Research On Transverse Flux Permanent Magnet Machine And Its Control System

In recent years,as a novel invert-fed and Permanent-magnetic machine, Transverse flux permanent-magnetic machine(TFPM) received wide attention. Particularly,they are attractive for electric vehicles,electric ships and industrial robots since they offer the distinct advantages of high torque density for electric launch and low speed operation for direct drive.Although so many fine characteristics,TFPM hasn't been commercialized up to now.The main drawbacks are the complicated configuration,the difficulty in manufacturing and higher cost of production,which restrict it development.According to what have done before, a novel TFPM geometry with assembled stator arrangement is proposed here. Based on this prototype,in-deep research works on the control system are carried out and have a good success as below.Firstly,a novel TFPM configuration which features an assembled stator and a sandwiched PM rotor is proposed.The stator is made up of U-cores which embrace the armature winding.These U-cores are configured by the outer core,inner core and joint core,which the outer and inner core of stator-poles can be inserted into slots easily just like the building blocks.Such assembly involves simple mechanical structures and hence low manufacturing cost.As no dimension is really larger than the others,the TFPM has a complex three-dimension(3D) flux pattern where the magnetic flux passes radially,axially and circumferentially from the rotor to the stator.A 3D equivalent magnetic network(3DEMN) method suitable for 3D electromagnetic analysis is used to analyze the prototype,and some solution, such as air-gap flux distribution,no-load EMF,static torque.Experimental results agree with the design calculation.Secondly,the mathematic model for TFPM was established.The torque expression is achieved when sinusoidal armature current is applied.According to the phase-decoupling characteristic of TFPM,a novel torque control strategy based on the scalar conception of current is put forward.The shaft torque can be obtained by controlling the amplitude and the phase angle of the armature current without resort to vector transformation.The theory of power factor in TFPM is discussed and the relationship between the power factor and torque is studied in this paper. An universal modularized digital simulation model was developed on the platform of MatLab/SimuLink software package.Based on this platform,dynamic digital simulation for the prototype and its control system were executed,the operational performances under different modes are to be analyzed.Thirdly,the speed controller and current controller of the TFPM control system are discussed.The fuzzy-tuning PI controller is analyzed and designed for speed controller.Experiments and simulation results demonstrate that the fuzzy-tuning PI controller is superior to the traditional PI controller.A new stationary-frame(P+Resonant) ac current control strategy that can eliminate the steady-state error is proposed and applied to the control of transverse flux permanent-magnet machine(TFPM).Based on the principle of the modulation and demodulation,this ac controller can achieve the same frequency response characteristic as the equivalent dc controller.The validity of control system of TFPM using this current control strategy is confirmed by simulation results.Fourthly,a digital control system based on TMS320LF2407 DSP is designed and implemented.Arming at the limitation of sine-wave drive technique in hall sensor position signal with low resolution,a research on the continuous rotor estimation technique and related sine-wave driving technique is conducted.The working principal of rotor estimation and its realization process are given in the paper as well as the analysis on the estimation error.Finally,the frequency modulated pulse width modulation(PWM) is introduced.Based on the Fourier Transformation and Bessel function,the power spectral density of the SPWM voltage-source H-inverter with periodic and randomized switching frequency is presented.Since the chaotic sequence has the randomized characteristic and continuous power spectrum,a low EMI non-periodic modulation strategy based on chaotic sequence obtained from the logistic map is proposed.With the adoption of the chaos-based SPWM technique, the resulting power spectrum of the voltage-source H-inverter can be compelled to be continuous,while the harmonic peak can be reduced by 15dB.Both computer simulation and experimental results is given to verify the proposed modulation strategy.