Research On Dynamic Characteristics And Control Strategy Of Flip-flow Screen Driven By Double Motors

The excitation motor of the single-motor-driven flip-flow screen is mounted on the fixed screen frame.The amplitude and the phase for the fixed screen frame and the floating screen frame vary according to the amount of incoming material.At the same time,the vibration phase difference for the two screen frames is difficult to maintain at 180 degrees,which is the ideal angle.Resulting in the polyurethane screen panel,during the movement process,cannot reach the optimal acceleration value required for material ejection,so that the collision possibility of the coal particles is relatively low,and the screening efficiency is undermined.To solve the problems mentioned above,a flip-flow screen principle model driven by double motors and its control system was established.Compared with the ordinary flip-flow screen,the two screen frames in the double-motor-driven flip-flow screen principle model control system are driven by two separate motors,and the control system is connected with the two excitation motors.The vibration phase difference for the two screen frames reaches 180 degrees by changing the speed and phase of the excitation motor of flip-flow screen,so that the exciting force on the fixed screen frame was reduced,and the ideal dynamic characteristics of the flip-flow screen can be realized.In this thesis,first,the mechanical model for the principle model structure of the double-motor-driven flip-flow screen was established.The mathematical model of the vibration system was established through the Newton’s second law method and Lagrangian method respectively.The vibration displacement and the vibration phase angle between the fixed and floating screen frame were obtained along x and z direction.By solving the differential equation,the relationship between the vibration phase difference angle for the two screen frames,and the phase difference angle for the two eccentric blocks of the double excitation motors can be obtained,so that the control target for the phase difference for the eccentric blocks of the two excitation motors can be obtained.The motion equation for the main shaft of the excitation motor under the condition of variable angular velocity was established using the analytical method,and the average vibration damping torque of the excitation motor under a periodic synchronous operation state,namely the external load characteristic of the excitation motor,was obtained.Three-dimensional modeling of the principle model of flip-flow screen driven by double motors was established in Solidworks.The corresponding constraints,drive,stiffness,damping were added to multi-rigid dynamics simulation software Adams.The acceleration,displacement,vibration characteristics and vibration phase difference of the two screen frames of the double-motor-driven flip-flow screen were studied from start-up to smooth operation,which prove the rationality of the structure of flip-flow screen driven by double motors and provide a theoretical basis for the flip-flow screen virtual prototype.In constant voltage ratio control,the voltage-frequency coordinated control mode and its corresponding mechanical characteristics of the constant voltage frequency ratio below the fundamental frequency and the constant voltage frequency conversion above the fundamental frequency were analyzed.According to the load characteristics of the excitation motor,the electromechanical coupling mathematical model of the asynchronous motor based on constant voltage ratio was built in Simulink.A cross-coupling-based speed synchronization control algorithm was adopted between the double excitation motors.It can be seen that the double motor has good following performance from the start to the smooth operation stage.A principle prototype of a double-motor-driven flip-flow screen and dSPACE semi-physical simulation platform were built for experimental research.According to the four operating states of the double eccentric blocks phase difference of the two screen frames excitation motors in one cycle,the speed synchronization based on cross-coupling and the improved Bang-Bang phase compensation control algorithm were proposed.According to the structure parameters of the double-motor-driven flip-flow screen principle prototype and the solution of vibrational differential equation,it can be obtained that the vibration phase difference of the two screen frames can reach the ideal 180 degrees when the phase difference of the double eccentric blocks are 170 degrees.The analysis of the experimental results shows that the phase difference of the eccentric blocks between the double excitation motors and the vibration phase difference between the two screen frames satisfy the control requirements,which proves the stability,rapidity and accuracy of the control strategy.