Characteristics and Control of the Motor System in E-bikes

Abstract: This study is based on e-bikes, mainly the ‘Pedelecs’ (under Swedish standards). Pedelecs' is the category of e-bikes which indicates electric bicycles only, that has specific standard in terms of motor power and speed limitations. We are concerned with respect to Sweden, in the analysis, especially because though it is already defined by EU for Europeans, it still varies in some countries, within Europe itself. In this research and experiment, we have brought useful revelations about its features in terms of power, comfort and cost. Likewise, our efforts have been to test its reliability on technical grounds, geographical conditions, people’s awareness and interests. Similarly, on effective grounds, ratio of bike users, import conditions, its growth and declines trends, and other influencing factors have been analyzed to understand e-bike’s possibilities in Sweden. To highlights e-bike’s features and importance, we have done a thorough investigation, taking comparative analysis with ordinary bicycles and normal vehicles, by using common elements like cost effectiveness, power efficiency, leisure service, easy accessibility, environment effects and so on. The findings have proven e-bikes to be the most effective solution on various grounds than any other transport alternatives especially in short distance and inner city traveling. In theoretical details on e-bikes, we have introduced details about the components applicable in e-bike, how they operate, their importance in terms of effectiveness with respect to power consumption and energy dispatching (motor capacity), quality of performance (types of components and features) and other comparative technical aspects. To understand the ground reality better, a short survey have been conducted to give some understanding about the awareness people are having regarding e-bike, their remarks towards this product, and based on their conclusions, our predictions report on its development and popularity chances in Sweden. While analyzing facts in general, we discovered that pedelecs for US may not be pedelecs for Sweden, because of standard varies from country to country. According to European classification standard, a pedelec must have the motor capacity up to 250 W, and must stop the motor when the speed is above 25 km/h. Speaking about the popularity of e-bike, In China the number of e-bikes sold reached up to 200 million, Germany is leading the way in Europe, therefore by the favorable situations available in Sweden, we can predict high potential in Sweden. The statistics data proved that Sweden is a bicycle country, where the amount of bicycles sold in 2012 was around 525,000, among which 6,500 were e-bikes imported the same year, suggesting its potential of growth being real. While analyzing mathematically e-bike’s functions, the four different calculations have been analyzed, keeping the weight of the person constant, but varying other common parameters that in use, in order to personify the drag in equation. By doing so taking the average power we have observed that it requires around 157 watts going up the hill when gradient is 4%, at the speed around 10 Km/h. This result have been again tried to be verified in the experimental works as well. Based on these relevant information, in the experiment we have tested to find how much energy is dissipated in 2 minutes, taking six samples to authenticate our result. After not being successful taking angle measurements by riding outside or inside lab, it is achieved to some degree after applying it on running machine in gym with some complications. The result that have been achieved signifying that the voltage of the battery dropped to 37.8V, which in the beginning of the experiment have been recorded 40.8V when current applied have been around 4.8A. Angle measurement here precisely indicating the behavior of e-bike on various degrees of hillsides, because there comes the angle, which is formed in relation to the plane surface. When e-bike goes uphill it creates a positive angle, that is where we have our main concern, because then the difference in power consumption suddenly increases. The angle is also form when e-bike moves downhill but that is a negative angle, and cost no difference on power consumption, therefore we are giving emphasis on angle measurements to positive ones only. The battery that has been used in the experiment rated 36V/9Ah (i.e., 0.324 kWh). Using this battery we have got the reading that it can hold (when completely charged) up to 32 Km distance (or 10 Wh/km), which is inversely proportional'' to rider’s weight and drag. To sum up the experiment, the results have revealed that battery performance directly depends upon whether condition, weight of the rider and area where the cycle is ridden. These are among the discovered facts found in the experiment. When e-bike is used in hilly areas the speed slows down considerably to 13km/hour, because of the disequilibrium force, and that is when excessive power is consumed. This part has been difficult to test correctly in the lab because to simulate the disequilibrium drag or pull could not be realized accurately, besides when it has been tried outdoor, we could not get stable running motor because of the pedal dependent motor system, it has also not been so fruitful for precise readings. Afterwards when it has been tried in the gym, the outcome is that at every angle the power consumed by the battery or the energy dissipated is around 3.7watt. Even then it is still not possible to calculate measurements that must be available in real like situations, because the other affected parameters like wind, friction, tire size, weather, rider’s weight is not possible to take into considerations. ___________ 'Pedelec is the abbreviation form of "Pedal Electric Bicycle". The characteristics of Pedelec is to assist human input power rather than replacing it completely. ''It is obvious that when the weight of the rider is heavy then it takes more power to draw him ahead, which directly indicates that the consumption of power rises, which again means that e-bike’s total covering distance is simultaneously reduced. This is also true when there is a drag, which stops e-bike’s natural flow on normal conditions. That again means it needs additional power to run, therefore when these factors rise, the efficiency of power subsequently declines, accordingly the total coverage distance of an e-bike.