1. Components of Mechatronic Systems AUE 425 Week 2 Kerem ALTUN October 3, 2016

2. Mechatronic Systems

3. Components of a Mechatronic System Sensors measure and feedback physical parameters of a system. Actuators supply the driving and corrective forces to achieve a desired output. Controller generates actuator commands according to feedback from the sensors and the implemented control algorithm.

4. Signal Conditioning Usually, the sensors and actuators can not be connected to the controller directly, but through an interface – A/D and D/A conversion – filters – amplifiers – motor drivers

5. Sensors Used to perceive the environment around the system Analog sensors – Potentiometers, photoresistors, IR range, ultrasonic etc. Digital sensors – Buttons, switches, inductive sensors, etc.

6. Actuators (Electric motors) DC motors RC Servomotors Step motors

7. DC motors To drive a DC motor, it is necessary to create a voltage potential between its poles provided with a sufficient current supply. Speed ~ Voltage Torque ~ Current Direction ~ Polarity

8. DC motors

9. RC Servomotors RC (remote control) servomotors are simple DC motors with built-in closed loop control circuitry Potentiometer is used as a feedback device and controller is a simple P-controller They work between 0-180 degrees (there are ones that work between 0-720 degrees) hence they can’t make full rotation

10. RC Servomotors Potentiometer

11. They can be modified (called hacking) to make full rotation. In this configuration feedback loop is removed Hacked RC servomotors are more preferable than standard DC motors because of their low price, low weight and many different models Hacked RC servomotors are driven by using a suitable motor driver like L293D or L298 RC Servomotors

12. Step motors Have more windings than a DC motor Low torque Open-loop control Speed ~ Frequency of pulses

13. Types of Controllers Analog Controllers: Use analog components like capacitors, resistors and op-amps. Expensive to build. Implement limited control algorithms like PID control. Suffer from component aging and temperature. Hardwired, difficult to upgrade or modify.

14. Types of Controllers Digital Controllers: Use processor as a computational hardware, A/D converter and D/A converter. Inexpensive to build. Implement complex control algorithms like optimal control and adaptive control. No problem due to component aging and temperature. Flexible, software controllable, easy to modify and upgrade.

15. Computational Hardware There are several choices for the computational hardware for a digital control system. Microcomputer Microcontroller

16. Basically consists of a processor, memory, ports and bus. Needs peripherals Microcomputer

17. Microcontroller Carries peripheral devices like A/D, D/A converters, I/O ports and communication ports needed for control applications.

18. Arduino Uno

19. ATmega328P microcontroller 5V operating voltage 16 MHz clock speed 14 programmable digital I/O pins 6 analog input pins USB interface to PC 32K of flash memory to store programs 2K of RAM to store runtime variables – may run out fast 1K of EEPROM (like flash; not deleted after power is turned off)

20. Electronic Control Units in Automotive Engine control unit Transmission control unit Speed control unit Brake control unit Door control unit

21. Motor Drivers Outputs of digital controllers are not sufficient in driving DC motors, which mostly require higher voltage and current sources that cannot be supplied by controllers Drivers are mechanisms that provide a connection between the power supply and the motor according to controller commands

22. Motor Drivers

23. Usually H-bridge or op-amp motor drivers are used L293D and L298 are two most common H- bridge motor drivers L293D can supply up to 600mA per motor

24. H-Bridge Structure

25. Analog to Digital Conversion Digital controllers can only read logic 1 (+5V) and logic 0 (0V) and not any voltage in between (such as 2.5V or 3.6V) In some cases you need to read voltages in between (for example if you want to read voltage in a potentiometer which gives a continuous output voltage values)

26. Analog to Digital Conversion Important properties of A/D converters are: – Resolution: Is the number of bits used to represent input voltage (ie 8 bits, 12 bits) – Output Type: Output can be either series or parallel. If series; 1 pin is used for output. If parallel; output pin number is equal to number of bits (resolution) – Conversion Frequency: Is the frequency that A/D converter can make sucessive conversions (10kHz, 20kHz) – Input Voltage Range: Is the voltage range that A/D converter works (0-10V, -10V to 10V)

27. Analog to Digital Conversion Resolution: – 8 bit means that input is mapped to an 8 bit number (from 0 to 2^8 bits =255) which means that output can take 256 different values – If minimum input voltage is adjusted to 0V and maximum input voltage is adjusted to 5V minimum detectable voltage is (5V-0V)/255 = 0.0196V – Hence an input voltage of 0V will give an output of 0 (decimal) and an input voltage of 0.0196V will give an output of 1 (decimal)

28. – Output of A/D converter can be plotted as:

29. Analog to Digital Conversion Type of Output: Output is either parallel or series. – Parallel Output Type the individual bit values (for the above example it is 8) making the decimal output comes in parallel at least 8 output lines are necessary for 8 bit converters operation is fast (all the bits come at once) – Series Output Type the individual bit values come in series sequentially one output is enough for output operation is slow (at least 8 times slower than the same Parallel Output Type A/D converters

31. Computer control

32. Sensors Position sensing – potentiometers a variable resistor used for angular position sensing https://youtu.be/XR8ede6V6eA?t=120 – linear potentiometers – linear variable differential transformer (LVDT) – rotary encoders

33. Sensors Position sensing – absolute encoder – https://upload.wikimedia.org/wikipedia/common s/4/42/Encoder_disc.png

34. Sensors Speed sensing – rotary encoders – https://www.youtu be.com/watch?v=v 4BbSzJ-hz4 https://www.youtu be.com/watch?v=v 4BbSzJ-hz4

35. Sensors Temperature sensing – thermocouples – bimetallic strip

36. Sensors Vibration measurement/accelerometers

37. Sensors Pressure sensors Force and torque sensors Flow sensors Gas sensors and concentration sensors