Thrust-vectoring automatic shield tunneling technology: Method, verification and application

Recognizing the formidable challenge of achieving millimeter-level precision in controlling shield machine attitudes amidst thrust forces exceeding thousands of tons on a global scale, a thrust-vectoring automatic shield tunneling technology was introduced to effectively mitigate potential inaccuracies stemming from human intervention. Initially, a load-thrust “dual-vector” motion control mechanism was adopted, grounded in defining the shield thrust vector and establishing the interactive correlation between shield attitude deviation points and thrust action points in both horizontal and vertical orientations through comprehensive data assessments. Subsequently, a parallel proportional-integral-derivative control law was devised for stability control of shield machines, delineating the functional link between alterations in shield attitudes and displacements of thrust action points, with initial validation conducted via full-scale model trials. A motion trajectory for correcting shield attitudes was devised, and a thrust vector control approach was formulated by amalgamating feedforward calculations with feedback adjustments. The application of this thrust-vectoring automatic tunneling technology in a large-diameter shield tunneling endeavor yielded the subsequent key findings: a consistent deviation of approximately 2.5% was upheld between target and actual thrust forces, with actual shield velocity managed within a –1 to +1 mm/min range from the target value. To ensure robust steering capability of the shield machine, target thrust moments in both horizontal and vertical directions marginally exceeded actual values, with satisfactory execution. The interplay between shield attitudes and thrust action points in both horizontal and vertical dimensions exhibited a characteristic akin to “sugar-coated haws on a stick”. Despite notable “kowtow” occurrences during segment assembly, statistical analysis indicated that deviations in shield attitude in horizontal and vertical planes were ultimately contained within –20 to +5 mm and –45 to –28 mm ranges, respectively, markedly surpassing average manual control standards.