Optimal Usage of Robot Manipulators

Abstract

4.1 Single Objective Optimization The results confirm that the problem of path placement in a robot work cell is an important issue in terms of manipulator cycle time. Cycle time greatly depends on the path position relative to the robot manipulator. Up to the 37.2% variation of cycle time has been observed which is remarkably high. In other words, the cycle time is very sensitive to the path placement. Algorithm and tool were developed to determine the optimal robot position by path translation and path rotation approaches. Several case studies were considered to evaluate and verify the developed tool for optimizing the robot position in a robotic work cell. Results disclose that an increase in productivity up to 37.2% can be achieved which is profoundly valuable in industrial robot application. Therefore, using this tool can significantly benefit the companies which have similar manipulators in use. It is certain that employing this methodology has many important advantages. First, the cycle time reduces significantly and, therefore, the productivity increases. The method is easy to implement and the expense is only simulation cost, i.e., not any extra equipment is needed to be designed or purchased. The solution coverage is considerably broad, meaning that any type of robots and paths can be optimized with the proposed methodology. Another merit of the algorithm is that convergence is not an issue, i.e., reducing the cycle time can be assured. However, a disadvantage is that a global optimum cannot be guaranteed. The importance of the developed methodology is not confined only to the robot end-user application. Robot designers can also take advantage of the proposed methodology by optimizing the robot parameters such as robot structure and drive-train parameters to improve robot performance. As a design application example, the idea of optimum relative position of robot and path can be applied to the design of a tool such as welding device or glue gun which is erected on the mounting flange of the robot. The geometry of the tool can be optimized by studying design parameters to achieve shorter cycle time. Another possibility can be to use the developed methodology for optimal robot placement to realize other optimization objective in robots such as minimizing the torque, energy consumption, and component wear. One interesting issue that can be investigated is to consider the general problem of finding the optimum by translation and rotation of the path simultaneously. What has been demonstrated in section 2 of the current chapter is to find the optimum path location by either translation or rotation of the path. Obviously, it is also possible to apply both these approaches at the same time. This would probably further shorten the cycle time in comparison to the case when only one approach is used. However, developing an optimal strategy for concurrently applying both approaches is an interesting challenge for future research. Another important subject to be investigated is to take into account constraints for avoiding collisions. In a real application, a robot is not alone in the work cell as other cell equipments can exist in the workspace of the robot. Hence, in real robot application it is important to avoid collision. 4.2 Multi-Objective Optimization It is noteworthy that although the methodology is implemented in RobotStudio, the algorithm is general and not dependent on RobotStudio. Therefore, the same methodology