Variable-speed quadrupedal bounding using impulse planning: Untethered high-speed 3D Running of MIT Cheetah 2

Abstract

This paper introduces a bounding gait control algorithm that allows a variable-speed running in the MIT Cheetah 2. A simple impulse planning algorithm is proposed to design vertical and horizontal force profiles which make net impulse on the system during one cycle zero. This design of force profiles leads to the conservation of linear momentum over a complete step, providing periodicity in horizontal and vertical velocity. When designed profiles are applied to the system, periodic orbits with an ability to change running speed are obtained. A virtual compliance control in the horizontal and vertical direction has been added onto the designed force profiles to stabilize the periodic orbits. The experimental results show that the algorithm successfully achieved untethered 3D running of the MIT Cheetah 2, with speeds ranging from 0 m/sec to 4.5 m/sec on treadmills as well as on grassy fields.