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P R O F . S L A C KP R O F . S L A C KP R O F . S L A C KP R O F . S L A C K

L E C T U R E R , E L E C T R I C A L A N D M I C R O E L E C T R O N I C E N G I N E E R I N G

G B S E E E @ R I T . E D U

B L D I N G 9 , O F F I C E 0 9 - 3 1 8 9

( 5 8 5 ) 4 7 5 - 5 1 0 5

R O C H E S T E R I N S T I T U T E O F T E C H N O L O G YR O C H E S T E R I N S T I T U T E O F T E C H N O L O G YR O C H E S T E R I N S T I T U T E O F T E C H N O L O G YR O C H E S T E R I N S T I T U T E O F T E C H N O L O G Y

7 9 L O M B M E M O R I A L D R I V E

R O C H E S T E R , N Y 1 4 6 2 3 - 5 6 0 3

FORWARD

This lecture This lecture This lecture This lecture offers PRACTICAL guidelines and offers PRACTICAL guidelines and offers PRACTICAL guidelines and offers PRACTICAL guidelines and

considerations on your pathway considerations on your pathway considerations on your pathway considerations on your pathway to to to to selecting, selecting, selecting, selecting,

integrating, simulating, prototyping a motor driving integrating, simulating, prototyping a motor driving integrating, simulating, prototyping a motor driving integrating, simulating, prototyping a motor driving

scheme. scheme. scheme. scheme.

This is NOT a motor design lecture. This is NOT a motor design lecture. This is NOT a motor design lecture. This is NOT a motor design lecture.

� If you need to understand the internal design of a motor, please search “electrical

motors” using Wallace Library website. There are a number of very useful books on

this topic.

� http://library.rit.edu/collections/wallace-library.html

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MOTOR CONTROLS BLOCK DIAGRAM

MOTOR TYPES

1.1.1.1. DC DC DC DC

� DC Motors Brushed

� DC Motor Controls

� H Bridge

2.2.2.2. ServoServoServoServo

� 180° rotation

� Continuous

3.3.3.3. Position SensingPosition SensingPosition SensingPosition Sensing

4.4.4.4. Stepper Stepper Stepper Stepper

5.5.5.5. Three Phase DCThree Phase DCThree Phase DCThree Phase DC

6.6.6.6. AC AC AC AC –––– Light IndustrialLight IndustrialLight IndustrialLight Industrial

Appendix Appendix Appendix Appendix –––– Added infoAdded infoAdded infoAdded info

• Determining Motor needsDetermining Motor needsDetermining Motor needsDetermining Motor needs

• GeneratorsGeneratorsGeneratorsGenerators

• Controls: Know your SpecificationsControls: Know your SpecificationsControls: Know your SpecificationsControls: Know your Specifications

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DC MOTORS BRUSHED

Many DC motors used in Senior Design are brushed DC motors. These are

simple to control, inexpensive and effective in many applications. Operational

sequence:

1. Two external motor leads are connected to two internal brushes which

contacts a 180° split circular ring called a commutator.

2. This split ring acts as a mechanical inverter. The incoming DC current flips

or inverts current direction every 180°.

3. This enables the N and S magnets to “push” the coil of wires often called

the armature.

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SIMPLE SIMPLE SIMPLE SIMPLE DC MOTOR CONTROLDC MOTOR CONTROLDC MOTOR CONTROLDC MOTOR CONTROL

If your project requires single direction If your project requires single direction If your project requires single direction If your project requires single direction rotation, rotation, rotation, rotation, then a simple switch or then a simple switch or then a simple switch or then a simple switch or transistor is all that is needed. transistor is all that is needed. transistor is all that is needed. transistor is all that is needed. Add a diode Add a diode Add a diode Add a diode to suppress back to suppress back to suppress back to suppress back EMF when EMF when EMF when EMF when the motor is switched off by the transistor. That is, as the motor the motor is switched off by the transistor. That is, as the motor the motor is switched off by the transistor. That is, as the motor the motor is switched off by the transistor. That is, as the motor inductive current continues to flow, the diode will discharge back to the inductive current continues to flow, the diode will discharge back to the inductive current continues to flow, the diode will discharge back to the inductive current continues to flow, the diode will discharge back to the other terminal of the motor.other terminal of the motor.other terminal of the motor.other terminal of the motor.

If speed control is needed, then use PWM function on a microcontroller. If speed control is needed, then use PWM function on a microcontroller. If speed control is needed, then use PWM function on a microcontroller. If speed control is needed, then use PWM function on a microcontroller. � ….. or simply a 555 oscillator if manual control is sufficient.

DIRECTION CONTROL – H BRIDGE

• This schematic offers

forward and reverse

motor direction.

• H-bridge got its name

from its schematic shape.

That is, it forms an H.

Four switching elements

at the "corners" of the H

and the motor forms the

cross bar.

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HOW H BRIDGES WORK

TheTheTheThe switchesswitchesswitchesswitches areareareare turnedturnedturnedturned onononon inininin pairs,pairs,pairs,pairs,eithereithereithereither highhighhighhigh leftleftleftleft andandandand lowerlowerlowerlower right,right,right,right, ororororlowerlowerlowerlower leftleftleftleft andandandand highhighhighhigh right,right,right,right, butbutbutbut neverneverneverneverbothbothbothboth switchesswitchesswitchesswitches onononon thethethethe samesamesamesame "side""side""side""side" ofofofofthethethethe bridgebridgebridgebridge.... IfIfIfIf bothbothbothboth switchesswitchesswitchesswitches onononon oneoneoneonesidesidesideside ofofofof aaaa bridgebridgebridgebridge areareareare turnedturnedturnedturned onononon ititititcreatescreatescreatescreates aaaa shortshortshortshort circuitcircuitcircuitcircuit betweenbetweenbetweenbetween thethethethebatterybatterybatterybattery plusplusplusplus andandandand batterybatterybatterybattery minusminusminusminusterminalsterminalsterminalsterminals....

AnythingAnythingAnythingAnything thatthatthatthat cancancancan carrycarrycarrycarry aaaa currentcurrentcurrentcurrent willwillwillwillwork,work,work,work, fromfromfromfrom fourfourfourfour SPSTSPSTSPSTSPST switches,switches,switches,switches, oneoneoneoneDPDTDPDTDPDTDPDT switch,switch,switch,switch, relays,relays,relays,relays, transistors,transistors,transistors,transistors,MOSFETsMOSFETsMOSFETsMOSFETs....

BrakeBrakeBrakeBrake modemodemodemode.... UpperUpperUpperUpper orororor lowerlowerlowerlower switchesswitchesswitchesswitchesclosedclosedclosedclosed....

SUPPRESSION DIODES AND ARCING

WhyWhyWhyWhy? Protect the four transistors. ? Protect the four transistors. ? Protect the four transistors. ? Protect the four transistors.

How do Suppression Diodes help? First, note thesediodes are reversed from normal power supply so nocurrent will flow when the motor is off or when themotor is on.

The issue is when a motor switches off. Since internalelectrical circuitry of a motor is a coil of wire (i.e.inductor), current in an inductor needs to continue toflow. When the diagonal transistor pair switches offand thus causing IC go to zero, the motor coils (i.e.inductors) are still charged with current and must flowthrough the internal inductors in the motor. This iscalled Back EMF. Without suppression diodes, thecurrent must flow through the transistors which areswitched off. Since the transistors are off, the BackEMF will go in 100’s of voltages to push the currentthrough the motor’s inductor circuitry. This Back EMGvoltage is high enough to damage transistors. So thecurrent path when the transistor pair switches off isthrough the motor (Back EMF), through thesuppression diode to V+, through the power supply,through the Gnd, through the lower suppression diodeand then back into the motor. This current surge willend without damaging the electronics. Okay whencurrent flows into the positive lead of the power supply,the voltage level will dip or perhaps even go negativefor a short period of time. You can trigger your scope tosee this. Electronics such as a microcontroller caneasily reset itself when this happens. Some times atrandom.

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BUY OR BUILD H BRIDGE?

Your project’s Needs!Your project’s Needs!Your project’s Needs!Your project’s Needs!

�Cost?

�Reliability?

�Features?

If you buy an H Bridge, there are 100’s to pick from! For If you buy an H Bridge, there are 100’s to pick from! For If you buy an H Bridge, there are 100’s to pick from! For If you buy an H Bridge, there are 100’s to pick from! For

your DC motor, know your voltage and current your DC motor, know your voltage and current your DC motor, know your voltage and current your DC motor, know your voltage and current

specifications. As an example of a small H bridge,specifications. As an example of a small H bridge,specifications. As an example of a small H bridge,specifications. As an example of a small H bridge,http://www.ti.com/lit/ds/symlink/drv8837.pdf

This “small power” IC drives a 11V at 1.8A DC motor.This “small power” IC drives a 11V at 1.8A DC motor.This “small power” IC drives a 11V at 1.8A DC motor.This “small power” IC drives a 11V at 1.8A DC motor.�Has a brake function, arc suppression (they all do….)

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SERVO MOTOR PARTS SERVO MOTOR PARTS SERVO MOTOR PARTS SERVO MOTOR PARTS

AAAA ServoServoServoServo isisisis aaaa motoredmotoredmotoredmotored devicedevicedevicedevice thatthatthatthat hashashashas anananan outputoutputoutputoutput shaftshaftshaftshaft

thatthatthatthat cancancancan bebebebe positionedpositionedpositionedpositioned totototo specificspecificspecificspecific angularangularangularangular positionspositionspositionspositions bybybyby

sendingsendingsendingsending thethethethe servoservoservoservo codedcodedcodedcoded signalsignalsignalsignal....

As long as the coded signal exists on the input, the servo will maintain

the angular position of the shaft. As the coded signal changes, the

angular position of the shaft changes.

FreescaleFreescaleFreescaleFreescale Servo NotesServo NotesServo NotesServo Notes: https://community.freescale.com/docs/DOC-1027

HOBBY RC SERVO

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HOBBY RC - 180° SERVO MOTOR PWM CONTROL SIGNAL

NoteNoteNoteNote thatthatthatthat onlyonlyonlyonly aaaa singlesinglesinglesingle PWMPWMPWMPWM signalsignalsignalsignal isisisis

neededneededneededneeded fromfromfromfrom anananan externalexternalexternalexternal controllercontrollercontrollercontroller....

TheTheTheThe servoservoservoservo electronicselectronicselectronicselectronics areareareare “smart”“smart”“smart”“smart”

enoughenoughenoughenough totototo determinedeterminedeterminedetermine thethethethe motormotormotormotor shaftshaftshaftshaft

rotationalrotationalrotationalrotational positionpositionpositionposition basedbasedbasedbased offoffoffoff aaaa PWMPWMPWMPWM

signalsignalsignalsignal pulsepulsepulsepulse widthwidthwidthwidth.... NoNoNoNo externalexternalexternalexternal

feedbackfeedbackfeedbackfeedback isisisis neededneededneededneeded totototo determinedeterminedeterminedetermine

placementplacementplacementplacement.... AAAA rangerangerangerange ofofofof 30303030 totototo 50505050

millisecondsmillisecondsmillisecondsmilliseconds betweenbetweenbetweenbetween pulsespulsespulsespulses isisisis typicaltypicaltypicaltypical....

ServoServoServoServo maymaymaymay havehavehavehave serialserialserialserial interfaceinterfaceinterfaceinterface (i(i(i(i....eeee....

USB,USB,USB,USB, RSRSRSRS232232232232,,,, CAN)CAN)CAN)CAN) andandandand maymaymaymay bebebebe ableableableable totototo

wirewirewirewire severalseveralseveralseveral inininin seriesseriesseriesseries....

SoftwareSoftwareSoftwareSoftware isisisis readilyreadilyreadilyreadily availableavailableavailableavailable....

SERVO CONTROLLERS (non-RC)

DesigningDesigningDesigningDesigning aaaa ServoServoServoServo ControllerControllerControllerController requiresrequiresrequiresrequires PIDPIDPIDPID (proportional(proportional(proportional(proportional––––integralintegralintegralintegral––––derivative)derivative)derivative)derivative) controlcontrolcontrolcontrol andandandand knowledgeknowledgeknowledgeknowledge ofofofof projectprojectprojectproject dynamicsdynamicsdynamicsdynamics.... ForForForFor advancedadvancedadvancedadvancedprojectprojectprojectproject requirements,requirements,requirements,requirements, recommendationrecommendationrecommendationrecommendation isisisis totototo purchasepurchasepurchasepurchase aaaa controlcontrolcontrolcontrol unitunitunitunitandandandand ServoServoServoServo MotorMotorMotorMotor asasasas aaaa matchedmatchedmatchedmatched pairpairpairpair....

ServoServoServoServo MotorMotorMotorMotor systemssystemssystemssystems useuseuseuse aaaa closedclosedclosedclosed looplooplooploop controlcontrolcontrolcontrolsystemssystemssystemssystems totototo preciselypreciselypreciselyprecisely positionpositionpositionposition mechanicalmechanicalmechanicalmechanical devicesdevicesdevicesdevices....

WhereWhereWhereWhere areareareare Servo’sServo’sServo’sServo’s used?used?used?used? PCPCPCPC HardHardHardHard drives,drives,drives,drives, inkinkinkink jetjetjetjetprinters,printers,printers,printers, industrialindustrialindustrialindustrial needsneedsneedsneeds requiringrequiringrequiringrequiring precisionprecisionprecisionprecision and/and/and/and/orororor speedspeedspeedspeed....

AAAA goodgoodgoodgood example,example,example,example, onononon campuscampuscampuscampus isisisis thethethethe “pick“pick“pick“pick &&&& place”place”place”place”PCBPCBPCBPCB layoutlayoutlayoutlayout machinemachinemachinemachine inininin buildingbuildingbuildingbuilding 78787878....

4 4 4 4 minute YouTube minute YouTube minute YouTube minute YouTube explanation explanation explanation explanation http://http://http://http://www.youtube.com/watch?v=rFwxH6zqz98www.youtube.com/watch?v=rFwxH6zqz98www.youtube.com/watch?v=rFwxH6zqz98www.youtube.com/watch?v=rFwxH6zqz98

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POSITION SENSING

DC DC DC DC motors are motors are motors are motors are not necessary sufficiently accurate due to not necessary sufficiently accurate due to not necessary sufficiently accurate due to not necessary sufficiently accurate due to

varying mechanical loads. varying mechanical loads. varying mechanical loads. varying mechanical loads.

Shaft encoder and a home position offers Shaft encoder and a home position offers Shaft encoder and a home position offers Shaft encoder and a home position offers feedback feedback feedback feedback to to to to

motor motor motor motor controller for precise controller for precise controller for precise controller for precise movementmovementmovementmovement....

Detailed theory of encoders:Detailed theory of encoders:Detailed theory of encoders:Detailed theory of encoders:

� http://www.automationdirect.com/static/manuals/d4hsc

/appxa.pdf

� http://www.lynxmotion.com/p-653-gear-head-motor-

12vdc-301-200rpm-6mm-shaft.aspx

� http://www.pololu.com/catalog/product/1442

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POSITIONING : SHAFT ENCODERS

Color Function

Black motor power

Red motor power

BlueHall sensor Vcc (3.5 –

20 V)

Green Hall sensor GND

Yellow Hall sensor A output

White Hall sensor B output

Encoder Encoder Encoder Encoder

Viewed from the back side of a DC Motor. This encoder is built into the motor.

POSITIONING: HALL SENSOR A AND B OUTPUTS

• This will tell the RPM speed. Often 400 pulses/ rev

• A and B pulses are offset by 90°. This offers rotational direction of motor. That is, “A” lead edge is leading “B”, thus indicates CW direction. When “A” leads “B”, then CCW.

• Some encoders (not this one) have another sensor output (i.e. C) labeled “Home Position” which offers one pulse per revolution.

• Some encoders have serial interface and calculates RPM and periodically sends various parameters.

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STEPPER MOTOR DESCRIPTION

A A A A stepper motor (or step motor) is stepper motor (or step motor) is stepper motor (or step motor) is stepper motor (or step motor) is a brushless DC electric motor that a brushless DC electric motor that a brushless DC electric motor that a brushless DC electric motor that divides a full divides a full divides a full divides a full

rotation into a number of equal steps. The motor's position can then be rotation into a number of equal steps. The motor's position can then be rotation into a number of equal steps. The motor's position can then be rotation into a number of equal steps. The motor's position can then be

commanded to move and hold at one of these steps without any feedback commanded to move and hold at one of these steps without any feedback commanded to move and hold at one of these steps without any feedback commanded to move and hold at one of these steps without any feedback

sensor. sensor. sensor. sensor. Source: Wikipedia

Stepper Motors by their inherent design are well controlled motors. Stepper Motors by their inherent design are well controlled motors. Stepper Motors by their inherent design are well controlled motors. Stepper Motors by their inherent design are well controlled motors.

These motors have a series of internal windings that will turn the These motors have a series of internal windings that will turn the These motors have a series of internal windings that will turn the These motors have a series of internal windings that will turn the

armature to the next coil winding. Like a DC Motor, a stepper motor armature to the next coil winding. Like a DC Motor, a stepper motor armature to the next coil winding. Like a DC Motor, a stepper motor armature to the next coil winding. Like a DC Motor, a stepper motor

uses DC power. A Stepper Motor will “step” when given a specific uses DC power. A Stepper Motor will “step” when given a specific uses DC power. A Stepper Motor will “step” when given a specific uses DC power. A Stepper Motor will “step” when given a specific

pulse.pulse.pulse.pulse.

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STEPPER MOTOR INTERNAL COMPONENTS

This stepper motor has a rotor

of 50 teeth and the stator has

8 poles with 5 teeth each

(total of 40 teeth), the stepper

motor is able to move 200

distinct steps to make one

complete revolution. This

means that shaft of the motor

will turn 1.8° per step.

Many stepper motors have integrated gear down

transmissions to increase torque and decrease

the step increment. That is a 10:1 transmission

will give 0.18 degree step and increase the

torque by nearly that much.

STEPPER MOTOR DESIGN HELP

Anaheim Automation is a primary manufacturer of quality or Anaheim Automation is a primary manufacturer of quality or Anaheim Automation is a primary manufacturer of quality or Anaheim Automation is a primary manufacturer of quality or

industrial Stepper Motors. industrial Stepper Motors. industrial Stepper Motors. industrial Stepper Motors.

http://www.anaheimautomation.com/

Helpful Helpful Helpful Helpful link to select the correct stepper motor and controller.link to select the correct stepper motor and controller.link to select the correct stepper motor and controller.link to select the correct stepper motor and controller.

httphttphttphttp://://://://www.anaheimautomation.com/products/stepper/stepperwww.anaheimautomation.com/products/stepper/stepperwww.anaheimautomation.com/products/stepper/stepperwww.anaheimautomation.com/products/stepper/stepper----

products.php?gclid=COWer7products.php?gclid=COWer7products.php?gclid=COWer7products.php?gclid=COWer7----41rICFcdlOgodQ2YAMQ41rICFcdlOgodQ2YAMQ41rICFcdlOgodQ2YAMQ41rICFcdlOgodQ2YAMQ

Least expensive: Permanent Least expensive: Permanent Least expensive: Permanent Least expensive: Permanent Magnet (PM) Stepper Magnet (PM) Stepper Magnet (PM) Stepper Magnet (PM) Stepper Motors.Motors.Motors.Motors.

Texas Texas Texas Texas Instruments Evaluation Kit, highly recommended to learn Instruments Evaluation Kit, highly recommended to learn Instruments Evaluation Kit, highly recommended to learn Instruments Evaluation Kit, highly recommended to learn

electronics.electronics.electronics.electronics.

http://www.ti.com/tool/drv8412-c2-kit

Less critical applications are a number of less expensive motors Less critical applications are a number of less expensive motors Less critical applications are a number of less expensive motors Less critical applications are a number of less expensive motors

from several sources.from several sources.from several sources.from several sources.� http://www.automationdirect.com/adc/Home/Home

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STEPPER CONTROLLER - EVALUATION KITS

Recommendation: Texas Instruments Evaluation Kit:Recommendation: Texas Instruments Evaluation Kit:Recommendation: Texas Instruments Evaluation Kit:Recommendation: Texas Instruments Evaluation Kit:DRV8412 Integrated Motor Driver for Brushed and Stepper Motors with Piccolo F28035 - $199 includes motors.

http://www.ti.com/tool/drv8412http://www.ti.com/tool/drv8412http://www.ti.com/tool/drv8412http://www.ti.com/tool/drv8412----c2c2c2c2----kitkitkitkit

Stepper Stepper Stepper Stepper Motor controllers are fairly simple but Motor controllers are fairly simple but Motor controllers are fairly simple but Motor controllers are fairly simple but purchase an evaluation purchase an evaluation purchase an evaluation purchase an evaluation board for circuit and board for circuit and board for circuit and board for circuit and software starting point. software starting point. software starting point. software starting point.

Many Many Many Many onononon----line schematics and software are line schematics and software are line schematics and software are line schematics and software are available.available.available.available.

COMPARING SERVO AND STEPPER MOTORS AND

CONTROLLERShttphttphttphttp://://://://www.ni.com/whitewww.ni.com/whitewww.ni.com/whitewww.ni.com/white----paper/3656/enpaper/3656/enpaper/3656/enpaper/3656/en

One One One One of the main differences between servo motors and stepper motors is that servo motors, by of the main differences between servo motors and stepper motors is that servo motors, by of the main differences between servo motors and stepper motors is that servo motors, by of the main differences between servo motors and stepper motors is that servo motors, by

definition, run using a control loop and require feedback of some kind. A control loop uses feedback definition, run using a control loop and require feedback of some kind. A control loop uses feedback definition, run using a control loop and require feedback of some kind. A control loop uses feedback definition, run using a control loop and require feedback of some kind. A control loop uses feedback

from the motor to help the motor get to a desired state (position, velocity, and so on). There are many from the motor to help the motor get to a desired state (position, velocity, and so on). There are many from the motor to help the motor get to a desired state (position, velocity, and so on). There are many from the motor to help the motor get to a desired state (position, velocity, and so on). There are many

different types of control loops. Generally, the PID (Proportional, Integral, Derivative) control loop is different types of control loops. Generally, the PID (Proportional, Integral, Derivative) control loop is different types of control loops. Generally, the PID (Proportional, Integral, Derivative) control loop is different types of control loops. Generally, the PID (Proportional, Integral, Derivative) control loop is

used for servo motors. For more information, see the related link, used for servo motors. For more information, see the related link, used for servo motors. For more information, see the related link, used for servo motors. For more information, see the related link, PID Controller: Theory and PracticePID Controller: Theory and PracticePID Controller: Theory and PracticePID Controller: Theory and Practice....

When using a control loop such as PID, you may need to tune the servo motor. Tuning is the process of When using a control loop such as PID, you may need to tune the servo motor. Tuning is the process of When using a control loop such as PID, you may need to tune the servo motor. Tuning is the process of When using a control loop such as PID, you may need to tune the servo motor. Tuning is the process of

making a motor respond in a desirable way. Tuning a motor can be a very difficult and tedious making a motor respond in a desirable way. Tuning a motor can be a very difficult and tedious making a motor respond in a desirable way. Tuning a motor can be a very difficult and tedious making a motor respond in a desirable way. Tuning a motor can be a very difficult and tedious

process, but is also an advantage in that it lets process, but is also an advantage in that it lets process, but is also an advantage in that it lets process, but is also an advantage in that it lets the engineer and the engineer and the engineer and the engineer and user have more control over the user have more control over the user have more control over the user have more control over the

behavior of the motor. behavior of the motor. behavior of the motor. behavior of the motor.

Since servo motors have a control loop to check what state they are in, they are generally more Since servo motors have a control loop to check what state they are in, they are generally more Since servo motors have a control loop to check what state they are in, they are generally more Since servo motors have a control loop to check what state they are in, they are generally more

reliable than stepper motors. When a stepper motor misses a step for any reason, there is no control reliable than stepper motors. When a stepper motor misses a step for any reason, there is no control reliable than stepper motors. When a stepper motor misses a step for any reason, there is no control reliable than stepper motors. When a stepper motor misses a step for any reason, there is no control

loop to compensate in the move. The control loop in a servo motor is constantly checking to see if the loop to compensate in the move. The control loop in a servo motor is constantly checking to see if the loop to compensate in the move. The control loop in a servo motor is constantly checking to see if the loop to compensate in the move. The control loop in a servo motor is constantly checking to see if the

motor is on the right path and, if it is not, it makes the necessary adjustments.motor is on the right path and, if it is not, it makes the necessary adjustments.motor is on the right path and, if it is not, it makes the necessary adjustments.motor is on the right path and, if it is not, it makes the necessary adjustments.

In general, servo motors run more smoothly than stepper motors except when In general, servo motors run more smoothly than stepper motors except when In general, servo motors run more smoothly than stepper motors except when In general, servo motors run more smoothly than stepper motors except when microsteppingmicrosteppingmicrosteppingmicrostepping is used. is used. is used. is used.

Also, as speed increases, the torque of the servo remains constant, making it better than the Also, as speed increases, the torque of the servo remains constant, making it better than the Also, as speed increases, the torque of the servo remains constant, making it better than the Also, as speed increases, the torque of the servo remains constant, making it better than the

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SERVO VS STEPPER - SUMMARY

Advantages Servo over StepperAdvantages Servo over StepperAdvantages Servo over StepperAdvantages Servo over Stepper

High intermittent torqueHigh intermittent torqueHigh intermittent torqueHigh intermittent torque

High torque to inertia ratioHigh torque to inertia ratioHigh torque to inertia ratioHigh torque to inertia ratio

High speedsHigh speedsHigh speedsHigh speeds

Work well for velocity controlWork well for velocity controlWork well for velocity controlWork well for velocity control

Available in all sizesAvailable in all sizesAvailable in all sizesAvailable in all sizes

QuietQuietQuietQuiet

Advantages of Stepper over Servo Advantages of Stepper over Servo Advantages of Stepper over Servo Advantages of Stepper over Servo

Functions open loop Functions open loop Functions open loop Functions open loop –––– no feedback requiredno feedback requiredno feedback requiredno feedback required

No tuning of control loop parameters (i.e. PID)No tuning of control loop parameters (i.e. PID)No tuning of control loop parameters (i.e. PID)No tuning of control loop parameters (i.e. PID)

Stepper motor system is less expensiveStepper motor system is less expensiveStepper motor system is less expensiveStepper motor system is less expensive

5. THREE PHASE DC

3 Phase motors are used in devices such as hard drives, ink jet printers and other

applications where precision is needed.

Recommendation: Purchase a Development Kit such as Texas Instruments 3-Phase

BLDC Motor Kithttp://www.ti.com/tool/dk-lm3s-drv8312?DCMP=D_MCU_C2000_C2000&CMP=KNC-GoogleTI&247SEM

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6. AC MOTOR – LIGHT INDUSTRIAL

Sometimes referred to as “Sometimes referred to as “Sometimes referred to as “Sometimes referred to as “FFFFarm Duty”. Can be plugged directly into arm Duty”. Can be plugged directly into arm Duty”. Can be plugged directly into arm Duty”. Can be plugged directly into an AC receptacle and/ or controlled by a wall switch. an AC receptacle and/ or controlled by a wall switch. an AC receptacle and/ or controlled by a wall switch. an AC receptacle and/ or controlled by a wall switch.

1.1.1.1. 60 60 60 60 hzhzhzhz, , , , single single single single phase, 115/ 230 phase, 115/ 230 phase, 115/ 230 phase, 115/ 230 VACVACVACVAC

2.2.2.2. Fixed RPM. Typical range: 600 to 3600 RPM. Fixed RPM. Typical range: 600 to 3600 RPM. Fixed RPM. Typical range: 600 to 3600 RPM. Fixed RPM. Typical range: 600 to 3600 RPM.

3.3.3.3. Reversible by moving wire connections under an inspection plate Reversible by moving wire connections under an inspection plate Reversible by moving wire connections under an inspection plate Reversible by moving wire connections under an inspection plate on the motor. on the motor. on the motor. on the motor.

4.4.4.4. Motor cases come in many forms to match your mounting Motor cases come in many forms to match your mounting Motor cases come in many forms to match your mounting Motor cases come in many forms to match your mounting application.application.application.application.

Advantages: Inexpensive, powerful, reliable, abusive environments, no Advantages: Inexpensive, powerful, reliable, abusive environments, no Advantages: Inexpensive, powerful, reliable, abusive environments, no Advantages: Inexpensive, powerful, reliable, abusive environments, no DC power supply or controller needed.DC power supply or controller needed.DC power supply or controller needed.DC power supply or controller needed.

Disadvantages: Can not perform more advanced control unless Disadvantages: Can not perform more advanced control unless Disadvantages: Can not perform more advanced control unless Disadvantages: Can not perform more advanced control unless controllers are used.controllers are used.controllers are used.controllers are used.

APPENDIX: ADDED INFO

Determining Motor needsDetermining Motor needsDetermining Motor needsDetermining Motor needs

Controls: Know your SpecificationsControls: Know your SpecificationsControls: Know your SpecificationsControls: Know your Specifications

GeneratorsGeneratorsGeneratorsGenerators

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DETERMINING MOTOR NEEDS

Mechanical Power NeedsMechanical Power NeedsMechanical Power NeedsMechanical Power Needs

� Torque (i.e. oz-in, ft-lbs, newton-meter)

Electrical Electrical Electrical Electrical Power Power Power Power NeedsNeedsNeedsNeeds

� (i.e. kW, W, Hp, voltage, current) to meet your mechanical power needs

RPM active range RPM active range RPM active range RPM active range

Cost Cost Cost Cost

Precision? Precision? Precision? Precision?

� Encoders, Motor type

Locking, Locking, Locking, Locking, Braking?Braking?Braking?Braking?

� When the motor is off, will the shaft move? Is this an issue? Vibration?

(continued)

DETERMINING MOTOR NEEDS (CONTINUED)

Linear Linear Linear Linear versus rotational motionversus rotational motionversus rotational motionversus rotational motion

� Gear reduction versus belt & pulley reduction

Heavy Heavy Heavy Heavy starting loadsstarting loadsstarting loadsstarting loads

Safety designSafety designSafety designSafety design

� Kill switch, software monitoring, torque & RPM sensing

CompactnessCompactnessCompactnessCompactness

QuietnessQuietnessQuietnessQuietness

Environmental situationsEnvironmental situationsEnvironmental situationsEnvironmental situations

Fire hazardFire hazardFire hazardFire hazard

Periodic Servicing Periodic Servicing Periodic Servicing Periodic Servicing needsneedsneedsneeds

10/15/2012

17

CONTROLS: KNOW YOUR SPECIFICATIONS

Lab Bench Testing Lab Bench Testing Lab Bench Testing Lab Bench Testing

�Current sensing circuitry

�Shaft Tachometer

�Torque instrumentation; torque wrench

�Ammeter

�Heat/ temperature

GENERATORS

Convert Convert Convert Convert mechanical energy to electrical energy. Rotating an armature, which carries mechanical energy to electrical energy. Rotating an armature, which carries mechanical energy to electrical energy. Rotating an armature, which carries mechanical energy to electrical energy. Rotating an armature, which carries

conductors, in a magnetic field and thus inducing an conductors, in a magnetic field and thus inducing an conductors, in a magnetic field and thus inducing an conductors, in a magnetic field and thus inducing an emfemfemfemf in these conductors. A in these conductors. A in these conductors. A in these conductors. A

relative motion must always exist between the conductors and the magnetic field relative motion must always exist between the conductors and the magnetic field relative motion must always exist between the conductors and the magnetic field relative motion must always exist between the conductors and the magnetic field

in such a manner that conductor cut through the field. in such a manner that conductor cut through the field. in such a manner that conductor cut through the field. in such a manner that conductor cut through the field. Many have manual Many have manual Many have manual Many have manual

resettable fuses. resettable fuses. resettable fuses. resettable fuses.

AC Generators (also known as alternators when rectifiers are AC Generators (also known as alternators when rectifiers are AC Generators (also known as alternators when rectifiers are AC Generators (also known as alternators when rectifiers are integrated) integrated) integrated) integrated)