Dimensionlessness and threshold denoising in multi-joint arm calibration model with distance constraints

Considering that the matrix of multi-joint arm calibration model with distance constraints, in which there were different orders of column magnitude, may cause ill-posed problem and the error in the process of calibration may affect the accuracy of the result, a method was proposed to modify the calibration matrix. Dimensionlessness and threshold denoising algorithms were used in the calibration matrix's calculation. Recalibration and iteration were used to calculate the calibration matrix after dimensionlessness and threshold denoising. Experimental study was carried out on a 6-joint arm with a standard ruler, of which the distance was 711.199mm. The experiments showed that the method can protect the calibration equation from ill-posed problem; the standard deviation of length measurement was 0.103mm after dimensionlessness and threshold denoising, which were effective and suitable for the requirement of measurement.