Slip Sensor Research Articles

Thick-film piezoceramics and devices

Over the past 20 years, thick-film (screen printed) technology has been shown to possess a variety of desirable characteristics, which are particularly suitable for the realisation of micro-sensors and actuators. In particular, thick-film sensors are noted for their robust, versatile, compact and inexpensive nature. This paper will describe how screen printed thick-films can be used as the basis for a variety of piezoelectric a transducers. It will be shown how the technology can be combined with MicroElectroMechanical Systems (MEMS) to generate new types of microengineered structure. The evolution of the technology to a successful enabling mechanism for modern-day solid state sensors is described. The paper begins with a brief overview of piezoelectric thick-films including a discussion of the main factors relating to paste formulation, characterisation and techniques for fabricating devices. There is also a description of methods for fabricating thick-films on silicon, which opens up the possibility of using thick-film technology in the field of MEMS. A number of specific sensors and actuators are described, including accelerometers, micropumps, ultrasonic motors, slip sensors for prosthetic hands, resonators, elastic wave sensors and ultrasonic separators.

Wheel slip measurement in 2WD tractor

A microcontroller-based slip sensor was developed for a 2WD tractor to indicate slip values during on-farm use. The ‘zero condition’ considered for the development of slip sensor was – tractor supplied with a driving torque to propel any device across a tarmacadam surface while delivering zero net traction (self-propelled condition). This sensor comprised of four components: power supply; sensing of throttle position, gear position, and wheel rpm; processing of collected data; and display unit. Power was taken from the tractor battery. Rotary potentiometer and proximity switches were installed on the tractor to measure throttle position and wheel revolution, respectively. The performance of developed slip sensor was evaluated both on tarmacadam surface as well as in the field. The variations between indicated and actual slip were found to be within 0–5% for both the surfaces, thus indicating the accuracy of slip measurement by the developed slip sensor.

2P2-B19 局所滑りセンサを用いたマスタ・スレーブシステムにおける把持力制御

2P2-B19 局所滑りセンサを用いたマスタ・スレーブシステムにおける把持力制御

Thick-film force and slip sensors for a prosthetic hand

In an attempt to improve the functionality of a prosthetic hand device, a new fingertip has been developed that incorporates sensors to measure temperature and grip force and to detect the onset of object slip from the hand. The sensors have been implemented using thick-film printing technology and exploit the piezoresistive characteristics of commercially available screen printing resistor pastes and the piezoelectric properties of proprietary lead-zirconate-titanate (PZT) formulated pastes. The force sensor exhibits a highly linear response to forces up to 50 N with a maximum hysteresis of less than 1.4% of full scale. When configured as a pseudo half-bridge measurement circuit, the force sensor demonstrates superior insensitivity to the position of the force on the fingertip than when configured as a classic half-bridge circuit. The force sensor response is also extremely stable with temperature, typically showing variation in the output response of less than ±0.04% over the temperature range −10 °C to +35 °C when loaded with forces up to 10.8 N. The ability of the piezoelectric PZT vibration sensor to detect small vibrations of the cantilever, indicative of object slip, has also been demonstrated.

Thick-film force, slip and temperature sensors for a prosthetic hand

Thick-film static and dynamic force sensors have been investigated for their suitability to measure the grip forces exerted upon an object held by a prosthetic hand, and to detect and correspondingly react to the possible slip of a gripped item. The static force sensors exploit the piezoresistive characteristics of commercially available thick-film pastes whilst the dynamic slip sensors utilize the piezoelectric behaviour of proprietary PZT (lead zirconate titanate) pastes. The sensors are located upon stainless steel cantilever type structures that will be placed at the fingertips of each digit of the prosthetic hand. Temperature sensors are also included to provide temperature compensation for the force sensors and to prevent accidental thermal damage to the prosthesis. Results have shown that the static force sensor is capable of measuring fingertip forces in excess of 100 N, with an electrical half-bridge configuration sensitivity approaching 10 µV V−1 N−1 (with scope for improvement) and maximum hysteresis below 4% of full scale, depending on the manner in which the cantilever sensor array is attached to the finger. Failure in the bonding mechanism that secures the PZT layer to the stainless steel cantilever meant that the proposed dynamic force sensor could not be evaluated. However, investigations using the same sensor design fabricated on an alumina substrate have shown the potential of the PZT dynamic force sensor to measure the vibration and hence potentially operate as a slip sensor.

音響共鳴型テンソルセル触覚センサによる滑り予知と把持動作への応用

This paper describes a slip sensor using Acoustic Resonant Tensor Cell (ARTC) . This slip sensor is made smaller than previous researches. We conducted a finite element method simulation to ensure the hypothesis of slip detection. Then we propose how to feedback the slip information to grasping force. Furthermore its performance of slip detection is shown through experiments for evalueation.

SENSORY SUBSTITUTION IN PROSTHETICS

Use of arm and hand prostheses may be essential for many amputees to facilitate activities of daily life and interaction with society. A major drawback that reduces the use of prostheses, however, is the lack of sensibility. Current strategies for sensory feedback in commercially available prostheses are based on force and slip sensors in the mechanical hand for independent grasp control in an opening and closing function. Developing principles for providing conscious sensibility is discussed, including new techniques where hearing is used as substitution for sensation based on sense substitution.

多関節多指ロボットハンドによる物体操作における滑り検出と計測

This paper describes a new method of detection and measurement of fingertip slip on the surface of a manipulated object in a multi-fingered precision manipulation with rolling contact. Due to the fact that slip sensors are still in a basic research phase and no slip sensor is compatible with the actual fingertip manipulation, our method is based on the multi-sensor fusion of vision, joint-encoders of the fingers, and finger-tip force/torque sensors. Position of the contact between the object and the fingertip is computed in realtime from the measured pose of the object and the fingertip position. Slip displacement of the fingertip contact is then separated from the displacement by rolling mo-tion of the fingertip. Reliability of the slip detection from the noisy data is improved using the tangential-to-normal ratio of the measured force at the contact and the mutual relationship between the tangential force and the direction of the contact displacement. Results of the experiments show the effectiveness of the method.

Development of a Flexible Artificial Hand System Equipped with a Slip Sensor.

This study develops a flexible artificial hand system with slip sensors. The artificial hand is composed of four flexible actuators. Two pairs of two opposite actuators are driven by the independent air pressure sources each. In each pair, one of opposite pair of actuators is equipped with a slip sensor. The slip sensor is composed of a photo reflector and a conductive rubber sensitive to load force. The contact of the hand to an object is detected by the change of resistance of the conductive rubber. After the detection of contact, the slip velocity is measured by calculating the cross-correlation function of the output voltage waveforms of two photo transistors in the photo reflector. The grasping force of the hand is increased according to the measured slip velocity. The calculation of the cross-correlation function and the generation of control signals are made in a host personal computer. From the experimental results of holding several objects, the hand system is proved to grasp suitably the object whose weight is previously unknown.

ロボットハンドのための指紋を備えた高周波微振動検出式滑り覚センサ

ロボットハンドのための指紋を備えた高周波微振動検出式滑り覚センサ

Development of a Flexible Artificial Hand System Equipped with a Slip Sensor.

This study develops a flexible artificial hand system with slip sensors. The artificial hand is composed of four flexible actuators. Two pairs of two opposite actuators are driven by the independent air pressure sources each. In each pair, one of opposite pair of actuators is equipped with a slip sensor. The slip sensor is composed of a photo reflector and a conductive rubber sensitive to load force. The contact of the hand to an object is detected by the change of resistance of the conductive rubber. After the detection of touch, the slip velocity is measured by ca]culating the cross-correlation function of the output voltage waveforms of two photo transistors in the photo reflector. The grasping force of the hand is increased according to the measured slip velocity. The calculation of the crosscorrelation function and the generation of control signals are made in a host personal computer. From the experimental results of holding several objects, the hand system is proved to grasp suitably the object whose weight is previously unknown.

Force and explicit slip sensing for the AMADEUS underwater gripper

The design of the fingertip sensing subsystem constructed for use in a dextrous underwater gripper is presented. Two distinct types of sensor were developed specifically for this application, a force sensor and a slip sensor. The force sensor is used to determine the force exerted by the gripper on the target object, and hence to allow the force hop closure required to carry out dextrous manipulation and to handle delicate marine samples. The function of the slip sensor is to detect the occurrence of slippage between the fingertip and the target, and this information can be used in a variety of ways: for example, providing a warning system to the force control loop or enhancing the gripper's exploratory capabilites in areas of poor visibility. Due to changes in ambient pressure, the force sensor is a simple robust device based on strain gauge technology developed specifically for this application. The sensor is capable of being incorporated on an artificial fingertip mounted at the extremity of the finger of a dextrous gripper. The slip sensor is an extremely small P VDF-based device capable of being shaped to suit the curvature of the fingertip. An analysis of both sensors' operation is presented, along with calibration measurements and results for the first prototypes.

AMADEUS: advanced manipulation for deep underwater sampling

AMADEUS is a dexterous subsea robot hand incorporating force and slip contact sensing, using fluid filled tentacles for fingers. Hydraulic pressure variations in each of three flexible tubes (bellows) in each finger create a bending moment, and consequent motion or increase in contact force during grasping. Such fingers have inherent passive compliance, no moving parts, and are naturally depth pressure-compensated, making them ideal for reliable use in the deep ocean. In addition to the mechanical design, development of the hand has also considered closed loop finger position and force control, coordinated finger motion for grasping, force and slip sensor development/signal processing, and reactive world modeling/planning for supervisory 'blind grasping'. Initially, the application focus is for marine science tasks, but broader roles in offshore oil and gas, salvage, and military use are foreseen.

Slip sensors for the control of the grasp in functional neuromuscular stimulation

In this paper we present the results of research on the role of slip and force sensors in the control of grasp by means of functional neuromuscular stimulation (FNS) when applied to plegic subjects. From our study, it emerged that a reliable control strategy can be more efficiently based on the slip signal than on the signal related to the force exerted by the fingers. A prototype system involving both slip detectors, realized by means, of inductive transducers, and force sensors has been designed.

Determination of Grasp Forces for Robot Hands Based on Human Capabilities

This paper discusses a physiological approach motivated by the study of human hands for robot hand force control. We begin with the analysis of a humanʼs grasping behavior to see how humans determine the grasp forces. The human controls the grasp force by sensing the friction force, that is, the weightof an object which is felt on his hand, but when slip is detected by sensing skin acceleration, the grasp forcebecomes much greater than the minuscule force required for grasping by adding the force which is proportionaltothe acceleration. And two methods that can predict when and how fingers will slip upon a grasped object are considered. To emulate the humanʼs capabilities, we propose a method for determination of a grasp force, which uses the change in the friction force. Experimental results show that the proposed method can be applied to control of robot hands to grasp objects of arbitrary weight stably without skin-like slip sensors

A clinical experience with a hierarchically controlled myoelectric hand prosthesis with vibro-tactile feedback

Improved performance of externally powered myoelectric hands is possible when the direct control of the digit flexion and grip force are given over to an electronic controller which frees the operator to concentrate on other demands. A commercial myoelectric hand was modified to take the new touch and slip sensors and novel control method. An adult male with a traumatic mid-forearm amputation. The range and ease of use of the prosthetics system. The hand was easily and usefully operated in the home and work environment. Hierarchical control of a hand is possible using sensory feedback to a sophisticated electronic controller. Such a control method reduces the demands on the user's concentration and enhances the hand's range.

Characterization of an optical and acoustic touch and slip sensor for autonomous manipulation

Feedback signals from a transducer in an artificial hand or robot gripper are essential for the successful manipulation of objects. A series of different control strategies have been developed to improve the performance of an anthropomorphic prosthesis by detecting when the object slips. The methods are designed to be independent and so their combination improves the system's total performance by removing the false detection of slides whilst increasing sensitivity. The principal method of transduction uses a novel combined touch and slip sensor to detect the contact force as well as the vibrations set up when the object slips within the hand's grasp. Static and dynamic characteristics of the sensor are described. While the target application for this method is prosthetics, similar techniques can be applied to more general classes of robotic manipulation. These methods would improve a robot's response because the device does not require detailed recognition of a target object or its orientation prior to handling.

Algorithms for processing data from a photoelastic slip sensor

Methods of processing the camera output of a new photelastic slip sensor are investigated. These all involve grouping the outputs of the individual camera pixels and treating the gross output of each group as that of a single macro pixel. The grouping has the advantage of reducing noise as well as processing time and storage space, without adversely affecting resolution. The paper discusses the design of macro pixels, the problems of resolution and noise, and the different algorithms for processing the macro pixel outputs.

格子像投影型非接触小型スリップセンサの開発

The problem of slip detection has to be explored so that an industrial robot may certainly grasp objects with the appropriate grasping force. Slip Sensors must be able to detect fine slip to be used for controlling grasping force. Slip sensors are classified into two types; tactile slip sensors and nontactile slip sensors. The tactile slip sensors must be pressed against the object surface. If the sensor is pressed with an insufficient force, it can't detect slip correctly. If the sensor is pressed with an excessive force, the object may be damaged. A method of nontactile slip detection have been proposed before. In this method, the sensor detects intensity of scattered light from an object surface at the position of fringes of the phenomenon of two-beam interference. In this paper, we describe development of a nontactile slip sensor using the method above mentioned. The slip sensor has features as follows; 1. NonTactile, 2. The fine slip can be detected by projecting a grating image on the object surface, 3. The sensor is miniaturized by using semiconductor laser and by assembling components of the sensor in one case.

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.