Paul Alexandre

Gait analysis and implementation of a six leg walking machine

This paper describes a successful attempt to have Mechanical Engineering and Electrical Engineering final year students working together on a mechatronics project. The work consisted of constructing a prototype six leg walking machine on which arbitrary gaits could be implemented and tested. This vehicle was also used to conduct some basic studies on terrain adaptive gaits and pit avoidance strategies. The test machine consists of a 38 cm long, 1.3 kg rectangular hexapod. Each leg has two degrees of freedom, actuated by position controlled servomotors, and a contact switch in the foot. The electromechanical part was first constructed and interfaced with a PC, via an umbilical. Later, a on-board microcontroller (Intel 8096) was installed, to make the vehicle semi-autonomous. In order to emphasize the influence of the gait on the vehicle behaviour, the paper begins with a review of the stability properties of some well known regular symmetric gaits on flat ground. This work is part of a EEC sponsored TELEMAN project aiming at developing a legged inspection vehicle for disordered, hostile environment.<<ETX>>

A conceptual walking vehicle for planetary exploration

A lightweight, small size walking robot currently being developed at the Universite Libre de Bruxelles as a conceptual vehicle for planetary exploration is described. The robot consists of three articulated bodies connected by universal joints. Each body has two legs with two degrees of freedom each. Each universal joint is provided with two actuators and torque sensors; a compliant behaviour is achieved by force feedback. This particular device improves considerably the agility of the walking vehicle by allowing the central body to follow the ground profile. Furthermore, the vehicle can walk on both sides and can recover from roll-over thanks to the actuated universal joints which allow an autonomous transfer from back to belly.

ON THE GAIT CONTROL OF A SIX-LEGGED WALKING MACHINE

The paper reviews the main strategies for the leg co-ordination of a six-legged walking machine. A “free gait” algorithm is presented which allows a smooth and stable motion for an arbitrary velocity vector of the vehicle, including a rotation about the vertical axis. It consists of a rule-based central decision process, based on the analysis of a six component vector called ‘leg phase state’ The co-ordination strategy consists of preventing gait states where two neighbouring legs are lifted simultaneously. It is shown that, for a uniform translation with no spin, the free gait algorithm is optimal with respect to static stability.

An Autonomous Micro Walking Machine with Articulated Body

Abstract This paper describes of a lightweight, small size walking robot currently being developed at ULB as a conceptual vehicle for planetary exploration. The robot consists of three articulated bodies connected by universal joints. Each body has two legs with two degrees of freedom each. Each universal joint is provided with two actuators and torque sensors; a compliant behaviour is achieved by force feedback. This particular device improves considerably the agility of the walking vehicle by allowing the central body to follow the ground profile. Furthermore, the vehicle can walk on both sides and can recover from roll-over thanks to the actuated universal joints which allow an autonomous transfer from back to belly.

Development of legged robots for use in disordered environments

The SIC/R laboratory is conducting a research program called Autonomy of Mobile Robots in Unstructured Environments (AMRU), focusing on the realization of light low-cost legged robots for indoor and outdoor applications, study of image and speech processing, development of path planners. This paper summarizes the description of the first four robots (AMRU 1 to 4) of the table 1. Low cost allows the sacrifice and the replacement of the robots used in dangerous environmental conditions (minefield, battlefield, nuclear site, etc.) and implies the choice of low level proprioceptive and exteroceptive sensors coupled with a simple digital control system, light structure facilitates their transportation (by air, land or sea) to the application site.

On the Gait Control of a Six-Legged Walking Machine

Abstract This paper reviews the main strategies for the leg coordination of walking machines with emphasis on the free gait . A free gait algorithm is presented which allows a smooth and stable motion for an arbitrary velocity vector of the vehicle.

A Free Gait Algorithm for Improved Mobility Control of Walking Machines

This paper reviews the main strategies for the leg coordination of walking machines with emphasis on the free gait. A free gait algorithm is presented which allows a smooth and stable motion for an arbitrary velocity vector of the vehicle.