Abstract
This article proposes a dynamic feedforward control method for a four-degree-of-freedom parallel robot in decoupling space to improve the control accuracy and robust stability. The mass matrix and the gravity component are obtained from the rigid-body dynamic model that is formulated by means of the link Jacobian matrices and the principle of virtual work. Then using the positive definiteness of the mass matrix and singular value decomposition algorithms, a decoupling transformation matrix is obtained to convert the physical joint space to the decoupling modal space. In the modal space, a decoupling closed-loop controller design has been implemented for each driven leg. Afterward, by applying the gravity component of the dynamic model, a feedforward control subsystem has been designed to compensate the influence of gravity load on the parallel robot, which can further reduce the negative impacts caused by modeling inaccuracies. This numerical simulation analysis shows that the ideal control accuracy and robust stability have been achieved using the dynamic feedforward decoupling control method for the nonlinear and strongly coupled systems of the parallel robot. The described controller has a simple structure and can be easily realized in practice.
Highlights
Compared with serial robots, parallel robots have potential advantages of high precision, high stiffness, and heavy load capacity, so they have been widely applied in machine tools, motion simulators, high speed operation, and so on.[1,2,3,4,5] Due to the simplicity in design and versatility in application,[6,7] the control of low-mobility parallel robots has attracted lots of attention
A dynamic feedforward decoupling control has been designed for a 4-DOF parallel robot, which has strongly nonlinear dynamic characteristics in its physical space to provide an accurate and steady control strategy
The rigid-body dynamic model has been achieved based on the link Jacobian matrices and the principle of virtual work
Summary
Parallel robots have potential advantages of high precision, high stiffness, and heavy load capacity, so they have been widely applied in machine tools, motion simulators, high speed operation, and so on.[1,2,3,4,5] Due to the simplicity in design and versatility in application,[6,7] the control of low-mobility parallel robots has attracted lots of attention. Keywords Parallel robot, four degrees of freedom, rigid-body dynamic model, decoupling control, feedforward control To improve the dynamic response performance of the parallel robot control system and eliminate the influence of the nonlinear and coupling dynamic characteristics, the dynamic feedforward decoupling control method is designed based on the proposed dynamic model.
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