# AI-For-Mobility--A New Research Platform for AI-Based Control Methods
## 2 Vehicle Architecture
### Suspension Design  
In order to be able to demonstrate vertical dynamics control applications on the AFM, the vehicle is equipped with a semi-active suspension technology. First of all, it allows for addressing safety aspects since the road-holding can be influenced. In addition, it helps to eliminate undesirable effects regarding drive comfort (e.g., kinetosis) by minimizing vehicle body accelerations. Since automated driving functions become more widespread and passengers gain more time for other activities, the demands on driving comfort increase. Overall, semi-active dampers enable adaptation to varying road excitations, reaction to critical driving situations and optimization of both driving safety and comfort (cf. [15]).  
The goal of the suspension conversion was to maintain the same vehicle height as that of the basic vehicle in order to keep the AFM as closely as possible to comparable production vehicles. For this purpose, a damper (including its housing, piston rod, etc.) was completely redesigned and remanufactured (see left-hand side of Figure 3).  
The manufactured dampers were measured on a Roehrig damper test rig. As a result, a two-dimensional characteristic map linking the damper velocity \(v_{d}\) and the current \(i_{d}\) to the damper force \(F_{d}\) was identified (see right-hand side of Figure 3).  
\[F_{d}=f(v_{d},i_{d}) \tag{1}\]  
The top mount bushing possesses a complex characteristic (6D damping, frequency dependence, etc.). In order to investigate the influence of the damper control on the vertical dynamics behavior, as well as to drive the AFM in a more precise and direct way, the standard top mount bushings were replaced by a uniball bearing.  
The damper currents are controlled by an embedded controller unit (ECU). Vertical dynamics control algorithms can be computed in a stand-alone mode either on the ECU or on a Rapid Control Prototyping (RCP) platform. The latter then sends the current demand values to the dampers via the interconnected ECU [16]. The modified suspension system was inspected by an independent technical testing authority resulting in the AFM's approval for public road use even with controlled dampers.  
To investigate the vertical dynamics characteristic of the complete vehicle and to design and evaluate controllers, the AFM's behavior was analyzed on a 4-post test rig (see Figure 4).  
During this process, the vehicle is placed on four hydraulically driven vertical posts, each following its predefined position signals. The posts induce a vertical movement of the vehicle. In this way, driving on precisely defined road profiles (such as, for instance, synthetic profiles according to ISO 8608 [17]) can be simulated in a reproducible manner. Moreover, it is possible to install additional sensors under unvarying conditions of the test rig. Its sensor system allows the measurement of the post position, speed, accelerations and wheel loads. In addition to the test rig sensors, the AFM is equipped with its own vertical dynamics sensors as described in Section 3.3. They enable recording of many important quantities. In several hundred separate experiments with different excitations, more than 50 measured variables were recorded in each case. The measurement data were used,  
Figure 3: The remanufactured dampers for front and rear axle (left-hand side) and the two-dimensional characteristic map of AFM’s dampers.  
among others, to identify and validate the vertical dynamics part of the AFM's high-fidelity vehicle model (cf. Section 4).