Papers by Keyword: Tactile Sensor

Abstract: Tactile sensors in wearable devices have gained attention for their potential applications in enhancing amenability, generation, and functionality for the human body, including sensing and control. This study elaborates on the design of a tactile sensor consisting of EeonTex conductive stretchable elastic fibre, which possesses a bi-directionally stretchable elastic fibre, and was formulated by coating nylon/spandex with a long-lasting conductive formulation. This fabric has proven to be beneficial for use in various different e-tactile applications. The authors systematically investigated the performance of the tactile sensor via 2 different manipulative gestures on a part of the upper limb of two different subjects. The tactile sensor was observed to change its electrical resistance when mechanical force was applied to its surface. It was also noted to be lightweight, inexpensive, stretchable, flexible, and easy to design and set up. This type of tactile sensor possesses the ability to recognise the intention of muscle movement and measure the muscle activities from the forearm. The prime objective of this study was to use such sensors as sleeves mounted on the forearms of the upper limbs. The reasoning behind this was that when muscle contract, they change their shape which in turn results in mechanical pressure being applied to the sensor. Experimental results showed that the tactile sensor’s feedback successfully detected open/closed hands when the sensor sleeve was worn on the forearm region.

Abstract: The polyvinylidene fluoride (PVDF) nanofiber has widely investigated as a sensor and transducer material, because of its high piezo and Ferro electric properties. The novel nano structure of PVDF has attracted considerable interest in the bio sensing and biomedical application. This paper deals with PVDF Tactile sensor. Basically The PVDF acts as piezoelectric effect which convert load into electrical signals. The tactile sensor has a main role for visual handicap and robotics. Any physical activities of robotic in all industrial the tactile sensor is a crucible role, whether it can left the object or handling glass parts pressure of object is main. The Sandwich type PVDF base tactile sensor has been fabricated using nanofiber. Using electro spinning method, the PVDF based nanofiber coated over coper the electrodes. In normal, the PVDF has α-phase and while applying electric pulse the PVDF polymer would be changed from α-phase into β-phase. Only in β-phase, the PVDF act as piezo electrics sensor and measure the piezoelectricity simultaneously measure pressure and temperature in real time. The pressure was monitored from the change in the electrical resistance via the piezo resistance of the material. The enhancement of PVDF properties has been carried by using SEM. The SEM image result showed that the size of nanofiber, the size of nanofiber is varied in the range of (180 nm-400 nm) with smooth surface. The X-Ray diffraction has shown that the PVDF was aggregated with the β-phase crystalline nature. Due to β-phase it was act as a piezo electric prosperity’s and its results are very high sensitivity.

Abstract: In recent years, autonomous robots have been increasingly deployed in unstructured and unknown environments. In order to survive in theses environments, robots are equipped with sensors. One of the main sensors is tactile sensor which provides the robots with tactile information like texture, stiffness, temperature, vibration and normal and shear forces. In this paper, we propose a flexible capacitive tactile sensor which is designed for measuring both normal and shear forces. The tactile sensing unit consists of five layers, a bottom layer of Polyethylene Terephthalate (PET) with a pillar, two copper electrodes embedded into a Polydimethylsiloxane (PDMS) film, a spacer, a Polyimide (PI) film and finally a top PI bump. The bump and the pillar structure play a significant role in producing a torque for shear force measurement. Finite element modeling (FEM) is conducted to analyze the deformation of the sensing unit and simulated using COMSOL Multiphysics. The change of capacitance verse normal and shear forces are obtained, a comparison between the proposed sensor and other pervious sensor is conducted. The sensitivity of a cell is 0.22%/N within the full scale range of 10 N for normal force and 4%/N within the full scale range of 10 N for shear force.

Abstract: This work presents multi-functional robot arm gripper design along with vision and tactile sensor for efficient grasping and manipulation tasks. The design emulates human’s hand fingers structure using linkages and direct drive through slider-crank mechanism transmission. The structural elements are optimized for a finest performance in motion and force transmissibility of the gripper fingers. The main future of this design is its reliability to grasp and manipulate unknown object while its system complexity is reduced. The gripper has a tool change fixture incorporated into its palm, which will reduce time wastage and do assembling in one go. The gripper is equipped with two cameras in its palm; subsequently it will efficiently seek the target object and perform its prehensile task with intelligently determined grasping force.

Abstract: As the robotics is moving its interest from the machine tools for industrial production to biomimetic, even human-like systems, the need for materials that fulfill skin role arises. Skin presents a structure that has multiple roles such as protection and tact. The basic requirements for a skin mimetic material are flexibility and a measurable physical property triggered by the pressure. In this work hybrid piezoelectric materials are prepared and characterized. The flexibility of materials is assured by the polymeric matrices while ceramic oxide fillers grant a piezoelectric response. Polyvinilidene fluoride (PVDF) is used both in its piezoactive β-form and piezopassive α-form, in order to investigate the contribution of the organic phase to the overall response. Polymethylmethacrylate (PMMA) is also used in order to compare the behavior of an amorphous and a semi-crystalline polymer. Lead-based ceramics were avoided, despite they are known to be the most effective piezoelectric materials, to prevent complications in terms of toxicity. Ceramic materials with lower piezoelectric coefficient, but more suitable for human robotics such as barium titanate and zinc oxide are preferred. Organic matrices and ceramic powders are then employed for preparing composites with different compositions, microstructures and mechanical behaviors, in order to evaluate their piezoelectric response in view of their application as sensing skin for robots.

Abstract: A walking-assistant robot guided by the intention and power-driven is presented, its purpose is to provide physical support and walking assistance for the elderly to meet their needs of walking autonomy, friendliness, and maintaining the ability of walking and taking care of themselves. Tactile and slip sensor is selected as the human interface to perceive the users walking intent, and the sensor is also used to detect the user's slip trend. And the paper researches the feature representation and extraction method of tactile and slip signal for driving control pattern recognition. An improved classification and identification method combining K-means in clustering and K-nearest neighbor algorithm in classification is proposed. The paper introduces the overall design schemes of tactile and slip drive control system of walking-assistant robot, perception system, motion control system. Finally the feasibility and effectiveness of the entire system are verified by experiment.

Abstract: This paper presents experimental results of object handling motions to evaluate tactile slippage sensation in a multi fingered robot arm with optical three-axis tactile sensors installed on its two hands. The optical three-axis tactile sensor is a type of tactile sensor capable of defining normal and shear forces simultaneously. Shear force distribution is used to define slippage sensation in the robot hand system. Based on tactile slippage analysis, a new control algorithm was proposed. To improve performance during object handling motions, analysis of slippage direction is conducted. The control algorithm is classified into two phases: grasp-move-release and grasp-twist motions. Detailed explanations of the control algorithm based on the existing robot arm control system are presented. The experiment is conducted using a bottle cap, and the results reveal good performance of the proposed control algorithm to accomplish the proposed object handling motions.

Abstract: A type of tactile sensors based on piezoresistive principle is designed for the robot grab force detection and control. According to human behaves and awareness, the robot grabbing control program imitate human hand grasp active perception and action mechanisms. With the tactile sensors, the slip and grasping process pressure signal is sampled and analysed by general time-domain statistical parameter, and a simpler control algorithm is researched. In the experiment the robot has accomplished soft grabbing by modeling human hand action and applied appropriate grabbing force on objects of different weights or material by means of the control algorithm. Experiments suggest that this sensor and action biomimetic process is suitable to be used in the tele-presence technology application in the case of the visible range or visual equipment aid especially.

Abstract: Tactile sensation is one of essential perceptions for a functional robot hand to monitor slip states, grasp objects with proper force, and distinguish different properties of objects etc. A practical tactile sensor based on acoustic-electric converting principle is introduced. The grasp signals of objects of three sort materials are collected by the tactile sensor. The power spectrum feature vectors of them are taken as learning sample book set. Transfer function of neurons in hidden layer is tangent function and that in output layer is logarithmic function. L-M algorithm is selected and convergence precision set is as 0.0001. The hidden layer nodes are taken by experiments as 13. When neural network structure is 8-13-4, BP neural network has the fastest convergence rate and short running time of milliseconds.

Abstract: Pressure-sensitive conductive rubber has been investigated as sensitive material due to its good pressure-resistance characteristics. This paper presents a flexible tactile sensor with new structure. The sensing mechanism is based on body piezoresistive effect of conductive rubber filled by carbon black. To improve the sensor’s flexibility, there is a smart angle design in the arrangement of the wires in lower electrodes layer. Besides, the force model of the sensor has been described. The simulation results indicate the validity of 3-D force measurement of the sensor.