Mechatronics System Design - Sensors

Transcription

1 Mechatronics System Design - Sensors

2 Aim of this class 1. The functional role of the sensor? 2. Displacement, velocity and visual sensors? 3. An integrated example-smart car with visual and displacement sensors. Grouping?

3 Car Sensors

4 Sensors in Animal Eye Ear stone Lateral line

5 Sensor in Aircraft Apollo 10: Rocket part sensors Spaceship part sensors Spacecraft: 185 sets of integrated instrument Acceleration, temperature, pressure, vibration, flow speed, strain stress etc.

6 Sensor around us Growing sensing technology in our daily life

7 Sensing devices 1 Sensor function, classification 2 Displacement Sensors 3 Vision Sensor 4 An integrated example 5 Our project

8 Significance of the sensor 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.

9 Sensor definition What is a sensor? A device that is able convert measurement variables into electrical signals, and then been digitalized by computer. 9

10 Sensor definition What are sensors consist of Sensor is generally composed of three parts: sensing element, transition element, conversion circuit. Physical Input sensing element Amplificati on element conversion circuit Digital Output

11 Sensor function, classification and basic requirements Course equipment sensors

12 Encoder Encoder

13 Limitation switch sensor Optical limit switch

14 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.)

15 Sensor classification Measurement category Thermal value Mechanical value Be measured Temperature, heat, heat; pressure, pressure, vacuum; flow, velocity, wind Displacement (linear displacement, angular displacement), the size, shape; force, moment, stress; weight, quality; speed, line speed; vibration amplitude, frequency, acceleration, noise

16 Sensor classification Measurement category Physical properties and composition Status calculation Be measured The chemical composition of gas, liquid chemical composition; acidity (PH value), salinity, density, viscosity; density, specific gravity Color, transparency and the amount of wear, cracks or defects within the material, gas leakage, surface quality

17 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.

18 Sensing devices 一 Sensor function, classification and basic requirements 二 Displacement measurement sensors 三 Vision Sensors 四 Selection principles and precautions 五 Measurement circuit and computer interface

19 Category: Displacement measurement sensors Linear displacement: linear potentiometers, grating, magnetic foot Angular displacement: Rotary potentiometer, encoder, resolver, circular grating, a round magnetic feet

20 Displacement measurement sensors - Encoders 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

21 Displacement measurement sensors - Encoders

22 Displacement measurement sensors - Encoders

23 Displacement measurement sensors - Encoders

24 Displacement measurement sensors - Encoders

25 Displacement measurement sensors Encoders

26 Displacement measurement sensors Measurement Frequency

27 Displacement measurement sensors Pulse width measurement method

28 Sensor 1 Roll, classification, and basic requirement of sensor. 2 Displacement sensor 5 3 Vision sensor 4 Selection principles and precautions Measurement circuit and computer interface

29 Principles and Applications of Vision Sensor

30 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

31 Principles and Applications of Vision Sensor CCD vision sensor CCD sensor, also known as charge-coupled device, is a special semiconductor material, which is consist of a large number of independent photosensitive diodes.

32 Principles and Applications of Vision Sensor 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.

33 An integrated example Smart car

34 An example of vision Sensor application Smart Car Camera System Overview. Resource allocation in microcontroller chip. Camera and image processing. Slide 2

35 Principles and Applications of Vision Sensor Smart Car with Camera Driver module and DC motor CCD Camera Optical encoder ColdFire family of MCU MCF52259 Minimum System Smart car system board Futaba S3010 servo

36 Principles and Applications of Vision Sensor Smart Car Camera System Overview. Block diagram of the system Power Management Module Servo Steering wheel CCD image acquisition module MCF52259 Controller BTS7960 driver module DC motor Wheels Bluetooth serial communication module Optical encoder Slide 36

37 Principles and Applications of Vision Sensor Smart Car Camera System Overview. 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

38 Principles and Applications of Vision Sensor Resource allocation in microcontroller chip. The car function module Signal 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 PA Input Servo Digital(PWM) PWM module Output Motor driver module Bluetooth serial Comm. module Digital(PWM) PWM module Output Digital SCI module Input and output * Transfer direction refers to MCU

39 Principles and Applications of Vision Sensor 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: CCD CMOS Sensitivity High Low Cost High Low Resolution High Low Noise ratio Low High Power dissipation High Low High sensitivity determines the image dynamic, high-resolution determines the forward distance. Therefore CCD camera is a better choice.

40 Principles and Applications of Vision Sensor Camera and image processing CMOS CCD Slide 40

41 Principles and Applications of Vision Sensor Camera and image processing 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

42 Principles and Applications of Vision Sensor Image processing Black line Track picture White background Curve Cross Irrelevant information Straights Slide 42

43 Video

44 Principles and Applications of Vision Sensor Image processing Slide 44 Binarized black and white image

45 Principles and Applications of Vision Sensor Image capture module Module Schematic CCD LM1881 Line breaks Market disruption ECT I/O MCU LM393 Function: hardware binary, dynamic threshold TLC5615 DA converter chip Slide 45

46 Sensors in my projects

47 Question time Prof. Wang Prof. Li Wen 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: ;Pan: ; Courseware Download: Password: xdjdkz2014 Homework submission:

48 Thank you