Design and Analysis of Vibration Reduction System to Improve the Track Accuracy of Robot Arm-Tip

Jittering vibration at a robot arm-tip is unavoidable and is one of the key factors affecting its trajectory accuracy. Because a robot arm is a high-dimensional complex system, the actual causes for the vibration at the robot of the arm-tip are very complicated, and very difficult to identify, if it is not impossible. This work presents a novel and practical device for mitigating such vibrations. The present vibration-mitigator consists mounting box with a plate spring carefully designed based on the frequency of the arm-tip vibration. It can be conveniently mounted on the arm-tip. The key idea is to transmit the jittering at the arm-tip to the vibration of an oscillator nested inside the jittering-mitigator box, so that the vibration of jittering-mitigator box can be reduced. The jittering-mitigator box can in turn serve as the working end for the robot arm. The present device requires only the knowledge of the frequency of the jittering vibration at the arm-tip, without the need to explore the underlying causes of the vibration. An actual device is made and it is mounted on a six-axis tandem robot. A systematic study is conducted to examine the effectiveness of the device, by numerical modeling and simulations. The jittering at the arm-tip of the robot is firstly measured under the working conditions using accelerometers connected to LMS Test Lab. Through FFT analysis, the dominating frequency is identified. The parameters of the jittering-mitigator are then calculated theoretically. A finite element model is next established to simulate the reduction effect of the jittering mitigator. The results show that the average amplitude of the jittering vibration at the arm-tip is significantly reduced by as much as 65%.