Though computer technology has brought about virtual manufacturing to expedite design and analysis through simulation and visualization, machines remain essential, as ultimately products need to be made. This paper presents a new type of 5-axis parallel machine tool based on a 3 degrees of freedom parallel platform manipulator with base mounted prismatic actuators. This machine tool is different from the Stewart platform type parallel machine tool in that its feed motion in X-direction is realized by the worktable on which work-piece is fixed and the parallel manipulator sliding on the gantry structure of the machine tool is responsible for the translation along Y-direction instead of the movable platform of the manipulator. Due to this special architecture, the workspace in X-direction and Y-direction of the new machine tool is enlarged greatly. And its rigidity is higher because of the adaptation of gantry structure. This machine tool is controlled by a PC based NC system in simultaneous 5 axes control mode.
Performance evaluation is a necessary stage in development of tracking control strategy of autonomous vehicle system, which determines the scope of application and promotes further improvement. At present, most of the tracking control strategies include performance evaluation. However, performance evaluation criteria differ from work to work, lacking comprehensive evaluation system. This article proposes a multidimensional integrated tracking control evaluation system based on subjective and objective weighting, taking into account the tracking accuracy, driving stability, and ride comfort. Through the co-simulation of CarSim and Simulink, qualitative analysis and quantitative analysis based on multidimensional evaluation system of five coupled longitudinal and lateral control strategies (lateral: pure pursuit feedforward control, dynamic-model-based optimal curvature control (dynamic feedforward control), Stanley feedback control, kinematics feedback control, and dynamic feedback control; longitudinal: the incremental proportion–integration–differentiation control) under typical operating conditions are carried out to analyze the operating range and robustness of each tracking control strategy. The results show that the Stanley tracking control strategy and the dynamic feedback tracking control strategy have a wide range of applications and robustness. The consistency of qualitative analysis results and the quantitative analysis results verify the validity and feasibility of the evaluation system.
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