Motion Control of Industrial Robots in Operational Space: Analysis and Experiments with the PA10 Arm

Since their appearance in the early 1960’s, industrial robots have gained wide popularity as essential components in the construction of automated systems. Reduction of manufacturing costs, increase of productivity, improvement of product quality standards, and the possibility of eliminating harmful or repetitive tasks for human operators represent the main factors that have determined the spread of the robotics technology in the manufacturing industry. Industrial robots are suitable for applications where high precision, repeatability and tracking accuracy are required. These facts give a great importance to the analysis of the actual control schemes of industrial robots (Camarillo et al., 2008). It is common to specify the robotic tasks in terms of the pose (position and orientation) of the robot’s end–effector. In this sense, the operational space, introduced by O. Khatib (1987), considers the description of the end–effector’s pose by means of a position vector, given in Cartesian coordinates, and an orientation vector, specified in terms of Euler angles. On the other hand, the motion of the robot is produced by control signals applied directly to the joint actuators; further, the robot configuration is usually measured through sensors located in the joints. These facts lead to consider two general control schemes: