Rotary galloping with a lock–unlock elastic spinal joint

Abstract

The effect of the spinal joint on dynamic performance of quadrupedal model in galloping gait is presented in this paper. A 12-DOF sagittal planner galloping model with one spinal joint and four actuated legs including hip and knee joints is introduced. The spinal joint is controlled by a lock–unlock mechanism, in which the spinal joint is locked when maximum extension or flexion is obtained and unlocked when proper conditions are met (at the instance of the back trailing leg touches the ground or at a certain body angle). The differences between the dynamic models with and without a spine and the effect of different initial angles of the spinal joint, different postures (landing angle differences, swing angles and initial heights of center of mass), and different horizontal velocities on the dynamic performance are analyzed. It is illustrated that a quadrupedal model using a slightly controlled spinal joint with proper body postures when galloping exhibits considerable improvement of dynamic performance, and legged systems should not employ rotary galloping pattern until running speeds are sufficient.