# Adaptive Cruise Control in Electric Vehicles with Field-Oriented Control
## 2 Adaptive Cruise Control  
Cruise control allows driving at a constant set speed value without the need to keep the acceleration pedal pushed. This provides more comfort for the driver and ensures safe operation. The classic variant of cruise control endures only speed control, and an updated version is adaptive cruise control [6; 8; 10]. In the last decades advanced variants of cruise control were implemented based on the front radar. Advanced Driver Assistance Systems, known as ADAS in the literature, provide various technologies for driving assistance. One of the main technologies in the ADAS group is an adaptive cruise control system, having the ability to accelerate so that the vehicle speed is kept as the set value, but using a distance sensor, it is possible to detect if there is another vehicle in front, so a lower constant speed is set to ensure a safe distance between the vehicles [8; 11]. Advances in radar application and intelligent control systems have allowed the development of several other variants of cruise control. For classic vehicles, a cruise control system can ensure economical driving, but that is not really the purpose; it is more a driving safety and comfort option. Electric vehicles, on the other hand, still must handle the range anxiety problem, and some studies have shown that efficient driving can still extend the vehicle range. Therefore, many advanced cruise control variants were developed, such as efficient cruise control, predictive cruise control, optimized cruise control, and other variants in which, besides safe driving distance, the traffic signal status is also considered to predict braking [5; 6; 7; 8; 9]. Adaptive cruise control has two control loops: one is the classic speed control, such as in cruise control; the control block keeps the vehicle running at the set speed value. The second control loop is a distance control, which involves scanning the road and in case there is another vehicle ahead, the set speed is adjusted to keep a safe distance between the host vehicle and the detected leading vehicle. To detect leading vehicles and obstacles on the road, adaptive cruise control requires radar or laser sensors to scan the road [8; 11; 13; 30; 31]. When there is no vehicle or obstacle in front of the host vehicle, adaptive cruise control works only in the speed mode, while in classic cruise control, the vehicle is running with the driver's set speed value [11; 13; 30; 31]. When a leading car is detected, the inter-vehicle distance is determined and compared with the safe distance value. If the inter-vehicle distance is higher than the safe distance value that the host vehicle is running at the set speed value, the adaptive cruise control system works in the speed mode. If the intervehicle distance is lower than the safe distance value, than the host vehicle speed is adjusted to ensure a safe distance between the vehicles, so the adaptive cruise control works in the safe distance mode [8; 11; 13; 30; 31]. Figure 1 illustrates the two modes of operation of an ACC system. The inter-vehicle relative distance is determined based on the initial distance between the two vehicles (\(\mathrm{d_{o}}\)), the velocity of the host car (\(\mathrm{v_{host}}\)), and a time constant (\(\mathrm{t_{safe}}\)) that ensures a safe time for the driver safe brake reaction. The inter-vehicle safe distance is obtained using Equation (1), as follows:  
\[\mathrm{d_{safe}}=\mathrm{d_{o}}+\mathrm{\ t_{safe}}\cdot\mathrm{v_{host}} \tag{1}\]  
Regardless of the operating mode, the ACC system should provide the corresponding acceleration to ensure the desired velocity or the safe distance. For ICE vehicles, the commands from ACC are applied to the throttle control block. Based on the acceleration value from the ACC block and the throttle position sensor, the throttle valve is controlled based on the acceleration from the ACC block and the feedback from the throttle position sensor. Figure 2 presents a block diagram of an ACC system in the case of an ICE vehicle.