IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 9, NOVEMBER 2009 4741 Intelligent Vehicle Power Control Based on Machine Learning of Optimal Control Parameters and Prediction of Road Type and Traffic Congestion Jungme Park, Zhihang Chen, Leonidas Kiliaris, Ming L. Kuang, M. Abul Masrur, Senior Member, IEEE, Anthony M. Phillips, and Yi Lu Murphey, Senior Member, IEEE Abstract—Previous research has shown that current driving efficiently control the energy flow through the vehicle system. conditions and driving style have a strong influence over a vehicle’s Our research focuses on the latter. Vehicle power management fuel consumption and emissions. This paper presents a methodol- has been an active research area in the past decade and has ogy for inferring road type and traffic congestion (RT&TC) levels from available onboard vehicle data and then using this informa- intensified recently by the emergence of hybrid electric vehicle tion for improved vehicle power management. A machine-learning technologies. Most of the previous approaches were developed algorithm has been developed to learn the critical knowledge about based on mathematical models or knowledge derived from fuel efficiency on 11 facility-specific drive cycles representing dif- static vehicle operation data. The application of optimal control ferent road types and traffic congestion levels, as well as a neural theory to power distribution and management has been the learning algorithm for the training of a neural network to predict the RT&TC level. An online University of Michigan-Dearborn most popular approach, which includes linear programming [1], intelligent power controller (UMD_IPC) applies this knowledge to optimal control [2], and, particularly, dynamic programming real-time vehicle power control to achieve improved fuel efficiency. (DP) [3]–[5]. In general, these techniques do not offer an online UMD_IPC has been fully implemented in a conventional (non- solution because they assume that the future drive cycle is hybrid) vehicle model in the powertrain systems analysis toolkit entirely known. However, these results can be used as a bench- (PSAT) environment. Simulations conducted on the standard drive cycles provided by the PSAT show that the performance of the mark for the performance of online power control strategies. If UMD_IPC algorithm is very close to the offline controller that is only the present state of the vehicle is considered, optimization generated using a dynamic programming optimization approach. of the operating points of the individual components can still be Furthermore, UMD_IPC gives improved fuel consumption in a beneficial, but the benefits will be limited [6]–[8]. Interesting conventional vehicle, alternating neither the vehicle structure nor its components. techniques for deriving effective online control rules based on the results generated by offline DP and quadratic programming Index Terms—Fuel economy, machine learning, road type (QP) can be found in [3] and [9]. and traffic congestion (RT&TC) level prediction, vehicle power management. Recent research has shown that current driving conditions and the driver’s driving style have a strong influence over a vehicle’s fuel consumption and emissions [10], [11]. Driving I. INTRODUCTION patterns exhibited by a real-world driver are the product of USTOMER demand for improved fuel economy is chal- the instantaneous decisions of the driver to respond to the C lenging the automotive industry to produce affordable (physical) driving environment. Specifically, varying road type new vehicles that deliver better fuel efficiency without sacri- and traffic conditions, driving trends, driving styles, and vehicle ficing performance, safety, emissions, or reliability. To meet operating modes have had varying degrees of impact on vehicle this challenge, it is very important to optimize the architecture fuel consumption. However, most of the existing vehicle power and the various devices and components of the vehicle system, control approaches do not incorporate knowledge about driving as well as the energy-management strategy that is used to patterns into their vehicle power-management strategies. The main contribution of this paper is an algorithm for optimization Manuscript received October 1, 2008; revised March 12, 2009 and May 14, of vehicle power management that utilizes inferred knowledge 2009. First published July 17, 2009; current version published November 11, of road type and traffic congestion (RT&TC). Only recently has 2009. This work was supported in part by the State of Michigan through the 21st Jobs Fund under a grant and in part by the Institute of Advanced Vehicle the research community in vehicle power control begun to ex- Systems, University of Michigan-Dearborn, under Grant 06-1-p1-0727. The plore ways to incorporate knowledge about driving patterns into review of this paper was coordinated by Dr. M. S. Ahmed. online control strategies [12]–[15]. A comprehensive overview J. Park, Z. Chen, L. Kiliaris, and Y. L. Murphey are with the Department of Electrical and Computer Engineering, University of Michigan-Dearborn, of intelligent system approaches for vehicle power management Dearborn, MI 48128 USA (e-mail: [email protected]). can be found in [16]. M. L. Kuang and A. M. Phillips are with the Ford Motor Company, Dearborn, MI 48120 USA. This paper presents our research on intelligent vehicle power M. A. Masrur is with the U.S. Army RDECOM-TARDEC, Warren, MI management using machine learning. Specifically, we will 49307 USA. present machine-learning algorithms for learning about the Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. optimal power control parameters for all 11 standard facility- Digital Object Identifier 10.1109/TVT.2009.2027710 specific (FS) drive cycles proposed in [17] and [18] and 0018-9545/$26.00 © 2009 IEEE 4742 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 9, NOVEMBER 2009 Fig. 1. Intelligent power control in a vehicle system. about predicting road types and traffic congestion, as well as tem for predicting roadway type and traffic-congestion level, an online University of Michigan-Dearborn intelligent power Section IV presents the intelligent online vehicle power- controller (UMD_IPC) that applies the knowledge obtained management system, namely, UMD_IPC, Section V presents through machine learning to online vehicle power control with the experiment results, and Section VI presents the conclusion. the online prediction of driving environment by a neural net- work. UMD_IPC has been fully implemented in a conventional II. OPTIMAL POWER CONTROL IN A CONVENTIONAL vehicle model built using the powertrain systems analysis tool- VEHICLE SYSTEM USING MACHINE LEARNING kit (PSAT) (http://www.transportation.anl.gov/software/PSAT/ Fig. 1 illustrates the interaction between the proposed in- index.html) simulation program and tested on 11 drive cycles telligent power controller UMD_IPC and the major power provided by the PSAT library. PSAT is a high-fidelity sim- components in a conventional vehicle system. At any given time ulation software developed by Argonne National Laboratory, during a drive cycle, based on the current vehicle state, which is Argonne, IL, under the direction of and with contributions represented by the current vehicle speed, driver power demand, from Ford, General Motors, and Chrysler. PSAT is a “forward- electrical load and state of charge (SOC) of the battery, the looking” model that simulates vehicle fuel economy and per- UMD_IPC calls the neural network NN_RT&TC to predict the formance in a realistic manner—taking into account transient current RT&TC level and calculates the electric power set point behavior and control system characteristics. It can simulate a to the battery controller and a resultant feedforward torque com- broad range of predefined vehicle configurations (conventional, pensation to the engine controller. The variable P , representing electric, fuel cell, series hybrid, parallel hybrid, and power split s the power actually to be charged (P > 0) or discharged (P < hybrid). s s 0) from the battery, is set by the UMD_IPC with the aim of In this research project, the PSAT software is used to build minimizing fuel consumption. The desired engine power P , a high-fidelity vehicle model; simulate drive cycles to gener- eng which is calculated based on the optimal value of P ,isusedto ate numerical data, such as fuel consumption and emissions s find the feedforward torque compensation through the engine and vehicle performance; and implement an intelligent power fuel-efficiency map. The functional relationship between P controller UMD_IPC. Experiments will show that the online eng and P is shown as follows: performances of UMD_IPC are very close to the offline optimal s controller built based on DP. In comparison with the default Peng = Pd + Ge2m(Pe,ω) (1) controller used by the vehicle model in PSAT, our results Pe = Pl + Pb (2) showed a maximum of 3.95% fuel reduction in an urban drive P = η (P , SOC,T) (3) cycle. Furthermore, the implementation of UMD_IPC does not b in2out s require the change of any vehicle components. Although the where research results presented in this paper were generated based ω engine speed; on a conventional vehicle model, the proposed technology can Pd driver demanded power at the wheels; be extended to a hybrid vehicle system, which is the authors’ Pe electrical power from the alternator; ongoing effort. Ge2m(Pe,ω) mechanical power required by the alternator This paper is organized as follows. Section II presents the based on alternator efficiency map Φalt to machine-learning process of optimal power control in a con- produce a given electrical power Pe at a ventional vehicle, Section III presents a neural network sys- given speed; PARK et al.: VEHICLE POWER CONTROL BASED ON MACHINE LEARNING OF OPTIMAL CONTROL PARAMETERS 4743 where γ(Ps,t) is the fuel consumed as a function of Ps(t) at time t. The fuel-consumption function γ(Ps,t) is approximated as a convex quadratic function, i.e., 2 γ(Ps,t)≈ϕ2(t)Ps(t) +ϕ1(t)Ps(t)+ϕ0(t),ϕ2 >0 (5) where ϕi represents time-varying coefficients.