On Locomotion Control Using Position Feedback Only in Traversing Rough Terrains with Hexapod Crawling Robot

Abstract

In this paper, we report on our results on improved locomotion control of small and affordable hexapod crawling robot using only position feedback from the utilized servo motors. Multi-legged robots represent complex mechanical systems with many degrees of freedom from which they can benefit in traversing rough terrains. However, the crucial ability of multi-legged robots is maintaining stable locomotion over irregularities of the terrain which makes the locomotion control complex and requires reliable and timely detection of the leg contact point with the ground. Such detection may require additional sensory equipment which can increase the cost of the multi-legged platform. Therefore, we focus on exploiting capabilities of nowadays intelligent servo motors with position feedback to develop a minimalistic set up in which the robot uses solely the position feedback of the servo motors to sense the ground reaction force. The first achievements enable a small hexapod crawling robot to navigate rough terrains using stable pentapod gait, where only one leg moves at a time, and five legs support the robot. Later on, we improved the locomotion control to enable faster locomotion using three simultaneously moved legs in the so-called tripod motion gait. This paper reports on further advancements with a faster control loop enabled by hardware based acceleration of the communication latency with the utilized Dynamixel AX12 servo motors that improve the locomotion capabilities of the robot. The reported results indicate the robot locomotion with the used adaptive motion gait is speeded up by a factor of 1.4 with the same stability in traversing the rough terrain of the experimental laboratory mock-up.