Optimized Calculation of the Economic Speed Profile for Slope Driving: Based on Iterative Dynamic Programming

In order to improve eco-driving performance, a speed profile for a vehicle has been investigated. For its great effect on fuel economy, an economic speed planning method based on iterative dynamic programming (IDP) with a high calculation efficiency is proposed for slope driving. Taking fuel economy as an optimized goal, a transient fuel consumption model is developed, which plays an important role in the economic evaluation of fuel consumption. Moreover, a discrete form of the speed planning model is established based on the vehicle dynamics equations. Based on the dynamic programming (DP) algorithm, the calculation complexity is analyzed in detail, and the fuel-saving characteristics of the DP algorithm are verified in a comparative experiment with the fixed-speed cruise control (FCC) method and the velocity set-point (VS) method. To overcome the low calculation efficiency of the DP algorithm, a new algorithm based on iterative dynamic programming is proposed to reduce the size of search domain. Furthermore, an improved IDP (i-IDP) algorithm with variable step size is proposed, which further optimizes the performance of IDP in terms of distance step size. Additionally, the calculation accuracy is also guaranteed while reducing the calculation scale and improving the efficiency of speed planning. What the calculation results have shown that under the same level of accuracy, the new algorithm can save the calculation time by more than 90%, with possibilities for real-time speed profile optimization for vehicles.