Robotic sensors

Robotic sensors are used to estimate a robot's condition and environment. These signals are passed to a controller to enable appropriate behavior.

Sensors in robots are based on the functions of human sensory organs. Robots require extensive information about their environment in order to function effectively.

Classification
Sensors provide analogs to human senses and can monitor other phenomena for which humans lack explicit sensors.

Simple Touch: Sensing an object's presence or absence.
Complex Touch: Sensing an object's size, shape and/or hardness.
Simple Force: Measuring force along a single axis.
Complex Force: Measuring force along multiple axes.
Simple Vision: Detecting edges, holes and corners.
Complex Vision: Recognizing objects.
Proximity: Non-contact detection of an object.

Sensors can measure physical properties, such as the distance between objects, the presence of light and the frequency of sound. They can measure:

Object Proximity: The presence/absence of an object, bearing, color, distance between objects.
Physical orientation. The co-ordinates of object in space.
Heat: The wavelength of infrared or ultra violet rays, temperature, magnitude, direction.
Chemicals: The presence, identity, and concentration of chemicals or reactants.
Light: The presence, color, and intensity of light.
Sound: The presence, frequency, and intensity of sound.

Motion controllers, potentiometers, tacho-generators and encoder are used as joint sensors, whereas strain-gauge based sensing is used at the end-effector location for contact force control.

Internal sensor
It is the part of the robot.Internal sensors measure the robot's internal state. They are used to measure position, velocity and acceleration of the robot joint or end effectors.

Position sensor
Position sensors measure the position of a joint (the degree to which the joint is extended). They include:

Encoder: a digital optical device that converts motion into a sequence of digital pulses.
Potentiometer: a variable resistance device that expresses linear or angular displacements in terms of voltage.
Linear variable differential transformer: a displacement transducer that provides high accuracy. It generates an AC signal whose magnitude is a function of the displacement of a moving core.
Synchros and Resolvers

Velocity Sensor
A velocity or speed sensor measures consecutive position measurements at known intervals and computes the time rate of change in the position values.

Applications
In a parts feeder, a vision sensor can eliminate the need for an alignment pallet. Vision-enabled insertion robots can precisely perform fitting and insertion operations of machine parts.

Types of Sensors In the Robot
There are many types of sensors that can be embedded in a robot. By having various functions too. Among others are;

Touch Sensor. Is a type of sensor that will detect when touched, like skin . Touch Sensors are basically switches that have various types of shapes. The robot is used for example; detect objects that are on the robot's hand , prevent collisions on wheeled robots, and much more. The simplest example of touch sensor is the Push Button.

Light Sensor. This sensor detects light or is sensitive to light around it. With this sensor the robot can know the darkness and light of an object, place, day or night . To determine the dark and light an ordinary place uses the LDR Sensor, while for the purposes of the Robot Follower (Line Follower) using the InfraRed Sensor.

Color Sensor. Just like a light sensor or Infra Red sensor, the color sensor can also detect dark light by capturing black and white . But besides that, Color Sensor can also detect other colors like red , blue , yellow , and so on. In its application, the color sensor can also be used to make the robot Line Follower, even more sophisticated, namely: it can follow lines with more specific colors.

Distance Sensor. Is a type of sensor used to detect objects by measuring the distance of the object. This sensor can measure distances very accurately. In robots, Distance Sensors are useful as eyes. Robots can see objects in front of them with this sensor. Example of Distance Sensor which is most often used is Ultrasonic sensor. The way it works is exactly like the mouth and ears of the bat.

Sound Sensor. Detecting the sound around the robot, its function is of course like the ear . Through this sensor program can distinguish loud sounds, sounds that are not loud, and quiet . The intensity can be set manually, or through a program, depending on the type of Sound Sensor used. Even for Voice Recognition, it can be programmed to hear the word (language) used by humans.
Balance Sensor. Usually used to make the robot stay balanced. Knowing the slope, and help wake up when the robot falls. One example is the Gyroscope, used also on Smartphones.

Gas Sensor. Serves to detect various types of gases or fumes around. Like the nose in humans, it can distinguish which gas is a normal gas which is dangerous. Examples of gas sensor applications are for Bomb tamer robots, or GreenBird robots.

Temperature Sensor. Just like skin that can feel heat and cold . With Temperature Sensor can recognize the temperature around it.

Actually there are many more sensors that you can use for robots. But the 8 sensors above are the most commonly used.

Source from Wikipedia