Force Controlled Robotic Surface Finishing with Variable Tool Centre Point (TCP)
PUBLICATION DATE: 8 August, 2023 PUBLICATION AUTHOR/S: Balci, B, Roberts, J, Donovan, J & Corke, PWritten by Barış Balcı Balci, PhD researcher from QUT funded through the IMCRC and the Australian Cobotics Centre.
IEEE Robotics and Automation Society’s (RAS) flagship conference on automation, the IEEE Conference on Automation Science and Engineering (CASE), is just around the corner! QUT Researchers from the Australian Cobotics Centre will present a paper at CASE 2023, which will be held on 26-30 August 2023 in Auckland, New Zealand.
The paper, “Force Controlled Robotic Surface Finishing with Variable Tool Centre Point (TCP)” by Barış Balcı, Jonathan Roberts, Jared Donovan, and Peter Corke investigates the idea of updating an industrial robot’s tool centre point during a surface finishing task to create better contact between an abrasive tool and a workpiece.
The tool centre point (TCP) is a coordinate frame defined somewhere on the tool, which the robot uses to position the tool to a desired pose. Although the definition of the TCP drastically affects how a contact between the tool and the workpiece is initiated, traditionally, TCP is determined once before programming and remains unchanged. The paper proposes two methods for online adjustment of the TCP to improve contact quality. The first method uses the surface normals of the workpiece, and the second uses human input.
In the experiments, an orbital sander was used to finish a curved cast aluminium workpiece. During the tests of the first method, the TCP was initially defined on the centre of the sanding disc and changed according to the surface normal information gathered from the workpiece’s CAD model. When the TCP was on the centre of the disc and constant, the tool couldn’t create proper contact with some of the sections on the defined finishing path. On the other hand, the variable TCP approach ensured that the tool always had proper contact. In the cases where the surface normal information is not useful, the user input-based second method can be used for achieving desired contact. In this method, the user provides the desired TCP configurations and their corresponding timing beforehand. Based on the time, the robot transitions between the given TCPs while following the finishing path. This method was also tested on the same setup, and it showed it could cover more sections than the constant TCP approach. Both methods were equipped with an admittance controller to ensure the TCP change can occur while keeping the applied finishing force constant. During the experiments, the TCP change in the first method did not cause significant disturbances, but poorly chosen user inputs for the second method led to uneven force distribution.
While a constant TCP can be enough for most robotics applications, the proposed variable TCP approach can improve a robot’s capability when dealing with complex geometries.
More information about CASE 2023 can be found here: https://case2023.org/
Full details on Baris’ PhD research can be found on the Australian Cobotics Centre website: https://www.australiancobotics.org/project/project-1-4-robotic-surface-finishing-for-custom-manufacturing/
RELATED PROGRAM/S:Biomimic Cobots RELATED PROJECT/S:
Project 1.4: Robotic Surface Finishing for Custom Manufacturing
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