1. 1 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Hardware Components: Sensors, Actuators, Converters + Nikil Dutt UC Irvine ICS 212 Winter 2005 +Copyrighted Material adapted from Peter Marwedel, Frank Vahid and Tony Givargis Templates from Prabhat Mishra

2. 2 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Simplified Block Diagramactuators

3. 3 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Sensors and Actuators Sensors:  Capture physical stimulus (e.g., heat, light, sound, pressure, magnetism, or other mechanical motion)  Typical generate a proportional electrical current  May require analog interface Actuators  Convert a command to a physical stimulus (e.g., heat, light, sound, pressure, magnetism, or other mechanical motion)  May require analog interface solenoid mic laser diode/transistor speaker dc motor compass accelerometer

4. 4 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Sensors Processing of physical data starts with capturing this data. Sensors can be designed for virtually every physical stimulus  heat, light, sound, weight, velocity, acceleration, electrical current, voltage, pressure,... Many physical effects used for constructing sensors.  law of induction (generation of voltages in an electric field),  light-electric effects.

5. 5 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Example: Acceleration Sensor Courtesy & ©: S. Bütgenbach, TU Braunschweig MEMS device Small mass in center When accelerated:  Mass displaced from center  Resistance of wires connected to mass change  Detect change in resistance and model acceleration

6. 6 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Charge-coupled devices (CCD) Image Sensors: Based on charge transfer to next pixel cell

7. 7 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters CMOS Image Sensors Based on standard production process for CMOS chips, allows integration with other components.

8. 8 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Comparison CCD/CMOS sensors Source: B. Diericks: CMOS image sensor concepts. Photonics West 2000 Short course (Web)

9. 9 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Example: Biometric Sensors Example: Fingerprint sensor (© Siemens, VDE): Integrated into ID mouse.

10. 10 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Example: Artificial eyes © Dobelle Institute (www.dobelle.com)

11. 11 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Artificial eyes (2) He looks hale, hearty, and healthy — except for the wires. They run from the laptops into the signal processors, then out again and across the table and up into the air, flanking his face like curtains before disappearing into holes drilled through his skull. Since his hair is dark and the wires are black, it's hard to see the actual points of entry. From a distance the wires look like long ponytails. © Dobelle Institute (www.dobelle.com)

12. 12 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Other examples of sensors  Heart monitoring sensors  “Managing Care Through the Air” »IEEE Spectrum Dec 2004  Rain sensors for wiper control  High-end autos  Pressure sensors  Touch pads/screens  Proximity sensors  Collision avoidance  Engine control sensors  Audio sensors  Motion sensors  Thermal sensors  SARS detection (“high fever”)

13. 13 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Simplified Block Diagramactuators

14. 14 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Sensors and Actuators Sensors:  Capture physical stimulus (e.g., heat, light, sound, pressure, magnetism, or other mechanical motion)  Typical generate a proportional electrical current  May require analog interface Actuators  Convert a command to a physical stimulus (e.g., heat, light, sound, pressure, magnetism, or other mechanical motion)  May require analog interface solenoid mic laser diode/transistor speaker dc motor compass accelerometer

15. 15 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Actuators Output physical stimulus varies in range and modality  Large (industrial) control actuators  Pneumatic systems: physical motion  Optical output  IR  Thermal output  Small motor controllers (stepper motors)  MEMS devices  List goes on…..

16. 16 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Stepper Motor Controller Stepper motor: rotates fixed number of degrees when given a “step” signal  In contrast, DC motor simply rotates when power applied, and coasts to stop Rotation achieved by applying specific voltage sequence to coils Controller greatly simplifies this

17. 17 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters MEMS Actuators Huge variety of actuators and output devices. Microsystems motors as examples (© MCNC) (Dimensions in the order of several microns) (© MCNC)

18. 18 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Actuators Courtesy and ©: E. Obermeier, MAT, TU Berlin

19. 19 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Simplified Block Diagramactuators

20. 20 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Sample-and-Hold Circuit Sampling: how often the signal is converted. Quantization: how many bits used for sampling. Model: Vx = Ve when Clock = 1

21. 21 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Aliasing Potential Consequence of sampling, e.g.: Signal frequency: 5.6 Hz Sampling frequency: 9 Hz

22. 22 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Analog to Digital Conversion Sampling: how often is the signal converted?  Twice as high as the highest frequency signal present in the input Quantization: how many bits used to represent a sample?  Sufficient to provide required dynamic range  Under-loading: dynamic range not used properly  Clipping: input signal beyond the dynamic range Aliasing: erroneous signals, not present in analog domain, but present in digital domain  Use anti-aliasing filters  Sample at higher than necessary rate

23. 23 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Analog-to-Digital Converter

24. 24 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Flash A/D Converter Parallel comparison with reference voltage Speed: O(1) HW complexity: O(n)  n= # of distinguished voltage levels

25. 25 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Successive Approximation Key idea: binary search: Set MSB='1' if too large: reset MSB Set MSB-1='1' if too large: reset MSB-1 ….. Speed: O(log(n)) Hardware complexity: O(log(n)) with n= # of distinguished voltage levels; slow, but high precision possible. Speed: O(log(n)) Hardware complexity: O(log(n)) with n= # of distinguished voltage levels; slow, but high precision possible.

26. 26 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Successive Approximation Given an analog input signal whose voltage should range from 0 to 15 volts, and an 8-bit digital encoding, calculate the correct encoding for 5 volts. 01000000 ½(V max – V min ) = 7.5 volts V max = 7.5 volts. ½(7.5 + 0) = 3.75 volts V min = 3.75 volts. 00000000 01000000 ½(7.5 + 3.75) = 5.63 volts V max = 5.63 volts ½(5.63 + 3.75) = 4.69 volts V min = 4.69 volts. 01010000 ½(5.63 + 4.69) = 5.16 volts V max = 5.16 volts. 01010000 ½(5.16 + 4.69) = 4.93 volts V min = 4.93 volts. 01010100 ½(5.16 + 4.93) = 5.05 volts V max = 5.05 volts. 01010100 ½(5.05 + 4.93) = 4.99 volts 01010101

27. 27 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Signal Processing Digital signal S 0, S 1, S 2 … S n-1 What can we do with it?  Transpose: e.g., Z i = S i + K  Amplify: e.g., Z i = S i    Compose: e.g., Z i = (S 1 i   1 + K 1 ) + (S 2 i   2 + K 2 )  Filter: e.g, Z i = (S i + S i+1 ) / 2  Compress: e.g., using Huffman codes  Archive, match against database, etc. Or, process after converting to frequency domain  Spectral analysis

28. 28 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Frequency Domain Any continuous time varying signal can be represented as the sum of cosine functions of different amplitude and frequency  E.g., input signal captured as the sum of 4 cosine functions Once in frequency domain, certain manipulations become trivial (e.g., filtering)

29. 29 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Simplified Block Diagramactuators

30. 30 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Digital-to-Analog (D/A) Converters Various types, can be quite simple, e.g.:

31. 31 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Due to Kirchhoff‘s laws: Current into Op-Amp=0: Hence: Finally: Output voltage  no. represented by x

32. 32 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Reconstruct Analog from Digital? According to Nyquist theorem:  Analog input to sample-and-hold can be precisely reconstructed from its output if  sampling frequency  double the highest input frequency in input voltage and assuming voltages remain analog.  Digitizing values in the A/D generates additional uncertainty preventing precise reconstruction of initial values. Can be modeled as additional noise. S/H A/D-converter D/A-converter = ? Inter- polate Will this work?

33. 33 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Control Systemsactuators

34. 34 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Control Systems Control systems are a common class of embedded systems Goal is to make a system’s output track a desired reference value  Cruise control, thermostat, VCR tape speed, etc. We’ll take a look at open-loop and closed-loop control systems

35. 35 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Control System Control physical system’s output  By setting physical system’s input Tracking E.g.  Cruise control  Thermostat control  Disk drive control  Aircraft altitude control Difficulty due to  Disturbance: wind, road, tire, brake; opening/closing door…  Human interface: feel good, feel right…

36. 36 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Tracking Good tracking Bad tracking

37. 37 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Open-Loop Control Systems Plant  Physical system to be controlled  Car, plane, disk, heater,… Actuator  Device to control the plant  Throttle, wing flap, disk motor,… Controller  Designed product to control the plant

38. 38 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Open-Loop Control Systems Output  The aspect of the physical system we are interested in  Speed, disk location, temperature Reference  The value we want to see at output  Desired speed, desired location, desired temperature Disturbance  Uncontrollable input to the plant imposed by environment  Wind, bumping the disk drive, door opening

39. 39 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Other Characteristics of open loop Feed-forward control Delay in actual change of the output Controller doesn’t know how well thing goes Simple Best use for predictable systems

40. 40 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Closed Loop Control Systems Sensor  Measure the plant output Error detector  Detect Error Feedback control systems Minimize tracking error

41. 41 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Benefit of Computer Control Cost!!!  Expensive to make analog control immune to  Age, temperature, manufacturing error  Computer control replaces complex analog hardware with complex code Programmability!!!  Computer Control can be “upgraded”  Change in control mode, gain, are easy to do  Computer Control can be adaptive to change in plant  Due to age, temperature, …etc  “future-proof”  Easily adapt to change in standards,..etc

42. 42 ICS212 WQ05 (Dutt) Hardware Components: Sensors, Actuators, Converters Summary Sensors and Actuators Converters  A/D and D/A Signal Processing Control Systems