Research On Power Balance Control For Three-Motor Driving System At Starting Process Of The Pipe Belt Conveyor

Due to the viscoelastic mechanical properties of the belt and the location of the drive motors,a larger tension generated during the starting process of the pipe belt conveyor,which leads to the power allocated to each motor usually varies greatly,and power imbalance among the driving motors.In extreme cases,some motors may be overloaded and damaged.This paper proceeds from the viscoelastic characteristics of conveyor belt and the power balance control of driving system,focuses on the pipe belt conveyor whose head is driven by two motors and the tail is driven by one motor.Based on the three-phase asynchronous motor direct torque control,the three-motor power balance principles are presented.A method for power balance among motors based on master-slave control is proposed where the head master motor is controlled by speed given,the input torque of head slave motor is given by the output torque of the speed regulator in the master motor,and the tail slave motor follows the speed-given of the master motor.A joint simulation model is built to simulate and study the pipe belt conveyor.The simulation and test results demonstrate the validity of the proposed dynamic mechanical model and the effectiveness of the proposed control method.The main research work of the paper is as follows:(1)The mechanical characteristics of the conveyor belt are very similar to the viscoelastic model through the analysis of the composition of the conveyor belt,and the Kelvin-Voigt model is used as the basis for building the dynamic model of the conveyor belt.Based on Kelvin-Voigt model,the stress analysis of dynamic model of conveyor belt is analyzed and then the kinetic equation of belt conveyors is derived.The dynamic mechanical model of pipe belt conveyor is built which is focused on the pipe belt conveyor whose head is driven by two motors and the tail is driven by one motor.Then the dynamic simulation model of pipe belt conveyor is built in AMESim.The simulation results show that the variation of belt speed and tension can be analyzed during the start-up process,and the trouble caused by direct start.(2)The reason of power imbalance among the driving motors of pipe belt conveyor and the existing problems in its starting process are analyzed.The power balance control principle of three-motor drive system is explained,and a method for power balance among motors based on master-slave control is proposed where the head master motor is controlled by speed given,the input torque of head slave motor is given by the output torque of the master motor,and the tail slave motor follows the speed-given of the master motor.A suitable starting control curve is analyzed and selected as the starting control curve for the pipe belt conveyor.The power balance control model of three-motors drive system of pipe belt conveyor is built via MATLAB-Simulink.(3)A joint simulation model is built Based on the built AMESim simulation model and the power balance control model of the three-motor drive system.The dynamic characteristics of the conveyor belt and the dynamic changes of the output torque and load of the driving motors during the start-up process of the pipe belt conveyor are analyzed by simulation under the condition of no-load and full-load.The simulation results indicate that the dynamic characteristics of the conveyor belt are more stable than that of the direct start and the load distribution and output torque curves among the driving motors are well consistent.(4)The experiments were performed to evaluate the ability of balancing the power of the three motors in the pipe belt conveyor.The output power and output torque of the driving motor were tested at different filling rates,and the test results were analyzed.The test results indicate that the power output and output torque of the main and slave motors are almost the same in the starting process of the pipe belt conveyor under different filling rates conditions,and indicate that the method adopted in this paper can achieve the power balance control of the main and slave motors of the pipe belt conveyor,and the larger the filling rate of the material,the lower the balance among the driving motors.