Research On Coupling Effect Of Two-Degree-of-Freedom Direct Drive Induction Motor

The realization of multi-degree-of-freedom（M-DoF）motion in traditional technology is usually completed by multiple single-degree-of-freedom（1-DoF）motors with intermediate transmission mechanism,which has the problems of complex structure,response slowly,inconvenient maintenance and difficult cooperative control.The M-DoF motor does not need the intermediate transmission link,and directly drives the load to realize rotary,linear and helical motions.It provides a new driving solution for industrial application fields that require M-DoF motion,such as mine intelligent drilling system,industrial robot and intelligent processing equipment.However,due to the particularity of its structure and the motion characteristics of M-DoF,between the rotating magnetic field and the traveling wave magnetic field,between the rotating motion and the linear motion,there are electromagnetic coupling and motion coupling effects,which affect the electromagnetic field of the motor and the distribution of the mover eddy current field.It not only reduces the operating performance of the motor,but also brings new theoretical and technical problems to the accurate modeling,optimization design and motion control of the motor.Therefore,aiming at its performance improvement and coupling effect suppression,this paper studies a linear-rotation two-degree-of-freedom direct-drive induction motor（2DoFDDIM）.Based on its electromagnetic design and characteristics analysis,coupling mechanism analysis,analytical modeling,coupling characteristics research,coupling effect suppression,and experiment are carried out.The main research work is as follows:（1）The electromagnetic design and characteristics analysis of 2DoFDDIM are carried out.According to its structural characteristics of’double arc stator,circumferential series,common mover’,the design index parameters and design principles are formulated.Based on the equivalent interchangeability of the double arc stator,the preliminary design of the key motor electromagnetic parameters is completed.The equivalent circuit model（ECM）considering the end effect is built and the electromagnetic design and characteristics analysis are carried out,which are verified by two-dimensional finite element analysis（2D-FEA）.Multi-objective optimization design and response surface methodology（RSM）are used to obtain the optimal combination scheme of key parameters affecting the performance of the motor to improve the electromagnetic characteristics of the motor.Considering the limitations of 2D-FEA,a3D-FEA model of the motor is established.A 3D finite element fast analysis method for2DoFDDIM is proposed to solve the motor characteristics and analyze the coupling effect between two degrees of freedom.The results show that the method is feasible to analyze the characteristics and coupling effect of 2DoFDDIM,furthermore saving the solving time.（2）The electromagnetic coupling effect of 2DoFDDIM is studied from two aspects including rotary coupling magnetic field（RCMF）and linear coupling magnetic field（LCMF）,and two perspectives including static coupling effect and dynamic coupling effect.Based on the analysis of the internal magnetic field of the motor in 1-DoF rotary,linear motions and M-DoF helical motion,the generation mechanism of RCMF and LCMF is explained.The 3D equivalent plate model of the motor is built,and the analytical modeling and characteristics analysis of the coupled magnetic field are carried out.The strength of the static coupling effect is evaluated according to the induced voltage generated by the coupling magnetic field in the unpowered degree of freedom.The speed coupling factors are introduced to characterize the influence degree of the dynamic coupling effect,and the characteristics of RCMF and LCMF are analyzed.The results show that the static coupling effect and dynamic coupling effect of RCMF and LCMF have consistent change rules.Their static coupling effect increases with the increase of power supply frequency and the absolute speed of the mover,while the dynamic coupling effect has a positive relationship with the rotary and linear speed.（3）Based on the analysis of the independence and unitarity of electromagnetic coupling effect and motion coupling effect,the motion coupling effect of 2DoFDDIM is studied from two perspectives of rotary motion coupling effect（RMCE）and linear motion coupling effect（LMCE）.According to the analysis of the changes of air gap magnetic field and mover magnetic field in helical motion,the essence of motion coupling is revealed,and the independent and unified internal relationship between it and electromagnetic coupling is clarified.After defining RMCE and LMCE,the additional thrustΔF_RMCE and additional torqueΔT_LMCE are used to characterize the hindrance of RMCE to linear motion and LMCE to rotational motion,respectively.Based on the simplified equivalent plate model,the expression of additional electromagnetic force between two degrees of freedom is derived,and the mathematical models of RMCE and LMCE are established.The proportion of additional force ratio k L-RMCE and additional torque ratio k R-LMCE is introduced to evaluate the influence of motion coupling effect.Then the correctness of the established motion coupling effect analysis model is verified by 3D-FEA.It is also found that the hindering effect of the motion coupling effect on the 2-DoF increases with the increase of the rotary speed and n R the linear speed v L of the synthetic helical motion.（4）The coupling effect suppression of 2DoFDDIM is studied from the perspectives of motor operating conditions adjustment,structure optimization,and 2-DoF motion control.Based on the adjustment of operating parameters such as motor running slip rate and power supply frequency,it is found that increasing the slip rate and appropriately reducing the frequency of the linear unit can suppress the coupling effect.From the structure of the motor,it is found that increasing the circumferential spacing of the double arc stator has a better suppression effect on LMCE.At the same time,the eddy current path of the mover is optimized,and a grid-type mover 2DoFDDIM with orthogonal slots on the surface of mover is proposed.Compared with the smooth mover structure,the coupling effect is weakened to a certain extent,which is beneficial to the performance improvement of the motor.In addition,the coupling inductance and the end effect coefficient are introduced to establish the motor mathematical model considering the coupling effect.The sliding mode adaptive control system is built based on the load observation to suppress the coupling effect in terms of motion control.（5）Prototype performance test and coupling effect experimental research.According to the design scheme of the 2DoFDDIM prototype platform,the engineering design of the prototype and its test platform is carried out,and the processing and assembly debugging are completed.A prototype experimental platform integrating motor body,drive control,guidance and positioning,detection and loading is built.Then the prototype performance test and coupling effect experimental analysis are carried out,and the experimental test results are compared with the analytical calculation and3D-FEA results to verify the correctness and feasibility of various analysis models.It provides theoretical and practical basis for the comprehensive research and industrial application of this type of M-DoF motor.There are 150 figures,54 tables and 152 references.