Joint Motion Planning of Industrial Robot Based on Modified Cubic Hermite Interpolation with Velocity Constraint

Yasong Pu,Wenbin Zhang,Pan Zhao,Xiaojun Lin,Yaoyao Shi

doi:10.3390/app11198879

Yasong Pu, Wenbin Zhang + Show 3 more

Open Access

https://doi.org/10.3390/app11198879

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Abstract

As for industrial robots’ point-to-point joint motion planning with constrained velocity, cubic polynomial planning has the problem of discontinuous acceleration; quintic polynomial planning requires acceleration to be specified in advance, which will likely cause velocity to fluctuate largely because appropriate acceleration assigned in advance is hardly acquired. Aiming at these problems, a modified cubic Hermite interpolation for joint motion planning was proposed. In the proposed methodology, knots of cubic Hermite interpolation need to be reconfigured according to the initial knots. The formulas for how to build new knots were put forward after derivation. Using the newly-built knots instead of initial knots for cubic Hermite interpolation, joint motion planning was carried out. The purpose was that the joint planning not only satisfied the displacement and velocity constraints at the initial knots but also guaranteed C2 continuity and less velocity fluctuation. A study case was given to verify the rationality and effectiveness of the methodology. Compared with the other two planning methods, it proved that the raised problems can be solved effectively via the proposed methodology, which is beneficial to the working performance and service life of industrial robots.

Highlights

Industrial robots are widely used in handling, painting, welding, assembly, packaging and other fields
For the industrial robots’ PTP joint motion planning with velocity constraint, cubic polynomial planning has the problem of angular acceleration discontinuity, which will cause vibrations and impacts
As for quintic polynomial planning, angular accelerations at target points need to be given in advance and because it is hard to give appropriate angular accelerations in advance, it will lead to large velocity fluctuations which are not conducive to velocity control

Summary

Introduction

Industrial robots are widely used in handling, painting, welding, assembly, packaging and other fields. With the development of robot technology, industrial robots are gradually applied to polishing, monitoring, automatic manufacture system and so on [1,2]. The manipulator movements become more complex and need to satisfy higher working performances. Trajectory planning of industrial robots has to meet higher requirements. The most basic task of industrial robot motion planning is to meet the requirements for end-effector displacement and velocity [3]. Favorable trajectory planning should ensure smooth movements, fewer vibrations, impacts and mechanical wear so that it can improve working performance and extend service life [4]

Methods

Discussion

Conclusion