Walking up and down hill with a biologically-inspired postural reflex in a quadrupedal robot

This paper presents a control strategy, biologically-inspired postural reflex, based directly on animal behaviors, which allows a quadrupedal robot to walk up and down hill smoothly. A central pattern generator (CPG) and a hip-to-knee mapping function are employed to realize the basic rhythmic motion for the quadrupedal robot. The trunk pitch angle feedback of the robot is linearly introduced to the CPG, spontaneously changing the mid-positions of the four legs to make postural adjustments as the way a cat does. Thereby, slipping and falling-down are greatly reduced. Numerical simulations and experimental implementation on a physical quadrupedal robot demonstrate the effectiveness of the proposed approach.