Indirect Force Control of a Cable-Driven Parallel Robot: Tension Estimation using Artificial Neural Network trained by Force Sensor Measurements

In a cable-driven parallel robot (CDPR), force sensors are utilized at each winch motor to measure the cable tension in order to obtain the force distribution at the robot end-effector. However, because of the effects of friction in the pulleys and the unmodeled cable properties of the robot, the me...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2019-06, Vol.19 (11), p.2520
Main Authors: Piao, Jinlong, Kim, Eui-Sun, Choi, Hongseok, Moon, Chang-Bae, Choi, Eunpyo, Park, Jong-Oh, Kim, Chang-Sei
Format: Article
Language:English
Subjects:
artificial neural network
cable force sensor
cable tension estimation
cable-driven parallel robot
Cables
Control algorithms
Control systems design
force control
Force distribution
Friction
Kinematics
Motion control
Neural networks
pulley friction
Pulleys
Robotics
Robots
Sensors
Sliding friction
Stress concentration
Uncertainty
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Summary:In a cable-driven parallel robot (CDPR), force sensors are utilized at each winch motor to measure the cable tension in order to obtain the force distribution at the robot end-effector. However, because of the effects of friction in the pulleys and the unmodeled cable properties of the robot, the measured cable tensions are often inaccurate, which causes force-control difficulties. To overcome this issue, this paper presents an artificial neural network (ANN)-based indirect end-effector force-estimation method, and its application to CDPR force control. The pulley friction and other unmodeled effects are considered as black-box uncertainties, and the tension at the end-effector is estimated by compensating for these uncertainties using an ANN that is developed using the training datasets from CDPR experiments. The estimated cable tensions at the end-effector are used to design a P-controller to track the desired force. The performance of the proposed ANN model is verified through comparisons with the forces measured directly at the end-effector. Furthermore, cable force control is implemented based on the compensated tensions to evaluate the performance of the CDPR in wrench space. The experimental results show that the proposed friction-compensation method is suitable for application in CDPRs to control the cable force.
ISSN:1424-8220
1424-8220
DOI:10.3390/s19112520