gait generation in a small-sized spherical robot and its nonlinear control mechanism. A rhythmic rolling pattern mimicking Pleurotya caterpillar is produced for the spherical robot locomotion. A synergetically combined feedforward-feedback control strategy is proposed. The feedforward component is generated from centrally connected network of CPGs in conjunction with nonlinear robot dynamics. Two nonlinear feedback control methods namely integral (first order) Sliding Mode Control (SMC) and High (or second) Order Sliding Mode Control (HOSMC) are proposed to regulate robot stability and gait robustness in the presence of matched parameter uncertainties and bounded external disturbances. Design, implementation and experimental evaluation of both roll gait control strategies for the spherical robot are done on smooth (indoor) and irregular (outdoor) ground surfaces. The performance of robot control is quantified by measuring the roll angle stability, phase plane convergence and wheel velocities. Experimental results show that proposed novel strategy is efficient in producing a stable rolling gait and robust control of a spherical robot on two different types of surfaces. It further shows that proposed high HOSMC strategy is more efficient in robust rolling gait control of a spherical robot compared to an integral first-order SMC on two different ground conditions.
Keywordsbioinspired spherical robot rolling gait CPG rolling friction integral first-order SMC control HOSMC
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This work is supported by the Future Systems and Technology Directorate (FSTD), under the Ministry of Defense, Government of Singapore, under Grant IGDST1301013 for Systems Technology for Autonomous Reconnaissance and Surveillance (STARS) project. The authors gratefully acknowledge the support of the Temasek Lab @SUTD and the SUTD-MIT International Design Center. We would like to thank Mr. Akash Vibhute, Mr. Cheong Li Yang, Mr Chen Xiohan for key contributions for the mechanical CAD and dynamics design of spherical robot. We would acknowledge useful suggestions and feedback given by Mr. Che Kun Law of Purdue University, Mr. Hu Yuan of Robotics Institute, Carnegie Mellon University and Mr. Peter Ho (Co-founder) of HOPE Technik Pte. Ltd.
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