Biorobotics Laboratory BioRob

Simon Rutishauser (semester project 2008) - Cheetah: compliant quadruped robot

Abstract

In this project a new quadruped robot ``Cheetah'' is developed and implemented. ``Cheetah'' features three-segment legs with passive compliant knee joints. Each leg has two degrees of freedom - knee and hip joint can be actuated using RC servo motors.

Simple electronics to command the actuators from a desktop computer have been designed in order to test the robot. Ideas for more complete autonomous electronics are sketched.

Preliminary tests were performed to verify the correct functioning of the mechanical design.

Three-segment compliant pantograph leg

Several actuation principles and cinematics were evaluated - resulting in the leg design shown on the CAD picture.
The leg segment lengths were chosen such as to be energetically advantageous. In order to dimension the leg stiffness and actuators, a simple spring-mass model for walking and running was introduced and solved for the given leg dimensions and estimated stroke frequencies for different gaits.

Simple test electronics were designed using a PIC test board an a simple custom-made power supply board. Ideas for more powerful autonomous electronics and power supply have been drafted as well.

Pictures and Movies

The movies show some of the preliminary tests performed with the "Cheetah"-roboter:

cheetah1.avi: cheetah lifts its left fore leg
cheetah2.avi: crouching down and standing up again
cheetah3.avi: fast hip movement
cheetah4.avi: passive compliance in the knee joints

Report

cheetah_report.pdf