Abstract
To achieve high-accuracy tracking of a dual-linear-motor-driven (DLMD) gantry, high-level synchronization between redundant actuators becomes a non-negligible factor and also a difficult issue to be solved priorly. Especially, when both X and Y axes are simultaneously operating to accomplish complex tasks efficiently, additional coupling effects will be generated by the dynamic load presented on the crossbeam, which makes the synchronization issue more complicated than the case with static load. However, due to the absence of an accurate model to fully reveal the complete coupling characteristics, existing approaches to this issue still have inherent limitations. Therefore, this paper focuses on the systematic physical modeling and synchronization control of a DLMD gantry with a dynamic load presented on the crossbeam. A complete coupling mathematical model is established first, by fully considering two linear motions (X-axis and Y-axis) and also including the additional rotational motion of the crossbeam. Built upon the effective model information, corresponding solutions by compensating the dynamic load effects and actively controlling the rotational dynamics to regulate the internal forces have been proposed, leading to a novel adaptive robust synchronization control method. The results of comparative experiments verify the effectiveness and superiority of the proposed method in dealing with the synchronization issue subjected to dynamic load effects.
Highlights
Among the various types of precision Cartesian robotic systems, the H-type gantry with a dual-driven structure and direct actuators1–3 is widely used in industrial applications, in which a payload platform is driven by one motor along the crossbeam while two other parallel arranged motors are rigidly connected to drive the motion of the entire crossbeam
Combined with the basic requirements of highaccuracy tracking of both axes and high-level synchronization with dynamic load presented on the crossbeam for DLMD gantry systems, the detailed control objectives in this work are summarized as follows: Subjected to the aforementioned uncertainties and the dynamic load effects emphatically discussed in this paper, a proper control input uq is to be synthesized such that the linear motions of both axes x(t) and y(t) can track the corresponding smooth reference trajectories xd(t) and yd(t) as closely as possible, and simultaneously, the rotational motion α(t) has to be highly suppressed to avoid large internal forces during both transient and steady-state periods
The presented model clearly shows the generation of the rotational motion along with excessive internal forces, the dynamic load effects, and the complicated coupling properties in this system
Summary
Among the various types of precision Cartesian robotic systems, the H-type gantry with a dual-driven structure and direct actuators is widely used in industrial applications, in which a payload platform is driven by one motor along the crossbeam while two other parallel arranged motors are rigidly connected to drive the motion of the entire crossbeam. Taking into account two obvious linear motions (X-axis and Y-axis) and the usually ignored rotation of the crossbeam along with the deformations of bearing balls, an integrated 3DOF dynamical model is derived to clearly reveal the essence of dynamic load effects. Built upon this knowledge, following the idea by actively suppressing the rotational dynamics to effectively regulate the internal forces, a novel three-input three-output (TITO) synchronization control method is proposed. Both objectives are pursued in this paper, where the synchronization issue is mainly discussed
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