Research On Adaptive Load Sharing Control For Synchronous Driving System Of Cutterhead In Shield Machines

Shield machine is the Major technical equipment badly in need in national infrastructure construction, resource development and national defense construction. At present, the core technology of shield machine is mainly monopolized by a few developed countries. Due to the lack of core technology, China’s imports of hundreds of shield machine with limited service life has spent more than200billion yuan of funds. Therefore, it is of great significance to carry out theoretical studies of the shield machine and master its core technology, which reflects the development needs of China’s equipment manufacturing industry.The service conditions of shield machine is extremely complex. The driving interface load fluctuation caused by geological environment changes and multi field coupling of stress field, temperature field, seepage field in operation process, may lead into imbalance of redundant drive motors output torque in main driving system, even leading to the abnormal damage of drive shaft and other key components. Therefore, the shield machine driving synchronous control is one of the key technologies of shield machine. This article is in view of the shield machine main driving synchronous control, achieving the system’s adaptive load sharing, in order to adapt to the boring environment changes and improve the driving safety and efficiency.The main factors to affect the equilibrium distribution of drive torque include load fluctuations, the nonlinear factors of the transmission mechanism and the synchronization performance of the control system. The study is carried out around the above factors.Analyze the cutter torque ripple characteristics in complex geological conditions, study the impact of geology, shield depth, the driving speed and the cutter speed on load fluctuations, which can further determine its impact on the main drive system load sharing performance. Establish the load transfer model of main driving system with the multi-structural constraints of cutter structure, main bearings, supports, and the coupling of bending and torsion. Gear transmission system dynamics model is established considering the nonlinear factors of gear transmission, drive source and variable load effect.Establish the mathematical model of main driving system considering the nonlinear factors of gear transmission and the multi-motor parameter dispersion, based on multi-motor control system model and gear transmission system model. The validity of the model is verified through the simulation analysis method.Research the system synchronization performance using the existing main drive system control method, and a new ring-coupled synchronous control structure is proposed, which is closed-loop to the synchronization index, and can effectively improve the synchronization performance. A control parameter adaptive method is proposed which make motors have good dynamic and static performance. Put forward an algorithm to predict the current value trend of offset using historical data, and adjust the motor torque given value according to the predictive value, further improving the synchronization performance. Based on the actual engineering data simulation, verify the validity of the proposed control method. Design and set up the experiment platform with the gear transmission system and multi-motor drive system. The comparison of the synchronous performance of the two kinds of control strategies under the same load case is given to verify the proposed control strategy is effective.The research results show that the cutterhead torque decreases as the the muddy clay content increases, the degree of the cutterhead torque fluctuations increases linearly with the shield, increases nearly linear with the driving speed growth, and reduces in exponential form with the cutterhead speed growth. The oscillation amplitude of Gear load sharing coefficient suffer a big effect from load fluctuation rate, gear nonlinear factors and rotation speed of cutterhead, and the dispersion degree of gear load sharing coefficient curves is impacted by synchronous performance of driving torque, that is the load sharing coefficient of gear transmission in shield machine is influenced mainly by multi-driving synchronous performance.Put forward the electromechanical coupling model of shield machine main driving system based on a gear transmission system with a multi-motor synchronous control system as an organic whole. The validity of the model is verified through the simulation analysis based on real engineering data. The cause of the broken shaft accident is revealed that the existing synchronous control methods of cutterhead motor-drive system are open-loop control for the synchronization control targets without real-time synchronization error compensation, which have led to the synchronization performance of the existing main driving system is not ideal. When overloaded and load fluctuations, the drive shaft torque is not balanced, and even could lead to the safety shaft fracture or drive components of non-normal damage.The validity of the new control strategy is proved through mechanism analysis, and the simulation based on the actual engineering data verifies the superiority of the proposed control method. The simulation results show that system synchronization error transiently increases in load mutation, and increases with the increase of it. The new strategy can make the system synchronization error greatly reduced, thus it can effectively adapt to load mutation, and reduce shaft broken accident.The experimental table for main driving system can realize the comparison experiment of different synchronous control strategies, with monitoring of motor speed, torque and current data. The experimental results coincide with the simulation results, which can prove the validity of the the model and the experimental method, and the effectiveness of the new control strategy.