Two-stage two-dimensional force allocation strategy for tunnel boring machines based on a region-reconfigurable thrust system

Determining the group forces of the thrust system is essential for trajectory control of tunnel boring machines (TBMs). Existing methods for selecting an optimal solution mainly consider the force variance among groups, while ignoring other constraints, such as uneven segment loading and excessive hydraulic shock. In this study, we develop a more comprehensive and robust framework for force allocation. First, a novel region-reconfigurable hydraulic system is designed, which enforces consistency among the forces acting on each segment. Then on this basis, for the ramping-up tunneling stage, quadratic programming (QP) is used to optimize force uniformity across the spatial dimension. Compared to the on-site allocation result, the improvement in force uniformity reaches up to 32.89%. Moreover, to address the hydraulic shock caused by excessive adjustment to the force, hydraulic compliance is introduced and optimized together with force uniformity using the non-dominated sorting genetic algorithm II (NSGA-II), which outperforms weighted QP by 1.25×10 6 kN 2 in uniformity and 2.86 kN 2 in compliance. Analyzing performance in the steady tunneling stage, the service life of the components improves significantly. To avoid a non-existent solution for the thrust force vector, a genetic algorithm-based error tolerance method is developed. Therefore, all deviation rectification commands can be answered with a minor compromise of up to 3% in the fitting accuracy of the thrust force vector. In summary, this framework enhances the adaptability and robustness of the force allocation strategy, providing a reliable foundation for TBM trajectory control.