Research On Walking Gait And Control For Under-actuated Biped Robot

Biped robot is a subject that has broad application prospects. A lot has been achieved in this area after the tireless effort of scientists. But traditional initiative robots have problems of high energy consumption and slow walking speed. Under-actuated robots can help solve these problems, by high-speed dynamic walking with low energy consumption. An under-actuated robot is special with some of its joints not driven, which can make better use of kinetic features of walking. This paper studies gait planning, walking control and other aspects of a five-link, point-foot under-actuated robot. The content includes these following aspects:Firstly, a five-link, four-actuator model of robot is established. The kinetic model is obtained by Lagrange principle and a periodic walking controller is designed based on this model. The controller employs virtual constraints to achieve gait tracking. Simulation results illustrate the efficiency of this controller.Secondly, the form of periodic gait determined and a gait optimization method which suits this paper is designed based on multi-objective particle swarm optimization. Simulation results show that the gait optimization method can obtain gait set containing various walking speeds and having low energy cost.Thirdly, a dynamic matrix controller is designed on the basis of periodic walking and gait optimization to control walking speed of the robot. In addition, two starting methods utilizing kinetic energy and potential energy respectively, and a stopping method consisting of deceleration and stopping pace, are specially designed. Simulation results show that, the speed controller has better performance than PI controller and that starting methods and stopping method work.Finally, the.realization of control on physical prototype is designed, including hardware design and software design. The hardware system includes a industrial PC on the upper level and servo motors on the lower level connected by CAN bus. The software uses modular implementation, designed on the principle of convenience for using. In addition, the simulation system is re-designed taking the effects of hardware limitations into consideration, providing a more valuable reference for prototype realization.Innovation of this paper:first, a gait optimization method is specially designed to obtain low-energy-cost gaits of different walking speeds at the same time. Second, a Dynamic Matrix Control Algorithm of speed control is designed which has better- performance and stability than PI control. Third, starting and stopping methods are designed suiting under-actuated robots. Fourth, the realization of control on the prototype is designed on both hardware and software. Fifth, the simulation system is designed considering the hardware performance, making the simulation more realistic.