Recently, slurry shields are widely applied in tunnel constructions, since the shield tunneling method has distinct advantages over other methods in terms of efficiency, safety, environmental friendliness, etc. Based on the growth of traffic demand and the progress of shield construction technology, the shield tunnel diameter and the shield machine excavation diameter are constantly being refreshed, and the shield machines have a trend of super-large diameter. Large-diameter slurry shields face many challenges in the construction process, such as large cross-section, high rock strength and small turning radius. To improve the adaptability of large-diameter slurry shields in complicated stratum, a Cutterhead Swing System (CSS) and its control strategy are proposed. The cutterhead is fixed on one side of a radial joint bearing, a number of circular-distributed hydraulic cylinders are installed on the other side, and these compose the CSS. During the normal process of tunnel excavation, the hydraulic cylinders are locked and the cutterhead keeps vertically cutting. However, when the cutterhead tools wear or the cutterhead gets into jamming, the hydraulic cylinders will be active and then extend or retract to adjust the cutterhead pose flexibly. Thus, cutterhead clears out specific soil space, helping tool change or getting rid of shield’s jamming.To improve the accuracy and stability of the CSS which works in complicated stratum, a nonlinear pose control strategy has been proposed based on an adaptive extended disturbance observer. The strategy takes both the model uncertainties and the external disturbance into consideration. And the research process is presented as follows:First of all, analysis of cutterhead motion. The cutterhead space motion is decomposed based on Euler angles method, and the target displacement of each hydraulic cylinder is determined. The goal is to make the hydraulic cylinders track the target trajectory as closely as possible and adjust the cutterhead pose precisely.Secondly, dynamics model of the CSS. The nonlinear mathematical model is established according to the force balanced equation of hydraulic cylinders with load and disturbance, the flow equation of servo valves, and the flow continuity equation of hydraulic cylinders. Besides, the disturbance in the model is generally regarded as lumped parameter in previous researches.And then, controller design. The adaptive extended disturbance observer is based on hydraulic cylinder rod speed, which is one of the state vectors. The nonlinear controller is designed with a position tracking in outer loop and a load pressure control in inner loop. The outer position tracking loop is designed with sliding mode control to compensate disturbance estimation error, and the inner pressure control loop could provide the CSS the characteristic of servo valves. Both loops are designed via back-stepping method. The stability of the overall closed-loop system is proved based on Lyapunov theory.What’s more, validity of the proposed strategy is proved by MATLAB, AMESim and Adams co-simulation method.In conclusion, the results show that the proposed strategy has better performance in control accuracy and disturbance attenuation, compared with the traditional PID strategy.

Nonlinear Cutterhead Pose Control of Large-Diameter Slurry Shields in Complicated Stratum

Paper Proceedings: https://asmedigitalcollection.asme.org/FPST/FPMC2021/volume/85239

2021 ASME/BATH Symposium on Fluid Power and Motion Control (FPMC2021)

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