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Robot Tactile Sensing: Skinlike and Intrinsic Approach
Published in Spyros G. Tzafestas, Intelligent Robotic Systems, 2020
Antonio Bicchi, Giorgio Buttazzo
A piezoresistive transducer is characterized by modulation of its electrical resistance with the applied load: piezoresistive materials commonly utilized in tactile sensing are conductive elastomers, that is, rubbers or foams that can be easily deformed under load. If electrodes are placed on the faces of a sample of a conductive elastomer, the resistance variation caused by electrodes approaching under load can be easily measured. Several experimental devices based on this principle have been developed since 1981 (Purbrick, 1981); a common arrangement of such sensors consists of two sets of parallel conductive rubber stripes placed at right angles, taxels being formed at each intersection. The commercially available Sensoflex tactile system produced by Barry Wright Co. consists of 256 taxels whose centers are spaced 2. 5 mm apart. Conductive elastomers have several favorable features, such as low cost and good conformability; the bandwidth of the single taxels as an individual load cell is also good. Unfortunately, they suffer from high hysteresis and low sensitivity; moreover, taxel spacing in most of the proposed sensors is not satisfactory.
Artificial Skin
Published in Muhammad Mustafa Hussain, Nazek El-Atab, Handbook of Flexible and Stretchable Electronics, 2019
Corresponding techniques to achieve highly stretchable strain sensors include the use of innovative materials such as hybrid conductive elastomers or liquid metals [23]. Hybrid elastomers are characterized by conductivity along with high elasticity. Their soft, transparent, and piezoresistive nature enabled their use in highly stretchable strain, pressure, and acoustic sensors [10,23,65–69]. One of the main advantages of such conductive elastomers is the ability to tune the amount of conductivity versus stretchability depending on their function in the desired application. The high elasticity and conductivity of NW-based elastomer composites rendered them a desired choice for artificial skin developments [65,70,71]. As an example, a self-powered, stretchable, and transparent skin was demonstrated using AgNW/poly(3,4-ethylenedioxythiophene) (PEDOT): polystyrene sulfonate (PSS)/poly (urethane acrylate) (PUA) nanocomposite to build a highly sensitive strain monitoring system [72].
Elastomeric and Plastomeric Materials
Published in Narendra Pal Singh Chauhan, Functionalized Polymers, 2021
Mohsen Khodadadi Yazdi, Payam Zarrintaj, Saeed Manouchehri, Joshua D. Ramsey, Mohammad Reza Ganjali, Mohammad Reza Saeb
Various carbon-based nanomaterials such as carbon nanotubes and graphene can also be used to make conductive elastomers. It has been shown that incorporation of special MXene ( Ti3C2 nanoplatelets) can remarkably improve the electrical and thermal conductivities of SBR to make it even more efficient than reduced graphene oxide (Q. Li et al. 2019).
Feedback control of a pneumatically driven soft finger using a photoelastic polyurethane bending sensor
Published in Advanced Robotics, 2021
Yoshiki Mori, Mizuki Fukuhara, Mingzhu Zhu, Yuho Kinbara, Akira Wada, Masahiko Mitsuzuka, Yoshiro Tajitsu, Sadao Kawamura
Numerous previous studies on soft-fingered hands used only pressure control instead of position for the sensor feedback control. The feedback control from some types of sensors was required to improve positioning accuracy and suppress vibration. The sensor built into the soft finger is particularly useful. However, installing a general rotational-type sensor in a soft finger is difficult because a soft finger has no rotational axis and it is deformed. The sensor must be deformable so as not to encumber the soft finger motion. Common soft sensors used for finger bending are constructed from conductive elastomers [15–18], and flex strain sensors are commercially available [19,20]. The sensors described in [15–20] measure bending from the resistance change of sensor deformation and provide the position feedback control of soft fingers. However, the production of conductive elastomers is complicated, expensive and generally involves the injection of a conductive liquid metal (EGain) or carbon material, such as carbon nanotubes, into an elastomeric material like silicone. These sensors require internal wires made from conducting metal, and their performance can be degraded by electromagnetic noises.
Robust bin-picking system using tactile sensor
Published in Advanced Robotics, 2020
Sho Tajima, Seiji Wakamatsu, Taiki Abe, Masanari Tennomi, Koki Morita, Hirotoshi Ubata, Atsushi Okamura, Yuji Hirai, Kota Morino, Yosuke Suzuki, Tokuo Tsuji, Kimitoshi Yamazaki, Tetsuyou Watanabe
Various types of tactile sensors have been developed for robotic applications [13–15]. Since the robot contacts different kinds of materials including metal, rubber and plastic, it is preferable that the sensing principle is less dependent on the object material, such as those based on resistance change or optical observation. Vision-based tactile sensors are becoming more practical as devices become smaller and higher performance [16,17], but they need to be large from the contact surface in the depth direction due to the principle of optical observation. The resistive type with a conductive elastomer film is said to be superior in terms of robustness, low-cost, simple fabrication, flexibility and thinness [13]. We adopted the resistance type tactile sensor. One of the features of the sensor introduced in this system is that the structure of tactile cells has been customized according to the size and posture of the grasped object in parallel with the development of the robot motion in the practical task.
3D printing highly stretchable conductors for flexible electronics with low signal hysteresis
Published in Virtual and Physical Prototyping, 2022
Jun Zhou, Honghao Yan, Chengyun Wang, Huaqiang Gong, Qiuxiao Nie, Yu Long
The tensile test (according to GB/T528-2009) was loaded with a universal testing machine (UMT2000, 50N load cell, 500N load cell) at a speed of 100 mm min−1. We observed the surface microstructure morphology of the elastomer with an optical image measuring instrument (VMS300). The resistance of conductive elastomer was tested with LCR digital bridge (TH2832). Attenuated total reflection (ATR) FRIT spectroscopy was performed from 4000 to 650 cm−1 on a RTracer-100. All the elastomer samples were scanned 32 times at a resolution of 4 cm−1. Wide-angle X-ray diffraction (WAXD) patterns were collected on a D8 Discover X-ray diffractometer, using a scan speed of 3° min−1. The wavelength of the X-ray radiation was 1.5418 Å.