STATICAL BALANCING OF A ROBOT MECHANISM WITH THE AID OF A GENETIC ALGORITHM

Abstract--ln designing robots tatical balancing is of great importance. It enables essential reduction of the required motor power. Elimination of significant reduction of the gravity load at a powered joint can also lead to a simpler and more effective control system. It is shown that this problem can be formulated as an optimization problem. As objective function the average force on the gripper in the working area is used. It is shown that those forces can easily be derived with the aid of a Computer Algebra System. The lengths of the links and angles between them as well as the stiffness of springs can be considered as design variables. It is shown that a general design program based on Monte Carlo methods and genetic algorithms, that has a graphical interface that allows the user to modify search intervals, is very appropriate o these kinds of problems. As an example an industrial robot with 6-DOF is treated. The robot has a spring balancing system that has to be optimized. The robot with the parameters of its balancing system found this way is evaluated with an existing multibody dynamics program SPACAR that simulates the movements of the robot and calculates the forces at its powered joints. With the aid of MATLAB the forces in the working area are plotted in a 3D figure. The method escribed in this article is general and very appropriate o solve problems in practice without simplifications. © 1998 Elsevier Science Ltd 1