2. OVERVIEW
⢠INTRODUCTION
⢠OPERATION
⢠TYPES OF STEPPER MOTOR
⢠MODES OF OPERATION
⢠MICRO STEPPING MODE
⢠DRIVER OVERVIEW
⢠MICRO STEPPING CONTROL
SYSTEM
⢠EXPERIMENTAL RESULTS
⢠CONCLUSION
⢠REFERENCE
3. INTRODUCTION
Stepper Motor
âA stepper motor (or step motor) is a brushless,
synchronous electric motor that can divide a full
rotation into a large number of stepsâ
Multiple "toothed" electromagnets arranged around a central
gear-shaped piece of iron.
The electromagnets are energized by an external control
circuit, such as (eg;microcontroller )
4. Internal components of a stepper motor
Rotor
Stator
Coils
2
1
S
1
N
2
Outside Casing
Stator
Rotor
5. Step angle θs
âStep angle of the stepper motor is defined as the
angle traversed by the motor in one step.â
θs=360/S
s=m*N
m= no of phases
N=no of rotor teeth
7. TYPES OF STEPPER MOTOR
1 Variable reluctance
2 Permanent magnet
3 Hybrid
8. CHARACTERISTICS
ď Constant power devices.
ď Speed increases, torque decreases.
ď Steppers exhibit more vibration than other motor types, as the
discrete step tends to snap the rotor from one position to
another (called a detent).
ď âRinging" effect can be mitigated by accelerating quickly using
a micro-stepping driver.
9. ADVANTAGES & DISADVANTAGES
ADVANTAGES DISADVANTAGES
⢠High accuracy of motion ⢠High vibration levels due
to stepwise motion
⢠Easily adaptable to
digital control applications
â˘Dynamic instability, low
frequency oscillations
around Fs non linear
assembly of the control
system
⢠No stability problem
-----------------------------------
⢠Response can be
controlled by electronic
switching
-----------------------------------
10. MODES OF OPERATION
Half Step Operation
Full Step Operation
TwSoin-Cgloei-lC eoxilc eixtactitioatnion
Micro stepping
11. MICRO STEPPING MODE
ď âAn electronic control technique that proportions the current
in a step motorâs windings to provide additional intermediate
positions between poles.â
ď
Produces smooth rotation over a wide speed range and high
positional resolution.
ď It allows even smaller steps by using different
currents through the two motor windings.
12. ď h = ( a2 + b2 )0.5
x = ( S / (Ď / 2) ) arctan( b / a )
a -- torque applied by winding with equilibrium at 0 radians.
b -- torque applied by winding with equilibrium at S radians.
h -- holding torque of composite.
x -- equilibrium position, in radians.
S -- step angle, in radians.
13. Sine cosine microstepping
a= h1 sin((( Ď/2)/s)θ))
h1 = single winding holding current
((( Ď/2)/s)θ))=electric shaft angle
b= h1 cos((( Ď/2)/s)θ))
To hold motor rotor to angle θ
Ia= current through winding with equilibrium at angle 0â
Ib= current through winding with equilibrium at angle Sâ
Ia=Imax sin((( Ď/2)/s)θ)) Ib=Imax cos((( Ď/2)/s)θ))
MA=KM*Ia=Imax sin((( Ď/2)/s)θ))
MB=KM*Ib=Imax sin((( Ď/2)/s)θ))
Mo=KM*Imax
21. 1 Resonance are significantly reduced
11 Noise generation is considerably reduced
111 Precise position control
1V Very high step resolution
22. CONCLUSION
⢠Experimental results prove that a smooth and
continuous rotation is achieved.
⢠Velocity ripples are eliminated.
⢠Greatly improves performance at low rotational
speeds and helps avoid resonance problems.
⢠The method is found to be less complex and cheap
also
23. REFERENCES
[1] P. Acarnley, Stepping Motors: a Guide to Modern Theory and Practice, 4th ed.,
IEE Control Engineering Series 63, ISBN: 0-85296-029-8, Michael Faraday House,
2002, pp.48-5 1.
[2] T. Kenjo and A. Sugawara, Stepping Motors and Microprocessor Control, 2nd
ed., ISBN:0-19-859385-6, Oxford: Clarendon Press, 2003, pp.113-120.
[3] H. Maczala, Elektrische Kleinmotoren, ISBN: 3-8169-0909-4, Expert Verlag,
1993, pp.261-263.
[4] Gh. Baluta., Electrical Drives with Stepper Motors (in Romanian), ISBN:973-
621-034-0, Iasi: Gh. Asachi, 2003, pp.63-85.
[5] Gh. Baluta, Low Power Electrical Drives. Applications (in Romanian), IS.B.N:
973-621-072-3, Iasi: Politehnium, 2004, pp.40-48.