A Back-EMF Threshold Self-Sensing Method to Detect the Commutation Instants in BLDC Drives 老師 : 王明賢 學生 :MA 許哲源 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 62, NO. 10, OCTOBER 2015 Araz Darba, Student Member, IEEE, Frederik De Belie, Member, IEEE, and Jan A. Melkebeek, Senior Member, IEEE

OUTLINE Abstract INTRODUCTION SELF-SENSING CONTROL USING CONVENTIONAL BACK-EMF ZERO-CROSSING DETECTION using time difference between commutation and zero-crossing instant. dividing time difference between successive zero-crossing instants SELF-SENSING CONTROL USING BACK-EMF THRESHOLD A. Principles B. Indirect Measurement of Speed and Peak Back-EMF DETERMINATION OF Δt AND ITS LIMITS A. Maximum and Minimum Values of Δt B.Maximum Back-EMF Decrease During Load Increase C. Minimum Δt to Detect Commutation Instant 1) Linear Case 2) Nonlinear Case D. Adaptation of Δt for Nonlinear Case PERFORMANCE ANALYSIS DURING TRANSIENTS MEASUREMENT TECHNIQUES A. Current Measurements B. Back-EMF Measurements SIMULATIONS EXPERIMENTAL RESULTS A. Steady-State Tests B. Transient Tests 1) Uniform Acceleration 2) Loading and Unloading

Abstract Comparison and INTRODUCTION of the performance between the proposed method and a conventional back-EMF zero-crossing detection method. SELF-SENSING CONTROL USING CONVENTIONAL BACK-EMF ZERO- CROSSING DETECTION the time difference between the zero-crossing of the back-EMF and the current commutation instant is assumed constant. This assumption can be valid for steady-state operation. a different time span should be taken into account during transient operation of the BLDC machine. SELF-SENSING CONTROL USING BACK-EMF THRESHOLD based on the back-EMF magnitude instead of its zero-crossings higher accuracy in the commutation instants during speed variations and a more stable behavior. The calculation of the threshold is the main focus in this paper.

INTRODUCTION electrical machine drives involve torque, current, position, or speed control. states are directly or indirectly dependent on the position of the rotor. the trend in modern and cost-effective drives is to replace the noise-sensitive and less reliable mechanical sensors by numerical algorithms, which are often referred to as sensorless or self-sensing methods. A wide variety of different self-sensing methods has beenproposed by different authors for a wide range of rotor speeds from standstill to high speeds. a self-sensing method that detects the commutation instances more directly. By using the back-EMF signal rather than the back-EMF zerocrossing

SELF-SENSING CONTROL USING CONVENTIONAL BACK-EMF ZERO- CROSSING DETECTION the commutation instant occurring at the 30◦ electrical position after zero-crossing of the induced back-EMF in the unexcited phase. By using time difference between commutation and zero-crossing instant.

SELF-SENSING CONTROL USING CONVENTIONAL BACK-EMF ZERO- CROSSING DETECTION the commutation instant occurring at the 30◦ electrical position after zero-crossing of the induced back-EMF in the unexcited phase. By dividing time difference between successive zero-crossing instants

SELF-SENSING CONTROL USING CONVENTIONAL BACK-EMF ZERO- CROSSING DETECTION during transients such as acceleration and deacceleration, using T z,1 or Tz,2/2 results in a bad estimation of the 30 ◦ electrical position change due to a rotor speed change. Such an error can have a great influence in the speed estimation

SELF-SENSING CONTROL USING BACK-EMF THRESHOLD Proposed self-sensing method, including the timings and important events.

SELF-SENSING CONTROL USING BACK-EMF THRESHOLD Variation of the measured back-EMF signals due to a speed change and different threshold values due to the different values of Δt.

SELF-SENSING CONTROL USING BACK-EMF THRESHOLD DETERMINATION OF Δt AND ITS LIMITS Linear behavior assumption for merged parts of the back- EMF signal during the floating interval of the phases.

SELF-SENSING CONTROL USING BACK-EMF THRESHOLD Nonlinear (cosine) function to describe the behavior of merged parts of the measured back-EMF signal during the unexcited interval of the phases.

SELF-SENSING CONTROL USING BACK-EMF THRESHOLD Adaptation of Δt for Nonlinear Case

PERFORMANCE ANALYSIS DURING TRANSIENTS Comparison of the error between the proposed method and a conventional back-EMF zero-crossing detection method.

MEASUREMENT TECHNIQUES Electrical circuit used for simulation.

MEASUREMENT TECHNIQUES Simulation results: measurements of the back-EMF referred to the neutral point and referred to the virtual neutral point.

SIMULATIONS Speed control: acceleration and deacceleration.

SIMULATIONS Demonstration of the threshold-intersection instants of back-EMF and added Δt delay for generating real switching pulses during acceleration of the machine.

EXPERIMENTAL RESULTS shows the basic concept and schematic diagram of the test setup.

EXPERIMENTAL RESULTS Steady-State Tests Internal states of the controller and measured value of the back-EMF for different rotation velocities.

EXPERIMENTAL RESULTS Steady-State Tests Oscilloscope screenshot and speed control. ωm =500 r/ min and dc bus current of I = 0.8 A. VT 2 V/Div VT-V’n V’n Phase current

EXPERIMENTAL RESULTS Steady-State Tests Oscilloscope screenshot and speed control. ωm = 1000 r/ min and dc bus current of I = 1.7 A. 4V/Div VT VT-V’n V’n Phase current

EXPERIMENTAL RESULTS Transient Tests 1) Uniform Acceleration (Top) Δt value. (Bottom) Measured speed of the machine for a ramp speed command.

EXPERIMENTAL RESULTS Transient Tests 2) Loading and Unloading: Oscilloscope screenshot. Loading transients (rotor speed and phase current during the loaded condition are ωm = 470 r/ min and I = 2.6 A).

EXPERIMENTAL RESULTS Transient Tests 2) Loading and Unloading: Oscilloscope screenshot. Unloading transients (rotor speed and phase current during the no-load condition are ωm = 765 r/ min and I = 0.4 A).

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