On improving the accuracy of instrumented spatial linkage system

Calibration is important for improving the accuracy of instrumented spatial linkage (ISL) in the application of biomechanical studies. The assumption of the linear performance of the potentiometer transducer has limited the improvement of the linkage accuracy. We present a non-linear numerical calibration procedure and double potentiometer design to improve the accuracy of ISL. Through the use of a three-degree-of-freedom linkage, the non-linear calibration procedure and the double potentiometer design were shown to be effective in reducing the ISL errors. The error, i.e. standard deviation for the angle decreased from ± 0.38° to ± 0.12° while the same for the translation decreased from ± 0.41 to ± 0.16 mm. A high-accuracy linkage system using low-cost potentiometers could be constructed by using our calibration method and double potentiometer design.