Abstract

An anthropomorphic biped robot called AAU-Bot1 has been developed at Aalborg University. This robot is a part of cooperation between Department of Mechanical Systems and Department of Electrical Systems. Initially the robot was designed to perform the human gait or more precise the heel-toe gait. Currently the AAU-Bot1 is subjected to implementation of control schemes at Department of Electrical Systems. The arms of the robot are attached to the torso by means of revolute joints on the current robot. However it has been the aim from start of the cooperation to develop a robot that also could interact with humans in the form of a handshake. As the AAU-Bot1’s current arms are limited to a pitching motion around the shoulder joints. The focus of this project is to create a light and low power consuming mechanical design of an anthropomorphic robot arm (ARA) with seven degrees of freedom with the same working space as a human arm. The redundant setup of the robot arm will enhance the flexibility when it is to perform human-like motion. The robot arm is set to minimum perform two types of motion, standard gait and a human handshake motion. After manufacturing the designed ARA is to be mounted on AAU-Bot1. The design is limited to a system with four degrees of freedom. From a literature study the human wrist trajectories for gait and handshake was determined. To determine the unknown trajectory for the four degrees of freedom, a combination of weighed and damped pseudo inverse Jacobian has been used. Together with standard kinematic and inverse dynamic analysis, ARA motion and forces was determined. The weighed-damped pseudo inverse Jacobian method has been used together with an optimisation procedure based on the Complex method. The optimisation procedure was introduced to minimise ARA power usage and remove trajectories that would collide with the torso of AAU-Bot1. Kinematic and inverse dynamic analysis results have been used to select gear and actuators from catalogues. Simple calculation and intuitive design procedures have been used to design the structural parts of the robot arm. The work has resulted in a four degree of freedom conceptual design with human-like proportions and manipulability. The total mass of the initial design is approximately 5.8 kg that gives an additional mass for AAU-Bot1 of 4 kg per arm because of shared design parts. The arm can carry a payload of 2 kg. The distribution of joint degree of freedom follows the one of a human arm and is obtained with revolute joints in series. The design can perform standard human gait and handshake motion. At the same time the concept have been created sufficiently strong to perform other tasks. The designed anthropomorphic robot arm is designed to work for standard gait and handshake motion. The redundant setup ensures a flexible arm that can imitate the human arm. It should be investigated if the mass can be reduced with use of special purpose designed gears and extra gearing to minimise motor sizes. The design is to be expanded with three extra degrees of freedom so an anthropomorphic robot arm design with seven degree of freedom can be manufactured.

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A master thesis from Aalborg University

Design of Anthropomorphic Robot Arm: ARA-1