Balancing of the Orthoglide Taking into Account Its Varying Payload

Jing Geng,Damien Chablat,Philippe Lemoine,Vigen Arakelian

doi:10.3390/robotics10010030

Abstract

For fast-moving robot systems, the fluctuating dynamic loads transmitted to the supporting frame can excite the base and cause noise, wear, and fatigue of mechanical components. By reducing the shaking force completely, the dynamic characteristics of the robot system can be improved. However, the complete inertial force and inertial moment balancing can only be achieved by adding extra counterweight and counter-rotation systems, which largely increase the total mass, overall size, and complexity of robots. In order to avoid these inconveniences, an approach based on the optimal motion control of the center of mass is applied for the shaking force balancing of the robot Orthoglide. The application of the “bang–bang” motion profile on the common center of mass allows a considerable reduction of the acceleration of the total mass center, which results in the reduction of the shaking force. With the proposed method, the shaking force balancing of the Orthoglide is carried out, taking into account the varying payload. Note that such a solution by purely mechanical methods is complex and practically inapplicable for industrial robots. The simulations in ADAMS software validate the efficiency of the suggested approach.

Highlights

It is known that a mechanical system with an unbalanced shaking force/moment transmits substantial vibration to the frame
To achieve the shaking force balancing through the approach described above, it is necessary to consider the relationship between the input parameters ρ = and the center of mass positions P(px, py, pz) of the Orthoglide
It is known that the shaking force balancing by counterweights mounted on the moving links is more appropriate for serial and planar parallel manipulators

Summary

Introduction

It is known that a mechanical system with an unbalanced shaking force/moment transmits substantial vibration to the frame. The methods of shaking force balancing can be arranged as follows: By adding counterweight in order to keep the total mass center of moving links stationary [1]. S(t) i.e., to apply an optimal control of the total mass center of moving links that allows one to reduce the maximal value of its acceleration For this purpose, let us consider the control of the spatial parallel manipulator Orthoglide through the motion planning of its center of mass. To achieve the shaking force balancing through the approach described above, it is necessary to consider the relationship between the input parameters ρ = (ρx, ρy, ρz) and the center of mass positions P(px, py, pz) of the Orthoglide.

Illustrative Example via CAD Model

Balancing of the Orthoglide without Taking into Account the Payload

Sensitivity Analysis of the Shaking Force and Shaking Moment

Findings

Conclusions