Kinematics and robust control of a novel 3-RRPU parallel mechanism
Most of the existing three-translation parallel mechanisms have more than one forward solution and are difficult to achieve precise and stable motion control.Therefore,a novel 3-RRPU parallel mechanism with three translational degrees of freedom was proposed,and the kinematics and dynamics and trajectory tracking control method of the parallel mechanism was researched.Firstly,by using the screw theory,the mechanism principle of implementing three translations was analyzed,and the drive input joints were chosen and demonstrated,and the characteristics of platform singularity,drive singularity,and branch-chain singularity of the parallel mechanism were analyzed.Secondly,the kinematics model of the parallel mechanism was built with the kinematics theory,and the forward and inverse position analytic solutions were derived.Thirdly,by using the Lagrange's dynamics theory,the rigid-body dynamics model of the parallel mechanism within the operating space was set up.Finally,a nonlinear feedback decoupled adaptive slide-mode trajectory tracking control method was proposed,and the stability of the trajectory control method was proved,based on the dynamics model of the parallel mechanism,the accuracy and drive moment simulations of the trajectory tracking control were implemented.The research results show that the mechanism has unique analytic forward position under general space configuration,and there are very few of the platform and drive singularity configurations of the mechanism and there is no branch-chain singularity configuration.The proposed trajectory tracking control method can enable the mechanism to achieve high-precision complex trajectory tracking of 0.002 m under a load of 20 kg,a speed of 0.18 m/s,and an acceleration of 0.12 m/s2,and especially,the trajectory tracking control method based on the Sigmoid function can effectively weaken chattering of the control moment,which provides new method for the implementation of three translational motions of high-speed,high-precision,and high-performance in the industrial field.
three-translation parallel mechanismforward position solutionsingularityscrew theorynonlinear feedback decouplingadaptive sliding mode trajectory tracking control methodmechanism operating space
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