Sensor For Robotic Applications Research Articles

Progress on flexible tactile sensors in robotic applications on objects properties recognition, manipulation and human-machine interactions

The past decade has witnessed an emerging and fast-growing field on mechanically soft systems, ranging from soft materials (e.g. hydrogels) to soft devices (e.g. flexible electronics), and to soft functional systems (e.g. soft robotics). It is envisioned that soft systems will continue to thrive in the coming decades in academia and industrial communities. The launch of Soft Science is to provide the first dedicated platform for publishing research findings and to share the knowledge among the communities.

CapSense: A Real-Time Capacitive Sensor Simulation Framework for Physical Human-Robot Interaction

This letter presents CapSense, a real-time open-source capacitive sensor simulation framework for robotic applications. CapSense provides raw data of capacitive proximity sensors based on a fast and efficient 3D finite-element method (FEM) implementation. The proposed framework is interfaced to off-the-shelf robot and physics simulation environments to couple dynamic interaction of the environment with an electrostatic solver for capacitance computation in real-time. The FEM method proposed in this letter relies on a static tetrahedral mesh of the sensor surrounding without a-posteriori re-meshing and achieves high update rates by an adaptive update step. CapSense is flexible due to various configuration parameters (i.e. number, size, shape and location of electrodes) and serves as a platform for investigation of capacitive sensors in robotic applications. By using the proposed framework, researchers can simulate capacitive sensors in different scenarios and investigate these sensors and their configuration prior to installation and fabrication of real hardware. The proposed framework opens new research opportunities via sim-to-real transfer of capacitive sensing. The simulation approach is validated by comparing real-world results of different scenarios with simulation results. In order to showcase the benefits of CapSense in physical Human-Robot Interaction (pHRI), the framework is evaluated in a robotic healthcare scenario.

3D Printed Spring‐Type Electronics with Liquid Metals for Highly Stretchable Conductors and Inductive Strain/Pressure Sensors (Adv. Mater. Technol. 7/2022)

Spring-Type Electronics In article number 2101657, Tomoyuki Yokota, Takao Someya and colleagues develop soft spring-type electronic devices formed by core–sheath structures of liquid metals and 3D-printed elastomeric shells. The spring devices work not only as stretchable conductors with minor resistance change, but also as inductive strain/pressure sensors for robotic applications by using the change in the magnetic flux caused by the spring deformation.

Six-Axis Force/Torque Sensors for Robotics Applications: A Review

Six-axis force/torque sensors are transducers capable of measuring three dimensions of force and three dimensions of torque, and have a wide range of applications in robotic systems. The sensing principle behind the greatest majority of these is based on detecting strains in an elastic structure, and there are multiple modalities for strain measurement, including resistive strain gauge, piezoelectric, capacitive, and optoelectronic techniques. Developed sensors can be evaluated based on a range of parameters, including decoupling error, nonlinearity error, and measurement isotropy, where the primary design challenge is to maximise the allowable sensing range while minimising measurement errors. This literature review describes the state of the art of the field, and includes all relevant research associated with the search term “six-axis force/torque sensor” spanning 2015 - June 2021. The published literature for each sensing technique is summarised and evaluated, and a generalised sensor selection framework is proposed to assist the reader with the selection procedure for a state of the art sensor. In the period considered, there have been no significant improvements with the sensors documented in terms of measurement errors. Researchers have instead focused on features such as fault tolerance, alternative sensing techniques, cost reduction, and miniaturisation. These trends are expected to continue, and moving forward, the most significant challenge in the field is expected to be the lowering of manufacturing costs, as trends indicate measurement performance has reached maturity.

Flexible self-powered multifunctional sensor for stiffness-tunable soft robotic gripper by multimaterial 3D printing

Proprioceptive sensation via embedded flexible sensors is essential for soft robotic grippers to realize safe and dexterous grasping. We demonstrate a self-powered, flexible multifunctional sensor by combining a polyvinylidene difluoride film with a microstructured jamming layer. The jamming layers and the finger body are fabricated by a multimaterial 3D printing technology. The sensor built into the soft finger can provide passive proprioceptive sensations of curvature and stiffness, with maximum sensitivity of 0.55 mV m and 0.09 Vm/N respectively. It also acted as an active jamming element to tune finger stiffness (15–44 N/m) while not affecting the dynamics of the robotic movement. We demonstrate the multifunctional sensor with a three-fingered robotic gripper to successfully record finger bending and stiffening in the ‘pick and place’ process. This work shows potential of greatly enhancing the way in which a gripper interacts with objects that are manipulated and provide a route to achieve anthropomorphic grippers. • Sensitive enhancing layer was printed with soft finger by multimaterial 3D printing. • The self-powered sensor can measure curvature and stiffness up to 10 m -1 and 44 N/m. • The multifunctional sensor is able to sense finger curvature and stiffness. • This work suggests a new way of designing sensors in robotic applications.

A versatile 4D capacitive imaging array: a touchless skin and an obstacle-avoidance sensor for robotic applications

There are growing interests in the use of robots in collaborative environments with humans or other intelligent machines. Sensing the environment for which the robot is operating can be done in many ways, generally guided by skin-like sensors. Some of the skins are inspired by natural sensing in humans or other species. As humans, we use many of our senses, such as version, hearing, smell, and touch, to move around by avoiding colliding with other humans or objects. Different from humans, many other mammals also use whiskers as an additional sensor to help navigate around. In this paper, we demonstrate a touchless capacitive imaging-based sensor in the situation where the obstacles are in close vicinity to the robot. The proposed imaging system can sense the changes in areas near to the skin-like sensors by measuring the capacitances between the array of electrodes. A 4D sensing approach has been developed with the spatiotemporal Total Variation algorithm. The 4D operational mode gives sensors the time awareness that allows for dynamical responses and hence the better control of the robots. Several experiments are conducted to show the skin-like behaviour of this sensor by simulating various scenarios. The sensor shows the excellent ability to detect an object in its vicinity, where the depth is close to half of the planar sensor array size.

Design and Calibration of a Force/Tactile Sensor for Dexterous Manipulation.

This paper presents the design and calibration of a new force/tactile sensor for robotic applications. The sensor is suitably designed to provide the robotic grasping device with a sensory system mimicking the human sense of touch, namely, a device sensitive to contact forces, object slip and object geometry. This type of perception information is of paramount importance not only in dexterous manipulation but even in simple grasping tasks, especially when objects are fragile, such that only a minimum amount of grasping force can be applied to hold the object without damaging it. Moreover, sensing only forces and not moments can be very limiting to securely grasp an object when it is grasped far from its center of gravity. Therefore, the perception of torsional moments is a key requirement of the designed sensor. Furthermore, the sensor is also the mechanical interface between the gripper and the manipulated object, therefore its design should consider also the requirements for a correct holding of the object. The most relevant of such requirements is the necessity to hold a torsional moment, therefore a soft distributed contact is necessary. The presence of a soft contact poses a number of challenges in the calibration of the sensor, and that is another contribution of this work. Experimental validation is provided in real grasping tasks with two sensors mounted on an industrial gripper.

Structural design and output characteristic analysis of magnetostrictive tactile sensor for robotic applications

A novel magnetostrictive tactile sensor has been designed according to the transduction mechanism of cilia and Villari effect of iron-gallium alloy. The tactile sensor consists of a Galfenol beam, a pair of permanent magnets, a Hall sensor and a signal processing system. Compared with the conventional tactile sensor, our proposed tactile sensor can not only detect the contact-force, but also sense stiffness of an object. The performance and measurement range of tactile sensor have theoretically been analyzed and experimentally investigated. The results have revealed that the sensibility of tactile sensor for sensing force is up to 22.81mV/N at applied bias magnetic field of 2.56kA/m. Moreover, the sensor can effectively discriminate objects with different stiffness. The sensor is characterized by high sensitivity, good linearity, and quick response. It has the potential of being miniaturized and integrated into the finger of a robotic hand to realize force sensing and object recognition in real-time.

A Novel Six-Axis Force/Torque Sensor for Robotic Applications

This paper presents a novel six-axis force/torque (F/T) sensor for robotic applications that is self-contained, rugged, and inexpensive. Six capacitive sensor cells are adopted to detect three normal and three shear forces. Six sensor cell readings are converted to F/T information via calibrations and transformation. To simplify the manufacturing processes, a sensor design with parallel and orthogonal arrangements of sensing cells is proposed, which achieves the large improvement of the sensitivity. Also, the signal processing is realized with a single printed circuit board and a ground plate, and thus, we make it possible to build a lightweight six-axis F/T sensor with simple manufacturing processes at extremely low cost. The sensor is manufactured and its performances are validated by comparing them with a commercial six-axis F/T sensor.

Calibrating Distance Sensors for Terrestrial Applications Without Groundtruth Information

This paper describes a new calibration procedure for distance sensors that does not require independent sources of groundtruth information, i.e., that is not based on comparing the measurements from the uncalibrated sensor against measurements from a precise device assumed as the groundtruth. Alternatively, the procedure assumes that the uncalibrated distance sensor moves in space on a straight line in an environment with fixed targets, so that the intrinsic parameters of the statistical model of the sensor readings are calibrated without requiring tests in controlled environments, but rather in environments where the sensor follows linear movement and objects do not move. The proposed calibration procedure exploits an approximated expectation maximization scheme on top of two ingredients: an heteroscedastic statistical model describing the measurement process, and a simplified dynamical model describing the linear sensor movement. The procedure is designed to be capable of not just estimating the parameters of one generic distance sensor, but rather integrating the most common sensors in robotic applications, such as Lidars, odometers, and sonar rangers and learn the intrinsic parameters of all these sensors simultaneously. Tests in a controlled environment led to a reduction of the mean squared error of the measurements returned by a commercial triangulation Lidar by a factor between 3 and 6, comparable to the efficiency of other state-of-the art groundtruth-based calibration procedures. Adding odometric and ultrasonic information further improved the performance index of the overall distance estimation strategy by a factor of up to 1.2. Tests also show high robustness against violating the linear movements assumption.

A Flexible Low-Power 130 nm CMOS Read-Out Circuit With Tunable Sensitivity for Commercial Robotic Resistive Pressure Sensors

This paper presents a flexible and low-power Read-Out Circuit (ROC) with tunable sensitivity, designed to interface a wide range of commercial resistive pressure sensors for robotic applications. The ROC provides contact detection, monitoring small capacitance variations at low pressure ( $428\times 159~\mu \text{m}^{2}$ ) has a power consumption of 27.2 $\mu \text{W}$ , for $V_{\mathrm {DD}}~1$ V. Using digital control inputs, the ROC allows a wide range tuning of measurement sensitivity (6.7–46.4 mbar/LSB) and adjustable acquisition time (226.6–461.7 $\mu \text{s}$ and 648–890 $\mu \text{s}$ , for contact detection and pressure evaluation, respectively). The read-out time of $\sim 1$ ms is compatible with human response after touch.

An Extended Evaluation of Open Source Surface Reconstruction Software for Robotic Applications

With the raising popularity of 3D sensors in robotic applications, e.g., RGB-D cameras or laser scanners, the demand for fast and reliable methods for surface reconstruction from 3D point clouds increases. Currently, several freely available implementations of such algorithms exist. This paper presents an evaluation of the usability of different open source software packages for polygonal map generation in robotic contexts.

Development of an optoelectronic 6-axis force/torque sensor for robotic applications

This paper reports the development of a novel force/torque sensor for robotic applications. Optoelectronic components have been used as sensible elements, allowing a relatively simple and quite reliable implementation of the sensor. These properties allow an easier integration of the sensor in a number of different robotic systems, such as in the fingers of robotic hands or in industrial grippers. The basic working principle and the design of the sensor are presented, and experimental data are reported and discussed to illustrate its theoretical model and its main features. Finally, the implementation of a sensor prototype is shown, and its use as an intrinsic tactile sensor is investigated and experimentally validated.

Chemical Sensing in Robotic Applications: A Review

Robots are generally equipped with at least several different modalities of sensors. Vision and range sensors are the most popular, especially in mobile robots. On the other hand, olfaction (or chemical sensing in general) had long been ignored in the robotics community because of the technical difficulties involved in realizing artificial olfaction on robotic platforms. Over the past two decades, however, various attempts are made to use chemical sensors in robotic applications. With the help of chemical sensors, mobile robots can follow chemical trails laid on the ground, track chemical plumes to find their sources, and build distribution maps of chemical substances. This paper is intended to present a brief history and the current trends of the research in this emerging field.

Electromechanical characterization of piezoelectric PVDF polymer films for tactile sensors in robotics applications

In this paper an experimental setup and experimental procedures which allow a fast and complete characterization of piezoelectric films continuously over the 1 Hz–1 kHz frequency range are reported. Some results related to PVDF electro-mechanical characterization are also presented. This work is intended as the first step for the electro-mechanical design of innovative integrated transductions systems for tactile sensors in robotic applications. The article concludes with a summary and a discussion of future investigations.

Design and performance of a micro-sized biomorphic compound eye with a scanning retina

Proposes a design of a biomorphic micro visual sensor equipped with a mechanical scanning system. The sensor is inspired by the structure of the fly's compound eye, which was found to possess a unique muscle and tendon actuation system for its scanning retina. The improvement in micro-opto-electro-mechanical systems encourages the design of reliable, efficient, and integrated smart visual sensors for robotic applications, in particular, for the autonomous visually guided navigation of mobile robots. The authors have verified the effect of retinal scanning for a robotic visual system through the construction of a large-scale prototype at the millimeter scale. The performance of a newly fabricated microelectromechanical system prototype whose size approaches the order of the insects' compound eyes is then evaluated in comparison with that of the large-scale prototype. The micro-sized visual sensor is composed of a scanning microlens array (120 /spl mu/m in lens diameter) and a photo-diode array. The actuation of the microlens array induces a rotation of the visual axes. According to the principle of retinal scanning, the micro-sensor is able to retrieve the local angular velocity with enhanced reliability.

Modeling of a scanning laser range sensor for robotic applications

Modeling of a scanning laser range sensor for robotic applications

Modeling of a scanning laser range sensor for robotic applications

The geometric and noise modeling of a scanning range sensor is described. The parameters of the model are determined from data collected during the calibration of the real sensor. The models are shown to predict range scan results which accurately match those of the real sensor.

A novel tactile sensor for robot applications

SUMMARYThis paper examines a tactile slip sensor based on photoelastic effects. Photoelastic patterns are obtained using a Dynamic Ram with a resolution of 256 by 128 pixels. Software is developed to detect changes in the stress patterns when an object moves relative to the surface of the sensor. It is suggested that the stress patterns can be used to detect slippage at the object/gripper interface.

Logical optical detector: a new sensor for robotic applications

The advance of automated assembly equipment and robotics has led to the development of intelligent sensor systems. Analog optical-imaging systems are current, but signal processing and interfacing can make these cumbersome. It would speed up response if the optical information could be presented directly as binary data. A new class of sensor, the logical optical detector, is described. The sensor has an inbuilt threshold, which can be externally controlled and is sharply defined, permitting a form of feedback analog-to-digital conversion. Based on silicon technology, it has wide application, such as in an imaging sensor with memory.