A nonlinear adaptive (NA) controller in the task space is developed for the trajectory tracking of a 2-DOF redundantly actuated parallel manipulator. The dynamic model with nonlinear friction is established in the task space for the parallel manipulator, and the linear parameterization expression of the dynamic model is formulated. Based on the dynamic model, a new control law including adaptive dynamics compensation, adaptive friction compensation and error elimination items is designed. After defining a quadratic performance index, the parameter update law is derived with the gradient descent algorithm. The stability of the parallel manipulator system is proved by the Lyapunov theorem, and the convergence of the tracking error and the error rate is proved by the Barbalat's lemma. The NA controller is implemented in the trajectory tracking experiments of an actual 2-DOF redundantly actuated parallel manipulator, and the experiment results are compared with the APD controller.
The realization of automated chemical experiments by robots unveiled the prelude of artificial intelligent laboratory. Several AI-based systems or robots with specific chemical skills have been demonstrated, but conducting all-round scientific research remains challenging. Here, we present an all-round AI-Chemist equipped with scientific mind that is capable of performing all essential steps required for chemical research. Based on a service platform, the AI-Chemist is able to automatically read the literatures from cloud database and propose experimental plans accordingly. It can control a mobile robot in house or online to automatically execute the complete experimental process on 14 workstations, including synthesis, characterization, and performance test. The experimental data can be simultaneously analyzed by the computational brain of the AI-Chemist through machine learning and Bayesian optimization, allowing to propose new hypothesis for next iteration. The competence of the AI-Chemist has been scrutinized by three different chemical tasks. All-round AI-Chemists with scientific mind may dramatically change the landscape of the chemical laboratory in the future.
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