전기이륜차의 도로 부하를 구하는 새로운 방법과 모터 다이나모미터에서 주행 성능을 평가하는 시뮬레이터 개발

Abstract

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.