Theoretical Study And Control Methods Of Super High Speed And Large Thrust Linear Motor

The propulsion devices currently used extensively in space launches and trials are still chemical rocket launchers.Due to the high energy storage density and rapid burning rate of the propellant of the chemical emitter,the high temperature and high-pressure gas produced by the combustion makes the chemical emitter have a very high power density and can accelerate the spacecraft to an ultra high speed.However,limited by the mass of oxidant in the propellant and the limitation of the combustion temperature,the specific impulse of the rocket launcher basically reaches the upper limit,and it is difficult to increase the launch capability by reducing the proportion of the emitted fuel.In view of the limitations and deficiencies in the launch technology of chemical rockets,the search for an ultra-high-speed,large-load,and high-efficiency electromagnetic-assisted launch propulsion system has become an urgent need for humans.This article has conducted research on these issues.Firstly,through the theory of electromagnetic field,the air-gap magnetic field equation of the traditional continuous linear motor is established.The thrust and energy characteristics of the linear motor are calculated by solving the air-gap magnetic field,and the electromagnetic force density and energy characteristics of the linear induction motor and the linear synchronous motor are compared and analyzed..Through analysis,it is considered that the synchronous motor has a higher electromagnetic force density,but the induction motor has a larger thrust-to-weight ratio.According to the energy level characteristics and acceleration characteristics of ultra-high-speed electromagnetic emission,the thrust-to-weight ratio of the cored motor and the core loss at high speed are constrained to further increase the speed of the cored synchronous motor,and an ultra-high-speed and large-thrust air-core superconducting line is proposed.Synchronous motor solutions.Secondly,an ultra-high-speed,high-thrust,hollow superconducting linear synchronous motor was designed.The mathematical model of the air-core superconducting linear synchronous motor was established.Based on the model,the steady-state thrust and energy efficiency expressions of the motor were deduced,and the electromagnetic force and power characteristics of the air-core linear synchronous motor were analyzed.The accuracy of the derived theoretical model was verified by the finite element simulation method.Through parameter analysis,it is considered that the ratio of the air gap length of the motor and the length of the superconducting coil affects the distribution of the mutual inductance gradient.With reference to the currently used superconducting magnet parameters,the thrust characteristics and power characteristics of the superconducting hollow core linear motor were calculated.The results show that under the same stator parameters,the thrust density,thrust ratio,power factor and efficiency of superconducting hollow-core linear motors are much greater than those of iron core linear synchronous motors and linear induction motors.At last,the dynamic simulation of double-primary-long stator linear synchronous motor was performed.The peak-to-average force ratio of the motor was 1.0654,the power factor was 0.98,and the efficiency was 0.7756.Then,a control method of a linear synchronous motor is proposed.Based on the continuous mathematical model of the linear synchronous motor,the dynamic discrete model of the air-core linear synchronous motor is deduced;the mechanism and control algorithm of the current predictive control method are designed and analyzed.The delay is calculated and predicted for the digital control system.The control voltage command at a later time.The simulation results show that when the control period is 10 KHz and the motor pole pitch is 1.2m,the predictive current control method is used to ensure that the motor current phase lag does not exceed 10° when the motor operating speed reaches 333.4m/s.Aiming at the problem of large thrust fluctuation caused by gradient harmonic distortion of motor mutual inductance,a current compensation control strategy was proposed.Based on the position signal and velocity signal,the mutual inductance gradient information of the motor was calculated,and the desired current shape was designed according to the mutual inductance gradient and the desired electromagnetic force.The simulation results show that the current compensation control can effectively suppress the motor thrust ripple.Since the current compensation control is based on the known mutual inductance gradient information to solve the desired current,it can also suppress the thrust ripple caused by the harmonic distortion of the stator winding EMF.The simulation results show that the suppression of thrust ripple occurs when the number of phases per pole of the stator winding is small.The effect is also very good.This makes the stator structure of the motor simpler to design.At last,the principle prototype testing platform of air-core linear synchronous motor was built by using permanent magnet instead of superconducting mover.Equivalent current method was used to establish the model of permanent magnetic air-core linear motor.Through the static performance test of the motor,the accuracy of the design model was verified.The prediction current control and current compensation control algorithms are verified on the prototype test prototype.The test results are consistent with the simulation results,which shows the effectiveness of the control algorithm.Traction control experiments,test results verify the validity of the theoretical design and control methods.The dynamic emission test found that the power factor and efficiency of the motor are low,which is due to the too small magnetic induction generated by the permanent magnet.Therefore,the use of permanent magnets can only verify the principle of air-core motors.