Bolts constitute a very important subset of mechanical fasteners. In order to tighten bolts, a degree of bolt preload scatter is to be expected. Since the torque control of tightening bolts is the most popular means of controlling the preload, an appropriate tightening torque becomes pivotal. This paper investigates the torque control problem of bolt tightening process. This process is not as simple as it looks because the inherently nonlinear process contains many uncertainties. To conquer the adverse effects of the uncertainties, this paper designs an adaptive-gain second-order sliding mode controller. Theoretically, such design can guarantee that the bolt tightening process has the closed-loop stability in the sense of Lyapunov. From the aspect of practice, the control method is carried out by a platform. Some comparisons illustrate the feasibility and effectiveness of the designed controller.

中文翻译：

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基于自适应增益二阶滑模的螺栓紧固过程扭矩控制

螺栓构成了机械紧固件的一个非常重要的子集。为了拧紧螺栓，预计螺栓预紧力会出现一定程度的分散。由于拧紧螺栓的扭矩控制是控制预紧力的最流行的手段，因此适当的拧紧扭矩变得至关重要。本文研究了螺栓紧固过程中的扭矩控制问题。这个过程并不像看起来那么简单，因为固有的非线性过程包含许多不确定性。为了克服不确定性的不利影响，本文设计了一种自适应增益二阶滑模控制器。理论上，这样的设计可以保证螺栓拧紧过程具有李雅普诺夫意义上的闭环稳定性。从实践来看，该控制方法是通过一个平台来进行的。