nippon pulse stepper motor basics presentation
DESCRIPTION
Stepper Motor BasicsTRANSCRIPT
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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What is a Stepper Motor? <Stepper with Peripheral Construction>
Sequencer
Power Tr.
CPU or
Motion- Control-Chip
Vm (Motor Power)<Driver><Controller>
<Motor>
Vcc (Logic power) ELECTROMATE
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What is a Stepper Motor? <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 ELECTROMATE
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Stepper and Synchronous MotorsMovement Generation• Step Mode• Torque Generation• Characteristics• Reduced Duty Cycle• Synchronous Motor
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N S
N
S
S
NN S
S
N
S
NS N
S
N
SN
S N
N
S
S
NN S
N
S
S
NN S
S
N
S
NS N
S
N
SN
for the next step invert magnetic field in the other coilone step ⇒ invert magnetic field in 1 coilrotor follows the stator field
Movement Generation
S N
N
S
S
N
A stepper motor always needs electronic control.step angle depends on number of poles -> fixed by construction
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PhA1 (=GND) PhA2 (=open)+
SN
PhA1 (=open) PhA2 (=GND)+
NS
Movement Generation Unipolar Principle
• every coil end has only one polarity (”+” or ”ground (-)”)
• motor coils are unipolar
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PhA1 PhA2
S
GND+
N
Movement Generation Bipolar Principle
• every coil end will be positive (”+”) or ground (”-”)
• motor coils are bipolar
S
GND +
N ELECTROMATEToll Free Phone (877) SERVO98
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Movement Generation Unipolar Drive
• low side switches
+
GND
I
+
GND
I
• 4 switches for the whole motor
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Movement Generation Bipolar Drive
• 2 full bridges (or H-bridges) are needed = 8 switches
• switches in bridge configuration
+
GND
I
+
GND
I
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Movement Generation Tin Can Motor
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NS
N
S
N
S
N
SN
SN
S
N
S
N
S NS
N
S
N
S
N
S
NS
N
S
N
S
N
S
Movement Generation Tin Can Motor - Step Generation
N
N
N N
S S
S SS
S
S S
N N
N N
front side teethback side teeth
if there is only 1 magnetic system...N
SN
SNS
N
S N
SN
SN
SN
SN
SN
S
N
S
N
S
N
N
N N
S S
S SS
S
S S
N N
N NN
N
N N
S S
S SS
S
S S
N N
N N
NS
N
S
N
S
N
S
NS
NS
NS
NS
NS
NSN
S
N SN
SN
S
N
S
N
S motor is able to start in both directionsdirection is undefined
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CoilStator Core
Shaft
Permanent Magnet
Bobbin
Movement Generation Tin Can Motor
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N
N
N N
S S
S S
Movement Generation Tin Can Motor - Step Generation
2 magnetic systems = 2 stators...electrical phase shift 90 °direction is defined by coil control sequencing
coil 1coil 2
coil 1coil 2 direction CW
direction CCW
control pattern (bipolar motor):N
S
NS
NS
NS
N
N
N
N
S
S
S
SS
S
S S
N N
N N
N S
NS
NSN
S
S
S
S
S
N
N
N
N
N
SN
SN
SN
S
N
N
N N
S S
S S
N
SN
SNS
N
S
S
S
S S
N N
N N
N
SN
SN
SN
S
N
N
N
N
S
S
S
S
N S
NS
NSN
S
N
N
N N
S S
S S
NS
NS
NS
NS
S
S
S
S
N
N
N
N
N
SN
SNS
N
S
front side teethback side teeth
stator 1 stator 2ELECTROMATE
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Old Technology, No Longer Used
Movement Generation VR - Step Generation
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• Hybrid Motor Bobbin Teeth
Coil
ShaftP.M.
RotorStatorB.B. P.M.
Coil
StatorFlame
Rotor
Bracket
Movement Generation Hybrid - Step Generation
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S N
S
N
SN
Rotor follows the stator field
Rotor reaches the end stop noise
Rotor is not able to follow the stator field
Rotor swings back
Movement Generation Step Loss
S N
N
S
SNN S
N
S
S
NN S
S
N
S
NS N
S
N
S
NS N
N
S
SNN S
N
S
S
NN S
S
N
S
NS N
S
N
S
NS N
N
S
SN
Motor will always loose n·4 steps
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S N
S
N
SN
Rotor follows the stator field
Rotor reaches the end stop noise
Rotor is not able to follow the stator field
Rotor swings back
Movement Generation Step Loss
S N
N
S
SNN S
N
S
S
NN S
S
N
S
NS N
S
N
S
NS N
N
S
SNN S
N
S
S
NN S
S
N
S
NS N
S
N
S
NS N
N
S
SN
Motor will always loose n·4 steps
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Stepper and Synchronous Motors
• Movement Generation• Step Mode• Torque Generation• Characteristics• Reduced Duty Cycle• Synchronous Motor
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Step Mode Full Step Mode
• Step angle = catalogue value
N S
N
S
S
NN S
S
N
S
NS N
S
N
S
N
S N
N
S
S
NN S
N
S
S
NN S
S
N
S
NS N
S
N
S
N
S N
N
S
S
N
0
-1
1
I1 / I1max
I2 / I2max
1
0
-1
coil current in a bipolar motor
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Step Mode Half Step Mode
• Step angle = half catalogue value
NN S
NN
S
S
NNN SS NNN S
S
NN
S
N
S
NN
S
NS NN
S
NN
S
N
S NNSNS NN
NN
S
S
N
NN
S
S
N
0
-1
1
I1 / I1max
I2 / I2max
1
0
-1
coil current in a bipolar motor
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Step Mode Half Step vs. Compensated Half Step
0
-1
1
I1 / I1max
I2 / I2max
1
0
-1
0
-1
1
I1 / I1max
I2 / I2max
1
0
-1
1/√2
1/√2
-1/√2
-1/√2 ELECTROMATEToll Free Phone (877) SERVO98
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Stepper and Synchronous Motors
• Movement Generation• Step Mode• Torque Generation• Characteristics• Reduced Duty Cycle• Synchronous Motor
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Torque Generation Torque vs. Angle
Mel(torque)
Sαα1 2 3-1-2 4
MH(holding torque)
-MH
N
N
N N
S S
S S
N S
NS
NS
NS
N
N
N
N
S
S
SS
N
N
N N
S S
S S
N
SN
SN
SN
S
N
N
N
N
S
S
S
S
N
N
N N
S S
S S
N
SN
SN
SN
S
N
N
N
N
S
S
S
S
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Mel(torque)
Sαα1 2 3-1-2 4
MH(holding torque)
-MH
Mel
Torque Generation Positioning Accurancy
Δα...Step Angle Tolerance
(torque)
Sαα
2 Δα
Friction
Tolerance exists at every position, but it will not sum up!Accuracy depends on friction and motor tolerances (5-7% of step angle). ELECTROMATE
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α
M(torque)
M
α
(torque)
friction
step no. 1 2 3 4 5 6
Torque Generation Micro Step Modus
• micro step only for smoother travel at low frequencies
• with tin can motor:
• Current in coils increases/decreases in small increments
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Stepper and Synchronous Motors
• Movement Generation• Step Mode• Torque Generation• Characteristics• Reduced Duty Cycle• Synchronous Motor
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Characteristics Torque
with chopper(pull out graph)
reduced duty cycle = increased power consumption (pull out graph)
pull-out
fA fB
pull-in
torq
ue
frequencyf2f1
Resonances may influence application!
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Characteristics Influence of Inertia
Load inertia reduces start-stop-range.
torq
ue
f
f
FI
Inertia Factor FI = JROTOR
JLOAD + JROTOR
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Characteristics Output Power
torq
ue
frequency
pow
er
Motor output power : P = M · ω
with
M...torque
ω...angular velocity
zf⋅Π⋅
=2ω
f...step frequencyz...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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• 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.
Characteristics Resonance
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– 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!
Characteristics Resonance
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– If the settling doesn’t occur rapidly, or the ringing of the rotor gets worse, the motor can become unstable and lose position (stall).
Characteristics Resonance
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• 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.
• Loss of torque often leads to stalling.
Characteristics Resonance
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Stepper and Synchronous Motors
• Movement Generation• Step Mode• Torque Generation• Characteristics• Reduced Duty Cycle• Synchronous Motor
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• higher output power requires higher input power •-> power losses increase •-> duty cycle needs to be reduced, otherwise motor becomes too hot
Reduced Duty Cycle
•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.
“We need more torque!“
M...torque ω...angular velocity = revolution_per_steps2frequency_step π⋅
P = M · ω
· [Nm · rad/s]You need more output power.
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Reduced Duty Cycle Independence from Resistance
lm
ϕαΘ
RMnIS
PCu
ϑ
coil winding area ACu
Temperature ~ PCu ~ S2
For same duty cycle same current density is needed.PCu =const. ϑ=const. Duty Cycle=const. S is the parameter, not R!
.constAV mcuCu =⋅= lcopper volume
average length of a copper wiremagnetic fluxangle current linkage
magnetic resistance no. turns (winding)currentcurrent density
consumed energy
temperature
)R,n(f≠ϕ
CuASn ⋅=⋅=Θ IMRΘ
=ϕ
mM
Cu
M
Cu
RVS
RAS
l⋅⋅
=⋅
=ϕ
αϕ
=ddM
S~ϕ
torque
2Cu S~P
Cu22
Cu VS~RP ⋅⋅= I
CuP~ϑ
temperature
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• Duty cycle is based on 5 minutes cycle time (unless otherwise specified).
Reduced Duty Cycle Operations
t
T
maxϑΔ
t
T
maxϑΔ
tStB
t
T
maxϑΔ
tStB
continuous operation
operation with reduced duty cycle
tB ...ON-time
tS ...cycle time
%100ttEDS
B ⋅=Duty CycleELECTROMATE
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Reduced Duty Cycle A Simplified Calculation
input power at 100% duty cycle:
ph
kED
RUP
2
100 =UK ...supply voltage from catalogueRph ..coil resistance
real duty cycle:
%100%100%100100
2100
•=•⎟⎠⎞
⎜⎝⎛=•=
ED
ph
S
kED
RR
UU
PPED
PED100 ... Power for 100% duty cycleUS ... supply voltage in applicationRED100 ... coil resistance for 100% duty cycle
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Stepper and Synchronous Motors
• Movement Generation• Step Mode• Torque Generation• Characteristics• Reduced Duty Cycle• Synchronous Motor
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Synchronous Motor Schematic
U~
U~
Parallel Connection
Common, full voltage over both coils
Serial Connection
otherwise too many windings with too thin wire -> not possible
• electrical phase shift is done by capacitor instead• construction is similar to bipolar stepper motor
• stepper motorsstepper motors are used with DCDC• synchronous motorssynchronous motors are used with ACAC
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Synchronous Motor Frequencies
cloc
k
i1
i2
i1
i2 t
t
t
t
t
bipolar stepper motor
f = 200Hz
synchronous motor
f = 50Hz
Speed is equal !
f = step frequency = ff = step frequency = fss
f = frequency of coil current = ff = frequency of coil current = fii
• fs = 4·fi (for motors with identical construction)ELECTROMATE
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Synchronous Motor Operation Area
C
U
Resonance
thermal overload
min
imum
vol
tage
to s
tart
minimum capacity
operation area
UN ±10%
CN ±10%
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Competitors for Stepper MotorRotary:
Portescap (Danaher)HSI (Haydon Switch & Instrument)
Hybrid:Lin EngineeringPortescap (Danaher)Oriental MotorSanyo Denki, Shinano
Linear: HSI (Haydon Switch & Instrument)Lin Engineering
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NPM/NPA Products• Tin-Can Rotary
<PF/PFC Series> PF20, PF25, PF25C, PF35, PF35T, PF42, PF42T, PF42HPF55, 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 Anisotropic2: Ferrite Isotropic4: Neodymium
Winding CodeUnipolar> B:24V, C:12V, D:5VBipolar> P:12V, Q:5V
Step/Rev24: 15deg/step48: 7.5deg/step96: 3.75deg/step
Connector Version
Motor SizeDia. (mm)25, 35, 42, 55
Motor Length or High Torque VersionBlank: StandardT: Thin stack (Avail. In 35 and 42)H: High Torque (Avail. 42 and 55) ELECTROMATE
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Designation – PF/PF Series• PFC42H–48C1 G 1/10
Gear Ratio
G: w/ gear head
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Designation – PR Series• PR 42 H -25 – 04 04 J A
A: Shingle ShaftB: Double Shaft
Step AngleJ: 1.8deg/step (=200step/rev)M:0.9deg/step (=400step/step)
Step/Rev24: 15deg/step48: 7.5deg/step96: 3.75deg/step
Size (mm)
Stack Length (mm)
H: High TorqueS: Standard
Motor Current04: 0.4Amp/phase10:1.0Amp/phase
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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 ServoCost √Speed (600rpm) √
(3000rpm)
Power/Torque √Response √Silence √Easy to Use √
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Glossary -1Holding 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 the motor needs is calculated. ELECTROMATE
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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.
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Glossary -3
Allowable (Permissible) TorqueThe allowable torque represents the torque value limited by the mechanical strength of the gear.
BacklashThe 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 are 0. Driving the motor at greater than this pulse speed requires gradual acceleration or deceleration. This frequency drops when there is load inertia on the motor.
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Speed
Torque
Glossary -4
Pull-Output Torque Pull-in
Torque
Max. Starting Frequency
Holding Torque
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