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. 2021 May 21;21(11):3604.
doi: 10.3390/s21113604.

New Sensor Device to Accurately Measure Cable Tension in Cable-Driven Parallel Robots

Guillermo Rubio-Gómez  1 , Sergio Juárez-Pérez  1 , Antonio Gonzalez-Rodríguez  1 , David Rodríguez-Rosa  1 , Lis Corral-Gómez  1 , Alfonso I López-Díaz  1 , Ismael Payo  1 , Fernando J Castillo-García  1
Affiliations

New Sensor Device to Accurately Measure Cable Tension in Cable-Driven Parallel Robots

Guillermo Rubio-Gómez et al. Sensors (Basel). .

Abstract

Cable-driven parallel robots are a special type of robot in which an end-effector is attached to a fixed frame by means of several cables. The position and orientation of the end-effector can be controlled by controlling the length of the cables. These robots present a wide range of advantages, and the control algorithms required have greater complexity than those in traditional serial robots. Measuring the cable tension is an important task in this type of robot as many control algorithms rely on this information. There are several well-known approaches to measure cable tension in cable robots, where a trade-off between complexity and accuracy is observed. This work presents a new device based on strain gauges to measure cable tension specially designed to be applied in cable-driven parallel robots. This device can be easily mounted on the cable near the fixed frame, allowing the cable length and orientation to change freely, while the measure is taken before the cable passes through the guiding pulleys for improved accuracy. The results obtained from the device show a strong repeatability and linearity of the measures.

Keywords: cable-driven parallel robots; strain gauges; tension measurement.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Examples of commercial off-the-shelf devices for measuring cable tension.
Figure 2
Figure 2
Examples of commercial off-the-shelf devices for measuring cable tension.
Figure 3
Figure 3
Three-pulley devices based on measuring compression efforts.
Figure 4
Figure 4
Conceptualization of our proposal.
Figure 5
Figure 5
Scheme of the cable tension-measuring device. T = cable tension, r = pulley radius, A,B,C = pulley centers, P,Q = connection points between bars 2 and 3.
Figure 6
Figure 6
(a) Forces on the measuring bar. (b) Geometry of the measuring bar.
Figure 7
Figure 7
Strain gauges position for bending moment measurement. A,B,C = pulley centers, P,Q = connection points between bars 2 and 3.
Figure 8
Figure 8
Signal conditioning electronics. R = fixed resistance, Rg1 = upper strain gauge, Rg2 = lower strain gauge, V = supply voltage, e0 = output voltage.
Figure 9
Figure 9
Prototype for validation.
Figure 10
Figure 10
Experimental setup for validation.
Figure 11
Figure 11
CDF for empirical data.
Figure 12
Figure 12
Repeatability results.
Figure 13
Figure 13
Calibration results.
Figure 14
Figure 14
Sketch of the dynamic test approach.
Figure 15
Figure 15
Results of the dynamic test.
See this image and copyright information in PMC

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