Summary: A methodology for selecting the basic functional parameters of an electric car is presented, including such procedural elements as: defining functional assumptions, determining the values of the motion model parameters, selecting and determining the parameters of representative traffic conditions, determining traction characteristics at the drive wheels, theoretical test runs, developing a mathematical model, and simulation studies. The presented methodology is illustrated with sample calculation results performed as part of the ECO-Mobility project. The required values obtained for maximum power and force, as well as battery energy, are presented.1. INTRODUCTION
Work on the development of an electric car drive is part of the ECO-Mobility project funded by the European Union. The most important functional assumptions of the car focus on the fact that it is to be a four-seater city car cooperating with the P&R (Park & Ride) system, also enabling its use by disabled persons. These functions affect the basic parameters of the vehicle, which were established as follows: maximum speed 60 km/h, maximum acceleration 1.5 m/s, range without battery charging 100 km, body weight 500 kg.
It is initially estimated that the total maximum gross weight of the car (when occupied by four passengers and luggage), taking into account the estimated weight of the drive system (including the weight of batteries 290 kg, motor, converter, transmission shafts, and driven wheels), will be approx. 1300 kg.
The electric car drive system includes four basic drive devices: a reduction gear (in the case of using a high-speed motor), an electric motor, a power electronic converter, and a battery.
The operating condition limitations of each of these devices are characterized by different permissible parameters. The result of these limitations is the permissible ranges of vehicle force and speed at the wheels, describing the so-called permissible traction characteristics of the car. It is assumed that the parameters of these characteristics, such as maximum power, maximum tractive force, and maximum speed, are the basic functional parameters of the vehicle drive system. The methodology for their determination, presented for example in work [1], assumes solving the equations of the vehicle’s mathematical model for specific traffic conditions. (…)
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Source: Logistyka Magazine