Tactile sensor
Encyclopedia
The term tactile sensor usually refers to a transducer
that is sensitive to touch, force, or pressure. Tactile sensors are employed wherever interactions between a contact surface and the environment are to be measured and registered. Tactile sensors are useful in a wide variety of applications for robotics
and computer hardware
and even security systems.
A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. The term tactile refers to the somatosensory system
or more commonly the sense of touch. A tactile sensor is a device which receives and responds to a signal or stimulus having to do with force.
Tactile sensors are generally known and can be grouped into a number of different types depending upon their construction; the most common groups are piezoresistive, piezoelectric, capacitive and elastoresistive sensors.
Sensors that measure very small changes must have very high sensitivities. Sensors need to be designed to have a small effect on what is measured; making the sensor smaller often improves this and may introduce other advantages. Tactile sensors can be used to test the performance of all types of applications. For example, these sensors have been noted to be used in the manufacturing
of automobiles (brakes, clutches, door seals, gasket
), battery
lamination, bolted joints, fuel cell
, etc.
In robots designed to interact with objects requiring handling involving: precision, dexterity, or interaction with unusual objects it becomes increasingly necessary to provide sensory apparatus which is functionally equivalent to the various sensors which human workers are naturally endowed. Tactile sensors have been developed for use with robots. Tactile sensors can complement visual systems by providing information at the time contact is made between a gripper of the robot and an object being gripped. At this time vision is no longer sufficient, as the mechanical properties of the object cannot be determined by vision alone. Determining weight, center of mass
, coefficient of friction. And thermal conductivity
require object interaction and some sort of tactile sensing.
Several classes of tactile sensors are used in robots:
is a ‘tactile element’. Each tactel is capable of detecting normal forces. The advantage of tactel based sensors is that they provide a high resolution ‘image’ of the contact surface. Pressure sensor arrays are often available in thin-film form. They are primarily used as analytical tools used in the manufacturing
and R&D processes by engineers and technician, but have been adapted to be used in robots. Examples of such sensors available to consumers include arrays built from conductive rubber , lead zirconate titanate
(PZT), polyvinylidene fluoride
(PVDF), and metallic capacitive sensing
elements.
, where each are responsible for detecting the force or torque in a particular direction. The advantage of strain gauges is that when the information from each individual strain gauge is combined, the information allows determination of a pattern of forces or torques..
and force sensing both with human-like ability.
Advanced versions of biologically designed tactile sensors include vibration
sensing which has been determined to be important for understanding interactions between the tactile sensor and objects where the sensor slides over the object. Such interactions are now understood to be important for human tool use and judging the texture of an object . One such sensor combines force sensing, vibration sensing, and heat transfer sensing.
Transducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
that is sensitive to touch, force, or pressure. Tactile sensors are employed wherever interactions between a contact surface and the environment are to be measured and registered. Tactile sensors are useful in a wide variety of applications for robotics
Robotics
Robotics is the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots...
and computer hardware
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
and even security systems.
A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. The term tactile refers to the somatosensory system
Somatosensory system
The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...
or more commonly the sense of touch. A tactile sensor is a device which receives and responds to a signal or stimulus having to do with force.
Tactile sensors are generally known and can be grouped into a number of different types depending upon their construction; the most common groups are piezoresistive, piezoelectric, capacitive and elastoresistive sensors.
Uses
Tactile sensors are often in everyday objects such as elevator buttons and lamps which dim or brighten by touching the base. There are also innumerable applications for tactile sensors of which most people are never aware.Sensors that measure very small changes must have very high sensitivities. Sensors need to be designed to have a small effect on what is measured; making the sensor smaller often improves this and may introduce other advantages. Tactile sensors can be used to test the performance of all types of applications. For example, these sensors have been noted to be used in the manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
of automobiles (brakes, clutches, door seals, gasket
Gasket
thumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...
), battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
lamination, bolted joints, fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
, etc.
In robots designed to interact with objects requiring handling involving: precision, dexterity, or interaction with unusual objects it becomes increasingly necessary to provide sensory apparatus which is functionally equivalent to the various sensors which human workers are naturally endowed. Tactile sensors have been developed for use with robots. Tactile sensors can complement visual systems by providing information at the time contact is made between a gripper of the robot and an object being gripped. At this time vision is no longer sufficient, as the mechanical properties of the object cannot be determined by vision alone. Determining weight, center of mass
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...
, coefficient of friction. And thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
require object interaction and some sort of tactile sensing.
Several classes of tactile sensors are used in robots:
Pressure Sensor Arrays
Pressure sensors arrays are large grids of tactels. A tactelTactel
Tactel can mean:*Tactel - a single sensing point on a tactile sensor array. A tactel is equivalent to a pixel, in that an array of tactels represents an image of the surface being touched....
is a ‘tactile element’. Each tactel is capable of detecting normal forces. The advantage of tactel based sensors is that they provide a high resolution ‘image’ of the contact surface. Pressure sensor arrays are often available in thin-film form. They are primarily used as analytical tools used in the manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
and R&D processes by engineers and technician, but have been adapted to be used in robots. Examples of such sensors available to consumers include arrays built from conductive rubber , lead zirconate titanate
Lead zirconate titanate
Lead zirconate titanate , also called PZT, is a ceramic perovskite material that shows a marked piezoelectric effect. PZT-based compounds are composed of the chemical elements lead and zirconium and the chemical compound titanate which are combined under extremely high temperatures. A filter is...
(PZT), polyvinylidene fluoride
Polyvinylidene fluoride
Polyvinylidene fluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer.PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat and low...
(PVDF), and metallic capacitive sensing
Capacitive sensing
In electrical engineering, capacitive sensing is a technology based on capacitive coupling that is used in many different types of sensors, including those to detect and measure: proximity, position or displacement, humidity, fluid level, and acceleration...
elements.
Strain Gauge Rosettes
Strain gauges rosettes, are constricted from multiple strain gaugesStrain gauge
A strain gauge is a device used to measure the strain of an object. Invented by Edward E. Simmons and Arthur C. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable...
, where each are responsible for detecting the force or torque in a particular direction. The advantage of strain gauges is that when the information from each individual strain gauge is combined, the information allows determination of a pattern of forces or torques..
Biologically Inspired Tactile Sensors
A variety of biologically inspired designs have been suggested, . One characteristic of biologically inspired tactile sensors is that often incorporate more than one sensing strategy. For example, they might detect both the distribution of pressures, and the pattern of forces that would come from pressure sensor arrays and strain gauge rosettes. Hence, the advantage of a biologically designed tactile sensor is able to perform multiple types of sensing, e.g. two-point discriminationTwo-point discrimination
Two-point discrimination is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one. It is often tested with two sharp points during a neurological examination and reflects how finely innervated an area of skin is....
and force sensing both with human-like ability.
Advanced versions of biologically designed tactile sensors include vibration
Vibration
Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
sensing which has been determined to be important for understanding interactions between the tactile sensor and objects where the sensor slides over the object. Such interactions are now understood to be important for human tool use and judging the texture of an object . One such sensor combines force sensing, vibration sensing, and heat transfer sensing.
See also
- List of sensors
- Pressure measurementPressure measurementMany techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges....
- SensitivitySensitivity (electronics)The sensitivity of an electronic device, such as a communications system receiver, or detection device, such as a PIN diode, is the minimum magnitude of input signal required to produce a specified output signal having a specified signal-to-noise ratio, or other specified criteria.Sensitivity is...
- Sensors
- TransducerTransducerA transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
- Robots