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. 2021 Mar 9;21(5):1915.
doi: 10.3390/s21051915.

Tactile Sensors for Parallel Grippers: Design and Characterization

Andrea Cirillo  1 , Marco Costanzo  1 , Gianluca Laudante  1 , Salvatore Pirozzi  1
Affiliations

Tactile Sensors for Parallel Grippers: Design and Characterization

Andrea Cirillo et al. Sensors (Basel). .

Abstract

Tactile data perception is of paramount importance in today's robotics applications. This paper describes the latest design of the tactile sensor developed in our laboratory. Both the hardware and firmware concepts are reported in detail in order to allow the research community the sensor reproduction, also according to their needs. The sensor is based on optoelectronic technology and the pad shape can be adapted to various robotics applications. A flat surface, as the one proposed in this paper, can be well exploited if the object sizes are smaller than the pad and/or the shape recognition is needed, while a domed pad can be used to manipulate bigger objects. Compared to the previous version, the novel tactile sensor has a larger sensing area and a more robust electronic, mechanical and software design that yields less noise and higher flexibility. The proposed design exploits standard PCB manufacturing processes and advanced but now commercial 3D printing processes for the realization of all components. A GitHub repository has been prepared with all files needed to allow the reproduction of the sensor for the interested reader. The whole sensor has been tested with a maximum load equal to 15N, by showing a sensitivity equal to 0.018V/N. Moreover, a complete and detailed characterization for the single taxel and the whole pad is reported to show the potentialities of the sensor also in terms of response time, repeatability, hysteresis and signal to noise ratio.

Keywords: dexterous manipulation; sensor characterization; tactile sensing.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
CAD drawing of an assembled sensor (left) with all components (middle) and details about 3D machines used for the production (right).
Figure 2
Figure 2
Electronics block diagram.
Figure 3
Figure 3
Manufactured PCBs: sensing board (left) and power supply board (right).
Figure 4
Figure 4
Deformable layer and rigid grid characteristics (a). Mechanical assembly of mechanical and electronic parts (b). Section of the assembled parts with dimensions: full view (c) and zoom view (d).
Figure 5
Figure 5
Manufactured grid in black ABS (a), deformable layer in silicone (b), case in nylon (c) and complete assembled finger (d).
Figure 6
Figure 6
Elaboration system software design: software flow chart (a) and protocol sequence diagram (b).
Figure 7
Figure 7
Experimental setup for single taxel (a) and taxel numbering used in the experiment description (b).
Figure 8
Figure 8
Hysteresis experiment for taxel 17: applied force (a) and voltage variations (b).
Figure 9
Figure 9
Hysteresis graphs for taxel 5 (a), taxel 13 (b) and taxel 17 (c).
Figure 10
Figure 10
Repeatability experiment for taxel 17: applied force (a) and voltage variations (b).
Figure 11
Figure 11
Repeatability error graphs for taxel 5 (a), taxel 13 (b) and taxel 17 (c).
Figure 12
Figure 12
Response time graphs for taxel 5 (a), taxel 13 (b) and taxel 17 (c).
Figure 13
Figure 13
Power spectrum of taxels 5, 13 and 17.
Figure 14
Figure 14
Experimental setup for the whole pad characterization: components (a) and contact example (b).
Figure 15
Figure 15
Hysteresis experiment for the whole pad characterization: force profile (a) used to stimulate the pad and corresponding voltage variations (b).
Figure 16
Figure 16
Hysteresis graph for the whole pad characterization: a single voltage (a) and mean of voltages (b).
Figure 17
Figure 17
Repeatability graph for the whole pad characterization: a single voltage (a) and mean of voltages (b).
Figure 18
Figure 18
Sensitivity graph for the whole pad characterization.
Figure 19
Figure 19
Examples of tactile maps during the grasp of a cable: linear horizontal case (a), quadratic horizontal case (b), quadratic vertical case (c) and high curvature case (d).
See this image and copyright information in PMC

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