New torque-speed balance method to determine road load of electric two-wheeler and development of hardware-in-the-loop simulator for its driving performance testing on motor dynamometer

학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 2. 김민수.In this study, the new method to determine road load of electric two-wheelers was developed and the dynamic simulation, hardware in the loop simulation (HILS) to evaluate the drive performance on motor dynamometer was conducted and the applicability of this simulation method was analyzed. First, we developed a new method to determine the road load occurring in a road drive, different from the coastdown test generally applied to vehicles. In our proposed method, the correlation between the speed and the road load is derived from fitting the motors current consumption and speed while driving at constant speed on a uniform horizontal road. Because the inertial resistance is almost negligible while the vehicle drives at constant speed on a uniform horizontal road, the output of the engine or drive electric motor is the same as the running resistance. The output torque of drive motor of electric two-wheeler is proportional to current consumption and this linear coefficient is expressed by kt, torque constant. So the running resistance of electric two-wheeler driving at constant speed on a uniform horizontal road can be determined by measuring the current consumption of electric two-wheelers drive motor and calculating the drive motors output torque. The correlation between the output torque and the current consumption was derived from the motor characteristic test on a motor dynamometer. And during the motor characteristic test and the real road tests the temperature of motors windings was monitored so that the effects of the thermal equilibrium, saturation to the performance characteristics were evaluated. The difference between the road load which were derived in the case of the saturation state and non-saturation state respectively were 0.2 Nm. And the difference between the road load which were derived in the case of the non-saturation state and coastdown test was 1.0 Nm. If the new method is applied for determination of the road load, the road load can be determined through the new method though the coastdown test is not available for the regenerative braking when coasting. Also it was ensured from the road tests that the new method needed driving tracks shorter than that in the coastdown tests. Second, we conducted HILS on a motor dynamometer by including real hardware to simulate the e-bikes field drive test, through which we verified the applicability of our new method. In order to apply the road load the test motor on motor dynamometer, the load machines are necessary for the dynamic simulations and the powder brake and servo motor were used for load machine on the separate test bed. On the motor dynamometer equipped with the powder brake, after the road load was calculated from the correlation between the speed and the road load obtained from the coastdown tests, the rodad load was applied to test motor through the powder brake by setting the above road load as the set value of the PI controller and comparing and compensating the set value and the present value. Because the powder brake can impose a passive load, it cannot operate at speed control mode. So the powder brake operated at torque control mode during the dynamic simulation. Unlike the powder brake, the servo motor can operate both at speed control mode and torque control mode, so the servo motor can impose a passive load as well as an active load. While the servo motor applied the road load to the test motor at speed control mode, the simulation was sequentially progressed calculating the dynamic equation based on the torque and rotational speed measured from the sensor and the loop time. The powder brake and the servo motor included in the motor dynamometer simulated the road load derived from our proposed method and the coastdown test. If the dynamic simulation conducted in this study is applied for pre-evaluation of the drive module consisting of the motor, MCU, and battery, time, cost, and human resources necessary for the real road test being installed on the complete vehicles will be considerably reduced.Chapter 1. Introduction 1 1.1 Background of the study 1 1.2 Literature survey 11 1.2.1 Test method to determine road load 12 1.2.2 HILS of vehicle drive performance 13 1.3 Objective and scope of the study 15 Chapter 2. New torque-speed balance method to determine road load 18 2.1 Introduction 18 2.2 Dynamic equation in EV while driving 22 2.3 Motor characteristic test on motor dynamometer 25 2.3.1 Experimental setup 27 2.3.2 Test results 32 2.3.3 Correlation of current consumption and motors output torque 36 2.4 Field test 39 2.4.1 Coastdown test 43 2.4.2 New method under constant speed condition 46 2.5 Comparison of the test results between the coastdown test and new method 50 2.6 Summary 56 Chapter 3. HILS under torque control mode on motor dynamometer combined with the powder brake 58 3.1 Introduction 58 3.2 Experimental setup 59 3.2.1 Test setup for field test 59 3.2.2 Dynamic simulator 66 3.2.3 Calibration of the measurements from motor dynamometer test and field test 66 3.3 Coastdown test 69 3.4 Dynamic simualtion 73 3.5 Starting characteristics of the e-bike in the dynamic simulation 77 3.6 Comparative analysis of simulation and field test 82 3.7 Summary 95 Chapter 4. HILS under speed control mode on motor dynamometer combined with the servo motor 96 4.1 Introduction 96 4.2 Experimental setup 101 4.2.1 Test setup for field test 101 4.2.2 Dynamic simulator 104 4.3 Field test 105 4.3.1 Coastdown test 105 4.3.2 Acceleratin test 109 4.4 Dynamic simualtion 109 4.4.1 Simulation process 109 4.4.2 Coastdown simulation 116 4.4.3 Acceleration simulation 120 4.5 Energy efficiency evaluation on motor dynamometer 125 4.5.1 Effect of the weight 126 4.5.2 Effect of the aerodynamic resistance 128 4.6 Summary 130 Chapter 5. Conclusion 132 References 135 Abstract (in Korean) 143Docto

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학위논문(석사)--서울대학교 대학원 :기계항공공학부,2004.Maste