MOTOMAN

Design Modeling and Simulation of a Robot Arm Using MOTOMAN

Design Modeling and Simulation of a Robot Arm Using MOTOMAN



Introduction

This proposal considers the modelling and control of a robotic actuator to be used in a domestic environment. The commonly known robotic actuators are industrial actuators, which are designed for application in industrial robots. In general, industrial robots are unsafe for humans and not practically applicable in a domestic environment. The difference between industrial and domestic robotics is a direct consequence of their specifications. A differentiation in robotics based upon the robot's application is given in [Kara, 2006] and shown in Figure 1.1. Industrial robots are designed to combine speed and accuracy while domestic robots must be able to be mobile, interactive1 and safe. As a result, industrial robots are stiff, heavy (except for the moving parts) and powerful; domestic robots are small and light but less accurate and less powerful. One of the issues domestic robot research focusses on, is the actuation. Compared to industrial actuators, biologic actuators (muscles) have the ideal properties for domestic robots: strong, flexible, light and efficient. One type of actuators, approaching the biological muscle properties, are pneumatic artificial muscles or PAM's. The best known PAM is the McKibben muscle2, a light and strong actuator with nonlinear. characteristics. A disadvantage is that McKibben muscles are difficult to control.

Problem Statement

The problemstatement of this thesis project focusses on themodelling and control of a robotic system, actuated by four pneumatic artificial muscles. To investigate this, a two-degree-of-freedom (2DoF) robotic arm is built at Philips Applied Technologies in Eindhoven; an impression is given in Figure 1.4. The robotic arm is deliberately not designed according to the principal design rules to construct light and stiff [Koster, 2000]; the dynamics of the joints are coupled and the moving masses are relatively large compared to the stiffness.

This is done to resemble a possible layout of a domestic robot. The robotic arm consists of two revolute joints which are connected in series. Each joint is driven by a pair of McKibben muscles in an antagonist setup. McKibben muscles are known for their nonlinear behavior. Physical modelling of this behavior is considered to be difficult. Because of such complex dynamics, the control of robots actuated by McKibben muscles, has focussed on various complex control strategies. Classical feedback control has never been applied, simply because a linear approach seemed inadequate to handle the nonlinear characteristics.



Modern Industrial Motion Control

The design of industrial robots is characterized by lightweight and stiff structures. As a result the eigenmodes are located at high frequencies, which directly affects the feasible bandwidth of a robot. The mechanics are optimized for linearity to allow for the application of well-known classical linear control techniques.

There are a number of well-recognized production technologies capable of quickly producing complex objects or large objects, but there are few who can do both with low cost (Khoshnevis, 2004). Conventional additive rapid prototyping (RP), technology continues to improve in speed and accuracy, but the ability to produce large ...