Research On Multi-motor Cooperative Control Strategy Of Radial Circular Braider

Three-dimensional braided fabrics have excellent mechanical properties and are widely used in automobiles,ships and medical devices.Based on the characteristics of braider system and braiding technical requirements,this paper takes a large radial ring braider as the research object and researches its control technology,especially multimotor cooperative control strategy,in order to improve braiding efficiency and quality.Permanent magnet synchronous motor(PMSM)is usually used as the electrical drive part of the braider.Current ring is the inner ring of PMSM.Its control accuracy and performance are the key factors to determine the control accuracy and performance of the braider system.Aiming at the tedious calculation process of traditional three-vector model predictive current control,this paper proposes a simplified three-vector model predictive current control,which can effectively reduce the calculation amount and reduce the calculation burden,thus further improve the system steady-state performance by increasing the sampling frequency.Aiming at the difficult problem of system optimization caused by the difference of electrical and mechanical characteristics of radial circular braider,this paper takes a large radial ring braider as the research object and establishes a braider mechatronics system model.On this basis,the influence of non-smoothness,static transmission error,timevarying stiffness and time-varying damping of gear drive system backlash stiffness model on motor output torque is analyzed.In order to solve the problem of large output torque deviation between motors of braided ring motor unit in parallel control,this paper applies torque equalization control strategy to multi-motor synchronization control of braided ring motor unit according to the characteristic that each motor of braided ring is connected by gear hard shaft.It can effectively reduce the deviation of output torque between the motors,avoid overloading or even burnout of individual motors for a long time under heavy load,and further improve the overall load resistance of the system.For braided ring motor unit and sliding table motor speed,the proportional relation must be satisfied.However,in the starting and acceleration and deceleration stage,when traditional cross-coupling control is adopted,the compensation amount of tracking error is large due to the large error between actual speed and given speed.Therefore,under the limit of output amplitude of speed loop,the given current value of each motor final speed loop controller output to current loop controller is equal,and the coordinated error compensation amount is invalid.This causes the problem that the slightly loaded sliding platform motor takes longer time to reach the synergy requirement than the braided ring motor because it tracks its own speed too fast in pursuit of fast reaching the given speed.A cross-coupling decoupling control is proposed,which is suitable for two groups of motors whose rotational speeds need to satisfy the proportional synergy relationship.The control decouples the tracking error compensation from the synergetic error compensation and reduces the tracking error compensation to below the limit value in a certain proportion,and then couples with the synergetic error compensation.This ensures that the amount of coordinated error compensation is not weakened under the limit of speed ring output,and shortens the time for braided ring motor unit and traction platform motor to reach the coordinated requirements.In order to realize the control of the braiding workshop,a control software system for different braiding angles is developed.The experimental verification based on the system shows that the braider mechatronics system model established in this paper is accurate and the torque balance control strategy and cross-coupling decoupling control strategy are effective and feasible in the multi-motor collaborative control of radial circular braider.