Research Of The Six-axis Heavy Force Sensor Based On The Stewart Platform Structure

The giant heavy operating equipment is urgently needed in the high-efficiency and high-precision manufacturing of huge parts, which are used as key components in the field of nuclear power, ship building, chemical industry and national defense. In order to meet the higher operating ability and performance, the giant heavy equipment operator should have the ability of conformable control and coordinate control. So as the basic of precision motion control, the measurement and its feedback are becoming the key technology to be solved. In particular, in order to avoid conflict caused by the increased loading or invalid holding, the giant heavy operating equipment should have the ability of the force conformance according to the deformation of the huge parts. Thus, the study of the six-axis heavy force measurement as well as its feedback technology is becoming more and more important. Nowadays, the heavy force between 100kN and 100MN can be measured, but can only be realized on the single axis, and the existing six-axis measurement is also limited to small force. In this paper, we focus on the problem between the six-axis force measurement and the heavy force measurement to do some research.This paper firstly analyses the force Jacques matrix based on the Stewart structure and the theory of heavy force division, then brings out a new method of the six-axis heavy force measurement used on the giant heavy operating equipment. We use Finite Element Method to establish the model of the Stewart structure six-axis heavy force sensor, and then do some static structure analysis, and get the divided force on the six measuring poles. Compared with the undivided situation, the results show that the Stewart structure six-axis heavy force sensor has a good effect of force division. Through the modal analysis, we get the prime six formations and natural frequencies. Through the harmonic analysis, we input harmonic signals with different frequencies, and get the X, Y, Z harmonic displacement of the Stewart structure six-axis heavy force sensor.We design and assemble the Stewart structure six-axis heavy force sensor. During this period, we take the following innovations: using six pairs of bolts and sliders to realize the partial pre-loading; using ball and cone-shaped hole connection to realize the single-loading character of the measuring poles; using threaded connection to meet the length of the measuring pole adjustable; using the wedge-shaped device to realize the rigid connection between the sensor and the robot arm. Finally, we use our special calibration device to finish the static calibration of the Stewart structure six-axis heavy force sensor, and get the calibration curves and decoupled matrix based on experiment.The result of the static analysis shows the sensor has a good ability of force dividing, and proves the feasibility of the Stewart structure six-axis heavy force measurement. The dynamic analysis shows the sensor has a good dynamic performance, and its natural frequency is beyond the required 1000Hz. The calibration experiments show the sensor has good measurement accuracy. The research will give some technical support to the high-precision coordinate control of the giant heavy operating equipment.