As BDS is very similar in signal structure and frequencies to GPS, the observation models and satellite force models for GPS can be utilized directly for BDS with very slight modifications. Therefore, observable models and processing parameters are similar to the operational ZTD estimation at the German Research Center for Geosciences (GFZ) listed in Table 1.Table 1.Summary of observation models for ZTD estimation.It should be mentioned that Phase Center Offset (PCO) and Phase Center Variation (PCV) of neither satellites nor receivers are available now. Satellite attitude control mode is also not yet announced. The differences in PCO a
Advanced driver assistance systems (ADAS) are gaining more and more attention as a key technology to increase driver comfort and safety.

This is a wide research area that includes adaptive cruise control [1], navigation [2], and perception of vehicles [3], pedestrians [4] or traffic signs [5]. A common feature of ADAS is using cameras [6,7] and other sensors [8] to improve driver awareness. Furthermore, drive-by-wire systems [9] allow to implement haptic human/machine interfaces like actuated steering wheels [10,11]. Vehicles with one or more trailers, such as trucks or multi-body combinations for goods and passengers, can also benefit from ADAS because their maneuvering is complex even for skilled drivers [12,13].The position of hitches is relevant when pushing or pulling trailers [14]: A trailer hitch is ��on-axle�� if it lies on the preceding unit’s rear axle, and is ��off-axle�� otherwise. For example, most caravans have a passive off-axle hitch.

Furthermore, combinations of passive on- and off-axle trailers are frequent in vehicles such as airport luggage carriers and tourist road trains, whose wagons are usually made up of a front off-axle trailer and a rear on-axle trailer (see Figure 1).Figure 1.Examples of multi-trailer systems: Baggage carriers in an airport (left) and a tourist road train (right).In forward motion, the driver has to steer carefully in order to avoid inter-unit collisions [15]. Backwards, jackknife avoidance is a benchmark nonlinear control problem that has been approached with feedback linearization [16], fuzzy control [17,18], or switching control [19]. However, many of these theoretical approaches Brefeldin_A are difficult to implement and to tune [20,21] so practical solutions are necessary [22,23].

In this sense, driver assistance is a significant practical application [12], especially because unaided reverse driving with multiple passive trailers becomes utterly difficult, if not impossible.Haptic handwheels are an effective interface for steering assistance [10]. Thus, motorized steering-wheels have been employed as a warning mechanism for lane departure [24] and road obstacles [25].