This paper aims to obtain the optimal configuration and kinematic parameters of 7 degrees of freedom (Dofs) robots by a robot configuration optimization synthesis method based on “Shoulder Elbow”-“Wrist” separation.
The 7 Dofs robot is divided into two parts: the “Shoulder Elbow” part and the “Wrist” part; configuration synthesis of these two parts is, respectively, performed by using structural length indices and global performance indices. Three “Shoulder Elbow” configurations and five “Wrist” configurations are obtained, and 19 optimal configurations are obtained by combining the “Shoulder Elbow” and “Wrist” configurations. By evaluating kinematic control and structural design simplicity requirement of 19 optimal configurations, the optimal 7 Dofs configuration is obtained. Then, dimensional synthesis of this configuration is performed to ultimately obtain the optimal configuration parameters.
The link twist is a primary factor influencing the kinematic performance of robot configurations. The influence level of the link length, the link offset and index weights on the configuration synthesis results is relatively minor. The “spherical-roll-spherical” configuration can excellently meet the requirements of kinematic control and structural design simplicity. The genetic algorithm is used to optimize the kinematic parameters of this configuration.
The configuration optimization synthesis method proposed in this paper can address the shortcomings of existing research methods, simplify the configuration synthesis process and guide the design of 7 Dofs cobots. Based on this method, a 7 Dofs collaborative robot (cobot) is designed, and a grasping experiment of this robot in a narrow space is performed, demonstrating superior anthropomorphic and obstacle-avoidance performance of robots.
