Spherical mobile robot is a special non-chained nonholonomic system with underactuation and strong coupling, which make its trajectory tracking control very difficult and complex to realize. Precise trajectory tracking control depends on concise and accurate dynamic model. However, the current researches of trajectory tracking control rarely considered the influence of nonlinear factors and uncertain disturbances of spherical robot. In order to achieve strong robustness and anti-interference of trajectory tracking control of spherical robot, taking spherical mobile robot driven by a two-degrees of freedom pendulum as the research object, its complete dynamic model was established with Boltzmann-Hamel equation and simplified to obtain the one easy to control and with the key motion characteristics. Aiming at the modeling uncertainty of the spherical robot and the environment disturbances that may be encountered during movements, an adaptive sliding mode trajectory tracking control based on double power reaching law was proposed and proved to be stable by Lyapunov theorem. The effectiveness and robustness of the proposed control law are verified through simulations.
The plate girder bridge accounts for a large proportion of bridge types for its advantages of simple structure and convenience in construction. However, during the service stage, it is easy to suffer the hinge joint diseases, which badly weaken the integral rigidity of superstructure and affect the operation safety of the bridge. This paper presents a treatment technology for hinge joint diseases without interrupting traffic, and the main operation steps and key points of the technology are summarized. Through an example of the reinforcement of a plate girder bridge, the deformation data before and after the reinforcement is measured and compared, which verifies the effectiveness of the method.
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