AN ELECTRIC BRAKING SYSTEM CONTROLLER FOR BRUSHLESS DC MOTOR IN ELECTRIC VEHICLE APPLICATION

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1 International Journal of Electrical Engineering & Technology (IJEET) Volume 8, Issue 4, July-August 2017, pp , Article ID: IJEET_08_04_006 Available online at ISSN Print: and ISSN Online: Journal Impact Factor (2016): (Calculated by GISI) IAEME Publication AN ELECTRIC BRAKING SYSTEM CONTROLLER FOR BRUSHLESS DC MOTOR IN ELECTRIC VEHICLE APPLICATION Gaurav A. Chandak Department of Electrical Engineering, Government College of Engineering Aurangabad, India A. A. Bhole Department of Electrical Engineering, Government College of Engineering Aurangabad, India ABSTRACT In the world today, cities are getting more crowded with private mobilities and growing number of passenger vehicles because of which pollution index of cities is continuously increasing. Cities pollution levels are reaching to alarming rate giving rise to global warming. This can be avoided with the use of Electric Vehicle as it is pollution free and noiseless solution giving a same performance as like conventional gasoline powered vehicles. Nowadays electric vehicles are gradually coming on the roads in which a safety is very important parameter. The safety of passengers and driver is dependent on a braking operation. In this paper, brushless dc motor is used for motoring electric vehicle. This motor has various advantages like, high torque to weight ratio, constant torque and wide speed range. The designed controller model takes care of safety by intelligently sensing the speed and driver s requirement about braking through the brake pedal. The results of the proposed method are obtained and verified in MATLAB/ Simulink. Key words: Brushless DC Motor; Electric Vehicle; Hybrid Braking System. Cite this Article: Gaurav A. Chandak and A. A. Bhole. An Electric Braking System Controller for Brushless DC Motor in Electric Vehicle Application. International Journal of Electrical Engineering & Technology, 8(4), 2017, pp INTRODUCTION Nowadays the electric vehicles are coming in market with different types of braking pattern and strategy. For safety and to stop the vehicle Braking is very important. Usually, there are three types of braking observed in a vehicle they are, pure frictional braking, Hybrid braking system and Fully Electrical Braking system. In conventional braking system, braking is achieved by converting kinetic energy of vehicles into heat by friction between wheel and mechanical brakes. Fig 1 shows conventional pure frictional braking system [1]. With the 48 editor@iaeme.com

2 Gaurav A. Chandak and A. A. Bhole advent of technology hydraulic braking is used however, it also works on the same principle of frictional braking. Because of such braking operation energy is wasted in the form of heat as well as wear and tear of wheels also happen [2]. Electronic hydraulic braking system with antilock braking is also incorporated to use in emergency for fast and quick braking operation to avoid accident and to improve safety [3]-[4]. In electric vehicles, electric motor is used to propel drive train hence it produces an opportunity of electric braking to stop vehicle. The conjunction of mechanical braking and electric braking mostly opted in electric vehicle which is called as Hybrid braking system. While study is being done on fully electrified braking system [5]. Figure 1 Conventional pure frictional braking system. Among various motor available Brushless DC motor seems to be a viable option for electric vehicle. It gives constant torque, wide speed range, high torque to weight ratio and noiseless operation. Brushless DC motor is nothing but a permanent magnet synchronous motor with trapezoidal back EMF. The position of rotor is determined by hall sensors which are kept electric apart. Three phase inverter supply the power to BLDC motor with proper switching [6]. Normally, Electric vehicle is designed keeping in mind complex road condition to achieve the highest degree of safety [7]. However, safety is achieved, but cost of the vehicle increases because of sensors and complex structure of controller. Various controllers used are sliding mode controller, adaptive controller, neural network control, iterative learning control, Hybrid fuzzy PI and Neuro-fuzzy and PID control etc [8]-[13]. From the controller viewpoint, in this model combination of logical unit and PI controller tries to give smooth results. The controller unit performs logical operations while PI controller gives high steady state response. This paper first discusses structure and operation of proposed braking system later braking strategy and control algorithm with controller design is explained and logical equations are also represented. Results and analysis are written in the fourth section while at last, conclusion is stated. 2. STRUCTURE AND OPERATING MODE OF THE PRAPOSED SYSTEM The block diagram of the proposed system is shown in the Fig. 2. It consists of Brushless DC Motor, Inverter, battery unit, interpreter and control unit. Brushless dc motor hall sensors sense the rotor position and through decoder gives the signal to control unit. The inverter is supplied by the DC voltage through battery unit and controlled via gate input signal. Sensors used at brake pedal gives brake pedal angle which acts as an input to control unit. Controller obtains the motoring command by motoring signal and accordingly passes it to the error unit 49 editor@iaeme.com

3 An Electric Braking System Controller for Brushless DC Motor in Electric Vehicle Application to PI controller. According to the driver s requirement input signal changes and controller ultimately decides whether motoring mode or braking mode to perform. Figure 2 (a) Block diagram of a Proposed system (b) Three Phase BLDC Motor Model 2.1. Motoring Mode Every vehicle has at least two foot-pedals out of which one is for motoring or acceleration of the vehicle. In this mode, according to the acceleration of pedal or throttle, the motoring signal will be fed to control unit through interpreter. Depending on the input controller will pass control signals to gate driver and to PI controller. Furthermore, the battery will supply required power to the brushless dc motor through inverter Braking Mode In this mode, controller plays very important role of deciding braking mode of operation, which should be applied to the vehicle. As in this system model, vehicle is totally dependent on electric brake, hence braking force strength varies in various cases. The controller selects braking force value according to the degree of rotation of brake pedal at braking instant. Here for simplicity, it is assumed that brake pedal can rotate from 0 to Limitations of Braking Braking Torque and Motor speed are inversely proportional to each other. If the motor speed is high then braking torque applied should be low and vice versa. It is mainly because, if at high-speed high braking torque is applied then vehicle might turn toward one side and safety may come to risk. In the proposed system, designed controller takes care of such inverse relation of speed and brake torque [1]-[2]. 3. BRAKING SYSTEM AND CONTROL ALGORITHM One complete cycle of operation is of which is divided into six intervals. Each interval consists of 60 0 of operation. Hall sensor input is decided by rotor position. The South Pole of rotor s permanent magnet gives 0 whereas the North Pole gives 1. Table I shows the input values obtained from the hall sensors in six different intervals. Based on that, control unit decides switching states for motoring operation. Brushless dc motor obtains supply from inverter as shown in fig. 3. The inverter is fed by battery denoted by V batt [14]. Table 1 shows the control logic for motoring operation. According to the hall sensors input in each 60 0 two switches of inverter conduct. One switch is from upper arm and another from lower arm of the inverter, each switch conduct for editor@iaeme.com

4 Gaurav A. Chandak and A. A. Bhole Table 1 Main States of Control Signal for Motoring Operation Interval H1 H2 H3 Q1 Q2 Q3 Q4 Q5 Q6 I II III IV V VI Operation of Controller In the proposed model two braking situations are considered one is normal mode and other is braking in emergency, where fast braking is required and speed and braking torque relation are not considered utterly. In which mode, the system should operate is decided by controller. This decision is taken based on brake pedal input obtained from the driver and control logic in controller. Table II shows the control logic for braking operation in normal mode. Table 2 Main States of Control Signal for Braking Operation Interval H1 H2 H3 Q1 Q2 Q3 Q4 Q5 Q6 I II III IV V VI Based on brake pedal angle which is decoded from the brake pedal input obtained from driver requirement, controller opts braking operation in Normal mode or in Emergency mode. Normal mode: when vehicle is running at any speed and brake pedal moves in between 5 0 to 40 0 it comes in normal mode. Emergency Mode: If brake pedal rotates in between 40 0 to 60 0 then Emergency brake command will be given by controller. Proportional Integral Control (PI): PI controller is mainly used to achieve fast steady state in both motoring and braking operation. During Emergency braking controller gives Emergency brake signal as output which acts as an input to PI controller. In real life, sometimes during braking operation accelerating throttle and braking pedal both are raised and pressed at the same time due to psychological and emotional human behaviour. This creates ambiguous situation due to which safety of passengers and driver comes to risk. This risk gets eliminated by the proposed system controller as the same controller acts as a motoring and braking controller which ultimately enhanced the safety of vehicles. In this, out of two inputs of braking and motoring, only one input is processed for further operation. Furthermore, for safety braking has given more importance than motoring. This is because if both motoring and braking pedal are pressed at the same time then controller will prefer braking instead of motoring editor@iaeme.com

5 An Electric Braking System Controller for Brushless DC Motor in Electric Vehicle Application 3.2. Motoring and Braking Signal Brake Pedal Angle: Depending upon the situation the driver will push brake pedal. According to the movement of brake pedal between various states as shown in Table III Braking signal is decoded by interpreter in the language comprehensible to the controller. For simplicity, here it is assumed that brake pedal moves from 0 0 to 60 0 during braking condition. Speed: Considering standard driving cycle, first the relation between motor speed and speed on the dial of vehicle is formed. The vehicle is running from slowest 1 Km/hr to highest 180 km/hr speed. Interpreter decodes speed input from Km/hr unit to revolution per minute. This signal is then passed to the controller Controller Design The designed controller takes six inputs and gives seven outputs. Figure 3 (a) The Controller Block (b) The Controller Circuit Fig. 3 (a) and Fig. 3 (b) shows the controller block and controller circuit. As shown in the controller circuit three hall sensor signal and their compliment are given to AND logical operator. Equations are realized using logical operator in Simulink. The AND logical operator gives high and low values which are compared by relational operator. Three phase inverter used in proposed system has three arms in which each arm has upper leg and lower leg. High values obtained from relational operator are passed to upper leg switches like Q1, Q3, Q5 and low values gained from relational operator are delivered to lower leg switches like Q2, Q4 and Q6. For braking operation brake pedal input signal is processed. As shown in fig. 3 (a) and Fig. 3 (b) the brake pedal signal is given to Logical unit. Depending on the decision taken by controller according to given input values braking modes are decided. In normal mode, the Logical unit gives L1 signal which is passed to AND logical operator and then given to upper leg of three arm of inverter which ultimately stops motor. In case of emergency mode, Logical unit passes H1 output signal to PI controller. PI controller operates in such a way that motor stops instantly. In the proposed system, for electric braking of brushless dc motor dynamic braking and plugging is utilized. During Normal mode braking, dynamic braking is realized by using three AND logical operator and controller response. Dynamic brake here slows down the motor by the principle of residual magnetic flux. For emergency braking plugging is used, it is mainly because of requirement of fast braking. In plugging energy is wasted and hence only during emergency condition when 52 editor@iaeme.com

6 Gaurav A. Chandak and A. A. Bhole safety is on priority that time it is used. Energy lost in plugging is less than that of energy wasted in pure frictional braking system. 4. RESULTS AND ANALYSIS In this simulation results, simulation has run for 1 sec duration. It is assumed that for 0.6 sec motor runs in motoring mode and braking signal is applied at 0.6 sec. Following results shows the different time taken for braking in different modes of braking operation Braking Force Relation Normal and Emergency Brake Mode at High Speed Whenever the vehicle is at high Speed, the kinetic energy of the vehicle will be more as the kinetic energy of vehicle is directly proportional to the square of speed. If driver wants to apply brake at such instance then extra energy will be required to oppose the force of kinetic energy. Fig. 4 (a) shows the curve L1 for braking in normal Brake mode. The curve shows that motor stops at 0.76 sec, hence the time taken for motor to halt from 3000 rpm to zero is 0.16 sec. The motor comes to rest gradually. As in normal Brake mode reverse relation of motoring speed and braking torque is maintained so whenever the speed of motor is high in the range of 1500 rpm to 3000 rpm and there is no emergency to stop motor instantly, then this normal brake mode should be used. Fig 4 (b) shows curve H1 for emergency braking operation. In H1 curve motor stops at 0.66 sec, so braking time is 0.06 second. Figure 4 Stator current at High Speed (a) Normal Brake Mode (b) Emergency Brake Mode If we do comparison of curve L1 and H1, then normal mode brake L1 is constant brake while curve H1 stops the motor instantly. In an emergency, motor speed must drop quickly. In curve H1, in just sec motor speed drop from 3000 rpm to 500 rpm. In next seconds motor gradually comes to zero 4.2. Braking Force Relation in Normal and Emergency Brake Mode at Low Speed Normally people drive at middle speed, here it is considered that middle speed and low speed are same for ease of analysis. When the brake is applied at the speed of 60 to 70 Km/Hr that is 1300 rpm to less than 1500 rpm of motor, kinetic energy possessed by the vehicle would be surely less compared to high speed, Hence the vehicle will stop faster and skidding could be avoided. Fig. 5 (a) Shows the graph of braking curve in Normal mode at slow speed. The curve shows that motor stops linearly and finally come to rest at 0.69 sec. Fig 5 (b) Shows the braking curve in emergency mode at slow speed in which the motor stops at 0.65 sec so the required braking time is 0.05 sec editor@iaeme.com

7 An Electric Braking System Controller for Brushless DC Motor in Electric Vehicle Application Figure 5 Stator current at Low Speed (a) at Normal Brake Mode (b) Emergency Brake Mode 4.3. Current, EMF and Electromagnetic Torque Curve for Normal Brake Mode Fig. 6 (a) illustrate the graph of stator current and electromotive force in normal mode braking operation. After applying the brake at 0.6 sec stator current suddenly comes to zero and does not allow motor to rotate further. While electromotive force does not come to rest instantly. After almost 1.6 sec electromotive force becomes 0. The electromagnetic torque depends on the back EMF and stator current. Fig. 6 (b) shows the electromagnetic torque curve. The brushless dc motor gives constant torque irrespective of speed variation. Because of this, it becomes viable option to use in electric vehicle. Figure 6 (a) Stator Current I a and Electromotive Force in Normal Brake Mode (b) Electromagnetic Torque Curve in Normal Brake Mode 4.4. Current, EMF and Electromagnetic Torque curve for Emergency Brake Mode In emergency braking mode, for faster braking plugging is used. Fig. 7 (a) demonstrate the graph of stator current and electromotive force in Emergency braking mode operation. For 0.2 second reverse current flows through motor which forces motor to stop. After applying the brake at 0.6 sec stator current instantly comes to zero and does not allow motor to rotate further. While electromotive force comes to rest instantly after seconds. In brushless dc motor torque is directly proportional to current hence with reverse current reverse electromagnetic torque is applied to the motor. In this model, almost 15 Nm negative torque is applied for seconds. Fig. 7 (b) shows the electromagnetic torque curve for emergency brake mode editor@iaeme.com

8 Gaurav A. Chandak and A. A. Bhole Figure 7 (a) Stator Current I a and Electromotive Force (b) Electromagnetic Torque Curve at Emergency Brake Mode 5. CONCLUSIONS In this paper, an electrified braking system for an Electric vehicle has been proposed. The controller is designed with consideration of normal and emergency braking situation in real life. The logical unit used in controller make braking system simple and cost effective. Furthermore, PI controller provides fast steady state which results in enhancement in safety of vehicle. With the help of MATLAB/Simulink obtained results are presented and compared. The proposed system has the potential to brake in various speed range considering inverse relation of speed and braking force. In addition, the approach of controller to stop motor in normal and emergency gives vehicles good accuracy and control. In the future, there is a scope to design a hybrid braking system considering the objective of regenerative braking in conjunction with proposed braking system. REFERENCES [1] Ming-Ji Yang, Hong-Lin Jhou, Bin-Yen Ma, and Kuo-Kai Shyu, Member, IEEE, "A Cost- Effective Method of Electric Brake with Energy Regeneration for Electric Vehicles", IEEE Transactions on Industrial Electronics, vol. 56, no. 6, June 2009 [2] Xiaohong Nian, Fei Peng, and Hang Zhang, Regenerative Braking System of Electric Vehicle Driven by Brushless DC Motor IEEE Transactions on Industrial Electronics, vol. 61, no. 10, October 2014 [3] S. M. Reza Tousi, S. Omid Golpayegani, Ehsan Sharifian Anti-Lock Regenerative Braking Torque Control Strategy for Electric Vehicle, Industrial Technology (ICIT), 2016 IEEE International Conference on, March 2016 [4] A. Dadashnialehi, A. Bab-Hadiashar, Z. Cao, and A. Kapoor, Intelligent sensorless ABS for in-wheel electric vehicles, IEEE Trans. Industrial Electronics vol. 61, no. 4, pp , Apr [5] Guoqing Xu, Kun Xu, Chunhua Zheng, Xinye Zhang, and Taimoor Zahid, Fully Electrified Regenerative Braking Control for Deep Energy Recovery and Maintaining Safety of Electric Vehicles, IEEE Transactions on Vehicular Technology, Vol. 65, No. 3, March 2016 [6] T. Shi, Y. Cao, G. Jiang, X. Li and C. Xia, "A Torque Control Strategy for Torque Ripple Reduction of Brushless DC Motor With Nonideal Back Electromotive Force," in IEEE Transactions on Industrial Electronics, vol. 64, no. 6, pp , June 2017 [7] C. D. Xu and K. W. E. Cheng, "All-electric intelligent anti-lock braking controller for electric vehicle under complex road condition," 2016 International Symposium on Electrical Engineering (ISEE), Hong Kong, 2016, pp editor@iaeme.com

9 An Electric Braking System Controller for Brushless DC Motor in Electric Vehicle Application [8] Bo Long, Shin Teak Lim, Ji Hyoung Ryu and Kil To Chong January 2014., "Energy Regenerative Braking Control of Electric Vehicles Using Three- Phase Brushless Direct- Current Motors," Energies, vol. 7, pp , [9] V. Oghafy, H. Nikkhajoei and J. S. Zamani, "An adaptive controller for sensorless PM synchronous motor drive for electric vehicles,"ieee Vehicle Power and Propulsion Conference, Dearborn, MI, 2009, pp [10] Farshid Naseri, Ebrahim Farjah,Teymoor Ghanbari An Efficient Regenerative Braking System Based on Battery/Supercapacitor for Electric, Hybrid and Plug-In Hybrid Electric Vehicles with BLDC Motor, IEEE Transactions on Vehicular Technology [11] Z. Yi, X. Li, S. Hexu and D. Yan, "An Optimal Torque Controller Based on Iterative Learning Control for Switched Reluctance Motors for Electric Vehicles," 2010 International Conference on Optoelectronics and Image Processing, Haiko, 2010, pp [12] B. N. Kommula and V. R. Kota, "Performance evaluation of Hybrid Fuzzy PI speed controller for Brushless DC motor for Electric vehicle application," 2015 Conference on Power, Control, Communication and Computational Technologies for Sustainable Growth (PCCCTSG), Kurnool, 2015, pp [13] M. Akhila and P. Ratnan, "Brushless DC motor drive with regenerative braking using adaptive neuro based fuzzy inference system," 2016 International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT), Chennai, 2016, pp [14] A. Mohammad and M. Z. R. Khan, "BLDC motor controller for Regenerative Braking," 2015 International Conference on Electrical Engineering and Information Communication Technology (ICEEICT), Dhaka, 2015, pp. 1-6 [15] Shithin PV, Uma Syamkumar. Four Switch three Phase Brushless DC Motor Drive for Hybrid Vehicles. International Journal of Electrical Engineering & Technology, 5(12), 2014, pp [16] Amged S. El-Wakeel, F.Hassan, A.Kamel, A.Abdel-Hamed. Optimum Tuning of PID Controller for a Permanent Magnet Brushless DC Motor. International Journal of Electrical Engineering & Technology, 4(2), 2013, pp editor@iaeme.com