Mechatronics System Design - Sensorssoftrobotics.buaa.edu.cn/PPT/Chapter 3 Sensors.pdf ·...

Mechatronics System

Design - Sensors

1. The functional role of the sensor?

2. Displacement, velocity and visual

sensors?

3. An integrated example-smart car with

visual and displacement sensors.

Aim of this class

Grouping?

Car Sensors

Sensors in Animal

Eye Ear stone

Lateral line

Apollo 10:

Rocket part --- 2077 sensors

Spaceship part --- 1218 sensors

Acceleration, temperature, pressure, vibration, flow speed, strain stress etc.

Spacecraft:

185 sets of integrated

instrument

Sensor in Aircraft

Growing sensing technology in our daily life

Sensor around us

1 Sensor function, classification

2

4

Displacement Sensors

Sensing devices

An integrated example

3 Vision Sensor

5 Our project

o “Recent scientific progress is closely related to the development

of cutting-edge sensor technology”.- Nobel prize winner RR

Ernst.

o In recent 80 years, 38 people win Nobel Prize because of their

original contribution of sensor.

• Significance of the sensor

9

What is a sensor?

A device that is able convert measurement

variables into electrical signals, and then been

digitalized by computer.

Sensor definition

What are sensors consist of

• Sensor is generally composed of three parts:

sensing element, transition element, conversion

circuit.

Digital

Output

Physical

Input

sensing

element

Amplificati

on element

conversion

circuit

Sensor definition

Sensor function, classification and basic requirements

• Course equipment sensors

Encoder

Encoder

Optical limit switch

Limitation switch sensor

Sensor function, classification and basic requirements

• Classification according to the nature of the output signal:

Sensor

Switch type

(Binary type):

Analog:

Digital:

Contact (micro switch, touch switches, etc.)

Non-contact (optical switches, proximity switches,

etc.)

Resistance type (potentiometers, strain gauges, etc.)

Voltage and current type (thermocouple, photovoltaic

cells, piezoelectric element, etc.)

Inductance, capacitance type (inductive, capacitive

displacement sensors, etc.)

Count type (binary + counter)

Code type (encoders, magnetic tape, etc.)

Measurement

categoryBe measured

Thermal value

Temperature, heat, heat; pressure,

pressure, vacuum; flow, velocity,

wind

Mechanical

value

Displacement (linear displacement,

angular displacement), the size,

shape; force, moment, stress; weight,

quality; speed, line speed; vibration

amplitude, frequency, acceleration,

noise

Sensor classification

Measurement

categoryBe measured

Physical

properties and

composition

The chemical composition of gas,

liquid chemical composition; acidity

(PH value), salinity, density, viscosity;

density, specific gravity

Status

calculation

Color, transparency and the amount of

wear, cracks or defects within the

material, gas leakage, surface quality

Sensor classification

Sensor basic requirements

1. Small size, light weight, good adaptability to the

machine.

2. Greater sensitivity and tolerate to the

environmental noise.

3. Nice stability.

一Sensor function, classification and basic

requirements

二

四

五

Displacement measurement sensors

Selection principles and precautions

Sensing devices

Measurement circuit and computer

interface

三 Vision Sensors

Displacement measurement sensors

Category:

• Linear displacement: linear potentiometers, grating, magnetic

foot

• Angular displacement: Rotary potentiometer, encoder, resolver,

circular grating, a round magnetic feet

• The analog (displacement) of the mechanical rotation into an

electric signal in the form of a digital code, this type of sensor is

called encoder. Encoder for it’s high precision, high resolution and

high reliability are widely used in various displacement

measurements.

• There are many different types of encoder; divided pulsed disc

(incremental encoder) and the code disc encoder (absolute

encoder), the relationship is as follows:

Encoder

Pulsed disc encoder

(incremental encoder)

Code disc encoder

(absolute encoder)

Contactless Encoder

Magnetic Encoder

Optical encoder

Displacement measurement sensors - Encoders

Displacement measurement sensors - Encoders

Displacement measurement sensors – Encoders

Displacement measurement sensors –

Measurement Frequency

Displacement measurement sensors – Pulse width

measurement method

1Roll, classification, and basic

requirement of sensor.

2

4

5

Displacement sensor

Selection principles and

precautions

Sensor

Measurement circuit and

computer interface

3 Vision sensor

Principles and Applications of Vision Sensor

Classification

Depending on the working principle, vision sensors

can be divided into the following three categories:

Photoconductive vision sensor

CCD vision sensor

CMOS vision sensor


CCD vision sensorCCD sensor, also known as charge-coupled device, is a special semiconductor material, which is consist of a large number of independent photosensitive diodes.


CCD vision sensor-characteristic

1. Small size, light weight, low power consumption,

high reliability, long life.

2. High spatial resolution.

3. High optical sensitivity, wide dynamic range

4. Analog or digital output; with easy computer

interface.


Smart car

An integrated example

Smart Car Camera System Overview.

Resource allocation in microcontroller chip.

Camera and image processing.

An example of vision Sensor application

Smart Car with Camera

CCD Camera

ColdFire family of MCU

MCF52259 Minimum System

Futaba S3010 servo

Smart car system board

Optical encoder

Driver module and DC motor


MCF52259

Controller

Power Management

Module

CCD image

acquisition module

Bluetooth serial

communication module

Servo Steering wheel

BTS7960 driver module

DC motor Wheels

Optical encoder

Block diagram of the system



How Smart car works:

• Camera captures the image of the runway, and

transferred to the microcontroller;

• MCU which is an embedded controller for image

processing, to control the motor voltage output, car head angle

etc. according to the control strategy.

• Encoder emits pulses to the microcontroller by following the

running car. MCU records the number of pulses by pulse

counting module to calculate the motor speed, and adjust the

speed;

Slide 37



Resource allocation in microcontroller chip.

The car function

moduleSignal type

Corresponding

MCU module

Transmission

direction *

Image acquisition

CCD (for example)

Analog

(image info)

Digital

(interrupt signal)

AD, ECT input

capture

(or INT interrupt)

Input

Optical encoder Digital (pulse)ECT pulse

accumulate PAInput

Servo Digital（PWM） PWM module Output

Motor driver

moduleDigital（PWM） PWM module Output

Bluetooth serial

Comm. moduleDigital SCI module Input and output

* Transfer direction refers to MCU


Camera and image processing

Selection of camera

Classification according photosensitive device unit, there are two

types of cameras: CCD and CMOS, both compared as follows:

High sensitivity determines the image dynamic, high-resolution

determines the forward distance. Therefore CCD camera is a better

choice.

CCD CMOS

Sensitivity High Low

Cost High Low

Resolution High Low

Noise ratio Low High

Power

dissipationHigh Low


CMOS CCD



Divided by the output signal type, the camera can

be divided into analog and digital.

Analog can be seen in the CCD

and CMOS, only CMOS is

available in digital currently.

OV7620 digital camera



Image processing

Slide 42

Track picture

Black line

White background

Irrelevant information

Curve

Straights

Cross


Image processing

Slide 44

Binarized black and white image


Image capture module

Module Schematic

Slide 45

LM1881

LM393

MCU

Line breaks

Market

disruption

ECT

TLC5615

I/OCCD

Function: hardware binary,

dynamic threshold DA converter chip


Sensors in my projects

Question time

Prof. Wang Email: [email protected]

Prof. Li Wen Email: [email protected]

Class room：（一）307

Hand-on experiments room: New main building B307

Course duration: 1-17 week Tuesday (1. 2) 14:00-15:45

TA：Mamoon: 13260495830；Pan：13126522848;

Courseware Download：[email protected]，

Password： xdjdkz2014Homework submission：

[email protected]

mailto:[email protected]

mailto:[email protected]

Thank you

Mechatronics System Design - Sensorssoftrobotics.buaa.edu.cn/PPT/Chapter 3 Sensors.pdf ·...

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