Kinematic analysis and motion planning of a quadruped robot with partially faulty actuators

•The hydraulic robot are introduced and the kinematic model is built.•Constraints of faulty actuators on the robot are discussed using the Screw Theory.•The fault-tolerant motion planning method is explained.•The repeatable control problem is solved.•The effects of the fault-tolerant gait are proved by simulations and experiments.

Actuator failure is a serious problem for legged robots working in remote or complicated environments. Having a fault-tolerant gait is essential to keep the robot walking when actuator failures occur. This paper proposes an algorithm for the fault-tolerant gait to overcome the failure of more than one actuator. The idea is that the degrees of freedom (DOFs) of the robot body are divided into two parts: the major DOFs which are critical to maintain walking and the secondary DOFs. By finding an appropriate kinematic resolution of the motions of the secondary DOFs the motions of the major DOFs can be realized. In this process, a repeatable control problem is also solved by minimizing the actuator displacement function. This method can make full use of the remaining actuators of the robot. The performance of the fault-tolerant gait is demonstrated through a series of simulations and experiments on a hydraulic quadruped robot.

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