Research On Rotor Attitude Detection Of Spherical Motor Based On Mutual Inductance Modeling

In recent years,space motion robots,robotic arms and other precision mechanical devices have been more and more widely used,their multi-DOF movement requires multiple single-DOF motor combination to carry out,which leads to the whole system of large volume,low transmission efficiency and reliability of the problem.In order to solve these problems,multi-DOF spherical motors,which can be used in satellite attitude control,robot joints,photovoltaic trackers and other fields,are increasingly attracting the attention of scholars at home and abroad.The traditional rotor attitude detection method of single-DOF motor cannot be applied or directly applied to multi-DOF spherical motor,which becomes an urgent problem to be solved in the application of spherical motor engineering.At present,the attitude detection methods of spherical rotor at home and abroad can be divided into contact measurement methods and non-contact measurement methods according to whether the rotor is in contact with the measuring mechanism,among which the non-contact measurement is the future development direction.The mutual inductance between coils of wireless power transmission(WPT)system has good dynamic characteristics with the change of attitude.In this paper,it is applied to the rotor attitude detection system of spherical motor,and the rotor attitude detection method of multi-degree-of-freedom spherical motor based on mutual inductance modeling is studied.The main work and innovation of this paper are as follows:1.The basic structure and operation principle of the spherical motor are introduced.The rotor and stator coordinate systems are established based on the structural motion characteristics of the spherical motor.2.An attitude detection method based on multi-to-one coil mutual inductance model of circular coil is proposed and applied to the attitude detection of spherical motor.Two structural topologies are proposed,namely three-to-one structure and four-to-one structure,wherein the transmitting coil is uniformly arranged on the upper part of the rotor and the receiving coil is placed on the rotor shaft.A mutual inductance model was established.When the rotor of the motor rotated along the three motion states of pitch,spin and tilt,the receiving coil and the multi-transmitting coil would produce angular offset,and the rotor attitude could be obtained from the mutual inductance changes.The correctness of the model is verified by experiments.3.Based on the circular coil,the rotor position detection method of multi-to-one coils mutual inductance model with arbitrary coil receiving part is proposed.A mutual inductance model is established for the four different topologies of the receiving part,namely,triangle,quadrilateral,pentagonal and circular.Analysis and testing using 1 to 4 different numbers of transmitting coils show that higher accuracy can be obtained with 3 transmitting coils and 4transmitting coils.Experimental results show that the Angle detection error obtained by this model is basically controlled within 2%.4.Aiming at the problem that the forward rotor attitude method restricts the load motion range of the rotor output shaft,a new mutual inductance model of spherical receiving coil is presented and applied to the rotor attitude detection of spherical motor.The detailed mathematical derivation is given.The attitude estimation method is used to detect the permanent magnet spherical motor.The accuracy of the proposed attitude estimation method is verified by comparing with the results of MEMS.The detection error is less than 2%.5.Aiming at the problem that MEMS need to be disassembled and charged after working for a long time,a WPT system which can effectively charge MEMS is proposed.The system can detect the attitude information of the spherical motor rotor and realize multi-angle power transmission for MEMS without affecting the motion range of the spherical motor at the same time.The mutual inductance calculation model is established,and the experimental verification shows that the system can provide 5W of power and the transmission efficiency is up to 88% while effectively detecting the rotor attitude.