Abstract
This paper focuses on developing a pneumatic-driven and horizontal-structure linear delta robot (PH-LDR) and increasing its trajectory tracking performance on the three-degrees-of-freedom (3-DOF) space. With the investigation of inverse and forward kinematics, the parallel mechanism of PH-LDR is designed by using three high-power and low-cost rod-less pneumatic actuators (PAs) to track 3-DOF motion, and this has a horizontal structure to enlarge the workspace. Since the PH-LDR features nonlinear coupling among its three axes and is disturbed by the three high-nonlinear rod-less PAs, the tracking control performance is significantly decreased, subject to uncertain nonlinearity and parametric uncertainty. Therefore, a fuzzy-PID controller is used to achieve highly accurate 3-DOF trajectory tracking, and furthermore, this study exploits neural networks (NNs) to pre-compensate the impacts arising from the compressibility of air and temperature change. The control system for the PH-LDR also features an embedded controller that allows real-time control. Experimental demonstration verifies the developed PH-LDR with the proposed controller, and the dynamic tracking accuracy in 3-DOF trajectory can be achieved.
Highlights
Linear delta robots (LDRs) for industrial applications are superior to series manipulators, because they have a large carrying capacity and are highly precise and fast [1,2], so they are widely used for assembly detection, pick-and-place, positioning, and packaging [3]
This study develops a pneumatic-driven and horizontal-structure linear delta robot (PH-LDR) that consists of three rod-less pneumatic actuators (PAs) in a horizontal structure, so that a larger workspace can be yielded for the end-effector of LDR to achieve 3-DOF trajectory tracking
The parallel mechanism of the pneumatic-driven and horizontal-structure (PH)-LDR is analyzed based on a geometric method to determine the closed-form solutions of the kinematic chains
Summary
Linear delta robots (LDRs) for industrial applications are superior to series manipulators, because they have a large carrying capacity and are highly precise and fast [1,2], so they are widely used for assembly detection, pick-and-place, positioning, and packaging [3]. They are constructed using multiple independent closed-loop mechanisms, each of which has an arm that connects a fixed base to a moving platform. LDRs feature excellent positioning accuracy, because the position error from one single closed-loop kinematic chain is spread among the other chains. LDRs have some intrinsic drawbacks, such as a small workspace and complicated kinematics, but there has been increased demand for them in recent years
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