Design and Performance Analysis of Novel Robotic Arm

Industrial robots are widely used in the fields of handling, stacking and machining due to their advantages of large workspace, compact structure and good flexibility, but the stiffness of the robot is relatively weak due to the series structure. In addition, the external load of the robot is fully shared by servo motors which increase the driving power and energy consumption of the robot arm, especially for the big and small arms. In order to increase the robot stiffness and reduce the driving power of the robot arm, a robot structure with a novel robot arm was presented. A parallelogram structure with diagonal driven was adopted for robot big and small arms. The diagonal electric cylinders driven by ball screws using double nuts with preload to eliminate the reverse backlash, and the anti-backlash method was applied to the rotary base and the robot wrist to eliminate the transmission backlash. By using the parallel quadrilateral frame to balance the external bending moment, the driving power and the energy consumption of the mechanical arm were reduced in principle. The energy consumption of the novel robot and the corresponding industrial robot were compared under the same external load, and the simulation results showed that the driving power of the big arm can be reduced from 20% to 80% compared with the industrial robot and the small arm was equal to the industrial robot when only the external gravity load was applied. Moreover, the power consumption of the driving motor was not required when only external bending moment was applied. Finally, based on the strain energy and Castigliano's theorem, combining with the robot arms stiffness results using finite element analysis (FEA), the integral robot stiffness was calculated and the results showed that the overall stiffness of the robot was better than that of industrial robots, which made it beneficial to improve the load capacity in the operations of handling, stacking and so on. © 2017, Chinese Society of Agricultural Machinery. All right reserved.