# Speed Advisor for Fuel Consumption Minimisation Under Real Driving Conditions
## 1 Introduction
* Model and optimisation tool: In order to provide any advice to the driver about the vehicle speed profile that minimises fuel consumption, a model able to estimate in advance the impact of driver decisions and particularly of the vehicle speed on fuel consumption is required. This model in combination with an optimisation tool allows to compute the optimal speed profile to be followed. * Driver advisor: The computed optimal speed trajectory should be transmitted to the driver that will follow it in the best way possible. In the same way, the optimal speed trajectory should be continuously updated to make up for the deviations of the actual driving speed from the optimal profile. In the presented paper, a particular route between two cities has been selected for the optimization. The route consists mainly on highway driving with presence of speed limits and altitude variations but limited traffic and no vehicle stops. The optimal control problem of covering the route with minimum fuel consumption in a given time has been solved by DP for different time constraints in order to assess the compromise between fuel consumption and trip time. Once the optimal control problem has been solved offline, the desired action is expressed as a function of the states and the time step, and it is loaded in a prototyping system equipped on-board as a 3D look-up table. The control policy is passed with a display to the driver as a reference to minimize fuel consumption. The route has been covered a total of 35 times in independent days: 30 times with the default driving system while 5 days by the speed advisor display. The main contributions to previous works found in literature can be summarized in the following points:  
* A global optimization is found offline by using DP and pre-scheduling the route characteristics, i.e. slope and speed limitations. The optimal policy has been loaded in a prototyping system on-board as 3D look-up table which define the acceleration (or future desired speed) as a function of the current states and the time step. * The 3D open-loop tables contain the optimal control sequence between any state contained in the feasible set and the final one. This property is used in the present work to correct any deviation from the optimal speed profile, due to non considered disturbances, such as gear switches or unexpected vehicles on the line, or lack of accuracy of the driver. * The method has been tested onboard, in an EURO V vehicle, by generating the desired speed and displaying it to the driver. The route has been covered several times in different days to analyse the potential of the method in real driving conditions. The experimental validation shows that the application is real time capable with significant improvement in fuel consumption. Following the previous idea, the paper is structured as follows: First, in Section 2, the energetic model used for the fuel consumption optimization is described. Then, in Section 3, the problem to be addressed and the route considered is described in detail. Then optimization technique employed is introduced in Section 4. Latter, Section 5 is aimed to the description of the driver advisory implementation. Next, the experimental set up is explained in Section 6 and the obtained results are discussed in Section 7. Finally the conclusions of the paper are highlighted in Section 8.