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actuators for mechatronics applications

Actuators for Mechatronics Applications

BJ Furman

11MAR2014

https://www.jameco.com/Jameco/Products/ProdImag/1939589.jpg

http://www.firgelli.com/Uploads/ID3IMAGE1300907739.jpg

http://www.newport.com/images/web900w-EN/images/11633.jpg?img_width=600&img_height=448

outline
Outline

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Learning objectives

Context for this module

Permanent magnet dc (PMDC) motor theory

Interfacing to PMDC motors

RC servos

learning objectives
Learning objectives

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Explain how a permanent magnet dc (PMDC) motor works

Explain how an RC servo works

Interface a dc motor and an RC servo to a microcontroller

Control the speed of a DC motor and the angular orientation of an RC servo

context for this module

PowerSource

SignalConditioning

UserInterface

Actuator

Sensor

System toControl

ME 110

ME 136

ME 154

ME 157

ME 182

ME 189

ME 195

Context for this module

Mechatronics Concept Map

ME 106

ME 120

Controller(Hardware & Software)

ME 30

ME 106

ME 190

ME 187

PowerInterface

ME 106

INTEGRATION

‘Muscle’

ME 106

ME 120

ME 106

ME 154

ME 157

ME 195

ME 120

ME 284

BJ Furman 22JAN2011

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

pmdc theory
PMDC theory

Brush

+

Commutation ring

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Two fundamental phenomena occur
    • Generation of torque (Lorentz force law)
      • An electric charge moving in a magnetic field experiences a force
    • Generation of back EMF (Faraday’s law of induction)
      • A conductor moving in a magnetic field generates a voltage

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

pmdc theory torque
PMDC theory - Torque

Brush

Commutation ring

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Torque (Lorentz force law)
      • An electric charge moving in a magnetic field experiences a force
pmdc theory back emf
PMDC theory – Back EMF

Brush

Commutation ring

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Generation of back EMF (Faraday’s law of induction)
      • A conductor moving in a magnetic field generates a voltage at the negative rate of change of the magnetic flux through the circuit
simple dc motor
Simple DC motor

Brush

Commutation ring

Torque constant (Nm/A)

Back EMF constant (V/rad/s)

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

commutation torque increasing
Commutation – torque increasing

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Which way will the coil rotate?

commutation maximum torque
Commutation – maximum torque

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

commutation torque decreasing
Commutation – torque decreasing

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

commutation zero torque
Commutation – zero torque

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

commutation torque increasing13
Commutation – torque increasing

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

permanent magnet dc pmdc motor
Permanent magnet DC (PMDC) motor

http://www.maxonmotor.ch/e-paper/blaetterkatalog/pdf/save/bk_25.pdf

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

pmdc motor electrical model
PMDC motor electrical model
  • Reflection
    • What happens as the motor speed increases? (Assume Vs is constant)
      • How does I change?
      • How does the change in I affect torque? (remember, T=KTI)
    • What happens when motor speed reaches its maximum value?
      • What value will I be?
      • What value of torque will be available?
    • What happens when the motor speed is zero (locked rotor)?
      • What value will I be?
      • What value of torque will be available?

Introduction to Mechatronics, Figure 22.7 p. 538.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Write KVL around the loop

pmdc motor speed torque behavior
PMDC motor speed-torque behavior
  • Observations
    • Intercepts with speed axis
      • No-load speed
    • Intercepts with torque axis
      • Stall torque
    • Slope of speed-torque line
      • Speed regulation constant (speed-torque gradient)
  • When expressed in SI units, KT == KE

Introduction to Mechatronics, Figure 22.8 p. 539.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

From KVL equation

power and efficiency for a pmdc motor
Power and efficiency for a PMDC motor
  • Efficiency

Introduction to Mechatronics, Figure 22.10 p. 544.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Power
gearheads
Gearheads

http://www.maxonmotor.ch/e-paper/blaetterkatalog/pdf/save/bk_31.pdf

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

speed torque curve for a pmdc motor
Speed – Torque Curve for a PMDC Motor

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Mabuchi FF-130RH-15210 3V DC motor

speed torque curve for a pmdc motor20
Speed – Torque Curve for a PMDC Motor

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Finding operating parameters when torque is known

speed torque curve for a pmdc motor21
Speed – Torque Curve for a PMDC Motor

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Finding operating parameters when current is known

speed torque curve for a pmdc motor22
Speed – Torque Curve for a PMDC Motor

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Finding operating parameters when speed is known

speed torque curve for a pmdc motor23
Speed – Torque Curve for a PMDC Motor

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Effect of changing supply voltage

speed torque curve for a pmdc motor24
Speed – Torque Curve for a PMDC Motor

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Effect of internal resistance for battery supplies

speed torque curve for a pmdc motor25
Speed – Torque Curve for a PMDC Motor

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Effect of changing type temperature

speed torque curve for a pmdc motor26
Speed – Torque Curve for a PMDC Motor

https://www.jameco.com/Jameco/Products/ProdDS/1939589.pdf

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Mabuchi FF-130RH-15210 3V DC motor

actuators for mechatronics applications cont

Actuators for Mechatronics Applications, cont.

BJ Furman

15JUL2011 (for 19JUL2011)

https://www.jameco.com/Jameco/Products/ProdImag/1939589.jpg

http://www.firgelli.com/Uploads/ID3IMAGE1300907739.jpg

http://www.newport.com/images/web900w-EN/images/11633.jpg?img_width=600&img_height=448

outline28
Outline

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Additional actuators useful in mechatronics

Bi-directional control of PMDC motors

RC servos

RC servos interfacing to microcontrollers

Motor sizing

learning objectives29
Learning objectives

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

List additional actuators that are useful in mechatronic applications

Explain how an RC servo works

Interface a dc motor and an RC servo to a microcontroller

Control the speed of a DC motor and the angular orientation of an RC servo

Size a motor

brushless motors
Brushless motors
  • Disadvantages
    • More complicated to control
    • Higher cost

http://ww1.microchip.com/downloads/en/AppNotes/00885a.pdf

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Commutation is handled electronically, rather than mechanically
    • Advantages
      • No brushes to wear out
      • High speeds possible (>100 kRPM)
      • Low electrical noise
      • Low rotor inertia (fast dynamics)
linear motors
Linear motors

http://www.baldor.com/products/linear_motors.asp

Linear Stepper Motors:

Single and 2-axis

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • PMDC (brushless) and stepper varieties
    • Direct drive for linear actuation
      • No backlash from gearing or belt/pulley
    • High accelerations
linear actuators
Linear actuators

www.firgelliauto.com/

http://en.wikipedia.org/wiki/File:Linear_actuator_basic.gif

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Combine a motor with a leadscrew

linear motion stage
Linear motion stage

http://www.thomsonlinear.com/

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Buy complete or build your own

voice coil actuator
Voice-coil actuator

http://www.duxcw.com/digest/guides/hd/cheetah.gif

http://www.beikimco.com/actuators_linear_CYL.php

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

High acceleration

Smooth motion

Need position feedback to know where you are

picomotor
Picomotor

http://www.newport.com/

Cost ~$500 (driver not included)

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Piezo-actuated micropositioning device

picomotor actuating principle
Picomotor actuating principle

870x user manual Rev. C, p. 7.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Simple to drive – like a stepper motor (step and direction)

“Set and forget” operation

other piezoelectric actuators
Other piezoelectric actuators
  • High precision, with capacitive position sensing
    • Up to 38 micron travel, 1 nm position resolution
  • Large travel, flexure guided
    • 2000 micron travel, 160 N force

http://www.dynamic-structures.com/piezo.html

http://www.physikinstrumente.com/

  • Squiggle motor
    • Small package, low force, self-locking

http://www.newscaletech.com/

many other actuators
Many other actuators

http://www.ledex.com/

http://www.hydraulicpumpsmotors.com/wp-content/uploads/2011/02/Hydraulic-Actuator.jpg

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Solenoids
  • Pneumatic actuators
    • http://www.smcusa.com/smc.aspx
  • Hydraulic actuators
bidirectional control of motors
Bidirectional control of motors

‘Push-Pull’ pair

(totem pole)

Introduction to Mechatronics, Figure 23.11 p. 562.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • H-bridge – 4 transistors arranged in two ‘push-pull’ pairs
    • Allows current to flow through the motor in either direction with a single-polarity power supply
bidirectional control of motors lr current flow
Bidirectional control of motors – LR current flow

Introduction to Mechatronics, Figure 23.12 p. 562.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • H-bridge
    • What are the diodes used for?
    • Why a combination of NPN and PNP transistors?
    • Need to be careful of ‘shoot-through’ current when switching directions
bidirectional control of motors dynamic braking
Bidirectional control of motors – dynamic braking

Introduction to Mechatronics, Figure 23.14 p. 564.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Turning on only the upper transistors (or only the lower transistors) effectively shorts the motor terminals
    • Voltage drop across a diode and a transistor dissipates energy faster than simple coast down
h bridge chips
H-bridge chips

SN754410NE data sheet

L298 data sheet

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • SN754410NE
  • L293D
    • Quad half-H (2 full H-bridges)
    • Vcc2 can be 4.5 V to 36 V
    • 1 A max continuous per half-H
    • Kickback diodes are built-in (but not L293B)
  • L298
    • Dual, full-H (no diodes incl.)
    • Vsupplycan be 2.5 V to 46 V
    • 2 A max continuous per H
  • LMD18200
  • For higher currents
    • TLE5206 (single H, 5 A continuous, Vsupply6 V to 40 V)
    • DVR8402 (dual H, 5 A per H can be paralleled, Vsupply0 V to 50 V)
h bridge design example
H-bridge design example

http://www.electromate.com/db_support/webphoto/MaxonRE.jpg

(= Vsupply/Rterminal = 12 V/14.1 ohm = 0.851 A, okay)

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Design a bidirectional control interface using L293B for:
    • Maxon RE-13 motor using a 12 V power supply
      • Rterminal = 14.1 ohm
      • L = 0.48 mH
      • PWM frequency = 1 kHz
    • Procedure:
      • Check that L293B can handle Istall
      • Choose kickback diodes (need trr < 200 ns and that can handle inductive transient current and power)
        • If L293D were chosen, kickback diodes are built-in
        • 1N4935 has trr < 200 ns, 10 A peak intermittent, and 1 A max continuous Iforwardwith 1.2 V forward voltage drop  1.2 W
          • Assume diodes dissipate all transient energy (conservative)
h bridge design example schematic
H-bridge design example schematic

Introduction to Mechatronics, Figure 23.12 p. 562.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Bidirectional control for Maxon RE-13 motor using L293B
    • Could avoid external diodes by using L293D
speed control via pwm
Speed Control via PWM

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Pulse-Width Modulation (PWM)
    • Commonly used technique to control speed using digital output
    • Basic idea:
      • Switch power (applied voltage) to the motor on and off fast enough, so that the effect of switching is negligible
      • The resulting average voltage == fraction of time the voltage is on
        • Duty cycle (%) == “On time”/Period x 100%
      • See PWM_demo.vi
    • Choose period (1/freq) to be high enough that torque (and current) ripple can be tolerated
      • 10x shorter than the motor time constant, which is usually on the order of msec, so maybe 20 kHz
rc radio controlled servo
RC (radio controlled) Servo
  • Model airplanes, cars, toys, and more!
  • Simple, low cost
  • Controlled by PWM signal (0-5 V)
    • Pulse duration determines shaft angle
      • 0.5< t <3 ms pulse
      • 20 – 30 ms period

http://www.servocity.com/html/s3003_servo_standard.html

Futaba S3003 standard servo

http://www.pyroelectro.com/tutorials/servo_motor/servomotor.html

~1.5 ms is ‘centered’

(or white)

Introduction to Mechatronics, Figure 27.19 p. 637.

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Incorporates a PMDC motor, gearing, and control electronics

rc servo control system
RC servo control system

http://www.princeton.edu/~mae412/TEXT/NTRAK2002/292-302.pdf

http://mbed.org/cookbook/Servo

Pot

http://www-cdr.stanford.edu/dynamic/servo/

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Averaged PWM signal is compared to pot voltage
    • Controller moves the motor to eliminate the error
    • Can ‘hack’ for continuous rotation (PWM for speed control)
      • See http://www.seattlerobotics.org/guide/servohack.html
rc servo resources
RC Servo resources

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

    • http://mbed.org/cookbook/Servo
  • www.servocity.com
  • http://www.princeton.edu/~mae412/TEXT/NTRAK2002/292-302.pdf
  • http://pcbheaven.com/wikipages/How_RC_Servos_Works/
  • http://www.seattlerobotics.org/guide/servohack.html (modification for continuous rotation)
sizing a motor guiding ideas
Sizing a motor – guiding ideas

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Peak Torque, Tpeak
  • Effective Continuous Torque (RMS Torque), TRMS
  • Maximum Speed, max
  • Other Factors, e.g., size, weight, cost, etc.
sizing a motor procedure
Sizing a motor - procedure

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Make a ‘ballpark’ estimate of the power required using rough calculations, estimation, or measurements
    • P = Torque x angular speed (rad/s) or F x velocity
      • Torque = radius x F
  • Calculate, estimate, or measure Text, Tfric (Note: may need to make an estimated guess about any gearing that might be needed)
  • Calculate motion parameters (angular speed and acceleration)
  • Calculate inertia parameters ‘reflected’ to the motor shaft
  • Calculate Tpeak
  • Compare to your ‘ballpark’ estimate for a sanity check
  • Look for a motor with 1.5Tpeak capability
  • Check max
  • Iterate based on choices
  • Check TRMS
  • Make sure that the motor can also deliver a continuous torque of TRMS or higher
sizing a motor example
Sizing a motor - example

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Refer to handouts
    • Motor sizing example (hand written)
    • Motor sizing example (Mathcad)
    • Motion Control Mechanics
  • Outline of the example
    • Given information:
      • Polar moment of inertia of load
      • Friction torque
      • Motion profile
      • Supply voltage and current (5 A max at 24 V)
    • Select a motor that will meet the requirements
for more information
For More Information

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Mabuchi Motor Technical Reference

http://www.mabuchi-motor.co.jp/en_US/technic/index.html

  • DC Motor Tutorials from MicroMo

http://www.micromo.com/dc-motor-tutorials.aspx

  • Maxon Motor Academy

http://www.maxonmotor.com/maxon-academy.html

  • Maxon Motor e-Catalog

http://www.maxonmotor.ch/e-paper/

  • RC Servo tutorial

http://www.pyroelectro.com/category/tutorials/

stepping motors
Stepping motors

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Operating principle

Construction

Inherent characteristics

Features

Advantages/Disadvantages

pm stepper motor simplified model

A1

B1

B2

A2

PM Stepper motor – simplified model

S

N

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Rotor
    • Rotatable magnetized disk
  • Stator
    • Two windings (phases)
stepper motor operation full step mode 1a

A1

N

B1

B2

N

S

A2

S

Stepper Motor Operation - Full Step Mode 1a

N

high

high

S

low

N

S

low

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Step 1a
    • Energize windings
      • A1 and B1high
      • A2 and B2low
    • What happens to therotor?
stepper motor operation full step mode 1b

A1

N

B1

B2

N

S

A2

S

Stepper Motor Operation - Full Step Mode 1b

N

high

high

S

N

low

S

low

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Step 1b
    • Magnetic forces cause a torque
    • Rotor aligns with stator field
stepper motor operation full step mode 2a

A1

B1

B2

A2

Stepper Motor Operation - Full Step Mode 2a

S

low

S

high

S

N

S

N

low

N

N

high

  • Step 2a
    • Energize windings
      • A2and B1high
      • A1and B2low
    • What happens to therotor?

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation full step mode 2b

A1

B1

B2

A2

Stepper Motor Operation - Full Step Mode 2b

S

low

S

high

N

N

S

low

S

N

N

high

  • Step 2b
    • Magnetic forces causea torque
    • Rotor aligns with stator field

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation full step mode 3a

A1

B1

B2

A2

Stepper Motor Operation - Full Step Mode 3a

S

low

S

low

N

S

N

S

high

N

N

high

  • Step 3a
    • Energize windings
      • A2 and B2high
      • A1 and B1low
    • What happens to therotor?

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation full step mode 3b

A1

B1

B2

A2

Stepper Motor Operation - Full Step Mode 3b

S

low

S

low

N

S

N

S

high

N

N

high

  • Step 3b
    • Magnetic forces causea torque
    • Rotor aligns with stator field

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation full step mode 4a

A1

B1

B2

A2

Stepper Motor Operation - Full Step Mode 4a

N

high

N

low

N

S

N

S

high

S

S

low

  • Step 4a
    • Energize windings
      • A1and B2high
      • A2and B1low
    • What happens to therotor?

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation full step mode 4b

A1

B1

B2

A2

Stepper Motor Operation - Full Step Mode 4b

N

high

N

low

S

S

N

N

high

S

S

low

  • Step 4b
    • Magnetic forces causea torque
    • Rotor aligns with stator field
  • The process repeats…
    • Back to energizing:
      • A1 and B1 high
      • A2 and B2low
    • And the rotor rotates to position 1b

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation half stepping

A1

N

B1

B2

N

S

A2

S

Stepper Motor Operation – Half Stepping

N

high

high

S

N

low

S

low

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Initial state
    • Energize windings
      • A1 and B1 high
      • A2 and B2 low
    • Then, turn off the A winding
      • What happens?
stepper motor operation half stepping 1a
Stepper Motor Operation – Half Stepping 1a

low

A1

B1

high

S

B2

S

N

N

S

N

low

A2

low

  • Step 1a
    • Turn off A winding, leave B on
      • B1high
      • A1, A2and B2 low
    • What happens?

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation half stepping 1b
Stepper Motor Operation – Half Stepping 1b

low

A1

B1

high

B2

S

N

N

S

N

S

low

A2

low

  • Step 1b
    • Resultant field rotates 45°
    • Magnetic forces causea torque
    • Rotor aligns with stator field
      • Now the rotor turnsonly 45 degrees, onehalf of a step!

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation half stepping 2a

A1

B1

B2

A2

Stepper Motor Operation – Half Stepping 2a

S

low

S

high

N

S

N

S

low

N

N

high

  • Step 2a
    • Energize windings
      • A2and B1high
      • A1and B2low
    • What happens to therotor?

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation half stepping 2b

A1

B1

B2

A2

Stepper Motor Operation – Half Stepping 2b

S

low

S

high

N

N

S

low

S

N

N

high

  • Step 2b
    • Resultant field rotates 45°
    • Magnetic forces causea torque
    • Rotor aligns with stator field
      • Now the rotor turnsonly 45 degrees, onehalf of a step!
    • Continue the pattern

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor operation microstepping

A1

B1

B2

A2

Stepper Motor Operation – microstepping

S

low

S

high

N

N

S

low

S

N

N

high

  • Suppose partialenergizationof a winding?
    • Say, reduce B windingvoltage by 15%
      • What happens?

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

variable reluctance vr stepper m otor
Variable Reluctance (VR) Stepper Motor

Introduction to Mechatronics, Figure 26.4, p. 603

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Rotor
    • Just a magnetically permeablematerial, but with ‘teeth’
  • Teeth align to pole piecesdepending on which winding is energized
  • Advantages
    • Smaller steps
    • Lower cost
  • Disadvantages
    • No ‘holding’ torque without winding current
how torque is created
How torque is created
  • Torque is made in the air gap

STATOR

F

FN

ROTOR

FT

Slide courtesy of Nick Johantgen, Oriental Motors, Inc.

hybrid stepper m otor
Hybrid Stepper Motor

http://www.shinano.com/motors/docs/SKC_stepper_operation.pd

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Combines features of PM and VRstepper designs
  • Rotor
    • Toothed
    • End caps are indexed½ tooth pitch
    • Magnetized north on one end,south on the other
hybrid stepper motor operation
Hybrid Stepper Motor Operation

http://www.shinano.com/motors/docs/SKC_stepper_operation.pd

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

Typical

torque vs displacement

4

3

2

1

Torque vs. displacement

Slide courtesy of Nick Johantgen, Oriental Motors, Inc.

two phase torque ripple
Two phase torque ripple

Slide courtesy of Nick Johantgen, Oriental Motors, Inc.

torque speed curve

Holding

Torque

Max Running

Max Starting

Speed

Speed

Torque/Speed curve

Torque (oz-in)

Pullout

Torque

Pull-In

Torque

Start/Stop

Region

Speed

(PPS)

Slide courtesy of Nick Johantgen, Oriental Motors, Inc.

stepper motor drive configurations
Stepper motor drive configurations

http://www.probotix.com/stepper_motors/unipolar_bipolar/

http://www.astrosyn.com/shopimages/technicalguides/Guide%20to%20Stepper%20Motor%20Drive%20Selection.pdf

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

stepper motor drivers
Stepper motor drivers

http://www.allmotion.com/EZInchdescription.htm

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

low cost stepper motor drive
Low-cost stepper motor drive

Uses the SN754410 Quad Half-H chip

http://www.ti.com/lit/ds/symlink/sn754410.pdf

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

features
Features

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • Known, relatively accurate basic step angle
    • 7.2o, 3.6o, 1.8o, .9o, .72o, and 0.36oper step
      • ± 0.05oaccuracy
  • Non-cumulative error
    • Basic accuracy applies regardless of number of steps
  • Very high repeatability
  • One pulse, one step
  • Output speed == pulse rate
  • Relatively fast response
    • Low rotor inertia  high accelerations
  • Relatively high torque per volume
  • Brushless high reliability
advantages disadvantages
Advantages/Disadvantages

BJ Furman SJSU Mechanical and Aerospace Engineering ME 285

  • See ‘Features’ list
  • Can position without a sensor
  • May be more cost effective than other approaches
  • Disadvantages
    • Power dissipation
    • Vibration (particularly 2-phase motors. 5-phase much better)
    • Need to mind pull-in/pull-out torques
    • Relatively low-speed operation