Kirstukas S J, Lewis J L, Erdman A G
Department of Mechanical Engineering, University of Minnesota, Minneapolis 55455.
J Biomech Eng. 1992 Feb;114(1):101-10. doi: 10.1115/1.2895432.
The six-revolute-joint instrumented spatial linkage (6R ISL) is often the measurement system of choice for monitoring motion of anatomical joints. However, due to tolerances of the linkage parameters, the system may not be as accurate as desired. A calibration algorithm and associated calibration device have been developed to refine the initial measurements of the ISL's mechanical and electrical parameters so that the measurement of six-degree-of-freedom motion will be most accurate within the workspace of the anatomical joint. The algorithm adjusts the magnitudes of selected linkage parameters to reduce the squared differences between the six known and calculated anatomical position parameters at all the calibration positions. Weighting is permitted so as to obtain a linkage parameter set that is specialized for measuring certain anatomical position parameters. Output of the algorithm includes estimates of the measuring system accuracy. For a particular knee-motion-measuring ISL and calibration device, several interdependent design parameter relationships have been identified. These interdependent relationships are due to the configuration of the ISL and calibration device, the number of calibration positions, and the limited resolution of the devices that monitor the position of the linkage joints. It is shown that if interdependence is not eliminated, then the resulting ISL parameter set will not be accurate in measuring motion outside of the calibration positions, even though these positions are within the ISL workspace.
六旋转关节仪器化空间连杆机构（6R ISL）通常是监测解剖关节运动的首选测量系统。然而，由于连杆参数的公差，该系统可能无法达到预期的精度。已开发出一种校准算法和相关校准装置，以完善ISL机械和电气参数的初始测量，从而使六自由度运动的测量在解剖关节工作空间内最为准确。该算法调整选定连杆参数的大小，以减少所有校准位置处六个已知和计算出的解剖位置参数之间的平方差。允许加权以获得专门用于测量某些解剖位置参数的连杆参数集。算法输出包括测量系统精度的估计值。对于特定的膝关节运动测量ISL和校准装置，已确定了几个相互依存的设计参数关系。这些相互依存关系是由于ISL和校准装置的配置、校准位置的数量以及监测连杆关节位置的装置的有限分辨率所致。结果表明，如果不消除相互依存关系，那么即使这些位置在ISL工作空间内，所得的ISL参数集在测量校准位置之外的运动时也不会准确。
