A Novel Digital Control Technique for Brushless DC Motor Drives

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A Novel Digital Control Technique for Brushless DC Motor Drives

Adviser:Ming-Shyan WangStudent:Cih-Huei SHIH

Fernando Rodriguez, Student Member, IEEE, and Ali Emadi, Senior Member, IEEEIEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 5, OCTOBER 2007 2365-2373

PPT製作率 : 100%

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Outline

Abstract Introduction Novel Digital Control Conduction -Angle Control Current-Mode Control Controller Design Simulations Conclusion References

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Abstract

Brushless DC (BLDC) motor drives are continually gaining popularity in motion control applications. Therefore,it is necessary to have a low cost, but effective BLDC motor speed/torque regulator.

This paper introduces a novel concept for digital control of trapezoidal BLDC motors. The digital controller was implemented via two different methods, namely conduction-angle control and current-mode control.

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Introduction

This paper proposes a novel digital controller that treats the BLDC motor drive like a digital system which may only operate at a few predefined states that produce constant predefined motor speeds. Speed regulation is achieved by alternating states during operation, which makes the concept of the controller extremely simple for design and implementation purposes.

This novel concept will help reduce the cost and complexity of the motor control hardware. That, in turn, can boost the acceptance level of BLDC motors for commercial mass production applications, successfully fulfilling the promises of energy savings associated with adjustable speed drives.

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Novel Digital Control(1/2)

1) If the actual motor speed is less than the commanded speed, then switch or stay at state 2 ( ).

2) If the actual motor speed is greater than the commanded speed, then switch or stay at state 1 ( ).

Fig. 1. Proposed digital control.

W L

W H

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Novel Digital Control(2/2)

Fig. 2. Digital control actuation signal.

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Conduction -Angle Control

Fig. 3. Conduction-angle control state definitions.

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Current-Mode Control

Fig. 4.

Current-mode control state definitions.

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Controller Design(1/6)

Newton’s second law applied to rotary motion

The solution to the differential equationgives the instantaneous speed as a function of motor parametersand load conditions, see

TT Ld dt

tdwJbtw

)()(

Jtw

J

b

dt

tdw TT Ld

)()(

(1)

(2)

eTTTT tJb

LdLd

bw

btw

)())0(()(

(3)

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Controller Design(2/6)

Understeady-state conditions and with the substitution of the timeconstant into (3) yields (4)

The instantaneous torque sensitivity values kti , i = a, b, c are approximatedby kt which is the peak to peak value of kti . The current peak values are assumed to be constant since operation is insteady state

TTTw mLd

ss Jtw

)( (4)

IkikikikT tctcbtbatad (5)

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Controller Design(3/6)

Equation (5) is substituted into (4) and solved for the averagecurrent. The equation for the current is a function of the desiredsteady-state rotor speed. It can be used to find the necessarycurrent to produce ωL and ωH for a given load

)(1

)( TwTkw Lssmt

ss

JI (6)

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Controller Design(4/6)

IwwI HHss )(

IwwI LLss )(

(7)

(8)

Conduction-angle control state definitions.Fig. 3

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Controller Design(5/6)

The average current instate 1 must be equal to the integral over the partial conductionangle as shown below.

min,2

min,20

1

01

ddT II HL

min,2

0I H

min,2I H

IIH

L min,2

(9)

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Controller Design(6/6)

In summary, to implement the digital controller to any BLDC motor under a constant load torque, the following procedureshould be followed.

1)Find the following motor parameters from the manufac-turer’s data sheet. kt Torque sensitivity constant.

b Viscous friction constant. J Rotor moment of inertia. τm Mechanical time constant.2) Determine the desired operating speed and specify the load torque.3) Choose ωH and ωL to cover the desired speed range.4) Use (6) to determine the values of and , ( → CBmin and →

CBmax ).5) Use (9) to determine the value of (only necessary for conduction-

angle control).

I H I L I H I L

min,2

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Simulations(1/8)

1)Determine the conduction interval for all three phases. 2) Estimate the conduction interval duration (TC ). 3) Maintain the phase currents within the CB during the

conduction interval for all three phases. 4) Determine when is reached during a conduction

interval. 5) Choose the appropriate state to apply to the next conduc-

tion interval.

min,2

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Simulations(2/8)

Fig. 5. Counter stop and start indicators.

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Simulations(3/8)

Fig. 6. Instances of speed comparison for choosing state 1 or state 2.

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Simulations(4/8)

Block diagram of proposed digital control implemented in PSIM.Fig. 7.

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Simulations(5/8)

Fig. 8. Simulation results for a 0.3-N · m load (conduction-angle control). (a) Speed and current results for ω ∗ = 900 rpm with a 0.3 N · m load. (b) Speed andcurrent results for ω ∗ = 1000 rpm with a 0.3 N · m load. (c) Speed and current results for ω ∗ = 1100 rpm with a 0.3 N · m load.

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Simulations(6/8)

Fig. 9. Simulation results for a 0.3-N · m load (current-mode control). (a) Speed and current results for ω ∗ = 900 rpm with a 0.3 N · m load. (b) Speed and current results for ω ∗ = 1000 rpm with a 0.3 N · m load. (c) Speed and current results for ω ∗ = 1100 rpm with a 0.3 N · m load.

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Simulations(7/8)

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Simulations(8/8)

Fig. 10. Digital control Simulink model.

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Conclusion(1/5)

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Conclusion(2/5)

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Conclusion(3/5)

TABLE IVSUMMARY OF EXPERIMENTAL RESULTS FOR 0.3-N · m LOAD

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Conclusion(4/5)

The conduction angel control simulations and experimental results were in accordance with one another. Speed regulationfor all the commanded speeds were well within acceptable limits.

It is important tonote that all the measured speed ripples included the inherent speed ripple associated with trapezoidal BLDC motors. The inherent speed ripple is largely due to the nonideal trapezoidal back EMF, which does not have perfectly flat plateaus asassumed in the PSIM simulations.

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Conclusion(5/5)

In conclusion, this paper has presented the initial investigation and proof-of-concept for a new way of lookingat digital control for BLDC motors.

Further development and modification of the state definitions will allow for additional speed ripple reduction, making it suitable for high-performance motor drive applications.

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References [1] C. W. Lu, “Torque controller for brushless DC motors,” IEEE Trans. Ind.

Electron., vol. 46, no. 2, pp. 471–473, Apr. 1999. [2] P. Pillay and R. Krishnan, “Application characteristics of permanent mag- net

synchronous and brushless DC motors for servo drives,” IEEE Trans. Ind. Appl., vol. 27, no. 5, pp. 986–996, Sep./Oct. 1991.

[3] P. Pillay and R. Krishnan, “Modeling of permanent magnet motor drives,” IEEE Trans. Ind. Electron., vol. 35, no. 4, pp. 537–541, Nov. 1988.

[4] J. U. Lee, J. Y. Yoo, and G. T. Park, “Current control of a PWM inverter using sliding mode control and adaptive parameter estimation,” in Proc. IECON 20th Int. Conf., Sep. 1994, vol. 1, pp. 372–377.

[5] V. I. Utkin, “Sliding mode control design principles and applications to electric drives,” IEEE Trans. Ind. Electron., vol. 40, no. 1, pp. 23–36, Feb. 1993.

[6] M. A. El-Sharkawi, Fundamentals of Electric Drives. Pacific Grove, CA: Brooks/Cole, 2000, pp. 5–10.

[7] J. Chen and P.-C. Tang, “A sliding mode current control scheme for PWM brushless DC motor drives,” IEEE Trans. Power Electron., vol. 14, no. 3, pp. 541–551, May 1999.

[8] H. C. Chen, M. S. Huang, C. M. Liaw, Y. C. Chang, P. Y. Yu, and J. M. Huang, “Robust current control for brushless DC motors,” Proc. Inst. Electr. Eng.—Electric Power Applications, vol. 147, no. 6, pp. 503– 512, Nov. 2000.

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References [9] F. Rodriguez and A. Emadi, “A novel digital control technique for brush-

less DC motor drives: Conduction-angle control,” in Proc. IEEE Int. Elect. Mach. Drives Conf., May 2005, pp. 308–314.

[10] F. Rodriguez, P. Desai, and A. Emadi, “A novel digital control technique for trapezoidal brush-less DC motor drives,” in Proc. Power Electron. Technol. Conf., Chicago, IL, Nov. 2004.

[11] A. A. Aboulnaga, P. C. Desai, F. Rodriguez, T. R. Cooke, and A. Emadi, “A novel, low-cost, high-performance single-phase adjustable-speed mo- tor drive using PM brush-less DC machine: IIT’s design for 2003 Future Energy Challenge,” in Proc. 19th Annu. IEEE Appl. Power Electron. Conf., Anaheim, CA, Feb. 2004, pp. 1595–1603.

[12] International Rectifier, IR2130/IR2132(J)(S) & (PbF) 3-phase bridge driver. Data Sheet No. PD60019 Rev.P.

[13] dSPACE, Implementation Guide For Release 4.0: Real-Time Interface (RTI and RTI-MP). Documentation Guide, Aug. 2003.

[14] dSPACE, Experiment Guide For Release 4.0: Control-Desk. Documenta- tion Guide, Aug. 2003.

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