Marquette University e-Publications@Marquette Master's Theses (2009 -) Dissertations, Theses, and Professional Projects Hybrid Sensorless Field Oriented and Direct Torque Control for Variable Speed Brushless DC Motors Kellen Carey Marquette University Recommended Citation Carey, Kellen, "Hybrid Sensorless Field Oriented and Direct Torque Control for Variable Speed Brushless DC Motors" (2018). Master's Theses (2009 -). 451. http://epublications.marquette.edu/theses_open/451 HYBRID SENSORLESS FIELD ORIENTED AND DIRECT TORQUE CONTROL FOR VARIABLE SPEED BRUSHLESS DC MOTORS by Kellen D. Carey, B.S. A Thesis submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for the Degree of Master of Science Milwaukee, Wisconsin May 2018 ABSTRACT HYBRID SENSORLESS FIELD ORIENTED AND DIRECT TORQUE CONTROL FOR VARIABLE SPEED BRUSHLESS DC MOTORS Kellen D. Carey, B.S. Marquette University, 2018 The objective of this thesis is to design a hybrid sensorless closed-loop motor controller using a combination of Field-Oriented Control (FOC) and Direct Torque Control (DTC) for brushless DC motors used in multi-rotor aerial vehicles. The primary challenge is the wide range of desired working speeds, which can quickly vary from low speed to high speed. For this range, the control approach must be efficient, effective, and low-cost in order to provide fast response times during initial startup, steady-state, and transient operation. Additional design challenges include minimal response time to desired speed changes and small steady-state speed errors. Finally, the control approach must be robust to motor parameter uncertainties or variations and the operation of the final design must be robust to measurement noise. i ACKNOWLEDGMENTS Kellen D. Carey, B.S. I would like to thank my adviser, Dr. Cris Ababei, who provided the excellent mentoring and support that made this thesis possible. I also would like to thank my other committee members, Dr. Susan Schneider, and Dr. Edwin Yaz, for taking the time to review this thesis and provide their valuable feedback. Additionally, I would like to thank my fellow lab mates, Ian Barge, Milad Ghorbani, and Wenkai Guan who provided useful feedback and support throughout this thesis. ii TABLE OF CONTENTS ACKNOWLEDGMENTS . i LIST OF TABLES . iv LIST OF FIGURES . v 1 PROBLEM STATEMENT, OBJECTIVE AND CONTRIBUTIONS . 1 1.1 Problem statement . 1 1.2 Previous Work . 1 1.3 Contributions . 7 1.4 Thesis Organization . 8 2 BACKGROUND ON BRUSHLESS DC MOTORS . 9 2.1 General Motor Background . 9 2.2 Three-phase Brushless DC Motors . 11 2.3 Derivation of the Electrical Model for Brushless DC Motors . 13 2.4 Derivation of the Mechanical Model for Brushless DC Motors . 16 3 DESCRIPTION OF INDIVIDUAL CONTROL TECHNIQUES . 19 3.1 Field-Oriented Control (FOC) . 19 3.2 Direct Torque Control (DTC) . 24 3.3 Sliding Mode Observer . 28 3.4 Startup . 33 4 PROPOSED HYBRID CONTROL . 35 4.1 Hybrid Controller . 35 4.2 Matlab/Simulink . 36 5 RESULTS AND ANALYSIS . 42 5.1 Motor Model . 42 5.2 Optimization of Control Parameters via Exhaustive Search . 43 iii 5.3 Control Tuning . 45 5.4 Speed Response . 55 5.5 Noise Sensitivity . 56 5.6 Parameter Uncertainty . 58 5.7 Speed Profiles . 62 5.8 Load Response . 64 6 HARDWARE IMPLEMENTATION . 68 6.1 Experimental Setup . 70 6.2 Speed Results . 72 6.3 Power Results . 81 7 CONCLUSIONS AND FUTURE WORK . 84 7.1 Conclusions . 84 7.2 Future Work . 86 REFERENCES . 88 iv LIST OF TABLES 1.1 Various control schemes for brushless DC motors. 3 1.2 Various observers for rotor position estimation. 5 2.1 Six-step commutation control signals. 12 3.1 DTC Look-Up Table. 28 5.1 Parameters of the Bull Running BR2804-1700kV motor. 42 5.2 Values used for parameter search. 46 5.3 Results from varying the hybridization threshold. 46 5.4 Results from varying the DTC proportional gain. 48 5.5 Results from varying the DTC integral gain. 50 5.6 Results from varying the FOC proportional gain. 50 5.7 Results from varying the FOC integral gain. 52 5.8 Results from varying the Hysteresis Band. 53 5.9 The parameters that yielded the smallest value for the chosen cost function. 54 6.1 Mean-Square Error results from hardware trials. 80 6.2 Average motor speeds. 81 6.3 Current consumptions. 82 6.4 Average current consumption during experiments. 83 v LIST OF FIGURES 2.1 Four-pole motor diagram. 11 2.2 Brushless electrical motor diagram, showing the inverter and the equivalent circuit of the motor. 13 2.3 Trapezoidal and sinusoidal Back-EMF waveforms. 15 3.1 FOC flow diagram. 20 3.2 In Clarke’s Forward Transformation, three-phase (abc) current vectors are transformed into an alternate (ab) frame of reference. 22 3.3 In Park’s Forward Transformation, the rotating the ab frame of reference is transformed into the dq system by qe radians. 23 3.4 Space-vector diagram depicting a rotor position and control vectors that increase or decrease flux and torque. 27 4.1 Proposed hybrid controller. 36 4.2 System-level block diagram of the simulated system. 37 4.3 Motor model diagram utilizing input voltages to determine motor dynamics. 38 4.4 Block diagram of the proposed controller. 38 4.5 Block diagram of the SMO. 39 4.6 Block diagram of FOC. 39 4.7 Block diagram of DTC. 40 4.8 Diagram of the hybridization block. 41 5.1 The Bull Running motor. 43 5.2 Speed response when varying the hybridization threshold. 47 5.3 Speed response when varying the DTC proportional gain. 48 5.4 Speed response when varying the integral gain. 49 5.5 Speed response when varying the proportional gain. 51 5.6 Speed response when varying the integral gain. 52 5.7 Speed response when varying the hysteresis band. 53 vi 5.8 Speed response of the hybrid controller verified against FOC and DTC approaches. 55 5.9 Speed response for various voltage noise levels. 58 5.10 Speed response for various current noise levels. 59 5.11 Worst case noise sensitivity with standard deviations for voltage and current at 2V and 2A. 60 5.12 Results from inductance sensitivity testing. Inductance was changed from -10% to +20% of the actual value. 61 5.13 Results from resistance sensitivity testing. Resistance was changed from -10% to +20% of the actual value. 62 5.14 Results from step response test. 63 5.15 Results from ramp response test. 64 5.16 Maximum speeds attainable by no-load and propeller-loaded control. 66 5.17 Minimum speeds attainable by no-load and propeller-loaded control. 67 6.1 TI LAUNCHXL-F28027 development board. 69 6.2 TI BOOSTXL-DRV8305EVM development board. ..