Abstract: In experiment for evaluation of human body balance function, the center of pressure (COP) trajectory measuring method has been widely used. This paper introduces a kind of balance function test system based on FPGA. As the control center of the system, it realizes the measurement of six forces synchronously, calculating the center of pressure (COP) and plotting the trajectory simultaneously. Aimed at the problem that high frequency interference seriously affects accuracy of the measurement, research about reasonable setting of the smooth window in data preprocessing has been carried out. The result shows that using a smooth window which is half the length of the data frame can improve the smoothness of the trajectory effectively. Based on this system, experiment has been carried out using the method of bearing load to evaluate ergonomics. The result shows that this system can evaluate balance function accurately. During measurement, the length of trajectory and the area of envelope curve should be chosen depending on the shaking intensity to evaluate the balance function.

Key words: Balance function, Center of pressure, Trajectory smoothness