Generation of ground locomotion for a salamander robot

Patrice Salameh

July 2012

Project Description

This project relates to the locomotion of Pleurobot, a bio-inspired salamander robot. The first aim was to find a new design for the robot’s feet, enabling efficient locomotion in different environments. A simple ball-shaped design made of PDMS proved to be an adequate solution with its friction and compliance properties.

 

The main goal of the project was to establish the whole-body inverse kinematics. First, an inverse kinematics algorithm was conceived for the limbs, using the redundancy to obtain natural postures. The data used was extracted from an X-ray recording of a salamander in walking gait. The algorithm used the Jacobian pseudo-inverse method to converge iteratively towards the desired foot position, starting from a real limb posture.

Then, a simple 2D model of the robot consisting of the spine segments and using simple vectors to represent the limbs was created, in order to investigate the inverse kinematics of planar trajectories following. A simple joint motion minimization between each time step gave some surprisingly natural-looking spine postures.

 

The limbs inverse kinematics method was combined with the 2D model to obtain a whole-body 3D inverse kinematics algorithm, enabling the robot to follow smooth trajectories.

 

 

An analysis of the joint movements obtained enabled some interesting conclusions about the underlying principles of the postures used by the animal.