Research Of Main Drive VFD System's Control Strategy For Shield Machine

With the rapid development of the national economy,shield equipment has been widely adopted in the construction of national subway projects,Hydro-electric tunnels,mountain railway tunnels,national defense construction and other infrastructure projects.Shield equipment can adapt to the geological conditions determines that whether it can smoothly through a tunnel or not.Cutting wheel drive is in the forefront of shield tunneling,and most closely to the engineering geology.So cutting wheel is the core component in shield equipment.How to control drive system of the cutter wheel has far-reaching significance.This paper introduces the basic structure and working principle of the shield.The main drive of the cutterhead has the structure style include the electric drive and hydraulic drive.This paper introduces the current research situation of synchronous control of main drive,and designs the slip protection control PLC protection strategy of self-adaptive torque limiting.The simulation model is established by MATLAB,and the effectiveness of the control strategy is verified by the cutter wheel drive torque test bed which is drived by variable frequency.Firstly,the paper introduces the characteristics of the load of the cutter,and introduces the mathematical model of the induction motor vector control.Comparing and analysis of the current two main kinds of control mode of the main drive of cutter.According to the characteristics and performance of the two control methods,we choose open loop vector control for the foundation of the cutter frequency conversion control strategy.In simulation verification phase,the simulation model is carried out with MATLAB.Firstly,the mathematical model of slip control is established and the function of each module of model is explained.The control strategy model of uncoupled sliding loop vector control is established.The simulation analysis was carried out.It is verified that the softening effect of Droop algorithm on load loading of the blade is effective.In the end,the control optimization protection strategy for the slip control mode is proposed.The protection strategy include adaptive torque limitation strategy and the cutter run protection control in whole progress.In the experimental verification stage,a self-designed torque test bed for cutter variable frequency drive was tested.The style of adopted PLC is Siemens S7-300.The adopted PLC control asynchronous motor through control ATV71 inverter by means of communication.The load torque is given by the magnetic powder brake.In the two control strategies,PLC program and frequency converter parameter are setted respectively.The simulation is carried out to get the actual torque output response of cutter in the actual work environment.Finally,the curve fitting analysis is performed according to the output data from torque recorder.It can gain basic conclusions about the two different control strategy.The conclusions has some practical guiding significance for design and debugging of electrical control system in the electrical drive shield.