6-DOF Industrial Robot Optimization Techniques

As one of the most important production tools that have ever been invented by human, industrial robots are widely used in various industries, providing a highly efficient and stable productivity. Dimensional optimization is an important part of optimal robot design. It can satisfy the working requirements of the robot. And by performing topology optimization for each structure of the robot, we can get the best structure in terms of static and dynamic characteristics. As more and more robot companies turn to offline programming, absolute positioning accuracy of industrial robots is becoming increasingly important. By carefully selecting the structural error model and identifying kinematic parameters, industrial robots’positioning accuracy can be improved effectively.Firstly, the development of interval analysis is introduced and the operations of interval mathematics are given. The concept of service ball is described and the definition of dexterity is given accordingly. By using interval analysis and the dexterity defined by the service ball together, a dimensional optimization approach is proposed. Inverse kinematic of the robot wrist is derived to calculate dexterity. The ratio of lengths of links are chosen as the design variable. An interval optimization approach is proposed considering the working range and dexterity re-quirement. The algorithm is implemented using INTLAB toolbox and an optimization example is given.Secondly, Topology optimizations based on SIMP method are performed for three main structures of the SR-165 robot. Static analyses and modal analyses are taken to help establish the optimization problem with their results before the topology optimization. By using rigid elements, the amplification effect of the structural deformation are taken into account which makes selecting the objective function and the constraint much easier. Hyperworks software are used to perform the topology optimization for these structures. The comparison of different indexes shows that the optimizations are successful.Lastly, the impact factors on the accuracy of robot are analyzed. A kinematic parameter error modeling method based on a 6-parameter model is proposed. Conversion formulas from DH model to 6-parameter model are derived. A computer simulation is designed in which drive angular error and measurement error are considered. The simulation shows that the 6-parameter model is more effective than DH model. The pros and cons of these two model are discussed. A real robot test is carried out on a SR-165 robot. The accuracy of the robot has been significantly improved. An iterative inverse kinematic solution is given as the calibrated robot’s structure no longer satisfy the peiper criterion. A compensation method is then proposed. By using MATLAB GUIDE, a graphical user interface for the accuracy optimization program is developed.