An experimental teletaction system for sensing and teleperception of human pulse

Teletaction is the sensing of a remote object by transmitting tactile information from a remote tactile sensor to an operator’s skin through tactile interface devices. A tactile interface is used to reproduce the information such as force (static and dynamic), texture, roughness, temperature, and shape. This paper describes the design, modeling, simulation, fabrication and testing of an experimental teletaction system to detect and reproduce the human pulse. It consists of three major components: pulse sensing system, pulse teleperception system and the data processing system. Two 25 μm thick polyvinylidene fluoride (PVDF) film sensors had been fabricated and calibrated for pulse detection and force measurement. A computer controlled force feedback system was developed for achieving pulse teleperception. The simulation and experimental results demonstrated the close matching between the sensed and perceived pulse. A psychophysics test showed that the fingertip feeling at the pulse teleperception end closely matched the feeling of touching a human pulse directly.     

Dynamic contact sensing by flexible beam

This paper discusses a new dynamic sensing system capable of detecting the contact point between a flexible beam and an object. The proposed sensing system, named dynamic antenna, is simply composed of an insensitive flexible beam, a torque sensor, a joint position sensor, an actuator, and a payload at the tip end of the beam. The contact point can be detected through estimation of the oscillation frequencies of the beam in contact with the object. First, a dynamic model of the sensor is derived. Next, it is shown that information of the fundamental and the second natural frequencies is sufficient for unique determining of the contact point if the beam has uniform mass and stiffness distribution. In practical realization, the fundamental and the second natural frequencies of the beam in contact with the object are extracted from the torque sensor measurements with the use of the maximum entropy method. Then, the frequencies are mapped into the contact-point coordinate. Extraction of the frequencies and mapping them into the contact point constitute a sensing strategy which is tested under experiment     

A foot-wearable interface for locomotion mode recognition based on discrete contact force distribution

The knowledge of plantar pressure distribution is important in understanding human locomotion activities, and its integration with robotic assistive devices is an important potential application. In this paper, we aim to explore the potential of using discrete contact force distribution signals for locomotion mode recognition. A foot-wearable interface comprising a pair of sensing insoles, each with four sensors at selected locations, has been designed to record discrete contact forces during locomotion. Based on the information of discrete contact force distribution, we present a locomotion mode recognition strategy with decision tree and linear discriminant analysis classifiers. To verify the measurement performance of the sensing system, experiments are carried out to investigate the system stability in long term working conditions and its adaptation to different ground surfaces. To evaluate whether discrete contact force signals can be used for locomotion mode recognition, five able-bodied subjects and one amputee subject are recruited and asked to perform six types of locomotion tasks. With the proposed recognition strategy, reliable recognition performance is obtained. The average classification accuracy is 98.8% ± 0.5% for able-bodied subjects and 98.4% for the amputee subject, which is comparable to those obtained from systems based on other sensors. These experimental results indicate that monitoring of discrete contact force distribution is valuable for locomotion mode recognition. Its use can be combined with other sensing systems to achieve better performance of locomotion mode recognition for intelligent assistive device control.     

Measuring human–robot interaction on wearable robots: A distributed approach

This paper presents a novel, distributed approach to monitor physical interaction between a user and a wearable robot. We propose to apply a matrix of optoelectronic sensors embedded in a thin and compliant silicone bulk onto the user-robot contact surface. This distributed tactile sensor can measure the pressure distribution on the interaction area without affecting the comfort of the user, and does not require the robot to be specifically designed to house it. Besides the estimation of the interaction force/torque, the distributed approach allows to monitor the pressure on the user’s skin. This information is fundamental to assess the comfort and safety of the users which determine the final acceptability of the robot-mediated rehabilitation. The proposed method is preliminary evaluated on an elbow active orthosis during a repetitive rehabilitation task. Experimental results prove the relevance of this approach for the detection of the user motion intention through a measurement of the interaction force distribution.     

Review Article Tactile sensing for mechatronics—a state of the art survey

In this paper we examine the state of the art in tactile sensing for mechatronics. We define a tactile sensor as a device or system that can measure a given property of an object or contact event through physical contact between the sensor and the object. We consider any property that can be measured through contact, including the shape of an object, texture, temperature, hardness, moisture content, etc.A comprehensive search of the literature revealed that there was a significant increase in publications on tactile sensing from 1991 onwards. Considerable effort in the 1980s was spent investigating transduction techniques and developing new sensors, whilst emphasis in more recent research has focused on experiments using tactile sensors to perform a variety of tasks.This paper reports on progress in tactile sensing in the following areas: cutaneous sensors, sensing fingers, soft materials, industrial robot grippers, multifingered hands, probes and whiskers, analysis of sensing devices, haptic perception, processing sensory data and new application areas.We conclude that the predominant choice of transduction method is piezoelectric, with arrays using resistive or capacitive sensing. We found that increased emphasis on understanding tactile sensing and perception issues has opened up potential for new application areas. The predicted growth in applications in industrial automation has not eventuated. New applications for tactile sensing including surgery, rehabilitation and service robotics, and food processing automation show considerable potential and are now receiving significant levels of research attention.     

基于压电式新型三维力传感器的设计

从生物压电效应和人体“皮肤效应”原理出发，提出了一种基于压电式的新型三向力检测方法，阐述了三向力传感器的设计思想和基本组成结构，并从理论上对传感器工作原理进行了检测，推导了计算空间三向力大小和方向的公式。该三向力传感器不但可以用于机械空间力的测量，且还可用于机器人表皮的传感，为实现新型的智能机器人触觉力传感器系统提供了一种新的方法。     

Tactile sensory monitoring of clinician-applied forces duringdelivery of newborns

A tactile sensing system (TSS), consisting of a sensing device and a data acquisition system, is described for measuring finger tip-applied forces. The system consists of four commercially-available tactile sensors, each mounted on a flexible matrix a clinician can wear with minimal interference, as well as a modified data acquisition system. The authors report on using the TSS to measure clinician-applied forces during vaginal delivery of newborns, with particular emphasis on an obstetric emergency called shoulder dystocia. In 24 randomly-selected deliveries using the TSS, subjective classifications of delivery type made blindly by the clinician corresponded well with the average force, peak force, and impulse demarcations in the study. Preliminary results suggest that birth injury may be time-dependent; as a result, viscoelastic effects may need to be incorporated in any situation model     

新型三维力觉传感器的设计与分析

提出了一种基于PVDF膜的新型三向力触觉传感技术,阐述了触觉传感头的设计思想和基本结构,并从原理上进行了分析,得到了计算空间三向力的公式,为实现新型的能用于智能机器人触觉的力传感系统打下了基础。     

一种简单的电容式三维力柔性触觉传感器设计

随着机器人智能化程度不断提高,机器触觉和机器视觉技术均得到了很大发展,但是目前大部分触觉传感器均不能满足触觉感知应用的要求。因此,提出了一种新型的具有滑觉检测功能的柔性三维力触觉传感器。该传感器能够将力量变化转化为气隙变化,进而引起电容发生变化。然后将接触力建模为实测电容的多项式函数,对传感器输出进行校正进而实现法向力测量和滑动检测。测试结果显示,提出的传感器能够以较高的精确度测量法向力,重复性好,并且能够检测滑动现象,在0-100mN测量范围内的法向灵敏度约为0.4 pF/N,均方根误差为1%。此外提出的传感器结构简单、成本较低,易于大规模生产和应用。     

Highly Soft Viscoelastic Robot Skin With a Contact Object-Location-Sensing Capability

This paper concerns the development of robot skin capable of accurately sensing the location of objects in area contact with the skin surface. There has been no report on tactile sensing which attained not only skin deformation detection but also contact object location sensing with high accuracy. In the category of optomechatronics technology, we apply optical fibers to transmit surface deformation information of soft skin for sensing the location of an object in contact with the soft skin accurately. In the paper, we illustrate the structure of the robot skin, and describe the principle of both detecting the position of the reflector chips and sensing the contact location of an object. The robot skin is characterized by the fact that the surface is low cost and easily replacable, and the sensing performance is robust against any electromagnetic disturbance. We then show experimental results for verifying the principles using a wedge-shaped object. For evaluating the sensing accuracy, comparisons are made: 1) between the location of a real convex of the object and that of the corresponding estimated polygon and 2) for the position of two vertices of the object when independent fitting and Lagrangian fitting methods are applied.     

Whole-Body Force Sensation by Force Sensor With Shell-Shaped End-Effector

This paper proposes a tactile-sensing mechanism for a robot. The mechanism is composed of a force-sensor device and an end-effector of shell shape. Since the end-effector plays the role of an outer shell, a force can be sensed at any position on the body. Due to the aspect of its intrinsic contact sensing, position of the single contact point is calculable without any sensor array. Another advantage is that the six-axis resultant force is measurable. This paper shows that the mechanism is also available for the end-effector with an angulated shape. The only condition for the shape is to be a convex hull. Some experimental results evaluate sources of error in practical measurement and show the validity of the proposed mechanism.     

Recent Progress in Advanced Tactile Sensing Technologies for Soft Grippers

Tactile sensing technology is crucial for soft grippers. Soft grippers equipped with intelligent tactile sensing systems based on various sensors can interact safely with the unstructured environments and obtain precise properties of objects (e.g., size and shape). It is essential to develop state-of-the-art sensing technologies for soft grippers to handle different grasping tasks. In this review, the development of tactile sensing techniques for robotic hands is first introduced. Then, the principles and structures of different types of sensors normally adopted in soft grippers, including capacitive tactile sensors, piezoresistive tactile sensors, piezoelectric tactile sensors, fiber Bragg grating (FBG) sensors, vision-based tactile sensors, triboelectric tactile sensors, and other advanced sensors developed recently are briefly presented. Furthermore, sensing modalities and methodologies for soft grippers are also described in aspects of force measurement, perception of object properties, slip detection, and fusion of perception. The application scenarios of soft grippers are also summarized based on these advanced sensing technologies. Finally, the challenges of tactile sensing technologies for soft grippers that need to be tackled are discussed and perspectives in addressing these challenges are pointed out.     

Human-robot-contact-state identification based on tactile recognition

In this paper, we propose a method for designing an identification system for human-robot contact states based on tactile recognition. The following ideas are incorporated: experimentation for human-robot contact, verbalization of contact states, extraction of characteristic parameters from acquired tactile information, quantification of the recipient's tactile recognition incorporating its redundancy (identification confusability among contact states), evaluation of the identification confusability with a new criterion, and identification of contact states based on the received tactile stimulation. The proposed method allows a robot to quantify tactile recognition of a human (recipient) touched by other people (touch initiator), in which the verbal response by the recipient is matched with tactile stimulation acquired during physical contact utilizing a tactile interface. In addition, the method enables a robot that comes into contact with a human to identify contact states nearly similar to that of the recipient, based on the features of the received tactile stimulation. At this point, the reproduction of the identification confusability of the recipient's tactile recognition is also accomplished by using a neural network called modified counterpropagation (MCP). Once a tactile stimulation is induced on the robot body, the probability of corresponding contact states is calculated and outputted by the system, based on the degree of similarity of the characteristics between the newly received and previously stored tactile stimulation. Experimental results indicate that the constructed system allows a successful quantification of the recipient's contact-state recognition incorporating the identification confusability and the accomplishment of a high level of accuracy in contact-state identification. These results confirm that the proposed method is useful for identifying human-robot contact states based on tactile recognition.     

A conceptual framework for tactually guided exploration and shapeperception

A conceptual framework for tactually guided exploration and shape perception using a robotic medium is provided. The conceptual framework identifies the needed sensory information, the spatial and temporal transformations of this information, the control mechanism, both feedforward and feedback, for performing the missions and the perception machinery. These attributes, in turn, sharpen the focus on the major building blocks needed in design of artificial skins, tactile sensing, and processing systems of the future. These building blocks are identification of central nervous system (CNS) machinery in living systems that perform the required computations, mappings, processors for extraction of the needed manipulation and recognition parameters, processing of outputs of populations of natural tactile sensors, and finally, understanding the dynamics of sensor-imbedded skin and artificial skin in fixed, gliding, and rolling contact with known and unknown objects and surfaces     

A stick-slip piezoelectric actuator with an integrated sensing unit for the measurement and active control of the contact force

Output characteristics of the stick-slip piezoelectric actuators are intrinsically affected by the contact force between the driving foot and the mover. Therefore, it would be quite meaningful to measure and control the contact force. In this study, by integrating a group of strain gauges into the driving compliant mechanism, a stick-slip piezoelectric actuator with measured contact force was proposed. The main structural parameters of the driving compliant mechanism were designed and analyzed. Through experiments, the sensing unit was calibrated, and the results showed that it had good linearity, and the noise level was 3.5 mN. The contact force was measured by the sensing unit, and accordingly, the relationship between the contact force and the stepping characteristic was explored. It was shown that the change in contact force would lead to the evolution in stepping characteristic, which finally resulted in the motion nonlinearity of the actuator in large stroke output. Accordingly, by actively controlling the contact force, a method was proposed to tune the stepping characteristic. The comparative results demonstrated that this method could significantly improve the motion linearity of the actuator in large stroke output under various preloads and even very rough surface.     

Force control of a very lightweight single-link flexible arm based on coupling torque feedback

In this paper, a feedback control law is proposed for regulating the contact force exerted by a very lightweight single-link flexible manipulator when it comes into contact with a motionless object. This control law is based on a lumped-parameter model. The tracking of the desired contact force is obtained by using a feedback loop control of the coupling torque between the motor and the flexible arm. To achieve a good performance on the force control it is only necessary to measure the coupling torque at the root of the arm. Neither the contact force sensor nor the angular position sensor of the motor are used in the control method. A modified PID controller is proposed for this control law. In this work the force control problem is studied for both free and constrained motions of the flexible manipulator, and a collision detection algorithm is also described.     

Analysis and experimental validation of force bandwidth for force control

Controlling robots in contact with the environment is an important problem in industry applications. In the conventional force control, much research has paid attention to develop novel force control systems and implemented force sensors to detect external force. This paper shows that narrow bandwidth of force sensor has a big influence on the force control system. Generally, to solve the instability in force control, the velocity feedback gain is enlarged. The system becomes unstable with small velocity feedback gain, and robot's response becomes slow with large one. Inasmuch as there is a tradeoff between the stability and the response, it is considered that force control by robots is difficult. This paper proposes a force control system with disturbance observer. It is possible to obtain the force information with wide bandwidth by using the disturbance observer. This paper shows that bandwidth of force sensing is very important for contact motion control. By using the wide bandwidth of force sensing, both stability and response are improved. Furthermore, force control is attainable by the construction of the easiest force control architecture. Therefore, the ideal zero-stiffness-force control is attained. The numerical and experimental results show viability of the proposed method.     

Self‐Powered Tactile Sensor Array Systems Based on the Triboelectric Effect

With the arrival of intelligent terminals, tactile sensors which are capable of sensing various external physical stimuli are considered among the most vital devices for the next generation of smart electronics. To create a self‐powered tactile sensor system that can function sustainably and continuously without an external power source is of crucial significance. An overview of the development in self‐powered tactile sensor array system based on the triboelectric effect is systematically presented. The combination of multi‐functionalization and high performance of tactile sensors aimed at achieving highly comprehensive performance is presented. For the tactile sensor unit, a development is summarized based on the two primary modes which are vertical contact–separation and single‐electrode. For the pressure mapping array, the resolution is significantly enhanced by the novel cross‐type configuration based on the single‐electrode mode. Integrated with other mechanisms, the performance will be further elevated by broadening of the detect range and realizing of visualization of pressure imaging. Then, two main applications of human–machine interaction (HMI) and trajectory monitoring are comprehensively summarized. Finally, the future perspectives of self‐powered tactile sensor system based on triboelectric effect are discussed.     

Slip detection and control using tactile and force sensors

In this paper, some results concerning the detection and control of the relative motion (slippage) of two bodies in contact are presented. The main motivation of this research can be found in advanced manipulation with robotic systems, in which, depending on the particular task to be executed, it might be desirable either to avoid or to exploit the slippage of the manipulated object. The main contribution of this paper is that, besides the linear Coulomb friction effect, the rotational case is also addressed and, therefore, both translational and rotational motions are taken into account. This result is achieved by using an integrated sensor constituted by a force/torque and a tactile sensor. Experimental results are presented considering both the detection of the slippage and its subsequent control