Fig. 1. Diagram of sensor layout for the magnetic field measurement sledge

Fig. 2. Principle schematic of the laser 3D-positioning of the magnetic field measurement sledge

Fig. 3. Relationship between the retro-reflector and laser spot on the CCD in the horizontal direction

Fig. 4. Schematic diagram of flipping calibration principle for Hall probes position

Fig. 5. 3D diagram of iron wedge-shaped block adsorbed by a permanent magnet block

Fig. 6. Photograph of the magnetic field measurement sledge mounted on a 3D high-precision mechanical arm(a) Horizontally-placed sledge, (b) Vertically-placed sledge

Fig. 7. Magnetic field distribution measured by the three Hall probes(a) Horizontally-placed, (b) Vertically-placed, (c) Horizontally-placed with a flipped magnetic measuring sledge, (d) Vertically-placed with a flipped magnetic measuring sledge

Fig. 8. Diagram of retro-reflector position calibration apparatus

Fig. 9. Linear curve of the sledge displacement before (a) and after (b) sledge flipping and the coordinates of the centroid position

Fig. 10. Influence of the sledge manufacturing error on Hall probe calibration result (a) Horizontally-placed sledge, (b) Vertically-placed, (b) Flipped horizontally-placed magnetic measuring sledge, (d) Flipped vertically-placed magnetic measuring sled

Fig. 11. Influence of the discrepancy between the motion platform and magnetic field coordinate axes on the Hall probe calibration