Development of a compliant legged quadruped robot

Abstract

This paper presents the detailed steps for design and development of a compliant legged fault tolerant quadruped robot where each leg has two links and two motorized revolute joints for locomotion. The body and upper links of legs are rigid whereas the lower link of each leg is compliant. Amble gait is demonstrated on the developed robot. Safety and reliability are the most critical issues for the quadruped robot. During the failure of any joint, performance of quadruped robot is affected. In this paper, locked joint failure is also discussed. Strategies for fault tolerant control of the quadruped are developed and experimentally validated. The developed robot can be used for various hardware-in-the-loop controller prototyping such as reconfiguration, fault tolerant control, and posture control, etc. pertaining to quadruped robots.

Fault-tolerant control of a compliant legged quadruped robot for free swinging failure

“…These are common gait patterns of four-legged animals and they are discussed in our prior publications. 14,15 In the case of multi-legged robots, three appropriately placed legs are required to maintain static stability. Since at least one of the legs needs to be lifted off the terrain for locomotion, the minimum number of legs required is four.…”

“…Detailed modeling of the prismatic link is discussed in Merzouki et al 25 and Bera et al 45,46 Furthermore, the design and detail modeling of prismatic link as part of a quadruped robot is discussed in Gor et al 14 The bond graph model of the quadruped body containing a leg dynamics with compliant link is developed using bond graph software SYMBOLS. 47 The multi-bond graph (or vector bond graph) representation of the model is shown in Figure 6, where the model of one of the legs is given in expanded form and other legs follow similar models.…”

“…In this article, vector bonds are used to model the multi-dimensional system part ( Figure 6) and hence there is no such problem in causality assignment. However, for simulation purpose, the corresponding scalar bond graph form of the model 14,15 is used.…”

“…These authors' earlier works comprise the quadruped robot's multi-body dynamics model development and its validation with experiment 14,15 which was then followed by development of locomotion control laws in the workspace 16 and posture control. 17 In continuation, this article proposes locomotion strategy for free swinging failure.…”

“…The limitation of the method is that the speed of robot reduces due to reduced leg length after folding of legs and increased frictional resistance due to dragging the failed leg which often remains flat on the ground. To simulate the robot motion, a multibody dynamics model of quadruped robot with it control system is developed in Gor et al 14,15 using bond graph approach. Bond graph [18][19][20][21][22][23] is physics-based multi-energy domain modeling approach and it allows development of various control strategies by modifying the system architecture while retaining direct correspondence with the physical system.…”