Robotic Systems: Sensors

Sensors are the sensory system of a robot much like the five senses that humans have: touch, sight, sound, smell and taste and measure environmental data like touch, distance, light, sound, strain, rotation, magnetism, smell, temperature, inclination, pressure, or altitude. Sensors provide the raw data that must be processed to provide information to allow the robot to appropriately respond to its environment. Robots are equipped with sensors so they can have an understanding of their surrounding environment and make changes in their behavior based on the information they have gathered.

 

Sensors allow robots to detect objects and variations in the environment. A robot will invariably be equiped with a number of sensors which may include: an acoustic sensor to detect sound, motion or location, infrared sensors to detect heat sources, contact sensors, tactile sensors to give a sense of touch, or optical/vision sensors. A robot can also monitor itself with sensors.

 

Common Sensors

 

Rotation Sensors

Rotation sensors (also called encoders) measure the rotation of a shaft or axle. They are used to measure the angle of a robotic arm, or how far a mobile robot’s wheel has turned.

 

Global Positioning Systems

Global Positioning Systems (GPS) receive signals from orbiting satellites that pinpoint the location of an outdoor robot on the Earth.

 

Laser range Finder

Laser range finders use laser beams to measure the distance to objects. They are used for obstacle detection and navigation.

 

Computer Vision

Cameras are a very common sensor. Computer Vision is the field of study of interpreting camera images for a variety of purposes.

 

Touch Sensors

Touch sensors are basically variable switching devices that work through pressure.

 

Some Uses of a Touch Sensor

Detect contact between the robot and external objects like walls Detect contact with internal moving parts in the robot (arm or gripper). TableBot - detect contact with the ground so the robot doesn’t fall off the table. Input Device - push button or “remote” control

 

Light Sensor

Measures the level of light as a number between 0% (total darkness) and 100% (very bright). Can differentiate light levels reflected from bright and dark surfaces. Inside the light sensor is a photo-transistor. The photo-transistor acts like a valve for electricity. The more light energy it senses, the more electricity flows.

 

Uses of A Light Sensor

Navigation - follow a black line on a white surface (or vice versa). FireflyBot - find a very bright object in a room or area (light bulb). Color sorter - tell the difference between coloured objects . Input Device - different colors or gray levels

 

Rotation Sensor

Measures the rotation of an axle or shaft.The rotation sensor sends out a series of voltage pulses. There will be a number of pulses per rotation. In the lego robotics kits there are 16 of these pulses per one revolution. These pulses are also referred to as “ticks”, “clicks”, or “counts”.