| At a time when the basic resources of ground transportation tend to be exhausted,rail transit has become more and more important,and the role of the subway is very prominent.The safety standards of natural ventilation in subway tunnel needs to meet,which provide the air required for the normal activities of underground personnel,and respond to sudden fire accidents in the tunnel to achieve timely smoke removal.On the other hand,there is a requirement about rate for solving the fault,and a suitable control method is also particularly important.According to the requirements of the project,the traditional direct torque control system(DTC)was adopted.The steady state and dynamic model of the asynchronous motor were introduced,and the principle of the working module of the system was analyzed.In the traditional DTC system,the motor obtains the maximum torque mainly through direct control of the motor flux linkage and torque.Applying it to the braking process and the reverse start process during the inversion process,the motor can obtain a constant,maximum acceleration,which speeds up the reversal process.The large performance disadvantages such as torque ripple were belong to the traditional DTC system,and the improvement scheme is given and the performance advantage of the improved DTC system is analyzed.The function and design principle of SVPWM and synovial controller involved in the improvement scheme are analyzed,and the speed sliding mode regulator of the system is designed.Then,the complete system simulates the position information of the stator-rock flux transformation when the motor realizes the fast forward-reverse process under the control strategy.The DTC system based on sliding mode controller is simulated and verified by the small power asynchronous motor.The simulation results show that the new DTC system has a certain improvement in the system response speed compared with the traditional DTC system,thus confirming the new DTC system.The correctness of the improvement program.In order to improve the dynamic response capability of the system and speed up the reversal process,torque current feedforward compensation is added to the current loop of the DTC system based on the sliding mode controller.The effectiveness of the feedforward sliding mode DTC system is verified by simulation.Because the disadvantages of excessive current,poor dynamic performance and slow braking speed are belong to the axial fan speed control system,there are certain conflicts with the subject appeal.Therefore,it is considered to realize the rapid change of wind direction by adjusting the blade angle to realize the axial flow fan at the specified time.Quickly change the wind direction without stopping inside,the rotation direction of the motor does not need to be changed and improve the efficiency and stable operation of the fan.Finally,the blade adjustment structure is designed.The axial flow fan blade adjustment structure is ultimately attributed to the torque transmitted to the worm,which is generated from the stepper motor.The fluid-solid coupling dynamics simulation of the blade under different installation angles(30~o,20~o,10~o)was carried out,and the stress distribution characteristics of the impeller were obtained.According to the conclusion of cloud image analysis,the stress cloud diagram with the blade installation angle of 0~o is selected as the basis for the output torque of the stepping motor in the blade adjustment structure.According to the transmission characteristics of the worm-turbine,the output torque that the stepper motor should give is calculated.The axial flow fan blade adjustment structure works normally,which ensures the feasibility of adjusting the structure. |
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