Optimal path planning for a new type of 6RSS parallel robot based on virtual displacements expressed through Hermite polynomials. (August 2018)

• Record Type: Journal Article
• Authors: Milica, Lucian; Năstase, Alexandru; Andrei, Gabriel
• Is Part Of: Mechanism and machine theory. Volume 126(2018)
• Page Start: 14
• Page End: 33
• Publication Date: 2018-08
• Subjects: Parallel robot -- Path planning -- Virtual displacements -- Hermite polynomials; Machine theory -- Periodicals; Machinery -- Periodicals; Machines -- Périodiques; Génie mécanique -- Périodiques; Machine theory; Machinery; Periodicals; 621.81
• DOI: 10.1016/j.mechmachtheory.2018.03.015
• Languages: English
• ISSNs: 0094-114X

Abstract

Highlights: A novel method for optimal trajectory planning of a new type of 6RSS parallel robot, based on virtual displacements expressed through Hermite polynomials. Aiming to define the motion of the end effector, Hermite polynomial expressions have been used as time function of the geometric parameters. Determination of the optimal trajectory has been done by using two objective function for length and time minimization, respectively. The use of polynomial functions with the simplest expressions leads to a minimal effort for analyzing and formulating the optimization problem. A virtual investigation tool was devised to examine in-deep the workspace volume and the end effector trajectory which is decisive both in the design stage and operating phase. Abstract: The paper presents a method of determining the optimal trajectory of the characteristic point belonging to the end effector of a parallel robot with six degrees of freedom type 6R SS. The parallel robot is composed of a fixed plate and a mobile platform connected by six independent kinematic chains. Each of the six kinematic chains was part of one rotational actuating joint and two spherical joints. Based on the kinematic analysis, the motions of the end effector element were defined for manipulation operations using polynomial expressions of geometric parameters as time functions. By means of computational programs the polynomial variation of the motion parameters was determined. The data obtained were analysed on the basis of CAD programs through which the angular velocities of the actuating arms were determined when the end effector followed the trajectory described by the Hermite function. Using the same Hermite polynomials, two methods for optimizing the trajectory of the characteristic point were developed, the first intended to minimize its length and the second to minimize the runtime of the trajectory.