A position measurement method for 3-degree-of-freedom motion based on magnetic detection

Generally, optical methods for precision measurement have limitations when rotation of large angle (larger than 10°) and translation of large range occur simultaneously. To deal with the problem, an improved method based on spatial magnetic detection is proposed for planar 3-degree-of-freedom position measurement with large ranges in this article. The position-solving algorithm of the method calculates position by decoupling 3 degrees of freedom with the magnetic flux densities of the inherent magnetic field of the permanent-magnet synchronous planar motor detected by the proposed Hall-sensor array. On the basis of previous work, the calculation approach of decoupling is improved; as a result, the calculations for solving position are simplified. The characteristics of the sensor topology are exploited further, and a new calculation approach of decoupling is introduced to compensate the original one, achieving better robustness to noise. The ability of solving 3-degree-of-freedom position and the robustness to noise and magnetic-field imperfections are evaluated by simulation; the results show that the accuracies of translational and rotational motions are 10 µm scale and 0.1° scale in the case with noise of 0.01% of signal amplitude, while they are 100 µm scale and 10° scale in the case with the magnetic-field imperfections caused by parameter deviations. Comparison experiments with commercial sensors are conducted on a self-developed testing platform to verify the feasibility of the method, and the results show that the method can achieve sensing a large rotational angle and a large translational range with a simple implementation.