Nippon Pulse Stepper Motor Basics Presentation

Stepper Motors

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What is a Stepper Motor?
• The stepper motor is a motor which takes
input pulses and then takes proportional
steps to input these signals. You can use
for positioning and/or speed control for
most any applications. The stepper motor
needs a power circuit and a sequence
circuit for changing phase.
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<Stepper with Peripheral Construction>
Vm (Motor Power)
<Controller> <Driver>
CPU <Motor>
or
Motion- Sequencer
Control-Chip

Power Tr.
Vcc (Logic
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3

<Applications>
• Medical: Infusion Pump, Brad Test, X-ray,
Dialysis, DNA Extraction, Pump
• Semiconductor: Masking, Etching, Wafer
Handling, Test-equipment, Die-Bonder
• FA: Pick & Place, NC Machine, X-Y-Z stage
• OA: Printer, Fax, Scanner
• HA: HVAC, Cleaner Robot
• Other: Vending machine
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Stepper and Synchronous Motors
Movement Generation
• Step Mode
• Torque Generation
• Characteristics
• Reduced Duty Cycle
• Synchronous Motor

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Movement Generation

N
S

N
S N
S
S
N N
S
N
N
S NS

S
N

rotor follows the stator field
one step ⇒ invert magnetic field in 1 coil
for the next step invert magnetic field in the other coil
A stepper motor always needs electronic control.
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Movement Generation
Unipolar Principle
• motor coils are unipolar
• every coil end has only one polarity (”+” or ”ground (-)”)

PhA1 (=GND)
(=open) + PhA2 (=GND)
(=open)

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S
N N
S ELECTROMATE
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Movement Generation
Bipolar Principle
• motor coils are bipolar
• every coil end will be positive (”+”) or ground (”-”)

PhA1 PhA2
GND
+ GND
+

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N
S S
N ELECTROMATE
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Movement Generation
Unipolar Drive
• low side switches
• 4 switches for the whole motor

+

I
I
GND
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Movement Generation
Bipolar Drive

• switches in bridge configuration
• 2 full bridges (or H-bridges) are needed = 8 switches

+

I
I
GND
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Movement Generation
Tin Can Motor

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Movement Generation
Tin Can Motor - Step Generation

front side teeth
back side teeth
N
S
N

N NS S
N
N
N
S

S
S
S
SSN N if there is only 1 magnetic system...
NS
N

N
NN
N
N
S
S
S
S

motor is able to start in both directions
S NN N

S
N SS S

direction is undefined
N NS S
SNN
N

N
N

S
S

S
S
S
S
NS
S
SN

N
N
N
N
N

N
S
SNN N
N NS S
S
S
S
S
N
N
N
N
N
S
S
S

S

N
S
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Movement Generation
Tin Can Motor

Stator Core
Coil
Bobbin

Shaft

Permanent Magnet
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Movement Generation
Tin Can Motor - Step Generation

2 magnetic systems = 2 stators...
electrical phase shift 90 °
N
S N
S direction is defined by coil control sequencing
S
N
control pattern (bipolar motor):
N

N
N
S

S
S S N
N N
S
N
S
N

N
S
N
S
N
S

S
S S S

N
N

coil 1
N N

S S S
S S
N N
N N

N coil 2 direction CCW
N

S
S

N
S

S
N

N
N
N
S

S

NS
NS
N N NS
N N N
S
S S coil 1
direction CW
N
N
N
S

S

coil 2
N
S S
N
N
S
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Movement Generation
VR - Step Generation

Old Technology, No Longer Used

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Movement Generation
Hybrid - Step Generation

•Flame Motor
Hybrid Stator Bobbin Teeth

Coil
Coil

Rotor Shaft
P.M.
Bracket
B.B. P.M. Stator Rotor
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Movement Generation
Step Loss

N
S
Rotor follows the stator field

N
S
Rotor reaches the end stop noise
N
S N S
N Rotor is not able to follow the stator field
S N S
Rotor swings back
N
S
Motor will always loose n·4 steps

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Movement Generation
Step Loss

N
S
Rotor follows the stator field

N
S
Rotor reaches the end stop noise
N
S N S
N Rotor is not able to follow the stator field
S N S
Rotor swings back
N
S
Motor will always loose n·4 steps

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• Movement Generation
• Step Mode
• Characteristics
• Synchronous Motor Sold & Serviced By:

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Step Mode
Full Step Mode
• Step angle = catalogue value

N
S I1 / I1max
1

N
S N
S 0
S
N N
S -1
N
S NS I2 / I2max
1
0
S
N -1

coil current in a bipolar motor
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20

Step Mode
Half Step Mode
• Step angle = half catalogue value

N
N
S I1 / I1max
1

S S N
N N S 0

S
N S
N
NS S
N -1
N
SN NS I2 / I2max
S 1
0
S
S
N -1

coil current in a bipolar motor
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21

Step Mode
Half Step vs. Compensated Half Step
I1 / I1max
1
0
-1

1 I2 / I2max
0
-1

1 I1 / I1max
1/√2
0
-1/√2
-1

1
1/√2 I2 / I2max
0 Sold & Serviced By:

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• Step Mode
• Characteristics

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Torque Generation
Torque vs. Angle
Mel
(torque)
MH
(holding torque)

-2 -1 1 2 3 4 α
αS
-MH
N N
S

S N N N N

S
S

S

S
N
S

S
S

S
N S N
S S
N N

N
N

S S
N N

N N

S
S

N
N

S

N

N
S

S

N
N

S
N

N

S
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N
S N S

N
S N S
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S N
S
S

N
S

S
S

S
N Toll Free Phone (877) SERVO98
S

N N N N
S

S
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24

Torque Generation
Positioning Accurancy

Mel
(torque)

MH
(holding torque)
Friction

-2 -1 1 2 α3 4 α
αS αS
-MH
2 Δα Δα...Step Angle Tolerance
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25

Torque Generation
Micro Step Modus
• Current in coils increases/decreases in small increments
• with tin can motor:
• micro step only for smoother travel at low frequencies

M
(torque)

α
friction

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• Step Mode
• Characteristics

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Characteristics
Torque

Resonances may influence application!
torque

reduced duty cycle =
increased power consumption
(pull out graph)

with chopper
pull-in pull-out (pull out graph)

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Characteristics
Influence of Inertia
FI

JLOAD + JROTOR
Inertia Factor FI =
JROTOR

f
torque

Load inertia reduces start-stop-range.
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Characteristics
Output Power
torque

2⋅Π ⋅ f
power

Motor output power : P = M · ω with ω =
z
M...torque
ω...angular velocity
f...step frequency
z...steps per revolution

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Characteristics
Resonance

• Step motors are resonant because
in short their rotors behave much
like a classic “mass on a spring”.

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Characteristics
Resonance

• When a step motor takes a step, the rotor
reacts to the changing stator field in the
same way a mass on a spring reacts to a
change in position.

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Characteristics
Resonance

– Just like the mass on a spring,
the motion of the rotor settles
into position after each step.
– This settling can last as long as a
second or more in worst cases!

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Characteristics
Resonance

– If the settling doesn’t occur
rapidly, or the ringing of the
rotor gets worse, the motor can
become unstable and lose
position (stall).

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Characteristics
Resonance

• There are two major, negative side effects of
resonance.

– Rough motion
• When step motors resonate they generally vibrate
excessively.
• This can be bad for sensitive equipment.

– Loss of torque, which can lead to loss of position
• When step motors resonate much of the torque available in
the motor is used up in keeping the rotor synchronized with
the stator field, and in worst cases the motor will not have
enough torque to move the load. Sold & Serviced By:

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• Step Mode
• Characteristics

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Reduced Duty Cycle
“We need more torque!“ You need more output power. P = M · ω · [Nm · rad/s]

• higher output power requires higher input power
•-> power losses increase
•-> duty cycle needs to be reduced, otherwise motor becomes too hot

•Order a Motor with reduced duty cycle,
•specify cycle time,
•do not only request reduced coil resistance.

•Otherwise you get a motor with reduced coil resistance. But the
winding is changed so that it will have the same maximum power
dissipation, same duty cycle and therefore the same output torque. Sold & Serviced By:

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Reduced Duty Cycle
Independence from Resistance
copper volume VCu = A cu ⋅ l m = const. coil winding area ACu

torque temperature
dϕ
M=
dα ϑ ~ PCu
Θ
ϕ= Θ = n ⋅ I = S ⋅ A Cu
RM PCu = I2 ⋅ R ~ S 2 ⋅ VCu lm average length of a
copper wire
S ⋅ A Cu S ⋅ VCu ϕ magnetic flux
ϕ= = α angle
RM RM ⋅ l m Θ current linkage

ϕ ≠ f (n,R) ϕ~S PCu ~ S 2 RM magnetic resistance
n no. turns (winding)
I current
S current density
Temperature ~ PCu ~ S2 PCu consumed energy
ϑ temperature
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Reduced Duty Cycle
Operations
T
Δϑmax
continuous operation

t
T
Δϑmax
operation with
reduced duty cycle

tB tS t tB...ON-time
T
tS...cycle time
Δϑmax

tB
Duty Cycle ED = ⋅ 100%
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39

Reduced Duty Cycle
A Simplified Calculation

input power at 100% duty cycle:

Uk 2 UK...supply voltage from catalogue
PED100 = Rph..coil resistance
Rph
real duty cycle:
2
PED100 ⎛ Uk ⎞ Rph
ED = • 100% = ⎜ ⎟ • 100% = • 100%
P ⎝ US ⎠ RED100

PED100 ... Power for 100% duty cycle
US ... supply voltage in application
RED100... coil resistance for 100% duty cycle

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• Step Mode
• Characteristics

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Synchronous Motor
Schematic

• construction is similar to bipolar stepper motor
• electrical phase shift is done by capacitor instead
• stepper motors are used with DC
• synchronous motors are used with AC
Parallel Connection
Common, full voltage over both coils
U~

Serial Connection
U~
otherwise too many windings with
too thin wire -> not possible
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Synchronous Motor
Frequencies
clock

f = step frequency = fs
t
i1 t bipolar stepper motor
f = 200Hz
i2 t

Speed is equal !
i1 t
synchronous motor
f = 50Hz
i2
t
f = frequency of coil current = fi
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• fs = 4·fi

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43

Synchronous Motor
Operation Area

C to start

th
er
voltage

m
al
ov
er
CN±10% operation area lo
minimum

ad

ce
Resonan

minimum capacity Sold & Serviced By:

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44

Competitors for Stepper Motor
Rotary:
Portescap (Danaher)
HSI (Haydon Switch & Instrument)
Hybrid:
Lin Engineering
Portescap (Danaher)
Oriental Motor
Sanyo Denki, Shinano
Linear:
HSI (Haydon Switch & Instrument)
Lin Engineering Sold & Serviced By:

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NPM/NPA Products
• Tin-Can Rotary
<PF/PFC Series>
PF20, PF25, PF25C, PF35, PF35T, PF42, PF42T, PF42H
PF55, PF55H

• Tin-Can Linear:
<PFL/PFCL Series>
PFCL25, PFL35T

• Hybrid:
<PJB Series>
PJB42S, PJB56H
<PR Series> (Only for North America )
PR20, PR28, PR35, PR42, PR57
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Designation – PF/PF Series
• PF C 42 H – 48 C 1 Magnet Material
1: Ferrite Anisotropic
Connector 2: Ferrite Isotropic
Version 4: Neodymium

Winding Code
Motor Size Unipolar> B:24V, C:12V, D:5V
Dia. (mm) Bipolar> P:12V, Q:5V
25, 35, 42, 55
Step/Rev
24: 15deg/step
Motor Length or High Torque 48: 7.5deg/step
Version 96: 3.75deg/step
Blank: Standard
T: Thin stack (Avail. In 35 and 42) Sold & Serviced By:

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Designation – PF/PF Series
• PFC42H–48C1 G 1/10

Gear Ratio

G: w/ gear head

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48

Designation – PR Series
• PR 42 H -25 – 04 04 J A

A: Shingle Shaft
Size (mm)
B: Double Shaft

H: High Torque
S: Standard Step Angle
J: 1.8deg/step (=200step/rev)
Stack Length (mm) M:0.9deg/step (=400step/step)

Motor Current Step/Rev
04: 0.4Amp/phase 24: 15deg/step
10:1.0Amp/phase 48: 7.5deg/step Sold & Serviced By:

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Weakness and Settlements
Mis-step
-> 1. Taking Care Margin (Chose Best)
2. Closed loop (Add Encoder)
3. Use/Change Higher Current
Resonance
-> 1. Use High Resolution Motor
2. Use Microstep Driver
3. Adjustment (reduce) Current

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Stepper VS Servo (Brushless)

Stepper Servo
Cost √
Speed (600rpm) √ (3000rpm)
Power/Torque √
Response √
Silence √
Easy to Use √

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Glossary -1
Holding Torque
The holding torque is the maximum torque the stepping motor
has when rated current is being supplied but the motor is not
rotating (with consideration given to the permissible strength of
the gear when applicable). If you are setting "automatic current
down (Idle Current)" function at motor standstill, the holding
torque should be less than setting rated current.

Pullout Torque
Pullout torque is the maximum torque that can be output at
given speed. When selecting a motor, be sure the required
torque falls within this curve.

Rotor Inertia
This refers to the inertia of rotor inside the motor. This is
necessary when the required torque (acceleration torque) for
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Glossary -2
Rated Current
The rated current is determined by motor temperature rise. It is
the current value that can flow to the motor coils continuously
at motor standstill. As a general rule, the current must be set to
the rated current.

Step Angle
The step angle is the angular distance (in degrees) that the
motor moves at the input of one pulse from the driver. It differs
depending on the motor structure and excitation system.

Gear Ratio
This is the ratio in rotation speed between the input speed from
the motor and the speed of the ear output shaft. For example,
the gear ratio 10:1 is that when the input speed from the motor
is 10rpm, the gear output shaft is 1rpm. Sold & Serviced By:

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Glossary -3
Allowable (Permissible) Torque
The allowable torque represents the torque value limited by the
mechanical strength of the gear.

Backlash
The play of gear output shaft when the motor shaft is fixed.
When positioning in bi-direction, the positioning accuracy is
affected.

Maximum Starting Frequency (fs)
This is the maximum pulse speed at which the motor can start or
stop instantly (without an acceleration or deceleration period)
when the functional load and inertial load of the stepper motor
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Glossary -4

Torque Pull-Output
Torque Pull-in
Torque

Holding
Torque Max. Starting
Frequency

Speed
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Nippon Pulse Stepper Motor Basics Presentation