me 486 - automation automation building blocks by ed red automation building blocks by ed red...

ME 486 - ME 486 - AutomationAutomationME 486 - ME 486 - AutomationAutomation

Automation Building Blocks

By

Ed Red

Automation Building Blocks

By

Ed Red

Sensors

Analyzers

Actuators

Drives

Vision systems

Sensors

Analyzers

Actuators

Drives

Vision systems


Objectives

• To review basic building blocks for implementing automation

• To consider application conditions

• To introduce assessment criteria

• To test understanding of the material presented

Objectives

• To review basic building blocks for implementing automation

• To consider application conditions

• To introduce assessment criteria

• To test understanding of the material presented


Building Blocks• Sensors

• Analyzers

• Actuators

• Drives

• Vision system (integrated sensor/analyzer)

Building Blocks• Sensors

• Analyzers

• Actuators

• Drives

• Vision system (integrated sensor/analyzer)

Inductive proximityInductive proximitysensorssensors



Building Blocks – sensor features

• Accuracy and repeatability

• Precision

• Range

• Response time

• Calibration methods

• Minimum drift

• Costs and reliability

• Sensitivity

Building Blocks – sensor features

• Accuracy and repeatability

• Precision

• Range

• Response time

• Calibration methods

• Minimum drift

• Costs and reliability

• Sensitivity


We can characterize a sensor’s capability by it’s operating frequency or by its response time. Both determine how well the sensor might measure the desired property (proximity, length…) of a moving object. Using a sensor’s specification, how might we determine how fast a moving object might move past the sensor and the sensor still read the object parameter correctly?

We can characterize a sensor’s capability by it’s operating frequency or by its response time. Both determine how well the sensor might measure the desired property (proximity, length…) of a moving object. Using a sensor’s specification, how might we determine how fast a moving object might move past the sensor and the sensor still read the object parameter correctly?

Building Blocks – sensors & moving objectsBuilding Blocks – sensors & moving objects


Building Blocks – sensor devices

See text for in depth description!

• Photoelectric sensors

• Proximity switches (inductive and capacitive)

• Range sensors (ultrasonic/acoustic, laser reflectors…)

• Transducers (encoders)

Building Blocks – sensor devices

See text for in depth description!

• Photoelectric sensors

• Proximity switches (inductive and capacitive)

• Range sensors (ultrasonic/acoustic, laser reflectors…)

• Transducers (encoders)



Linear encoderLinear

encoderAbsolute rotary

encoderAbsolute rotary

encoder


Building Blocks – analyzers

Encoder example – An absolute optical encoder has 8 rings, 8 LED sensors, and 8 bit resolution. If the output pattern is 10010110, what is the shaft’s angular position?

Ring Angle (deg) Pattern Value (deg)1 180 1 1802 90 03 45 04 22.5 1 22.55 11.25 06 5.625 1 5.6257 2.8125 1 2.81258 1.40625 0

Total 210.94

Building Blocks – analyzers

Encoder example – An absolute optical encoder has 8 rings, 8 LED sensors, and 8 bit resolution. If the output pattern is 10010110, what is the shaft’s angular position?

Ring Angle (deg) Pattern Value (deg)1 180 1 1802 90 03 45 04 22.5 1 22.55 11.25 06 5.625 1 5.6257 2.8125 1 2.81258 1.40625 0

Total 210.94


Building Blocks – drives

• Stepper Motors (index by open-loop control)

• AC/DC servomotors (PID feedback control, holds torque when at rest)

• Kinematic devices (intermittent operation, e.g., geneva mechanism)

• Digital drives

Building Blocks – drives

• Stepper Motors (index by open-loop control)

• AC/DC servomotors (PID feedback control, holds torque when at rest)

• Kinematic devices (intermittent operation, e.g., geneva mechanism)

• Digital drives


Building Blocks – present drivesBuilding Blocks – present drives

Motion Motion Planning Planning

& & ControlControl

Set Points Set Points Amplifiers Amplifiers

Servo-loopsServo-loops

ApplicationApplication

ServocardServocard

ControllerController


Building Blocks – digital drivesBuilding Blocks – digital drives

• Microprocessors and Digital Signal Processors (DSP’s) are replacing analog components with digital components (i.e., digital drives).

•EIA RS-431, the outdated 10V standard, no longer need constrain control resolution.

• Revolutions in computer operating systems, applications, and networking.

• Networking standards, such as IEC 61491 and IEEE 1394, are changing motion control architectures and hardware configurations.

• Need for A/D and D/A interfaces is rapidly declining, being replaced by a high- speed network between the master host (a PC) and the distributed digital slave devices.

• Microprocessors and Digital Signal Processors (DSP’s) are replacing analog components with digital components (i.e., digital drives).

•EIA RS-431, the outdated 10V standard, no longer need constrain control resolution.

• Revolutions in computer operating systems, applications, and networking.

• Networking standards, such as IEC 61491 and IEEE 1394, are changing motion control architectures and hardware configurations.

• Need for A/D and D/A interfaces is rapidly declining, being replaced by a high- speed network between the master host (a PC) and the distributed digital slave devices.


Building Blocks – digital drivesBuilding Blocks – digital drives

Ormec’s servowire implementation of IEEE 1394

DMACDMAC


PWM and digital drives (binary control!)PWM and digital drives (binary control!)

PWM – Pulse Width Modulation - a constant frequency, two-valued signal (e.g., voltage) in which the proportion of the period for which the signal is on and the period for which it is off can be varied.

• Percentage of time on is called the duty cycle.

• Voltage value will depend on the application

• PWM frequency must be high enough so that motor cannot respond to a single PWM signal

PWM – Pulse Width Modulation - a constant frequency, two-valued signal (e.g., voltage) in which the proportion of the period for which the signal is on and the period for which it is off can be varied.

• Percentage of time on is called the duty cycle.

• Voltage value will depend on the application

• PWM frequency must be high enough so that motor cannot respond to a single PWM signal

On On

Off Off

T 2T 3T 4T T 2T 3T 4T

25% duty cycle 50% duty cycle

If direction is to be changed, requires another PWM signal. If direction is to be changed,

requires another PWM signal.


A/D Signal ConversionA/D Signal Conversion

Resolution of A/D is represented by number of conversion bits n:

Nq = number of quantitization levels = 2n

R = conversion resolution = Voltage range/(Nq – 1) (± 10 V)

Resolution of A/D is represented by number of conversion bits n:

Nq = number of quantitization levels = 2n

R = conversion resolution = Voltage range/(Nq – 1) (± 10 V)

± RVariable

(or Voltage)

Time


A/D Signal ConversionA/D Signal Conversion

Successive approximation method is similar to the method we used to extract the encoder value from the binary output but backwards. Here is simple example:

Range (± 10 V) Quantitizations Bit (on or off) Value6.8 V 5 1 51.8 2.5 01.8 1.25 1 1.250.55 0.625 00.55 0.3125 1 0.31250.2375 0.15625 1 0.156250.08125 = error 6.719 V

Successive approximation method is similar to the method we used to extract the encoder value from the binary output but backwards. Here is simple example:

Range (± 10 V) Quantitizations Bit (on or off) Value6.8 V 5 1 51.8 2.5 01.8 1.25 1 1.250.55 0.625 00.55 0.3125 1 0.31250.2375 0.15625 1 0.156250.08125 = error 6.719 V


D/A Signal ConversionD/A Signal Conversion

The decoding equation is:

Eo = Eref [0.5 B1 + 0.25 B2 + 0.125 B3+…+(2n)-1Bn]

where

Eo = output analog signal value Eref = ref voltage

For example: 10010 means B1 = 1, B2 = 0, B3 = 0, B4 = 1, B5 = 0

The decoding equation is:

Eo = Eref [0.5 B1 + 0.25 B2 + 0.125 B3+…+(2n)-1Bn]

where

Eo = output analog signal value Eref = ref voltage

For example: 10010 means B1 = 1, B2 = 0, B3 = 0, B4 = 1, B5 = 0


Current flow produces magnetic field and associated flux.

Changing field (flux) through a coil induces a reactive electromotive force (emf) e:

e = -N d/dt (Faraday’s Law) N = # turns in coil; is flux in webers

This in turn generates an induced current in opposite direction and a resulting opposing flux as described by:

e = -L d/dt L = inductance in henrys

Current flow produces magnetic field and associated flux.

Changing field (flux) through a coil induces a reactive electromotive force (emf) e:

e = -N d/dt (Faraday’s Law) N = # turns in coil; is flux in webers

This in turn generates an induced current in opposite direction and a resulting opposing flux as described by:

e = -L d/dt L = inductance in henrys

II

BB

FF == II ll xx BB FF == II ll xx BB

FFl l

II

ElectromagnetismElectromagnetism

BB


AC motorsAC motorsStator structure is composed of steel laminations shaped to form poles around which are wound copper wire coils. These primary windings connect to, and are energized by, the voltage source to produce a rotating magnetic field. Three-phase windings spaced 120 electrical degrees apart are popular in industry.

Rotor (or rotating secondary) is another assembly of laminations over a steel shaft core. Radial slots around the laminations’ periphery house rotor bars—cast-aluminum or copper conductors shorted at one end and positioned parallel to the shaft (see photo).

Stator structure is composed of steel laminations shaped to form poles around which are wound copper wire coils. These primary windings connect to, and are energized by, the voltage source to produce a rotating magnetic field. Three-phase windings spaced 120 electrical degrees apart are popular in industry.

Rotor (or rotating secondary) is another assembly of laminations over a steel shaft core. Radial slots around the laminations’ periphery house rotor bars—cast-aluminum or copper conductors shorted at one end and positioned parallel to the shaft (see photo).

The motor’s name comes from the alternating current (ac) “induced” into the rotor by the rotating magnetic flux produced in the stator. Motor torque is developed from interaction of currents flowing in the rotor bars and the stator’s rotating magnetic field.

The motor’s name comes from the alternating current (ac) “induced” into the rotor by the rotating magnetic flux produced in the stator. Motor torque is developed from interaction of currents flowing in the rotor bars and the stator’s rotating magnetic field.


(new tech) Linear motors(new tech) Linear motors

Slot-less refers to a special design of steel laminations where the windings go through holes in the stator rather than slots. The result is a smoother surface facing the magnet. This design also reduces cogging by eliminating variation in attractive force. Tubular linear motors roll up the unit about an axis parallel to its length. In one style, an outer thrust block carrying the motor coils envelops and moves along a stationary thrust rod that houses magnets. Another style has a central rod with magnets that moves relative to an outer stator member. Travel is limited since the thrust rod must be supported at both ends (or at one end for the moving-rod version).

Slot-less refers to a special design of steel laminations where the windings go through holes in the stator rather than slots. The result is a smoother surface facing the magnet. This design also reduces cogging by eliminating variation in attractive force. Tubular linear motors roll up the unit about an axis parallel to its length. In one style, an outer thrust block carrying the motor coils envelops and moves along a stationary thrust rod that houses magnets. Another style has a central rod with magnets that moves relative to an outer stator member. Travel is limited since the thrust rod must be supported at both ends (or at one end for the moving-rod version).

Tubular linear motor

Two basic classes: 1) permanent magnet (PM) brushless, and 2) asynchronous linear induction motors (LIMs).

PM brushless motors abound in various subclasses, such as the moving coil and moving magnet types. Ironless refers to a core containing only copper coils (and epoxy encapsulation). Smooth "cog-free" motion is produced since no attractive force exists between coil and magnet--but at the cost of lower force output.

Two basic classes: 1) permanent magnet (PM) brushless, and 2) asynchronous linear induction motors (LIMs).

PM brushless motors abound in various subclasses, such as the moving coil and moving magnet types. Ironless refers to a core containing only copper coils (and epoxy encapsulation). Smooth "cog-free" motion is produced since no attractive force exists between coil and magnet--but at the cost of lower force output.


(new tech) Switched reluctance motor(new tech) Switched reluctance motorReluctance - opposition of a material to magnetic lines of forceBoth stator and rotor of the switched reluctance motor have projecting poles. In the image, poles 1 and 1' are energized. These are wired in series. The rotor has no permanent magnets or windings. Thus when one of the four phases of the stator is energized, the closest set of poles of the rotor (made up of reluctance magnets) are pulled into alignment. By turning off phase 1 and energizing phase 2, you can visualize how the rotor will rotate 15' CCW to align the rotor poles closest to phase 2.

Reluctance - opposition of a material to magnetic lines of forceBoth stator and rotor of the switched reluctance motor have projecting poles. In the image, poles 1 and 1' are energized. These are wired in series. The rotor has no permanent magnets or windings. Thus when one of the four phases of the stator is energized, the closest set of poles of the rotor (made up of reluctance magnets) are pulled into alignment. By turning off phase 1 and energizing phase 2, you can visualize how the rotor will rotate 15' CCW to align the rotor poles closest to phase 2.

A four phase converter capable of accepting feedback is used to energize the coils in order to control the switched reluctance motor. The feedback is necessary to run the motor in self-synchronous mode, which enables a continuous smooth speed operation. By energizing the phases in reverse sequence, the motor can also run CW. The switched reluctance motor along with the four phase converter are meant to be used as a precise speed control device, and they are approximately 2% more efficient than the other AC speed control systems.

A four phase converter capable of accepting feedback is used to energize the coils in order to control the switched reluctance motor. The feedback is necessary to run the motor in self-synchronous mode, which enables a continuous smooth speed operation. By energizing the phases in reverse sequence, the motor can also run CW. The switched reluctance motor along with the four phase converter are meant to be used as a precise speed control device, and they are approximately 2% more efficient than the other AC speed control systems.


IEEE 1394,USB2,

Fiber Optic,etc.

Digital DriveNetwork

PCPC

Mot

ion

Pla

nn

ing

Mot

ion

Pla

nn

ing

& C

ontr

ol&

Con

trol

Windows ApplicationWindows Application

Controls ApplicationControls Application

DC

ID

CI

Set

Poi

nts

Set

Poi

nts

CPU 2CPU 2RTOSRTOS

CPU 1CPU 1

Control ServoControl Servo

DMACDMAC


Building Blocks AssessmentBuilding Blocks Assessment

1. Who are major vendors of proximity switches, servomotors?

2. What are the limits to sensor proximity distances?

3. What types of proximity accuracies might you expect from proximity sensors?

4. Which sensors work on which materials?

5. Are sensors affected by speed by which materials move past them?

6. What are weight to torque ratios for common servomotors?

1. Who are major vendors of proximity switches, servomotors?

2. What are the limits to sensor proximity distances?

3. What types of proximity accuracies might you expect from proximity sensors?

4. Which sensors work on which materials?

5. Are sensors affected by speed by which materials move past them?

6. What are weight to torque ratios for common servomotors?


Building Blocks AssessmentBuilding Blocks Assessment

7. What does torque speed curve look like for the motors typically used to control robots?

8. What is difference between absolute encoder and relative encoder? How do encoders measure directional changes?

9. What is difference between a resolver and digital encoder?

10. Costs of sensors, motors, etc.?

11. How do the new linear drives work, and what are their response characteristics?

7. What does torque speed curve look like for the motors typically used to control robots?

8. What is difference between absolute encoder and relative encoder? How do encoders measure directional changes?

9. What is difference between a resolver and digital encoder?

10. Costs of sensors, motors, etc.?

11. How do the new linear drives work, and what are their response characteristics?


Building Blocks – machine visionBuilding Blocks – machine vision

Definition – “Machine vision is the capturing of an image (a snapshot in time), the conversion of the image to digital information, and the application of processing algorithms to extract useful information about the image for the purposes of pattern recognition, part inspection, or part positioning and orientation”….Ed Red

Definition – “Machine vision is the capturing of an image (a snapshot in time), the conversion of the image to digital information, and the application of processing algorithms to extract useful information about the image for the purposes of pattern recognition, part inspection, or part positioning and orientation”….Ed Red

AlgorithmAlgorithm

PCPC


Equipment:Equipment:

• Computer

• Frame grabber

• Camera (CCD array)

• Lenses

• Lighting

• Calibration templates

• Algorithms

• Computer

• Frame grabber

• Camera (CCD array)

• Lenses

• Lighting

• Calibration templates

• Algorithms

Front

Back

Side

Structured

Strobe

Front

Back

Side

Structured

Strobe

Types:

Building Blocks – machine visionBuilding Blocks – machine vision


Machine Vision – structured lightingMachine Vision – structured lighting

Structured Lighting is used in a front lighting mode for applications requiring surface feature extraction. Structured lighting is defined as the projection of a crisp line of light onto an object. The patterned light is then used to determine the 3-D characteristics of an object from the resulting deflections observed.

Structured Lighting is used in a front lighting mode for applications requiring surface feature extraction. Structured lighting is defined as the projection of a crisp line of light onto an object. The patterned light is then used to determine the 3-D characteristics of an object from the resulting deflections observed.

Note the non-typical approach of projecting a grid array of light on an object to detect features

Note the non-typical approach of projecting a grid array of light on an object to detect features


Machine Vision – image processing Machine Vision – image processing

Segmentation – Define and separate regions of interest

Thresholding – Convert each pixel into binary (B or W) value by comparing bit intensities

Edge detection – Locate boundaries between objects

Feature extraction – Determine features based on area and boundary characteristics of image

Pattern recognition – Identify objects in midst of other objects by comparing to predefined models or standard values (of area, etc.)

Segmentation – Define and separate regions of interest

Thresholding – Convert each pixel into binary (B or W) value by comparing bit intensities

Edge detection – Locate boundaries between objects

Feature extraction – Determine features based on area and boundary characteristics of image

Pattern recognition – Identify objects in midst of other objects by comparing to predefined models or standard values (of area, etc.)


Machine Vision – applications Machine Vision – applications

Dimensional measurement

Object verification

Proper position/orientation

Flaws and defects

Counting

Guidance and control (offsets, tracking)

Dimensional measurement

Object verification

Proper position/orientation

Flaws and defects

Counting

Guidance and control (offsets, tracking)


Machine Vision – exampleMachine Vision – example

• 8-bit image of metallic iron as it appears in iron ore (lighter objects in the image represent the metallic iron)

• Histogram displays pixel intensity distribution …background appears at gray level 40, ore shows up at gray level 70, and high-intensity iron turns up at gray levels above 150. Image clearly differentiates components.

• Blob analysis - set threshold to gray level 148…all the pixels with gray levels of 148 or lower get set to zero. Pixels with gray levels of 149 or higher get set to one

• Morphology functions slightly change or eliminate the shapes of objects so imaging software can easily count them.

• 8-bit image of metallic iron as it appears in iron ore (lighter objects in the image represent the metallic iron)

• Histogram displays pixel intensity distribution …background appears at gray level 40, ore shows up at gray level 70, and high-intensity iron turns up at gray levels above 150. Image clearly differentiates components.

• Blob analysis - set threshold to gray level 148…all the pixels with gray levels of 148 or lower get set to zero. Pixels with gray levels of 149 or higher get set to one

• Morphology functions slightly change or eliminate the shapes of objects so imaging software can easily count them.


Machine Vision – exampleMachine Vision – example

Suppose we wish to calculate the area and centroid of the selected binary region in the last figure, how would you do it? Assume that you have a camera such that the pixels are square and you have a matrix of pixel values as depicted in the figure shown.

What equations would you apply?

Suppose we wish to calculate the area and centroid of the selected binary region in the last figure, how would you do it? Assume that you have a camera such that the pixels are square and you have a matrix of pixel values as depicted in the figure shown.

What equations would you apply?XX

YY


Machine Vision AssessmentMachine Vision Assessment1. Who are major vendors of vision systems and the various

components?

2. What are typical camera resolutions?

3. What are typical camera calibration techniques?

4. What is camera distortion?

5. Is color vision imaging used? In what applications?

6. How long does it take to process images? As a function of image processing function?

7. What are typical costs for imaging systems? For frame grabbers, cameras, lenses, lighting?

1. Who are major vendors of vision systems and the various components?

2. What are typical camera resolutions?

3. What are typical camera calibration techniques?

4. What is camera distortion?

5. Is color vision imaging used? In what applications?

6. How long does it take to process images? As a function of image processing function?

7. What are typical costs for imaging systems? For frame grabbers, cameras, lenses, lighting?


Building BlocksBuilding Blocks

What have we learned?What have we learned?

me 486 - automation automation building blocks by ed red automation building blocks by ed red...

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