# A Rapid Verification System for Automatic Emergency Braking Control Algorithm of Passenger Car
## 5 Discussion  
Based on the proposed verification system, an AEB hierarchical control algorithm was tested. Under the test conditions of CCRs, CCRm, and CCRb, the AEB hierarchical control algorithm can keep the relative distance between the VUT and the VT within a safe range, successfully avoiding vehicle collisions, which proves the effectiveness of the algorithm. However, when the AEB braking of the VUT ends, the relative distance between the VUT and the VT is large, which indicates that the AEB hierarchical control algorithm can be further optimized to avoid AEB triggering prematurely. The SIL testing results of the AEB hierarchical control algorithm are similar to the HIL testing results, but the specific values are different. The acceleration establishment time is defined as the time when the VUT reaches the target deceleration minus the time when the braking level is switched. The delay time is defined as the HIL acceleration establishment time minus the SIL acceleration establishment time. As shown in Figures 10-12, under each test condition, the AEB braking level of the VUT has been switched four times. The delay time of each braking level switching under the CCRs condition is 0.3 s, 0.3 s, 0.1 s, and \(-0.1\) s. The delay time of each braking level switching under the CCRm condition is 0.2 s, 0.2 s, 0.3 s, and 0.3 s. The delay time of each braking level switching under the CCRb condition is 0.1 s, 0. 0 s, 0.2 s, and 0 s. The average time delay of each braking level switching under three test conditions is 0.16 s. The braking delay of HIL testing is mainly caused by  
Figure 12: HIL testing and SIL testing results of CCRb condition: (**a**) speed of VUT and acceleration of VUT; (**b**) relative speed and relative distance. the characteristics of the pneumatic braking system, including the mechanical action time and the time of establishing and releasing braking pressure. The existence of braking delay will affect vehicle operation and AEB decision-making. The relative distance is an important observation parameter to verify the AEB control algorithm, which can be used to evaluate the anti-collision effect and safety margin. Equation (5) is used to evaluate the relative deviation value of the relative distance:  
\[D_{e}=|d_{rs}-d_{rh}| \tag{5}\]  
where \(D_{e}\) is the relative deviation of the relative distance between SIL testing and HIL testing; \(d_{rs}\) is the relative distance in SIL testing; \(d_{rh}\) is the relative distance in HIL testing. Under CCRs and CCRb conditions, the relative deviation of VUT at rest is 1.2 m and 0.6 m, respectively. Under the CCRm condition, when the speed of VUT is consistent with that of VT, the relative deviation is 3.3 m. The average relative deviation under the three test conditions is only 1.7 m, indicating that the SIL testing result is close to the HIL testing result. However, the control and optimization of relative distance should consider the influence of this factor. When the verification system and test scenarios are established, the time required for SIL testing or HIL testing is defined as a single test time, which is expressed as:  
\[T_{A}=t_{1}+t_{2}+t_{3}+t_{4} \tag{6}\]  
where \(T_{A}\) is the single test time; \(t_{1}\) is the establishment time of the data interface; \(t_{2}\) is the parameter adjustment and compilation time; \(t_{3}\) is the simulation time; \(t_{4}\) is the data collection time. Taking the verification process in Chapter IV as an example, the operations in Equation (6) were repeated 5 times. Typical time values of each stage are shown in Table 6. The data in Table 6 is the sum of the test time of the three test conditions. Table 6 shows that the single test time for SIL testing of the AEB hierarchical control algorithm is 228 s, and the single test time for HIL testing is 319 s. Note that the single test time does not include the time to verify the system construction and debugging.