A Force/Motion Control Approach Based on Trajectory Planning for Industrial Robots With Closed Control Architecture

Alejandro Gutierrez-Giles,Marco A. Arteaga,Carlos A. Cruz-Villar,Alejandro Rodriguez-Angeles,Luis U. Evangelista-Hernandez

doi:10.1109/access.2021.3085528

Abstract

Most industrial robots are provided by the manufacturer with a controller that cannot be modified by the user (e.g. a standard PID). This arrangement is commonly referred to as closed control architecture, since it is not possible to program arbitrary control laws. For the implementation of novel algorithms, it is on the contrary necessary to employ an open control architecture, which allows programming any control scheme. For that reason, it is customary to have testbeds that are made up of robot manipulators specially designed for this goal. Another disadvantage of the closed control architecture is that the controller provided by the manufacturer usually does not include a force control term since it allows only to program desired motion trajectories. To overcome these drawbacks without physically modifying the closed control architecture, this contribution presents a novel approach to simultaneously follow position and force trajectories by employing only motion planning, i.e. only by choosing the desired position trajectory. The approach is especially well suited for DC motor actuators with large gear reduction ratios as those of many industrial robots. The convergence of the manipulator position and applied force depends exclusively on the performance of the controller provided by the manufacturer. The approach is tested on a dual-arm cooperative manipulation system made up of two ABB IRB-2400 industrial robots with closed control architecture.

Highlights

Nowadays, as new and more complex tasks are performed by robots in the industry, they need to interact with human beings, other robots, or with the environment, and to move objects or tools
This configuration is known as closed control architecture since the control law is already programed and it is not meant to be modified at
For the user to implement innovative control schemes it is necessary to have an open control architecture, which for industrial robots can usually be achieved by replacing the manufacturer’s controller either with a higher option provided by the same company or by a ‘‘homemade’’ control device

Summary

Introduction

As new and more complex tasks are performed by robots in the industry, they need to interact with human beings, other robots, or with the environment, and to move objects or tools. For the user to implement innovative control schemes it is necessary to have an open control architecture, which for industrial robots can usually be achieved by replacing the manufacturer’s controller either with a higher (more expensive) option provided by the same company or by a ‘‘homemade’’ control device. This may allow the implementation of force controllers designed by the user, with external sensors and algorithms built at a high level [3]. It is worthy to notice that the performance of the overall system is limited by sampling and bandwidth considerations [4]

Methods

Discussion

Conclusion