A novel variable force ratio test system for force measurement

It is an important guarantee to precisely measure multi-dimensional force vector with variable directions. In this article, variable force ratio (force ratio is a concept of a ratio of maximum force over minimum force) test system based on piezoelectric effect is proposed to meet the requirement of force measurement characterized with variable force ratio. Force error analysis model of test system is established. Variable force ratio loading device is designed, realizing force ratios of loading forces from 1.4 to infinity by changing loading angle. The orthogonal static calibration, variable force ratio loading experiments as well as dynamic calibration can be completed based on the above systems. The results of orthogonal static calibration express that when resultant loading force is 5000 N, the maximum nonlinearity of X, Y, and Z direction is 1.95%, repeatability is only 0.06%. The results of static calibration of variable force ratio show that when angle is 2 degrees, 5 degrees, 10 degrees, and 30 degrees, the average deviation is 111.9 N (2.2% full of scale). The results of dynamic calibration show that the first natural frequency of test system is 463.99 Hz, which is twice the minimum test frequency (200 Hz). The results of tests reflect dynamic and static characteristic of variable force ratio test system. The system can be utilized for universal variable angle large force measurement (>500 N) in vector control engine (thrust vector control engine), friction stir welding, and large manipulator.