Robotics Lecture 3: Sensors for Robotic Systems

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Questions and Answers

What does a sensor provide in response to a specified physical input?

A mechanical output

A usable output (correct)

An automated process

A manual reading

Which type of sensor is used for measuring sound levels?

Thermal sensor

Gyroscope

Microphone (correct)

Ultrasound sensor

What is the correct formula expressed by Ohm’s Law?

I = V/R

R = I/V

R = V/I

V = IR (correct)

Limit switches are primarily used to detect what?

Proximity of a moving part Signup and view all the answers

What does the switch indicate when it is closed?

The presence of a workpiece Signup and view all the answers

What type of sensors measure distance?

Ultrasound and radar Signup and view all the answers

What is the voltage output when a switch is open?

0 volts Signup and view all the answers

Which of the following is NOT categorized as a type of sensor?

Electric motor Signup and view all the answers

What is the typical detection range of a capacitive proximity switch?

4 to 60 mm Signup and view all the answers

Which component carries out the on-off switch function in a transistor circuit activated by voltage?

Transistor Signup and view all the answers

How does a capacitive proximity switch detect non-metallic objects?

Through dielectric properties Signup and view all the answers

What determines the capacitance of a pair of plates in a capacitive proximity switch?

The distance between the plates Signup and view all the answers

What type of core is used in an inductive proximity switch?

Ferrous metallic Signup and view all the answers

What happens to the inductance in an inductive proximity switch when a ferrous object approaches?

It increases Signup and view all the answers

Which of the following statements about the operation of proximity switches is correct?

They can detect both metallic and non-metallic objects Signup and view all the answers

What is the relationship between capacitance and distance in a capacitive proximity switch?

Capacitance decreases with distance Signup and view all the answers

What is the primary function of a phototransistor in reflective opto-sensors?

To convert light into electrical signals Signup and view all the answers

Which application is NOT commonly associated with photoelectric sensors?

Ambient temperature measurement Signup and view all the answers

What impacts the effectiveness of photoelectric sensors according to their limitations?

Surface color and texture Signup and view all the answers

In light sensors, what change occurs as the brightness of light increases?

Lower resistance Signup and view all the answers

What role do potentiometers play in devices like stereos?

Adjust resistance for volume control Signup and view all the answers

What is the typical detection range for inductive proximity switches?

2 to 15 mm Signup and view all the answers

Which of the following is NOT an advantage of proximity switches?

High thermal sensitivity Signup and view all the answers

In which form are the main types of proximity switches available?

Cylindrical, rectangular, and slot Signup and view all the answers

What type of connections can proximity sensors use when connected to a power supply?

Two-wire and three-wire connections Signup and view all the answers

What type of circuit does an inductive proximity sensor use to detect ferrous metal objects?

Resonant circuit Signup and view all the answers

Which aspect of proximity switches improves their effectiveness in applications involving high-speed objects?

Effective response to high-speed approaches Signup and view all the answers

Which characteristic makes proximity switches preferable in toxic environments?

Durability to vibrations Signup and view all the answers

Which of the following devices can be activated by the current from a proximity switch?

Electronic switch circuit Signup and view all the answers

What does a retro-reflective photoelectric switch primarily use for reflecting the light beam?

Many small corner-cube prisms Signup and view all the answers

How does a diffuse-reflective photoelectric switch operate?

It relies on direct reflection from the detected object. Signup and view all the answers

What is the range of detection distances for photoelectric switches?

Less than 10 cm up to 1500 cm Signup and view all the answers

What is a characteristic of the 'Dark On' operation in photoelectric switches?

The switch is activated when the beam of light is interrupted. Signup and view all the answers

In which configuration are both the emitter and receiver placed in diffuse-reflective photoelectric switches?

In a single housing unit Signup and view all the answers

What occurs when an object interrupts the light beam in a 'Light On' operation?

The switch becomes de-energized. Signup and view all the answers

What is a common feature of both retro-reflective and diffuse-reflective photoelectric switches?

They use a single housing for integration. Signup and view all the answers

Which of these statements distinguishes retro-reflective from diffuse-reflective photoelectric switches?

Retro-reflective uses corner-cube prisms for reflection. Signup and view all the answers

What is the primary function of photoelectric switches?

To detect the presence of an object at long ranges Signup and view all the answers

Which type of photoelectric switch offers the longest sensing distance?

Through-beam switches Signup and view all the answers

What components are essential in a through-beam photoelectric switch?

Emitter and receiver units Signup and view all the answers

In which scenario might you commonly find break beam sensors used?

Counting objects passing through a boundary Signup and view all the answers

How does the sensing distance of a through-beam photoelectric switch depend on emitter and receiver alignment?

Perfect alignment maximizes sensing distance Signup and view all the answers

Which of the following describes the primary difference between retro-reflective and through-beam switches?

Retro-reflective switches use a mirror to return light Signup and view all the answers

What type of light can photoelectric sensors utilize for object detection?

Both visible and infrared light Signup and view all the answers

Which type of object detection technique do photoelectric sensors primarily use?

Optical beam interruption Signup and view all the answers

Study Notes

Robotics Lecture Notes

Robotics - Lecture presented by Mahmoud Abdelaal
Lecture 3 - Sensors for Robotic Systems I

Sensors for Robotic Systems

Definition: A sensor is an input device that provides an output based on a specific physical input. Example: A thermocouple converts temperature difference to an electrical output.
General Question: Given a sensor reading, what was the situation in the world like?
Example: Skin
Sensors: Range from simple to complex.

Types of Sensors

Contact: switches
Distance: Ultrasound, radar, infrared
Light level: photocells, cameras
Sound level: microphones
Strain: strain gauges
Rotation: encoders
Smell: chemical
Temperature: thermal, infrared
Inclination: inclinometers, gyroscopes
Pressure: pressure gauges (ex sensors)
Altitude: altimeters

Levels of Processing

Switch: Open = 0 volts, Closed = 5 volts
Digital scale
Microphone
Camera

Ohm's Law

V = IR
V = voltage (volts)
I= current (amps)
R = resistance (ohms)

Mechanical Switches/Limit Switches

Mechanical switch creates on/off signals when a mechanical input changes its state (e.g., presence/absence of a workpiece).
1 Level: corresponds to 24 VDC input
0 Level: corresponds to 0 VDC input
These switches are actuated by a cam, roller, or lever.

Limit Switches - Advantages

Limit switches are cheaper than proximity or photoelectric switches.
Wide range of sizes.

Proximity Switches

Basic types: inductive, capacitive, magnetic
Inductive operation: based on the variation of magnetic inductance.
Capacitive operation: variation of capacitance.
Magnetic operation: variation of magnetic flow.
Widely used in industrial applications: inductive and capacitive proximity switches.
Detection mechanism: presence of an object without physical contact.
Voltage amplitude: indicates proximity of metallic objects.
Range: typically 0.5 to 20 mm.

Capacitive Proximity Switch

Operates with metallic and non-metallic objects
Affected by the dielectric
The separation between two plates (sensor and the object) determines the capacitance.
The smaller the separation, the higher the capacitance
4 to 60 mm is the typical detection range.

Inductive Proximity Switch

Consists of a coil wound around a ferrous core.
Placing a ferrous metallic object near the core changes the inductance of the coil.
This change can be detected using a resonant circuit.
The change in the amount of current in this circuit signifies the object's presence.
Typically detects objects within a distance of 2 to 15 mm

Photoelectric Sensors and Switches

Photoelectric switches: Solid-state sensors for detecting objects at long ranges.
Operation: use light beams (visible or infrared) which are interrupted or reflected.
- Three types: Through-beam, retro-reflective, diffuse-reflective
- Through-beam: Uses separate emitter and receiver units; high distance sensing potential.
- Retro-reflective: Uses the same housing; utilizes multiple reflections to higher signal accuracy at lower distances.
- Diffuse-reflective: Reflects light off of the object.
Detection distance: Varies with the type, size, and model.
"Dark ON" / "Light ON" operation: Dark ON = energized when the light beam is interrupted, Light ON = energized when the light beam reaches the receiver
Sensor limitations: Affected by light reflectivity, surface color, texture, and ambient light.

Light Sensors

Light sensors act as variable resistors; the light intensity affects the sensor's resistance
Brighter light equates to lower resistance; darker light translates to higher resistance.

Potentiometers

Used for volume control in stereos.
Often called "pots."

GuideCane Application

Uses various sensors (ultrasonic, compass, fluxgate) for obstacle detection and guidance
A system for visually impaired individuals.

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Description

Explore the fundamentals of sensors in robotic systems with this informative quiz. Learn about various types of sensors, their definitions, and how they process input to output valuable data. Test your knowledge on contact, distance, and other sensor categories.