Fig. 1. Angle measuring system of precision reducer tester

Fig. 2. Schematic diagram of embedded control and signal acquisition system

Fig. 3. Experimental setup for calibration of angle measurement error

Fig. 4. Flow chart of automatic calibration

Fig. 5. Operation interface of automatic calibration system

Fig. 6. Angle measurement error data and harmonic compensation curve

Fig. 7. Angle measurement error model obtained by training point and harmonic neural network combined compensation method

Fig. 8. Comparison of residuals between error harmonic method and harmonic neural network combined compensation method

Fig. 9. Schematic diagram of autocollimator cross line tilt

Fig. 10. Data drift of autocollimator in X-axis