Dynamic Modelling and Control of an Underactuated Quasi-Omnidireccional Hexapod

Abstract

This chapter presents the mechanical design, dynamic model, and walking control law of an insect-like, asymmetric hexapod robot. The proposed model is an original walking mechanism designed with three actuators to provide quasi-omnidirectionality. One of the motivational aims is to reduce the number of actuators preserving similar holonomy as compared to popular 18-servo redundant hexapods with three servos per leg. This work includes the Klann mechanism as limb, two-drive differential robot's control, one per lateral triplet of legs. The legs of a triplet are synchronized in speed with different rotary angles phase. In addition, the six limbs are synchronized with bidirectional yaw motion. The proposed mechanical design has one servo for limbs yawing, one for the right limbs triplet and one motor for the left triplet. Thus, quasi-omnidirectional mobility is achieved. Furthermore, a dynamic control law that governs the robot's mechanisms motion is deduced, with an Euler-Lagrange approach. Kinematic and dynamic results are validated through numerical simulations using a tripod gait.