Variable speed drives A tutorialeavr.u-strasbg.fr/~bernard/education/3a_ta/techno_ass_tuto.pdf ·...

Variable speed drives

A tutorial

Bernard BayleTélécom Physique Strasbourg – Université de Strasbourg

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This course/tutorial

Course objectiveThis course deals with the technology of variable speed drives.Prerequisites: basics of electronics and power conversion.

DefinitionVariable speed drive (VSD): device that simultaneouslyprovides a motor with its power supply and input control.

Open access references:http://www.maxonmotor.com/maxon/view/content/academy

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http://www.maxonmotor.com/maxon/view/content/academy

Outline

1 Actuators technology

2 Angular position measurement

3 Variable speed drives: technology

4 Variable speed drives: control

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Actuation

ActuatorMechanical transmission + (electric) motorAngular position/velocity sensorsPower electronics: variable speed drive

Motors in roboticsUsual choice: DC brushed or brushless motors.

Some special choices include: AC motors, pneumatic andhydraulic actuators, piezoelectric and stepper motors.

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(Brushed) DC motors

Questions (1)

Explain how they workAdvantages and drawbacks?

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(Brushed) DC motors

Question (2)

Explain what is different from conventional DC motors

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Brusless DC motors - see B. Maurin course

PrincipleSynchronous motor with permanent magnet at the rotor, controlbased on the analogy with DC motor.

Advantages

Better efficiency, better mechanical characteristicsBetter torque-to-weight ratioHigher maximal angular velocityLess commutation electronic noise, no sparks

DrawbacksMore expensiveMore complex digital driveTorque cogging at low speed

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Transmission

Straight cut (spur) gears or helical gears

Multi stage and epicyclic gear trains

Questions (3)Why do we use speed reduction in actuators?What are the drawbacks/limitations of such gears ?

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Harmonic Drive

PrincipleStrain wave gearing has 3 components: an elliptical wavegenerator (WG), a flex spline (FS), and a circular spline (CS).

As the WG rotates, the FS teeth move, meshed with those ofthe CS. With fewer teeth on the FS than on the CS, the WGrotation results in a much slower rotation of the FS.

https://www.youtube.com/watch?v=bzRh672peNk9 / 33

https://www.youtube.com/watch?v=bzRh672peNk

Outline





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Sensors

Advantage

Measure the linear/angular position/velocity of each jointUsed for feedback control

DrawbacksA lot of potential drawbacks to be discussed for each type. . .

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Encoders

Questions (4)How do they work?Advantages? Drawbacks?How do the "absolute disk" version work?

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Encoders

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max

on s

enso

r

401

RE 25 179/181 75.3RE 25 179/181 GP 26/GP 32 336/338 •RE 25 179/181 KD 32, 1.0 - 4.5 Nm 347 •RE 25 179/181 GP 32, 0.75 - 6.0 Nm 339/342 •RE 25 179/181 GP 32 S 370-372 •RE 25, 20 W 180 63.8RE 25, 20 W 180 GP 26/GP 32 336/338 •RE 25, 20 W 180 KD 32, 1.0 - 4.5 Nm 347 •RE 25, 20 W 180 GP 32, 0.75 - 6.0 Nm 339/342 •RE 25, 20 W 180 GP 32 S 370-372 •RE 25, 20 W 180 AB 28 446 94.3RE 25, 20 W 180 GP 26/GP 32 336/338 AB 28 446 •RE 25, 20 W 180 KD 32, 1.0 - 4.5 Nm 347 AB 28 446 •RE 25, 20 W 180 GP 32, 0.75 - 6.0 Nm 339/342 AB 28 446 •RE 25, 20 W 180 GP 32 S 370-372 AB 28 446 •RE 25, 20 W 181 AB 28 446 105.8RE 25, 20 W 181 GP 26/GP 32 336/338 AB 28 446 •RE 25, 20 W 181 KD 32, 1.0 - 4.5 Nm 347 AB 28 446 •RE 25, 20 W 181 GP 32, 0.75 - 6.0 Nm 339/342 AB 28 446 •RE 25, 20 W 181 GP 32 S 370-372 AB 28 446 •RE 30, 15 W 182 88.8RE 30, 15 W 182 GP 32, 0.75 - 4.5 Nm 340 •RE 30, 60 W 183 88.8RE 30, 60 W 183 GP 32, 0.75 - 6.0 Nm 338-344 •RE 30, 60 W 183 KD 32, 1.0 - 4.5 Nm 347 •RE 30, 60 W 183 GP 32 S 370-372 •RE 35, 90 W 184 91.7RE 35, 90 W 184 GP 32, 0.75 - 8.0 Nm 338-345 •RE 35, 90 W 184 GP 42, 3.0 - 15 Nm 349 •RE 35, 90 W 184 GP 32 S 370-372 •RE 35, 90 W 184 AB 28 446 124.3RE 35, 90 W 184 GP 32, 0.75 - 8.0 Nm 338-345 AB 28 446 •RE 35, 90 W 184 GP 42, 3.0 - 15 Nm 349 AB 28 446 •RE 35, 90 W 184 GP 32 S 370-372 AB 28 446 •

1

9

2

10

110512 110514 110516

500 500 5003 3 3

100 100 100 12 000 12 000 12 000

3 4 6

s 45°es2 s = 90°e1..4s1s4s3

U

U

U

U

U

U

High

High

High

Low

Low

Low

90°e

R

R

R

May 2016 edition / subject to change maxon sensor

Stock programStandard programSpecial program (on request)

Encoder HEDL 5540 500 CPT, 3 Channels, with Line Driver RS 422

maxon Modular System+ Motor Page + Gearhead Page + Brake Page Overall length [mm] / • see Gearhead

Part Numbers

TypeCounts per turnNumber of channelsMax. operating frequency (kHz)Max. speed (rpm)Shaft diameter (mm)

Direction of rotation cw (definition cw p. 150)

Technical Data Pin Allocation Connection exampleSupply voltage VCC 5 V ± 10%Output signal EIA Standard RS 422 driver used: DS26LS31Phase shift ) 90°e ± 45°eSignal rise time (typically, at CL = 25 pF, RL = 2.7 k:, 25 °C) 180 nsSignal fall time (typically, at CL = 25 pF, RL = 2.7 k:, 25 °C) 40 nsIndex pulse width 90°eOperating temperature range -40…+100 °CMoment of inertia of code wheel d 0.6 gcm2

Max. angular acceleration 250 000 rad s-2

Output current per channel min. -20 mA, max. 20 mAOption 1000 Counts per turn, 2 Channels

The index signal , is synchronized with channel A or B. Terminal resistance R = typical 120 :

1 N.C. 2 VCC

3 GND 4 N.C. 5 Channel A 6 Channel A 7 Channel B 8 Channel B 9 Channel I (Index)10 Channel I (Index)

Pin type DIN 41651/EN 60603-13flat band cable AWG 28

Line receiverRecommended IC's:- MC 3486- SN 75175- AM 26 LS 32

Channel B

Channel B

Channel A

Channel A

Channel I

Channel I

GND

VCC

Enc

oder

, Lin

e D

river

, DS

26LS

31

Channel A

Channel B

Channel I

Cycle C = 360°ePulse P = 180°e

Phase shift

overall length overall length

Tachymetric generators

Questions (5)What is this?Advantages and drawbacks?

max

on s

enso

r

411

RE 25 179/181 76.8RE 25 179/181 GP 26, 0.75 - 2.0 Nm 336 •RE 25 179/181 GP 32, 0.75 - 4.5 Nm 338/339 •RE 25 179/181 GP 32, 0.75 - 6.0 Nm 342 •RE 25 179/181 GP 32, 1.0 - 4.5 Nm 347 •RE 25 179/181 GP 32 S 370-372 •RE 25, 20 W 180 65.3RE 25, 20 W 180 GP 22, 0.5 Nm 329 •RE 25, 20 W 180 GP 26, 0.75 - 2.0 Nm 336 •RE 25, 20 W 180 GP 32, 0.75 - 4.5 Nm 338/339 •RE 25, 20 W 180 GP 32, 0.75 - 6.0 Nm 342 •RE 25, 20 W 180 GP 32, 1.0 - 4.5 Nm 347 •RE 25, 20 W 180 GP 32 S 370-372 •RE 35, 90 W 184 89.1RE 35, 90 W 184 GP 32, 0.75 - 6.0 Nm 338-344 •RE 35, 90 W 184 GP 32, 8 Nm 345 •RE 35, 90 W 184 GP 42, 3.0 - 15 Nm 349 •RE 35, 90 W 184 GP 32 S 370-372 •

118909 118910

3 4

May 2016 edition / subject to change maxon sensor


DC Tacho DCT 22 0.52 Volt

maxon Modular System+ Motor Page + Gearhead Page Overall length [mm] / • see Gearhead

Part Numbers

TypeShaft diameter (mm)

Technical Data Connection exampleOutput voltage per 1000 rpm 0.52 V Max. current 10 mATerminal resistance tacho 37.7 W Tolerance of the output voltage ± 15 %Typical peak to peak ripple ≤ 6 % Rotor inertia (tacho only) < 3 gcm²Ripple frequency per turn 14 Resonance frequency with motors on p. 179 – 181 > 2 kHzLinear voltage tolerance, 500 to 5000 rpm ± 0.2 % with motors on p. 184 > 4.5 kHzLinear voltage tolerance with 10 kΩ load resistance ± 0.7 % Temperature range -20 ... +65 °CPolarity error ± 0.1 %Temperature coefficient of EMF (magnet) -0.02 % /°C Option: Pigtails in place of solder terminals.Temperature coefficient of coil resistance +0.4 % /°C

Important Information• Tacho with moving coil, maxon system.• Tacho with precious metal commutation.• To establish total inertia add motor and

tacho inertias.• With the output shaft turning CW as seen from

the mounting surface, the tacho output voltage will be positive at the + terminal.

• A high impedance load is recommended at tacho terminals.

• The tacho current should be kept low.• The indicated resonance frequency refers to the

motor-tacho rotor system.

Ripple = x 100 (%)

T

180 W

Resonance frequency Motor winding-Tacho winding fR 4 kHz

1 kW

UAC

0.1 mF

UDC

overall length overall length

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Outline





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Tri-phase, full wave rectifier, 4Q chopper for DC motors

i : current, Ω: rotational velocity Static converter example [adapted from Louis2002]

Questions (6)

Identify the different functional blocksExplain their principlesWhat are the other implementations for DC motors speedvariation (source of energy in particular)? 4Q?

Tri-phase, full wave rectifier, 4Q chopper for DC motors

i : current, Ω: rotational velocity

Static converter example [adapted from Louis2002]

i : current, c= torque,Ω, γ: rotational velocity/acceleration

4 quadrants operation [adapted from Louis2002]

Question (7)

Explain the 4Q trajectories

Outline





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Static converter modeling

Question (8)

How would you model the electronic power converters?

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DC motor modelling

v

f

R Li

e

i

Ω

cv

Question (9)

Write the DC motor transfer functions G(s) = Ω(s)/U(s)and GI(s) = I(s)/U(s)

Remark that, by construction e = Ke Ω and c = Km i

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Operating Range Comments

Continuous operationIn observation of above listed thermal resistance(lines 17 and 18) the maximum permissible windingtemperature will be reached during continuousoperation at 25°C ambient.= Thermal limit.

Short term operationThe motor may be briefly overloaded (recurring).

Assigned power rating

n [rpm]

max

onD

Cm

otor

Specifications


Order Number

May 2008 edition / subject to change maxon DC motor 83

maxon Modular System Overview on page 16 - 21

RE 36 !36 mm, Graphite Brushes, 70 Watt

Thermal data17 Thermal resistance housing-ambient 6.4 K / W18 Thermal resistance winding-housing 3.4 K / W19 Thermal time constant winding 44.2 s20 Thermal time constant motor 1120 s21 Ambient temperature -30 ... +100°C22 Max. permissible winding temperature +125°C

Mechanical data (ball bearings)23 Max. permissible speed 12000 rpm24 Axial play 0.05 - 0.15 mm25 Radial play 0.025 mm26 Max. axial load (dynamic) 5.6 N27 Max. force for press fits (static) 5.6 N

(static, shaft supported) 1200 N28 Max. radial loading, 5 mm from flange 28 N

Other specifications29 Number of pole pairs 130 Number of commutator segments 1331 Weight of motor 350 g

Values listed in the table are nominal.Explanation of the figures on page 49.

Tolerances may vary from the standardspecification.

OptionPreloaded ball bearings

Planetary Gearhead!32 mm0.75 - 4.5 Nm9

Planetary Gearhead!32 mm0.4 - 2.0 NmPage 237

Planetary Gearhead!42 mm3 - 15 NmPage 244

DC-Tacho DCT!22 mm0.52 VPage 271

Encoder HEDS 5540500 CPT,3 channelsPage 262Encoder HEDL 5540500 CPT,3 channelsPage 264

118797 118798 118799 118800 118801 118802 118803 118804 118805 118806 118807 118808 118809 118810Motor Data

Values at nominal voltage1 Nominal voltage V 18.0 24.0 32.0 42.0 42.0 48.0 48.0 48.0 48.0 48.0 48.0 48.0 48.0 48.02 No load speed rpm 6610 6210 6790 7020 6340 6420 5220 4320 3450 2830 2280 1780 1420 11803 No load current mA 153 105 88.6 70.4 61.4 54.6 41.6 32.6 24.7 19.5 15.2 11.5 8.97 7.314 Nominal speed rpm 5880 5530 6120 6350 5660 5740 4520 3600 2720 2090 1530 1010 651 3905 Nominal torque (max. continuous torque) mNm 70.2 78.2 77.1 77.9 79.9 79.5 81.5 82.2 83.6 84.1 84.1 83.8 84.1 83.16 Nominal current (max. continuous current) A 2.90 2.25 1.82 1.45 1.33 1.18 0.978 0.813 0.660 0.545 0.439 0.343 0.275 0.2267 Stall torque mNm 730 783 832 866 786 785 627 504 403 326 258 198 158 1278 Starting current A 28.6 21.5 18.7 15.3 12.6 11.1 7.22 4.80 3.06 2.04 1.30 0.784 0.501 0.3349 Max. efficiency % 84 85 86 86 86 86 85 84 82 81 79 77 75 72

Characteristics10 Terminal resistance " 0.628 1.11 1.71 2.74 3.35 4.32 6.65 10.0 15.7 23.5 36.8 61.3 95.8 14411 Terminal inductance mH 0.0988 0.201 0.300 0.487 0.597 0.760 1.15 1.68 2.62 3.87 5.96 9.70 15.1 21.912 Torque constant mNm / A 25.5 36.4 44.5 56.6 62.6 70.7 86.9 105 131 160 198 253 315 38013 Speed constant rpm / V 375 263 215 169 152 135 110 90.9 72.7 59.8 48.2 37.8 30.3 25.114 Speed / torque gradient rpm / mNm 9.23 8.05 8.27 8.18 8.14 8.25 8.41 8.65 8.67 8.80 8.96 9.17 9.21 9.5115 Mechanical time constant ms 6.00 5.89 5.84 5.81 5.81 5.80 5.81 5.81 5.82 5.83 5.84 5.86 5.85 5.8816 Rotor inertia gcm2 62.0 69.9 67.5 67.8 68.1 67.2 66.0 64.2 64.1 63.3 62.2 61.1 60.7 59.0

Planetary Gearhead!32 mm1.0 - 6.0 NmPage 240

Encoder MR256 - 1024 CPT,3 channelsPage 259

M 1:2

Recommended Electronics:ADS 50/5 Page 276ADS 50/10 277ADS_E 50/5 277ADS_E 50/10 277EPOS 24/5 294EPOS2 50/5 295EPOS P 24/5 297Notes 18

DC motor modelling

Questions (10)

Obtain/compute the paramaters of the RE36-118800Program the transfer function G(s) = Ω(s)/U(s)

Propose a simplified version of the model (justify)Program the transfer function GI(s) = I(s)/U(s)

Plot the angular velocity and current step responses

Questions (11)

Justify the cascade structure of the variable speed drive ofDC motors

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Current control synthesis

Approach

either use GI(s)

or (better): as the motor electromotive force changesslowly, it is considered as a disturbance in the equationV (s) = (R + Ls)I(s) + E(s), hence:

GI(s) =1

R + Ls=

1R

11 + τes

Questions (12)

Propose a controller type for the current loopCompute its parameters for a prescribed t5%

Discuss practical implementation

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Angular velocity and position control

Control structure: analog implementation

Once the current is controlled, angular velocity and position canbe controlled using a cascade architecture

kiI(s)

−

+Ω(s)

kΩVΩ(s) = kΩΩ(s)

Vr (s) +

CΩ(s) CI(s) DC motor

−

V (s)

DC motor angular velocity analog servoing

It is necessary to saturate the current servo loop reference (voltage ±ki IM )

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Velocity control synthesis

Questions (13):

Re-write the DC motors equation considering that thecurrent is now controlled (with a time constant that ismuch faster than the one of the velocity loop)Tune a well selected controllerSimulate the cascade architecture with Simulink,implement the saturation and observe the signals

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Maxon 4-Q-DC Servoamplifier ADS 50/5

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maxon motor 4-Q-DC Servoamplifier ADS 50/5 Operating Instructions

3 Minimum External Wiring for Different Modes of Operation

4 maxon motor control July 2009 Edition / Doc. No. 538837-07 / Subject to change


4.3 Adjustment of the Potentiometers 4.3.1 Pre-adjustment

With the pre-adjustment, the potentiometers are set in a preferred position. ADS units in original packing are already pre-adjusted.

Pre-adjustment of potentiometers

P1 IxR 0 %

P2 Offset 50 %

P3 nmax 50 %

P4 Imax 50 %

P5 gain 10 %

4.3.2 Adjustment Encoder mode

DC-Tacho mode 1. Adjust set value to maximum (e.g. 10 V) and turn potentiometer P3 nmax

so far that the required speed is achieved. IxR compensation 2. Set potentiometer P4 Imax at the limiting value desired.

Maximum current in the 0 ... 10 A range can be adjusted in linear fashionwith potentiometer P4. Important: The limiting value lmax should be below the nominal current (max. continuous current) as shown on the motor data sheet and may not exceed 5 A continuously.

3. Increase potentiometer P5 gain slowly until the amplification is set large enough. Caution: If the motor vibrates or becomes loud, the amplification is ad-justed too high.

4. Adjust set value to 0 V, e.g. by short circuiting the set value. Then set the motor speed to 0 rpm with the potentiometer P2 Offset.

In addition, only in the case of lxR compensation: 5. Slowly increase potentiometer P1 IxR until the compensation is set large

enough so that in the case of high motor load the motor speed remains the same or decreases only slightly. Caution: If the motor vibrates or becomes loud, the amplification is ad-justed too high.

Current controller mode 1. Set potentiometer P4 lmax at the limiting value desired.

Maximum current in the 0 ... 10 A range can be adjusted in linear fashionwith potentiometer P4. Important: The limiting value lmax should be below the nominal current (max. continuous current) as shown in the motor data sheet and may not exceed 5 A continuously.

2. Adjust set value to 0 V. Then set the motor current to 0 A with the poten-tiometer P2 Offset.

Note • A set value in the -10 ... +10 V range is equal to a current range of approx.

+Imax ... -Imax • Configured as a current controller, P1, P3 and P5 are not activated.


Maxon 4-Q-DC Servoamplifier ADS 50/5: an example

Questions (14)

Now consider an application that is different from classicalspeed variation, i.e. the motor is used to provide forcefeedback to a user:

Which motor physical parameter is of interest ?Propose ADS 50/5 wiring for this applicationWhat is difficulty w.r.t. control in such an application?

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6 Additional Possible Adjustments Potentiometer Function Position left right

P6 ngain speed gain low high

P7 Igain current gain low high

P8 Icont continuous current limit lower higher

P8 Icont

P7 Igain

P6 ngain

6.1 Adjustments potentiometer P6 ngain and potentiometer P7 Igain In most applications, regulation setting is completely satisfactory using potentio-meters P1 to P5. In special cases the transient response can be optimized by setting the P6 “speed regulation gain” potentiometer. The P7 “current regulator gain” potentiometer can, in addition, be adapted to the dynamics of the current regulator. It is recommend that the success of changes to the settings of P6 ngain and P7 Igain be checked by measuring the transient response with an oscilloscope at the “Monitor n” and “Monitor I” outputs. Pre-adjustment P6 ngain = 25 % and P7 Igain = 40 %.


maxon motor 4-Q-DC Servoamplificateur ADS 50/5 Notice d'utilisation

10 Schéma bloc

ReadyEnable-12V OUT

-12V

+12V

+5V

Supply

DIP6

-12V

+12V

PTC

Current

limitP8 I cont

PWM,

Control &

Protection

Logic

MOSFET

Full-Bridge

Current

Detector

Voltage

Detector

P1 IxR

P4 Imax

Monitor I

-Motor

+Motor

Power Gnd

+Vcc 12-50VDC

+12V OUT

1K +12V 1K

DIP1

P6 n gainP5 gain

DIP2

DIP3

P2 Offset

-12V+12V

Monitor n

P3 n max

DIP4

-Tacho Input

-Set value

+Set value

Encoder B\

Encoder B

Encoder A\

Encoder A

Gnd

+5V/80mA

DIP5

F/V Converter

+5V

P7 I gain

Poly-

fuse

LED

3

Ground

Safety

Earth

earth

optional

3

Case

11

2

4

5

11 Dimensions Dimensions en [mm]

14 maxon motor control Edition Juillet 2009 / Doc. No. 539149-06 / Sous réserve de modification

Variable speed drives A tutorialeavr.u-strasbg.fr/~bernard/education/3a_ta/techno_ass_tuto.pdf ·...

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