Location-Dependent Performance of Large-Area Piezoresistive Tactile Sensors Based on Electrical Impedance Tomography

Chen, Ying; Liu, Haibin

doi:10.1109/jsen.2021.3103988

Cited by 18 publications

(19 citation statements)

References 38 publications

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“…In addition to the two-point discrimination test [21], which has been presented to examine a deep neural network-based EIT method for large-area tactile sensing, we proposed a comprehensive testing protocol including two-point, three-point and four-point discrimination tests for evaluating the tactile spatial acuity of our sensor. Since the sensitivity to intensity of the EIT-based sensor varies across the sensing area, the spatial performance of the sensor is location-dependent [35]. Therefore, we selected two typical cases for the two-point discrimination tests similar to reference [21].…”

Section: B Multi-touch Indentation Testmentioning

confidence: 99%

“…The reconstructed images allow us to establish the mapping relationship between the strength of a touch force and the image intensity over the entire sensing area. However, the inherent location dependency of tactile sensitivity severely affects interpreting the strength information of a touch force from different locations of EIT-based sensors [35]. To overcome the location dependency of EIT sensing problems, we proposed a method of subregional fitting to calibrate the distributed forces for our large-area flexible tactile sensor.…”

Section: Touch Force Calibrationmentioning

confidence: 99%

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A Large-Area Flexible Tactile Sensor for Multi-Touch and Force Detection Using Electrical Impedance Tomography

et al. 2022

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For large area robot skin design, the distribution of rigid components and wires in traditional array sensors leads to the decrease of the flexibility and extensibility of sensors. The flexible sensors based on non-invasive electrical impedance tomography (EIT) can avoid these shortcomings. However, design of a large-area flexible tactile sensors using EIT technique is still challenging due to the tradeoff between manufacturability and spatial resolution. In this study, we proposed a novel non-array EITbased tactile sensor which is made of a porous elastic polymer and ionic liquid. The sensor free from internal array electrodes is straightforward to manufacture and can cover a large area with low cost. To improve the spatial resolution and touch sensitivity, we adopted a deep learning scheme Pyramid Scene Parsing Network (PSPNet) to postprocess the originally reconstructed images to enhance the sensor tactile perception. With this data-driven method, we achieved a singlepoint position detection error of 7.5±4.5 mm without using internal electrodes. To overcome the location dependency of EIT sensing problems, we proposed a method of sub-regional fitting to calibrate the distributed forces for the large-area flexible tactile sensor and obtained a quantitative relationship between the touch force and EIT measurement for the entire sensing area for continuous sensing. The real-time performance of the proposed prototype sensor system demonstrated that we can achieve more accuracy of multi-touch and distributed force detection on the non-array sensors for potential applications in human-robot interfaces.

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Section: B Multi-touch Indentation Testmentioning

confidence: 99%

Section: Touch Force Calibrationmentioning

confidence: 99%

A Large-Area Flexible Tactile Sensor for Multi-Touch and Force Detection Using Electrical Impedance Tomography

et al. 2022

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“…The sensor was able to discriminate up to four points without any additional image processing. For tactile robotic skin, it is preferable to detect multiple inclusions; for an EITbased sensor, four-point touch is acceptable [22]. Over a circular domain of only 174 mm diameter, four-point discrimination is sufficient for safety applications of robotic skin but may be insufficient for HRIs that involve emotional recognition.…”

Section: Static Imagingmentioning

confidence: 99%

“…In 2020, Zhao et al prototyped an ionic liquid-based EIT pressure sensor that featured a continuous domain [5]. Numerous studies on challenging aspects of EIT pressure sensing are shown in [13,[20][21][22][23] dealing with sensor design, sensor performance and image enhancement. A systematic comparison between fabric-and liquid-based skin could be an interesting future study.…”

Section: Introductionmentioning

confidence: 99%

E-Skin Using Fringing Field Electrical Impedance Tomography with an Ionic Liquid Domain

Soleimani

Friedrich

2022

Sensors

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Electrical impedance tomography (EIT) is a promising technique for large area tactile sensing for robotic skin. This study presents a novel EIT-based force and touch sensor that features a latex membrane acting as soft skin and an ionic liquid domain. The sensor works based on fringing field EIT where the touch or force leads to a deformation in the latex membrane causing detectable changes in EIT data. This article analyses the performance of this electronic skin in terms of its dynamical behaviour, position accuracy and quantitative force sensing. Investigation into the sensor’s performance showed it to be hypersensitive, in that it can reliably detect forces as small as 64 mN. Furthermore, multi-touch discrimination and annular force sensing is displayed. The hysteresis in force sensing is investigated showing a very negligible hysteresis. This is a direct result of the latex membrane and the ionic liquid-based domain design compared to more traditional fabric-based touch sensors due to the reduction in electromechanical coupling. A novel test is devised that displayed the dynamic performance of the sensor by showing its ability to record a 1 Hz frequency, which was applied to the membrane in a tapping fashion. Overall, the results show a considerable progress in ionic liquid EIT-based sensors. These findings place the EIT-based sensors that comprise a liquid domain, at the forefront of research into tactile robotic skin.

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“…16 Park et al proposed a deep neural network based on EIT reconstruction framework and obtained improved spatial resolution, sensitivity, and localization accuracy. 12 Chen and Liu 17 were one of the first to investigate the locationdependent spatial performance of EIT-based tactile sensors. They developed an intensity scaling method to correct reconstructed amplitudes with respect to the uniform sensitivity distribution.…”

Section: Introductionmentioning

confidence: 99%

A Skin-Like Hydrogel for Distributed Force Sensing Using an Electrical Impedance Tomography-Based Pseudo-Array Method

Chen

Yang

Geng

et al. 2023

ACS Appl. Electron. Mater.

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Hydrogels are compliant biomaterials that can be integrated with robotic systems to act like human skin for sensing and perception during interactions with their environments. The conventional method for fabricating skin-like hydrogel sensors is based on an array-type design which contains numerous discrete sensitive elements to obtain touch locations and force information. Array-based sensors are complex, with tiny communication units that make manufacturing complicated and expensive. Electrical impedance tomography (EIT) is a noninvasive imaging technique that can be easily implemented to create large-area tactile sensors into a "one-piece" structure without any internal wires. However, EIT-based tactile sensors suffer from low spatial resolution and sensitivity in areas far from the electrodes. This paper introduces a pseudo-array method to remedy the effect of location-dependent sensitivity on the spatial sensing of EIT-based hydrogel sensors and improve their performance for practical applications in detecting distributed contact forces without any arrays or internal wires. As a preliminary study, a skin-like hydrogel-based tactile sensor with an area of 400 cm 2 was fabricated using a simple manufacturing process. The entire piece of the tactile sensor is then divided into a 5 × 5 array, which is referred to as a pseudo-array for simulation and experimental calibration. Each "pseudo-array" unit was calibrated to obtain the mapping relationship between the force and the reconstructed conductivity. Subsequently, a quantitative relationship between the touch force and the EIT measurement for the hydrogel-based tactile sensor for continuous sensing was achieved. Finally, the real-time performance of the EIT-based hydrogel sensor demonstrates that the proposed pseudo-array method can realize more accurate force detection with an error of 1.62 N (10.15% of the maximum force) for sensing distributed force over a large area of 400 cm 2 with only 16 boundary electrodes.

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Location-Dependent Performance of Large-Area Piezoresistive Tactile Sensors Based on Electrical Impedance Tomography

Cited by 18 publications

References 38 publications

A Large-Area Flexible Tactile Sensor for Multi-Touch and Force Detection Using Electrical Impedance Tomography

A Large-Area Flexible Tactile Sensor for Multi-Touch and Force Detection Using Electrical Impedance Tomography

E-Skin Using Fringing Field Electrical Impedance Tomography with an Ionic Liquid Domain

A Skin-Like Hydrogel for Distributed Force Sensing Using an Electrical Impedance Tomography-Based Pseudo-Array Method

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