MICRO STEPPING MODE FOR STEPPER MOTOR

1. MICRO STEPPING MODE FOR
STEPPER MOTOR

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
“A stepper motor (or step motor) is a brushless,
synchronous electric motor that can divide a full
rotation into a large number of steps”
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
“Step angle of the stepper motor is defined as the
angle traversed by the motor in one step.”
θs=360/S
s=m*N
m= no of phases
N=no of rotor teeth

6. OPERATION
Basic stepper motor operation

7. TYPES OF STEPPER MOTOR
1 Variable reluctance
2 Permanent magnet
3 Hybrid

8. CHARACTERISTICS
 Constant power devices.
 Speed increases, torque decreases.
 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).
 “Ringing" 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
•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
 “An electronic control technique that proportions the current
in a step motor’s windings to provide additional intermediate
positions between poles.”

Produces smooth rotation over a wide speed range and high
positional resolution.
 It allows even smaller steps by using different
currents through the two motor windings.

12.  h = ( a2 + b2 )0.5
x = ( S / (π / 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((( π/2)/s)θ))
h1 = single winding holding current
((( π/2)/s)θ))=electric shaft angle
b= h1 cos((( π/2)/s)θ))
To hold motor rotor to angle θ
Ia= current through winding with equilibrium at angle 0’
Ib= current through winding with equilibrium at angle S’
Ia=Imax sin((( π/2)/s)θ)) Ib=Imax cos((( π/2)/s)θ))
MA=KM*Ia=Imax sin((( π/2)/s)θ))
MB=KM*Ib=Imax sin((( π/2)/s)θ))
Mo=KM*Imax

14. Example 1

15. Example 2

16. DRIVER OVERVIEW
USER
INTERFACE INDEXE
R
DRIVER
MOTO
R
HIGH LEVEL
COMMANDS STEP
PULSES
MOTOR CURRENT

17. Stepper motor with drive circuit
“Stepper motor performance is strongly dependent
on the drive circuit”

18. MICRO STEPPING CONTROL SYSTEM
Block
diagram

19. Electronic scheme of digital command block

20. EXPERIMENTAL RESULTS

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.

24. THANK YOU