Design and Analysis of a Robotic Modular Leg Mechanism

Abstract

This paper presents the design and analysis of a reduced degree-of-freedom Robotic Modular Leg (RML) mechanism used to construct a quadruped robot. This mechanism enables the robot to perform forward and steering locomotion with fewer actuators than conventional quadruped robots. The RML is composed of a double four-bar mechanism that maintains foot orientation parallel to the base and decouples actuation for simplified control, reduced weight and lower cost of the overall robotic system. A passive suspension system in the foot enables a stable four-point contact support polygon on uneven terrain. Foot trajectories are generated and synchronized using a trot and modified creeping gait to maintain a constant robot body height, horizontal body orientation, and provide the ability to move forward and steer. The locomotion principle and performance of the mechanism are analyzed using multi-body dynamic simulations of a virtual quadruped and experimental results of an integrated RML prototype.

Discrete modular serpentine robotic tail: design, analysis and experimentation

“…High torque servo motors rated for a stall torque of 10 N-m and no load speed of 55 rpm operated at an input voltage of 14 V drive the mechanism's two DOFs. Link lengths and pulley diameters were chosen to be L J2J = 60 mm R = 25 mm, and r i = [9,16,22,28,34]…”

“…Two methods of analyzing the system will be presented: an analytical model implemented in MATLAB for the pitch-angle disturbance rejection, and a model generated in a multi-body dynamics software package for stabilization. Figure 13 shows the DMST mounted vertically on a biped robot constructed of a pair of planar, two-DOF leg mechanisms developed by the authors 16,17 . Figure 14 shows the schematic diagram of the system.…”

“…Simulations of the proposed mechanism attached to a planar biped robot modeled analytically and using a commercial multibody dynamics package demonstrate the tail's performance enabling capabilities in disturbance rejection and quasi-static walking applications. The proposed work is part of ongoing research studying the design and implementation of a variety of robotic tails capable of augmenting a legged robot's ability for agile and robust terrain traversal in unstructured hazardous environments [8][9][10][11][12][13][14][15][16][17] .…”

A Two-DOF Bipedal Robot Utilizing the Reuleaux Triangle Drive Mechanism

“…The first generation Robotic Modular Legs (RM Leg) [10,11] and centipede like robots [12] [13] have two active DOFs per leg. The first generation RM Leg mechanism uses double four-bar mechanisms connected in series to restrict the orientation of the foot (Figure 2.1).…”

“…direction. While the first generation leg mechanism required two active DOF per leg [10,11], the RML-V2 can produce a forward walking gait approximately three times faster due to the continuous rotation of the Reuleaux triangle and does not require any motor direction changes or synchronization of control effort for producing a valid foot trajectory.…”