Maxon DC Servo Motor Sizing Made Easy Presentation Feb. 2013

Introduction drive seminar

Page 1 Page 1 © 2013, maxon motor ag

maxon seminar:

Drive systems with

low power DC motors

Typical performance and its significance

Selection of drive components

Use in dynamic drive systems

© 2012 maxon motor ag, Sachseln, Switzerland

Learning objectives

The participants … get an overview on the parts of a Servo Drive System and

the interaction between them.

learn to read the data sheets of DC motors, EC motors, gearheads.

know the main properties and application ranges of DC and EC motors and be able to select the correct system.

ELECTROMATEToll Free Phone (877) SERVO98

Toll Free Fax (877) SERV099www.electromate.com

[email protected]

Sold & Serviced By:

Introduction drive seminar

Page 2 Page 2 © 2013, maxon motor ag

Agenda Electromate seminar

09.00 – 09.45 Motor selection: What is it all about? – Application and situation analysis – Extracting key load parameters

09.45 – 10.10 Properties of brushed and brushless DC motors – Design variants – Commutation systems: brushed, brushless

10.10 – 10.20 Coffee break 10.20 – 10.50 Motor data sheets

– Characteristic motor lines – Operation ranges

10.50 – 12.30 Motor selection: Example – maxon selection program demonstration

12.30 – 13.00 Lunch 13.00 – 14.00 Introduction to ESCON and EPOS Systems

Media

„The Selection of high-precision microdrives“

maxon Formulae Handbook – epaper.maxonmotor.ch/formulaehandbook

maxon catalogue – epaper.maxonmotor.ch/en/

Presentation hand-outs www.maxonmotor.com

– Service & Downloads – Service Desk (FAQ) – maxon academy



[email protected]

Sold & Serviced By:

http://epaper.maxonmotor.ch/formulaehandbook/

http://epaper.maxonmotor.ch/formulaehandbook/

http://epaper.maxonmotor.ch/de/

http://www.maxonmotor.com/

1. Drive selection: What is it all about?maxon Seminar at Electromate, March 2010 © by maxon motor ag, 2010

DC motor sizing made easy

Drive Selection:What is it all about?

The context of motor selection Application and situation analysis Extracting key load parameters

Seminar at Electromate

© 2010, maxon motor ag, Sachseln, Switzerland

Systematic selection process: Step 1

Step 1overviewsituation

step 2 step 3 step 4 step 5+6 step 7+8load drive gear- motor type sensor

head winding controller

ambient condition

communication

power

Book: Chapter 3



[email protected]

Sold & Serviced By:



Gain an overview

operating mode

working points

power

control concept

boundary conditions

mechanics

motion profile

control accuracy

Drive system as a black box

environment temperature, atmosphere impacts, vibration …

mechanical power force, torque velocity, speed

electrical power current voltage

quality, accuracy resolution mech. play

task set values commands

emissions electro magnetic heat noise …

boundary conditions dimensions service life …



[email protected]

Sold & Serviced By:



Mechanical drive concept

Drive design: linear – rotation

Drive elements and coupling with load

relative position of motor and load– e.g. bridge a distance with a belt

Mechanical drive concept: Bearing

Support of all the forces– Eccentric drive, cam, pump

– rack guidance

– pulley bearings of conveyors, cranes and belt drives



[email protected]

Sold & Serviced By:



Operating modes

continuous (S1)

short term (S2)

working cycles

intermittent (S3)

time

load

Control concept Controlled variable

– torque, current– speed, velocity feedback sensor

– position

Controlled range, accuracy?– position resolution

– speed stability

What kind of communication?– communication with higher level host system

– set value range: 0 … 5 V or -10 … +10 V

– inputs and outputs (homing, temperature monitoring, ….



[email protected]

Sold & Serviced By:



Task and control accuracy

The accuracy of control is the combined result of allcomponents in a drive system!– resolution, precision

– signal amplification, control parameter

– phase shifts, time shifts, backlash, mech. play

command controller motorgearhead,

driveload

sensor

control loop

Particular boundary conditions dimensions

– length, diameter

service life– specific depending on load cycle, ambient conditions and application

– given as service hours or numbers of working cycles

– limited by the weakest component

temperature, atmosphere– can influence the achievable power and service life

noise, vibration– specific depending on load cycle, mounting and ambient conditions,

application

– influences on service life



[email protected]

Sold & Serviced By:



Systematic selection process: Step 2




ambient condition

communication

power

Book: Chapter 4

Working points Pair of

– torque and speed

– force and velocity

standard representation: (x,y) = (M,n) or (F,v)

speed nvelocity v

torque Mforce F

accelerationdeceleration

dwell



[email protected]

Sold & Serviced By:



Working point and motion profile

(M1,n1) acceleration friction and acceleration

(M2,n2) const. speed friction only

(M3,n3) deceleration friction helps during deceleration

(M4,n4) dwell depending on friction

n

M

t

n

1 2 3 14

12

34

extreme working point

Motion profiles

general parameters– duration ∆ttot

– max. velocity vmax

– distance ∆s

symmetrical triangular profile– for fast motions

– minimum acceleration

3/3 profile– minimum power

– thermally advantageous

Book: P. 24/25



[email protected]

Sold & Serviced By:



Operating modes

continuous operation (S1)– acceleration and deceleration can be neglected

– constant load

– duration: longer than all thermal time constants of the system

in thermal equilibrium: constant temperatures

typically: several minutes up to hours

time

load

temperature

Tmax

Operating modes

short term operation (S2)– very short operation time

only elements with a correspondingly short time constant can heat up

– long dwell times

drive can cool down completely

time

load

temperatur

Tmax



[email protected]

Sold & Serviced By:



Operating modes

cyclic operation (general case)– load profile to be repeated permanently with relatively short dwell

times

duration of a cycle: typically up to several seconds

– thermal equilibrium is reached on average only

temperature variations

– effective load (RMS) is an important key parameter

time

load

temperatureTmax

( )...MtMtMtt1

M 233

222

211

totRMS +++=

Operating modes

intermittent operation (S3) ON - OFF– special case of cyclic operation

temperature• winding• housing

1s 10s 100s 1000s 10000s 10s 100s 1000s Time

onoffon

onRMS M

ttt

M ⋅+

=



[email protected]

Sold & Serviced By:



Friction forces

difficult to evaluate– many influencing factors: state of

the interface layer

– varies upon time: ageing effects

– typical coefficients of friction from tables (book p. 30/31)

NR FF ⋅µ=

moving direction

normal force FN

body

basisinterface layer, lubrication

friction force FN

dF5.0M RR ⋅⋅µ⋅= estimation formula for ball bearings:

Acceleration of mass inertias

additional force / torque necessary– basic equations for

translation / rotation tn

30J

tJJM

tv

mamFa

∆∆π⋅=

∆ω∆⋅=α⋅=

∆∆⋅=⋅=

α

mass inertias– translation: mass m

– rotation: moment of mass inertia JX

with respect to axis x

– example cylinder:

∫ ⋅= dmrJ 2x

2x r

2m

J ⋅=Book: P. 40ff



[email protected]

Sold & Serviced By:



Constant forces, preloading forces

Example spring preload

Example gravity

without gravitywith gravity

speed nvelocity v

torque Mforce F

accelerationdeceleration

dwell

Determination of forces / torques

simple measurements– precision needed: 5-10%

– e.g. by means of pulleys and spring balances

estimation of friction torques by means of friction coefficients µR

using a motor for torque determination– by means of a current measurement and the torque constant kM

– in original conditions

– Suitable current measuring toolIkM M ⋅=



[email protected]

Sold & Serviced By:



Key load data for characterization

average effective load (RMS)

maximum load

duration of a load cycle

duration of the maximum load

max. velocity or speed

required position resolution

required speed accuracy

Load characterization dominating constant load

– typically in cases of high friction

– maximum forces exceed RMS load by less than 20%

– maximum forces applied during short terms only

=> selection based on RMS load is sufficient

dominated by peak load– typically in cases of highly dynamic drives with high acceleration

– RMS value of load very small (< 50 % of maximum load)

=> selection based on maximum load values

general case without domination of one load type

Remark: Acceleration and friction in the mechanical drive are not taken into consideration yet!



[email protected]

Sold & Serviced By:



Systematic selection process: Steps 3 & 4




ambient condition

communication

power

Book: Chapters 5&6

Mechanical transformation

by means of drive elements– also in series

characteristic variables– reduction i

– efficiency η– mass inertias

– backlash

transformation equations

bearings



[email protected]

Sold & Serviced By:



speed

torque

torque for acceleration

Screw drives

η⋅

π= out

in

F2p

M

outin vp60

n ⋅=

αα ∆

∆π⋅

πη+++=

tn

304pmm

JJM in2

2Sout

Sin,in

Spindle drives

spindel type: trapezoidal, metric, ball screws

spindle type has influence on – efficiency, heating

– possible working cycles, ON time

– costs

– accuracy, play, backlash

– maximum load

– life

– application: actuators or positioning units



[email protected]

Sold & Serviced By:



speed

torque

torque for acceleration

Gearhead stage

αα ∆

∆π⋅

η⋅+++=

tn

30iJJ

JJM in

G2G

2out1in,in

GG

outin i

MM

η⋅=

Goutin inn ⋅=

maxon gear

operation at high torques and low speeds

2 standard types:

material options– plastic: lower power, lower costs

– ceramic: higher power, longer life

bearing options– ball bearing: standard for larger planetary gears

– sleeve bearing: standard for GS and small GP

GS: spur gearhead

lower power density

GP: planetary gearhead

high power density



[email protected]

Sold & Serviced By:



Most important gearhead data

reduction - absolute reduction

efficiency – as a function of torque

gearhead limits– max. continuous torque (output)

– intermittent torque (short-term = 1s)

– max. input speed

– temperature (lubrication)

backlash

load on bearings

Operating range diagram

outputspeed

output torque M

Mcont

continuousoperation

intermittentoperation

Mmax

recommended gear input speed defines max. output speed

i

nn inmax,

outmax, =



[email protected]

Sold & Serviced By:







ambient condition

communication

power

Book: Chapter 7&8

DC motor designs

DC motors BLDC motors

conventional, with iron core

coreless

slotless

slotted external rotor

slotted internal rotor



[email protected]

Sold & Serviced By:







ambient condition

communication

power

Book: Chapter 9

Controller: The Heart of the Drive System

Sensor– measured

quantity– resolution

Communication– Host, Master– I/O

controlled quantity power digital – analogue …

Motor– motor type

– power

Controller

Gearhead, mech. drive– reduction ratio

– backlash

Power Supply– cont. current

– max. current– voltage



[email protected]

Sold & Serviced By:



PWM (e.g. 50 kHz)

Motion Control System

Application Program

Path Generator

Position/Speed Control loop

CurrentControl loop

Driver, Power Amplifier

Motor with Encoder and Drive

ActualCurrent

ActualPosition

PWMduty cycle

Clock(e.g. 10 kHz)

Position Set Value

Current Set Value

Clock(e.g. 1 kHz)

Cycle (e.g. 5 ms)

Pos

t

I

t

command11

001.

.

Sensors

ResolverIncremental EncoderDC Tacho

IxR Hall Sensor

PositionSpeedDirection

∆Pos/∆t

Set value

MeasurementFeedback

Output

Actuator



[email protected]

Sold & Serviced By:

2. DC and BLDC Motors with Permanent Magnetsmaxon Seminar at Electromate, March 2010 © by maxon motor ag, 2010


DC and BLDC Motors with Permanent Magnets

Design, design variantsCommutation: Graphite and precious metal brushesBrushless commutation

Seminar at Electromate© 2010, maxon motor ag, Sachseln, Switzerland

DC motor designsconventional, slottede.g. Dunker motor

corelesse.g. maxon



[email protected]

Sold & Serviced By:



Coreless maxon DC motor (RE 35)

el. connections

self-supporting winding

commutator

brushes

permanent magnet(in the centre)

housing (magn. return)

flange

commutator-plate

shaft

ball bearing

ball bearing

press ring

press ring

Advantage coreless: no coggingno soft magnetic teeth to interact with the permanent magnetsmooth running even at small speedsless vibration and noise

any rotor position can be controlled in a simple wayno nonlinear control behaviour



[email protected]

Sold & Serviced By:



Advantage coreless: no iron lossesno iron – no iron lossesconstant magnetizationhigh efficiency, up to above 90%low no load current, typical < 50 mA

no saturation effects in the iron coreEven at the highest currents the produced torque remains proportional to the motor current. stronger magnets = stronger motorscompact designsmall rotor inertia

Advantage coreless: small inductanceless brush fire– commutation: open and close a contact on an inductive load

higher live expectancyless electromagnetic emissionseasier to suppress interferences: – capacity between connections– ferrite core at motor cable

but fast reaction of the current– problems in combination with pulsed supply (choke needed)



[email protected]

Sold & Serviced By:



maxon DC motor: Variants

A-max-Motor with AlNiCo magnetprecious metal brushessintered sleeve bearing

RE-Motor withNdFeB magnetgraphite brushesball bearing

_++

_

1 4

1 52 52 63 63 74 74 15 15 26 26 37 37 41 4

12

345

67

Commutation process



[email protected]

Sold & Serviced By:



DC commutation systems

precious metalbronze brush body with plated silver (with palladium) contact areasilver copper commutatorsmall contact and brush resistance (50mΩ)CLL for extended service life

graphitegraphite brush with 50% coppercopper reduces contact and brush resistancegraphite acts as lubricantspring

the problem

solution- capacitors between neighbouring

commutator segments- energy is deviated into capacitor:

no arcs produced

Precious metal brushes: CLL

aftershort circuit

arc productioncommutatorwears off

RS

C

commutator

CLL disc

C

C



[email protected]

Sold & Serviced By:



DC commutation: pros and consgraphite

well suited for high currents and current peakswell suited for start-stop and reversed operationbigger motors

higher friction, higher no-load currentsnot well suited for small currentsmore audible noise and electromagnetic emissionmore expensive

precious metalwell suited for smallest currents and voltageswell suited for continuous operationsmaller motorsvery low friction and noiselow electromagnetic emissionfavourable price

not well suited for high currents and current peaksnot well suited for start-stop operation

maxon DC motor: service lifelife influencing factors

the electric load: higher currents = higher electric wear (arcing)

speed: higher speed = higher mechanical wear

type of operation: reversed operation = reduced service life

temperature

humidity with graphite brushes

CLL (with precious metal brushes) enhances service life

load on shaft (bearings)

service lifeno general statement possibleaverage conditions: 1'000 -3'000 hoursunder extreme conditions: less than 100 hoursunder favourable conditions: more than 20'000 hours

use graphite brushes and ball bearings for extreme operating conditions



[email protected]

Sold & Serviced By:



Brushless DC motornames: EC motor, BLDC motormotor behavior similar to DC motor– design similar to synchronous motor (3 phase stator winding,

rotating magnet)– the powering of the 3 phases according to rotor position

main advantages: higher life, higher speedsslotless windings – similar advantages as coreless DC motors– no magnetic detent, less vibrations

the more attractive, the smaller the costs and size of electronics

maxon EC motor / brushless DC motor

el. connections winding and Hall sensors

preloaded ball bearings

housing

PCB with Hall sensors

shaft

3 phase knitted maxon winding

control magnet

magn. return:laminated iron stack

rotor (permanent magnet)

balancing rings



[email protected]

Sold & Serviced By:



maxon EC motor design variantsslotless

slottedexternal rotor

slottedinternal rotor

features in common– rotating permanent magent

made of NdFeB– 3 phase winding in the stator

(3 winding connections)– preloaded ball bearings

– electronic commutation

maxon EC motor: Coreless designdesign with coreless maxon winding– internal rotor with 1 or 2 pole pair

maxon EC motor– many types: e.g. short – long,

sterilisable, integr. electronics, …– typically for high speeds

maxon EC-max– Philosophy: reliable EC motor at

reasonable price

maxon EC-powermax– Philosophy: the strongest possible motor



[email protected]

Sold & Serviced By:



maxon EC motor: Slotted designmaxon EC-i– Philosophy: strong EC Motor at

attractive price– dynamic motor, high cogging torque– slotted winding, internal rotor– several magnetic pole pairs

flat maxon EC motor– Philosophy: flat EC Motor at an

attractive price– slotted winding, external rotor– more than 4 magnetic pole pairs– relatively high torque but limited speed

and dynamics

DC and EC motor: Comparison

max. speed power density torque density mech. time const. (min-1) (W/cm3) (mNm/cm3) (ms)

maxon motor family RE (DC) EC EC-max(20 – 45 mm) EC-powermax EC-flat EC-i

40 000 min-1 5 W/cm3 2 mNm/cm3 10 ms



[email protected]

Sold & Serviced By:



Interaction of rotor and statorcurrent distribution in phases– 3 phases– 6 possible current distributions– 6 winding magnetic field directions

rotated by 60°– commutation every 60°

winding

field produced by winding

3 phases

block sine

hall sensors

comm.-Typ

rotor position feedback

external electronics

encoder (+ HS)sensorless

DEC family DESDECS

EPOS

common goal: Applying the current to get the maximum torqueperpendicular magnetic field orientation of

- rotor (permanent magnet)- and stator (winding)

knowledge of rotor position with respect to winding

Electronic commutations systems



[email protected]

Sold & Serviced By:



φ

Block commutationrotor position from Hall

sensor signals

1 1 0 0 0 1 10 1 1 1 0 0 00 0 0 1 1 1 0

Hall sensor

control magnet

0° 60° 120° 180° 240° 300° 360°

rotation angle φEC-max and EC flat: Power magnet is probed directly

south

north

Block commutation

controller +

_

power stage(MOSFET)

phase 1

phase 2

phase 3

EC motor (magnet, winding, sensor)

rotor position feedback

HS3

HS2

HS1

com

mut

atio

nlo

gics



[email protected]

Sold & Serviced By:



Multipole EC motor: commutation

15°

rotor position detection without (Hall) sensorsmeasuring the back EMF

star pointzero crossing of back EMFtime delay 30°difficult at low speeds

Sensorless block commutation

RR

R

EMF

0° 60° 120° 180° 240° 300° 360°

EMF

flyback pulse

sensorless commutation only for continuous operation at high speeds

special starting procedure similar to stepper motor



[email protected]

Sold & Serviced By:



virtual star pointvirtual star point in the electronics star or delta configuration

Sensorless block commutation

EMF~1kΩ

~1kΩ

controller for sensorless operation

Y

R

R

R

~1kΩ

∆R

R

R

Sinusoidal commutationrotor position

must be known very accuratelytypical 2'000 points per rev.500 pulse encoder (Hall sensors for start: absolute rotor position)resolver as an alternative

phase currentssinusoidal120° phase shiftsimilar to synchronous motor with variable frequency

rotation angle φ0° 60° 120° 180° 240° 300° 360°

winding current

Sinusoidal commutation for smooth running even at the lowest speeds



[email protected]

Sold & Serviced By:

3. Motor Data and Operating Rangesmaxon Seminar at Electromate, March 2010 © by maxon motor ag, 2010


Motor data and operating ranges of DC motors

Motor behaviour: speed-torque line, current Motor data and operating ranges


DC motor as an energy converterelectrical in mechanical energy– speed constant– torque constant– speed-torque line

applies to DC and EC motors– "EC" = "brushless DC" (BLDC)

IUPel ⋅= Mn30

Pmech ⋅π=

2J IRP ⋅=



[email protected]

Sold & Serviced By:



Characteristic motor datadescribe the motor design and general behaviour

independent of actual voltage or current

strongly winding dependent values (electromechanical)– terminal resistance (phase to phase) R– terminal inductance (phase to phase) L– torque constant kM

– speed constant kn

almost independent of winding (mechanical)– speed-torque gradient ∆n/∆M– mechanical time constant τm

– rotor mass inertia JMot

Winding resistance

low resistance winding

thin wire, many turnshigh rated voltagelow rated and starting currentslow specific speed (min-1/V)high specific torque (mNm/A)

thick wire, few turnslow rated voltagehigh rated and starting currentshigh specific speed (min-1/V)low specific torque (mNm/A)

high resistance winding

resistance increases from left to right



[email protected]

Sold & Serviced By:



Torque and current: torque constantforces:force on current leading conductor in a magnetic field

torque:sum of all forces at the distance to the rotating axis

influencing parameters:geometryfield densitywinding number

current I

design

application

IkM M ⋅=

current direction towards brush

force

force

current direction towards flange

magneticfield

Speed constant kn

Speed n and induced voltage Uind– law of induction: changing flux in a conductor loop– induced voltage proportional to speed– basically the inverse of kM, but in different units

Speed constant kn– mostly used for calculating no-load speeds n0

– unit: min-1 / V

Generator constant ke– inverse of kn: motor as a generator (e.g. DC-Tacho). How much

voltage is produced per rpm?– units: mV / min-1

V / 1000 min-1

Ukn n0 ⋅=

indn Ukn ⋅=



[email protected]

Sold & Serviced By:



Motor as an electrical circuitapplied motor voltage U:

+_

EMF LR

IU

IRUUind ⋅−=

Mn kMRU

kn

⋅−=

MMnUkn

MkR000'30Ukn

n

2M

n

⋅∆∆

−⋅=

⋅⎟⎟⎠

⎞⎜⎜⎝

⎛⋅

π−⋅=

EMF: induced voltage Uind

(winding) resistance R

winding inductance L • voltage losses over L can be

neglected in DC motors

indtI UIREMFIRLU +⋅≅+⋅+⋅=∂∂

Speed-torque linespeed n

torque M

U > UN

U = UN

MH

n0

∆n

∆M

Ukn n0 ⋅=

MMnUkn n ⋅

∆∆−⋅=

current IIA



[email protected]

Sold & Serviced By:



Speed-torque gradient

speed n

torque MMH

n0∆n

∆M

strong motor:• flat speed-torque line, small ∆n/∆M• not sensitive to load changes• e.g. strong magnet, bigger motor

weak motor:• steep speed-torque line, high ∆n/∆M• sensitive to load changes• e.g. weak magnet, smaller motor

by how much is the speed reduced ∆n, if the output motor torque is enhanced by ∆M?

M1, n1

M2, n2

iH

i2M M

nRk000'30

Mn

=⋅⋅π

=∆∆

Winding series

speed-torque gradientbasically constant for the winding series constant filling factor: a constant amount of copper fills the air gap

n

M

at U constant

thick wire

thin wire

numerous winding variants adjustelectrical input power (voltage, current of power supply) mechanical output power (speed, torque)



[email protected]

Sold & Serviced By:



Values at nominal voltageat rated voltage UN

at rated current IN

Motor at stall– resulting stall torque MH

– resulting starting current IA

rated working point– resulting rated speed nN

– resulting rated torque MN

No-load operating point– resulting no-load speed n0

– resulting no-load current I0

describe the special working points:

n

M

Current characteristics

MHMR

I0

IAIkM M ⋅=

M

HA k

MRUI ==

I0 IA

n0

mechanical losses

current I

torque M

current and torque• are proportional, torque

constant kM

• no-load current corresponds to the friction torque

• starting current corresponds to the stall torque



[email protected]

Sold & Serviced By:



Working pointsworking points are characterized by a load speed nL at a given load torque ML

working points lie on the speed-torque-line: select the motor voltage accordingly

deceleration acceleration

speed n

torque M

motor voltage

torque M

n0nL ,ML

time t

n0

nL

n0

nL

n0 nL ,ML

∆t

∆tτm

63%

100%

time t

Accelerationacceleration at constant voltage:

acceleration at constant current / torque:

n n

nn

M



[email protected]

Sold & Serviced By:



maxon standard toleranceswinding resistance +/- 7 %

magnetic properties +/- 8 %– kM directly proportional ∆kM +/- 8%

– kn indirectly proportional ∆kn -/+ 8%

– weaker magnet enhanced n0

– stronger magnet reduced n0

n

M

1.081.0

1.00.86 1.16

0.92

Influence of temperature

temperature coefficientsCu + 0.39 % per K AlNiCo - 0.02 % per K

Ferrite - 0.2 % per KNdFeB - 0.1 % per K

temperature resistance magnetic propertiesexample: RE motor∆T = + 50K R: + 19.5 % kn + 5 % (no-load speed)

kM - 5 % (more current!)stall torque MH : - 22 %



[email protected]

Sold & Serviced By:



Motor limits: operation ranges

- lower ambient temperature- good heat dissipation

- higher ambient temperature- heat accumulation

Speedn

continuous operation

short term operation

MNIN

torque Mcurrent I

nmax

Short-term operation



motor may be overloaded for a short time and repeatedlymax. permissible winding temperature must not be reachedduration depends on thermal time constant of winding τW and amount of overload

overload IN 2x IN 3x IN 4x INton/τW = 5 0.6 0.3

typical values



[email protected]

Sold & Serviced By:



Thermal motor datadescribe the motor heating and thermal limits

depend strongly on mounting conditionsstandard mounting:

heating and cooling– thermal resistance housing-ambient Rth2

– thermal resistance winding-housing Rth1

– thermal time constant of winding τthW

– thermal time constant of motor τthS

temperature limits– ambient temperature range– max. winding temperature Tmax

plasticplate

horizontal mounting

free convectionat 25 °C ambienttemperature

Rated Torque and Temperature

-20 0 20 40 60 80 100 Tamb °C

MN(TA)MN(25°C)

1.5

1.0

0.5

0.0

Rth2,mod= 0.5 Rth2

Example for Tmax= 125 °C



[email protected]

Sold & Serviced By:



Mechanical motor data

max. permissible speed– limited by bearing life considerations (EC)– limited by relative speed between collector and

brushes (DC)

axial and radial play– suppressed by a preload

axial and radial bearing load– dynamic: in operation– static: at stall

axial press fit force (shaft supported)

describe maximum speed and the properties of bearings



[email protected]

Sold & Serviced By:

4. Motor Selection: Introduction and Examplesmaxon Seminar at Electromate, March 2010 © by maxon motor ag, 2010


Motor Selection:Introduction and Examples

Continuous operationCyclic operationmaxon selection program


see also Book: Chapter 11

Systematic selection process


step 2 step 3 step 4 step 5+6 step 7load drive gear- motor type sensor


ambient condition

communication

power



[email protected]

Sold & Serviced By:



Example: Conveyor belt for samplespulley diameter 100 mmmaximum mass on belt 3 kgcoefficient of friction on support ca. 0.3friction force (empty belt) ca. 40 Nfeed velocity 0.5 m/ssupply voltage 24 V

Example: Conveyor belt for samplesspeed nL =

feed force FL =

torque ML =

power PL =

acceleration FLa =



[email protected]

Sold & Serviced By:



Step 4: Gearhead selection

outputspeed

outputtorque M

Mcont

continuousoperation

short termoperation

Mmax

max. reduction calculatedfrom speed:

1:601006000

nn

ioutmax,

inmax, ==<

torque Mcont > 2.5 Nm

Example: Conveyor belt for samplesplanetary gearhead

continuous torque – at least 3 stages

input speed– reduction

– efficiency

requirements motor– speed

– torque



[email protected]

Sold & Serviced By:



Step 5: Motor type selectionCombination with selected gearhead Rated torque (continuous torque)max. torquemax. permissible speed

MN

n

M

continuousoperation


deceleration acceleration

nmaxNRMS MM <

Further selection criteria motor typeCommutation: Graphite, metal, brushless– service life

combination with required sensor– encoder, DC tacho, resolver, …

shaft, bearing– diameter, length– drive element, pinion– bearing load radial, axial

electrical connections– cables, plugs

ambient conditions– temperature, …



[email protected]

Sold & Serviced By:



Example: Conveyor belt

speed

torque Mcurrent I

MNIN


short termoperation

rated torque MN > 70 mNm

max. speed > 5100 min-1

motmot M,n

according motor type MN suited?maxon modular system

Example: Conveyor belt for samples

RE 25, RE 26



[email protected]

Sold & Serviced By:



Step 6: Winding selectionGoal: Reach the required speed at maximum possible motor voltage under maximum loadfor a given motor size (motor type) this means: sufficiently high speed constant

LLtheor,0 MMnnn

∆∆+=

Un

kk theor,0theor,nn =>

systematic calculation:– calculate the needed no-load speed

as an auxiliary value– calculate required speed constant– select winding with a higher speed

constant– reserve of kn (ca.20 %)

Step 6: Winding selectionspeed n

torque M

speed-torque line high enough for the required load speed

motmottheor,0 MMnnn

∆∆+=

Mmot

n0,theor

nmot

mot

theor,0theor,nn U

nkk =>

speed-torque line too low for the required load speed

motmot M,n



[email protected]

Sold & Serviced By:



Example: Conveyor belt for samples

n

M

select motor – speed constant

needed current– with torque constant kM

Example: Cyclic operation

n = 60 min-1

0.5 2.5 3.0 3.7 time (s)

n

working cycle according to the speed diagram belowfriction torque: 300 mNmload inertia: 130'000 gcm2

power supply: 5 A, 24 VDCservo controller: LSC (2 A, ∆V = 5V)

1 2 3 4 1

Catalog p. 42/43



[email protected]

Sold & Serviced By:



Winding selection: Working cycles

speed n

torque M

braking

LLmaxn0 MMnnUkn

∆∆+>⋅=

acceleration

speed-torque line high enough

speed-torque line too low for all working points

Selection of motor/gearhead type

speed

torque MMN


short termoperation

effective torque (RMS) smaller than MN

( )...MtMtMtt1M 2

33222

211

totRMS +++=

braking acceleration



[email protected]

Sold & Serviced By:



Load data calculationtorque for acceleration:

4 stand still:

1 acceleration phase :

3 deceleration (friction helps):

2 constant speed:

average effective torque (RMS):

1 2 3 4 1

( ) mNm 280MtMtMtMtt1M 2

44233

222

211

totRMS ≈+++=

mNm 163Nm 163.05.0

6030

013.0tn

30JM L ==⋅π⋅=

∆∆⋅π⋅=α

Gearhead selectiontorque requirements:

continuous torque gearhead:peak torque gearhead:

possible gearhead type:maximum input speed:

maximum reduction:

chose 3 stage gearhead with:

requirements motor:

1 2 3 4 1



[email protected]

Sold & Serviced By:



Motor type selectionrequirementsmotor:

motor type MN suited?

possible motor types (according to maxon modular system)graphite brushes only (start-stop operation)

2 3 4 1

Winding selectionmotor type:

average speed-torque gradientrequired no-load speed

speed constant

winding selection:speed constant20 % speed reserveneeded current

1 2



[email protected]

Sold & Serviced By:



The MSPBased on an existing data base– maxon web database

Based on the maxon modular system– no combination numbers– including maxon motor control

No installation needed– can be started directly from the maxon CD ROM– or copy and start it

Easy to use, self-explaining user interface– minimum "help"

Book: Chapter 10

Selection of maxon products– for a given power supply– for a given drive layout: screws, belts, …– at a given load

Calculation of achievable load characteristicsGearmotor comparison– finding a maxon replacement product

Mass inertia calculator

1

2

3

Basic functions of the MSP

maxon selection program (MSP)



[email protected]

Sold & Serviced By:

5. Motion Control and EPOSmaxon Seminar at Electromate, March 2010 © by maxon motor ag, 2010


Motion Control Architectures

Overview and Components 1- and multi-axis systemsMotion Control Supervisor

Motion Control System OverviewPower Supply

I/O

EncoderMotor

Gearhead

Load

CAN

Supervisor / Master(PLC / PC)

Motion Controller



[email protected]

Sold & Serviced By:



Single axis and multi axes system

field bus

other modules

Single axis system

Multi axes system

Process control

Supervisor system

PC / PLC as Master

Process control

Supervisor system

PC / PLC as Master

Multi-axis motion card

Signal conditioning

Signal conditioning

Motion processor

Bus decode

D/Aconverter

AmplifierAxis 1

AmplifierAxis 2

AmplifierAxis 3

D/Aconverter

D/Aconverter

AmplifierAxis 4

D/Aconverter

Host

Motors

Encoder Feedback

Limits, I/O, etc

+/- 10Vanalogset value

+/- 10Vanalogset value

Bus

Power

Power

adapted from PerformanceMotionDevices



[email protected]

Sold & Serviced By:



Distributed control

Signal conditioning

Signal conditioning

Motion processor

Bus decode

Power Management

Amplifier

Host

Axis N

Encoder Feedback

Limits, I/O, etc

Bus

Power in

Axis 2

Axis 1

Distributedcontroller



Tightly Coupled Distributed Control


Signal conditioning

Signal conditioning

Position Control

Bus decode

Power Management

Amplifier

Host

Axis N

Encoder Feedback

Limits, I/O, etc

Power in

Axis 2

DistributedController

For real time synchronization – Position and velocity update: up to several times per msHigh speed deterministic network:– E.g. Sercos, Firewire, EtherCat, Ethernet/Powerlink

Axis 1


e.g. Firewire

Multi-axis path generationSynchronization



[email protected]

Sold & Serviced By:



Loosely Coupled Distributed Control

adaption from PerformanceMotionDevices

Signal conditioning

Signal conditioning

Motion processor

Bus decode

Power Management

Amplifier

Host

Axis N

Encoder Feedback

Limits, I/O, etc

e.g. CANopen

Power in

Axis 2


Axis 1


Typical commands directly from host: – "move to position X using a point-to-point profile" – takes several ms to executeLower speed network: e.g. CAN, RS 485– less deterministic network: e.g. Ethernet

Standalone Controller

Signal conditioning

Signal conditioning

Motion processor

Bus decode

Power Management

Amplifier Axis 1

Encoder Feedback

Limits, I/O, etc

Busoptional

Power in


Axis 2


Axis 3


I/Os PLC



[email protected]

Sold & Serviced By:



Multi-axis motion card

Signal conditioning

Signal conditioning

Multi-axisMotion

processorBus

decode

AmplifierAxis 1

AmplifierAxis 2

AmplifierAxis 3

AmplifierAxis 4

Host

Motors

Encoder Feedback

Limits, I/O, etc

Bus


Power Management

Power in

Application Program, Supervisor SystemProcess control systemof a machinetypically PC or PLC application program with the defined process control flow.coordination of all subsystemscommands every slave unit according to the defined process flow, e.g.

– fetches input data– starts a motor– etc.

Position Control Unit

I/OControl Unit

Motion command

I/O command

Program code

?

Process controlProcess control

Supervisor system



[email protected]

Sold & Serviced By:



Online commandedSingle commands

generated by a supervisor system

– process control– transmits single motion and

I/O-commands to a slave unit (e.g. for position control).

executed by a slave unit– "understands" a product-

specific command set– executes every command

immediately.

1.2.3.

4.

Position Control

Supervisor system

?

Process control

Supervisor system

Process control(program included)

4. Move Absolute

2. Read Input

1. Set Output

3. Input State

StandaloneMaster functionality integrated in the controllerPC used only for writing and downloading programDrive runs without additional master

1.2.3.

4.

Supervisor system

?

RS232

Programming tool

only for programming

Controller includes the Master

Process Control and Position Control



[email protected]

Sold & Serviced By:



The maxon EPOS Family

What's an EPOS P?

What's an MCD?

What's an EPOS?

EPOS2 Special

PWM (e.g. 50 kHz)

What's an EPOS?Application Program

Path Generator


CurrentControl loop



ActualCurrent

ActualPosition

PWMduty cycle

Clock(e.g. 10 kHz)

Position Set Value

Current Set Value

Clock(e.g. 1 kHz)

Pos

t

I

t

command

1100

1..

Cycle (e.g. 5 ms)Motion command (e.g. every 500 ms)

EPOS



[email protected]

Sold & Serviced By:



Motion ControllerFor maxon DC and EC motors with encoder– according CANopen Standard

Controller for position, speed, current (torque)– point to point position control– maximum speed: 25'000 min-1 (EPOS2: 100'000 min-1 block)– path generator with sinusoidal and trapezoidal profiles– feed forward for speed and acceleration

Special properties– with additional I/Os– Master Encoder Mode, Step Direction Mode– Gateway: RS232-CAN (EPOS2: USB-CAN)

Standard operation modes

t

Cur

cmd

Current modet

Pos

cmd

position modet

Vel

cmd

Velocity mode

cmd

t

Vel

cmd

Profile velocity mode

cmd

t

Pos

cmd

Profile position mode

vel

pos

for "slave" - modese.g. Synchronization, Master-Encoder, Step-Direction



[email protected]

Sold & Serviced By:



for maxon DC and EC motorsdifferent power rangesDC and EC motors– sinusoidal commutation

integrated motor chokes

EPOS 24 /19V – 24V1A / 2A

EPOS2 24/511V – 24V5A / 10A

EPOS 70 /1011V – 70V10A / 25A

EPOS2 50/511V – 50V5A / 10A

EPOS2 Module 36/211V – 36V2A / 4A

News EPOS2 (1/2)

Latest 32-bit Digital Signal Processor TechnologyEPOS2 communication via CANopen and/or USB and/or RS232EPOS2 Gateway Functionality USB-to-CAN and RS232-to-CAN

up to 100'000 min-1 for EC motors in block commutation maximum number of Encoder counts of 2'500'000 pulses for high resolution Encodermaximum Encoder input frequency 5 MHz for higher speeds



[email protected]

Sold & Serviced By:



News EPOS2 (2/2)

commanding in Position, Velocity and Current mode alternatively via an external analog voltage set value.Interpolated Position Mode PVT (Position, Velocity vs. Time) for synchronous run of a path specified by interpolating points

Trigger output (Position Compare) for emitting a digital signal at a predefined position valueUpgraded, easier to use „Regulation Tuning“

Communication with masterSingle axis with PC and RS232– setting up– testing – learning– setting parameters

motor with encoder

PC as a master

RS232

Process control



[email protected]

Sold & Serviced By:



other CANopen modules

I/O modules

Communication: CANopen with PC

CAN

PC as a master

PC-program with maxon Windows DLL‘s

CAN bus


I/O modules

Communication: CANopen with PLCPLC-program with maxon IEC 61131-3 library

PLC as a master P

LC

CA

N I/

F

I/O I/O Opt

. bus

CAN bus



[email protected]

Sold & Serviced By:



Special: I/O functionsfor inputs and outputs in the periphery of the axis

digital inputs– configurable : high/low active, open collector/drain– functionality configurable as reference switch, limit switch, …– for master encoder, step direction inputs

digital outputs– configurable : high/low active, functionality (Ready, Error)– special: for activating a holding brake

analogue inputs– e.g. for temperature sensor, distance sensor

Special: Gateway RS 232 to CAN

CAN bus

RS232


I/O modules



[email protected]

Sold & Serviced By:



EPOS2 communication via CANopen and/or USB and/or RS232

EPOS2 gateway functions:USB*-to-CAN RS232-to-CAN*EPOS2 Module needs external transceiver device

EPOS2 new technology: Communication

PWM (e.g. 50 kHz)

What's an EPOS P?Application Program

Path Generator


CurrentControl loop



ActualCurrent

ActualPosition

PWMduty cycle

Clock(e.g. 10 kHz)

Position Set Value

Current Set Value

Clock(e.g. 1 kHz)

Pos

t

I

t

command

1100

1..

Cycle (e.g. 5 ms)Motion command (e.g. every 500 ms)

EPOS P

EPOS



[email protected]

Sold & Serviced By:



What is the EPOS P?CAN-master + EPOS 24/5– programmable, stand alone operation

CA

N I/

F

PLC

CAN bus

EPOS P

EPOS

What is the EPOS P?same basic functionality as motion controller as the EPOSCAN master functionality

EPOS

EPOS P

CAN bus




[email protected]

Sold & Serviced By:



PLC functionality– PC tool for programming: OpenPCS– based on IEC 61131-3 standard

program flow controlled by – internal events (time, current,

position, speed...)– external events (digital inputs, CAN

inputs)

Programmable, standalone

PC for programming only

CAN bus

EPOS P

What is the MCD EPOS 60W?maxon compact drive– EPOS (P)– + EC-max 30 – + MR-Encoder

MCD EPOS P master version

MCD EPOS slave version

EPOS



[email protected]

Sold & Serviced By: