# An Eco-Driving Controller Based on Intelligent Connected Vehicles for Sustainable Transportation
## 4 Experimental Results and Discussion  
There was a 2-km road section in this experiment. As shown in Figure 7, a platoon consisting of a leading vehicle and two following vehicles was applied in each group of experiments. The change of the spacing between any of two following vehicles can be observed from the top view. In this scenario, we selected road curvature, vehicular velocity, and spacing, which are critical parameters as the inputs of the eco-driving controller. The desired acceleration and the desired front steering angle of each connected vehicle were defined as outputs. Besides, a set of information containing acceleration, velocity, position, fuel consumption, and carbon dioxide emissions were selected as the main indexes. Among them, the acceleration,  
Figure 5: The construction of the co-simulation platform. Figure 6: The ROS nodes of the cooperative car-following system for ICVs. velocity, and position were obtained from the ROS, and the fuel consumption and carbon dioxide emissions were calculated by Equations (2)-(4). In order to verify the effectiveness of the proposed controller, a strategy for the control of a standard MPC was proposed and developed. In addition, we considered the eco-driving constraints in the controller, and the improved MPC strategy was re-developed with the objective of being environmentally sustainable. The working procedure of the improved MPC strategy is shown in Figure 8. In the HIL simulation experiments, the emission coefficient of carbon dioxide was used to value the MOE [30], shown in Table 2. The parameters defined in Equations (2) and (3) in this paper are set up as Table 3.  
The parameters of the eco-driving controller of ICVs are displayed in Table 4, where \(p\) is the prediction horizon, \(c\) is the control horizon, and \(s\) is the control period. The velocity of the vehicle fell in [15, 30] m/s, and the acceleration was set up as [\(-3\), \(3\)] m/s. In addition, the initial states of vehicles are shown in Table 5.  
From Figures 9-12, the velocities and accelerations of vehicle 2 and vehicle 3 were compared with the standard and the improved MPC strategies. The velocity was gradually adjusted to 30 m/s after 30 s, and the accelerations were stable at 0. However, vehicle 2 and vehicle 3 showed their deceleration at the beginning of the standard MPC strategy. When vehicle 1 accelerated, the acceleration of the following vehicle under the improved MPC strategy was very small, which facilitated the convergence rate of the acceleration. Figure 11: The accelerations of the following vehicle under the standard MPC strategy in Scenario 1. Figure 12: The accelerations of the following vehicle under the improved MPC strategy in Scenario 1. Figure 10: The velocities of the following vehicle under the improved MPC strategy in Scenario 1. In the same state of vehicle 1, the fluctuations in the accelerations of the following vehicles occurred under the standard MPC between 10 s and 20 s, which was caused by the acceleration at 10 s. As shown in Figure 12, after vehicle 1 suddenly accelerated, the maximum acceleration of vehicle 2 could be up to 1.7 m/s\({}^{2}\), which reflects the moderate acceleration control of the improved MPC strategy. The accelerations in Figures 11 and 12 reflect that the change rate of acceleration of the standard MPC strategy is greater than that in the improved MPC strategy, which affects the fuel consumption and emissions of the vehicle. In addition, it can be seen from the maximum acceleration in these two figures that the improved MPC strategy was more adaptable to constraints compared to the standard MPC strategy. Figures 13 and 14 compare the movements of vehicle 2 and vehicle 3. The trends show that they were consistent with the movement of vehicle 1 under the two car-following strategies. As the velocity increased, the spacing between vehicle 1 and vehicle 2 increased, which was in line with the spacing caused by the CTH strategy.