Advanced Research Methods of Hybrid Electric Vehicles Performances

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1 Volume 56, Number 1-2, Advanced Research Methods of Hybrid Electric Vehicles Performances Bogdan Ovidiu Varga, Călin Iclodean Department of Automotive Engineering and Transports, Technical University of Cluj-Napoca Abstract This paper studies the performance of a hybrid electric vehicle bus (HEVB) by computer co-simulation using Cruise- software applications. The simulation tasks include fuel consumption calculation over the usual city bus drive cycle, maximum velocity calculation and acceleration time calculation. Based on obtained results, a comparative analysis is performed for this model of bus used for the urban passenger transport. Hybrid and electric vehicles have been modeled and simulated with the aims of improving overall energy efficiency in the exploitation regime and also to reduce local pollutant emissions. System and sub-system architecture in Cruise was used for developing and modeling the powertrain model. This approach allows fast model preparation as well as a better understanding of model building process for co-simulation features. Keywords Hybrid Electric Vehicle, modeling, simulation, energy efficiency, pollutant emission. 1. INTRODUCTION The development of vehicles with improved energy efficiency and performance targets implies ever more sophisticated powertrain sub-systems and electronic controllers being implemented, in conventional, hybrid electric and fully electric vehicles [1]. Vehicle modeling and simulation is a very important part in the design and development of hybrid and electric vehicles. To precisely simulate the powertrain running status, many commercial software products are applied into the development of control strategy. However, these models take too much time in the simulation analysis, which would be difficult to apply in the control strategy optimization [2]. A Cruise model is used as powertrain in Cruise co-simulation. System and sub-system architecture in Cruise is used to prepare Cruise powertrain model. This approach allows fast model preparation as well as better understanding of model building process for co-simulation feature. SAM Task (System Analysis Mode) in Cruise is specially developed for co-simulation calculation demands and therefore will be used in this procedure [3]. Cruise allows the simulation of vehicle driving performance, fuel consumption and emissions. This concept can be used for modeling all vehicle configurations with scalable fidelity. This approach allows the reuse of models or sub-systems in different optimization phases of a process in order to improve vehicle performances [4]. The suite is composed of two main components, the CarMaker/ Interface Toolbox (CIT) and the Virtual Vehicle Environment (VVE). The CIT contains a collection of tools for simulation control, parameterization, analysis, visualization and file management. The VVE represents the computer modeled composition of the vehicle with all its components such as powertrain, tires, brakes and chassis as well as the VVE which can be operated on a regular office computer or on a real-time system. Real-time operation allows investigation of deterministic behavior, office operation might lack real-time capabilities but is therefore applicable on almost any host computer and allows the simulation to run slower or faster than realtime depending on system performance and model complexity and does not require special hardware [5]. A virtual road is a digitized or computer modeled, which is a representation of a road, track or course, which simulates a real course or one, that is generated specifically for testing. A virtual driver is chosen from the computer software, which simulates the actions of a real driver. Everything that would normally be controlled by a real driver, such as turning the steering wheel, stepping on the gas, brake and clutch pedals, shifting gears in a manual transmission vehicle etc. is controlled by the virtual driver. The connection between the external environment and the system is achieved through the use of system parameters that characterize their input/output relationship of the presented entities Mediamira Science Publisher. All rights reserved

A vehicle powertrain consists of an engine and a driveline. The major parts of the driveline are transmission, shafts, clutch and wheels.

Table 1 - The Main Technical Data of Volvo 7700 Hybrid Bus Parameters Value U.M. Length 12074 mm The classical IC Engine and the Electric Machine are set for hybrid propulsion system.

2 112 ACTA ELECTROTEHNICA 2. MATERIAL AND METHODS The simulation model was developed based on a model of Volvo 7700 Hybrid bus, using technical data provided by the manufacturer and experimental measurements (Table I) [6]. A vehicle powertrain consists of an engine and a driveline. The major parts of the driveline are transmission, shafts, clutch and wheels. The driveline is one of the fundamental parts of a vehicle and its dynamics can be modeled in different ways depending on the research purpose [7]. Table 1 - The Main Technical Data of Volvo 7700 Hybrid Bus Parameters Value U.M. Length mm The classical IC Engine and the Electric Machine are set for hybrid propulsion system. This hybrid powertrain has two separated drivelines and each of them can drive the bus independently. The first driveline is just the same as the traditional drive pattern that has an IC Engine, a clutch and a transmission system. The second driveline is composed of an Electric Machine together with energy storage element Battery H [7]. The mechanical energy that enters in the electric motors is not equal to real value that it is saved in batteries because of the electric motor, inverter and battery charging efficiency [8]. Width 2520 mm Height 3216 mm Wheelbase 5945 mm Gross weight kg Curb weight kg Engine displacement 4760 cm 3 Engine maximum speed /min Engine maximum power 80 kw Engine maximum torque 800 Nm Battery capacity 250 Ah Actually the Cruise Interface is based on a co-simulation process using both and Cruise. If a Cruise powertrain is chosen in the Vehicle Data Set, starts the Cruise simulation program during the initialization phase of the TestRun simulation (Figure 1). Fig. 2. Cruise stand-alone simulation model Preparing a Cruise Powertrain for cosimulation requires the introduction of several new components in Cruise (CM-Truck Interface and Hub component) as usage of system GUI (Graphical User Interface) feature and SAM calculation task. The CM-Truck component defines the interface in co-simulation between Cruise powertrain models calculated with SAM calculation task and simulation package (Figure 3). Fig. 1. Interface The hybrid bus model in AVL Cruise (Figure 2) includes the following elements: Vehicle (1), IC Engine (2), Clutch (3), Gear Box (4), Final Drive Rear (5), Vehicle Wheels (6-11), Disk Brake (12-15), Electric Machine (16), Rear Differential (17), Cockpit (18), GB Control (19), GB Program (20), Battery H (21), Catalyst (22), Multiplex Function (23), Monitor (24) and AMT Control (25). Fig. 3. CM-Truck Interface The component Hub (Figure 4) is a combination of a Brake and a virtual Wheel. It is used in models with an interface to a co-simulation program that simulate the environment, the vehicle and the wheel. The component has the Data Bus inputs Torque and (wheel) Torque, which can be

Volume 56, Number 1-2, 2015 113 connected with an interface component like Cruise Interface or CM-Car.

and co-simulation with. Then setup SAM calculation task of co-simulation and exclude from the co-simulation model some special modules needed for Cruise stand-alone simulation (Vehicle, Cockpit etc.).

Hub component On side, the preparation for cosimulation implies to create a Cruise working directory, inside a directory of and export the selected Cruise powertrain in the working directory for

3 Volume 56, Number 1-2, connected with an interface component like Cruise Interface or CM-Car. On the Cruise side the preparations for cosimulation building a hybrid bus model requires specific modules for co-simulation, using System/Sub- System to switch between Cruise stand-alone simulation and co-simulation with. Then setup SAM calculation task of co-simulation and exclude from the co-simulation model some special modules needed for Cruise stand-alone simulation (Vehicle, Cockpit etc.). Fig. 4. Hub component On side, the preparation for cosimulation implies to create a Cruise working directory, inside a directory of and export the selected Cruise powertrain in the working directory for co-simulation [9]. The CM-Truck component defines the interface in co-simulation between Cruise powertrain models calculated by SAM calculation task and simulation model (Figure 5). visible by using check-box and exclude Sub-System from Cruise System. Select PT System and include Sub-Systems Powertrain and using the same procedure. will split the powertrain components into five distinct components: engine, clutch, gearbox, differentials, and wheels. The connections in the data bus for Sub-System are described in Table II. Table 2 Data Bus Connection for Sub-System Requires Input Delivering Output Drive Torque Output Torque Differential FL 1 Drive Torque Output Torque Differential FR 2 Engine On/Off Engine Operation Control Engine Speed Engine Engine Speed Engine Torque Engine Engine Torque Hub FR Torque Torque FR (FR Front Right) Torque Torque FR Hub RR Torque Torque RR (RR Rear Right) Torque Torque RR Hub FL Torque Torque FL (FL Front Left) Torque Torque FL Hub RL Torque Torque RL (RL Rear Left) Torque Torque RL The model with the co-simulation interface developed in Cruise will be saved in the working folder /Cruise, where it will be loaded and launched as project work in the application. It will choose the Powertrain folder in the Vehicle Data Set from and in the pulldown menu, choose further AVL Cruise (Figure 6). Fig. 5. simulation model The CM-Truck interface component is exchanging the information between Cruise and and through the Data Bus input channels establishes a working connection between Cruise powertrain model and model for co-simulation process. There are two Systems (Cruise and PT), each with three Sub-Systems (Vehicle, Powertrain and ). Next step for co-simulation is to group some of the Sub-Systems into each System, taking into account the main purpose of each System. Using Sub-System Tab in Systems section of Vehicle Model window, two different Systems will be created. Cruise System can only contain Sub-Systems Vehicle and Powertrain. Therefore select Cruise System and make Sub-Systems Vehicle and Powertrain active and Fig. 6. Cruise Interface

114 ACTA ELECTROTEHNICA To run the simulation, first the model must be connected with Cruise, (connection with the desired model must be checked), and then the road must be loaded, with the

. 3. RESULTS Fig. 9. Road model (IPGRoad) Fig. 7.

properties in order to build a complete road. To use this method, move to the second tab of the IPGRoad dialog box called Segments [10].

4 114 ACTA ELECTROTEHNICA To run the simulation, first the model must be connected with Cruise, (connection with the desired model must be checked), and then the road must be loaded, with the desired maneuvers (Figure 7). 3. RESULTS Fig. 9. Road model (IPGRoad) Fig. 7. Cruise co-simulation In IPGRoad, the road model of enables to calculate the position of any point on the road surface, including its friction coefficient, the centerline of the road (x, y, z) (Figure 8). The definition of the road geometry with a segment based approach and consists of a succession of various segments (straight lines, curves left or right) with correctly parameterized properties in order to build a complete road. To use this method, move to the second tab of the IPGRoad dialog box called Segments [10]. The main monitored parameters after the simulations were run are the following: the Current (A) in Figure 10, the Voltage (V) in Figure 11, the Energy (kj) in Figure 12, Energy Stored (kj) in Figure 13, Mechanical and Electrical Power (kw) in Figure 14 and Figure 15, Mechanical and Electrical Torque (Nm) in Figure 16 and Figure 17. Fig. 10. AVL_Cruise.efg.current Fig. 11. AVL_Cruise.efg.voltage Fig. 8. IPGRoad the road model of To evaluate the energy efficiency characteristics of the hybrid electric road cycle model was load and run from IPG (Figure 9). The total distance of this route is 4574 meters, maximum acceleration is 3.66 m/s 2, the average velocity is km/h and the total time is 976 seconds. Fig. 12. AVL_Cruise.efg.energy

Volume 56, Number 1-2, 2015 115 Fig. 13. AVL_Cruise.efg.energy_stored Fig. 17.

To use IPGControl online load the work model and start a simulation.

) and the the Reference Quantity (Time). They are selected from the tab Quantities AVL.cruise.

characteristics and drivability. Electric power is also used when the vehicle is at a standstill.

As a result, the bus produces no exhaust gases and is very quiet in operation. Fig. 18.

5 Volume 56, Number 1-2, Fig. 13. AVL_Cruise.efg.energy_stored Fig. 17. Electrical Engine Torque IPGControl is a tool that displays diagrams. To use IPGControl online load the work model and start a simulation. A diagram is created by choosing the Quantities (Car.ax, DM.Brake, DM.Steer.Ang etc.) and the the Reference Quantity (Time). They are selected from the tab Quantities AVL.cruise.efg and monitored in real time by IPGControl (Figure 18). Fig. 14. Mechanical IC-Engine Power. Fig. 15. Electrical Engine Power. The electric motor produces maximum torque right from start, which results in excellent starting characteristics and drivability. Electric power is also used when the vehicle is at a standstill. When the vehicle pauses at a bus stop or traffic light, the diesel engine switches off automatically. As a result, the bus produces no exhaust gases and is very quiet in operation. Fig. 18. IPGControl main window The statistical percentages of engine operating region for hybrid electric vehicle bus model are show in Figure 19. Fig. 19. Statistical percentages of engine operating region Fig. 16. Mechanical IC-Engine Torque Driving time distribution in consumption map for classical, hybrid and electric buses are show in Figure 20.

6 116 ACTA ELECTROTEHNICA REFERENCES Fig. 20. Driving time distribution in consumption map 4. CONCLUSIONS Hybrid electric vehicle bus (HEVB) can be considered to offer the best promise in short term to mid-term. The impact on the fuel economy generally improves by more than 50 % in urban passenger traffic using hybrid buses. For HEVB, the power distribution is proposed to determine the target operating points of the system components as the basis for maximal efficiency of the overall system in all operation modes. The modular vehicle co-simulation software Cruise - enables the simulation model to be comfortably adapted to widely different powertrain concepts and permits the on-board calculation of tractive power requirements for hybrid electric vehicle bus with reasonable calculation speed. However, the potential for optimization strongly depends on the route that it is applied to, disturbances from traffic and driving behavior as well as the customer s use of external charging stations. This implies including the driver into a HEVB s optimizing strategy still bears great potential for increasing its overall efficiency in the future. ACKNOWLEDGMENT This paper is supported by the Human Resources Development Programme POSDRU/159/1.5/S/ financed by the European Social Fund and by the Romanian Government. The simulations presented in the paper were done using the software AVL Cruise and IPG supported by AVL List GmbH, Austria. 1. S, Jones, E, Armengaud, H, Böhm, Safety Simulation in the Concept Phase: Advanced Co-simulation Toolchain for Conventional, Hybrid and Fully Electric Vehicles, Springer International Publishing Switzerland, 2014, pp , ISBN J, Wang, NV, Zou Hybrid electric vehicle modeling accuracy verification and global optimal control algorithm research, International Journal of Automotive Technology, Vol. 16, No. 3, 2015, pp , DOI /s y. 3. AVL Cruise version 2010, Cruise CarMaker/ Co-Simulation, AVL List GmbH, Graz, Austria, Document no , Edition Mariasiu, F. Possibilities for reducing tractor engine friction losses at cold start using an ultrasonic irradiation technique, in Turkish Journal of Agriculture and Forestry, No. 37, 2013, pp , ISSN: X. 5. S, Zieglerand, R, Höpler, Extending the IPG CarMaker by FMI Compliant Units, Proceedings 8 th Modelica Conference, Dresden, Germany, March 20-22, 2011, pp AVL Cruise version 2011, Database, AVL List GmbH, Graz, Austria, Document no , Edition K, Sundaravadivelu, G, Shantharam, P, Prabaharan, Analysis of vehicle dynamics using Co-Simulation of AVL-CRUISE and CarMaker in ETAS RT environment, Advances in Electrical Engineering (ICAEE), International Conference, 2014, pp. 1-4, DOI: /ICAEE B.O., Varga, C, Iclodean Numerical investigation of hybrid electric vehicle s performance, Proceedings of The International Congress Science and Management of Automotive and Transportation Engineering SMAT 2014, Vol. 1, pp P, Srinivasan, U, Kothalikar, Performance Fuel Economy and CO2 Prediction of a Vehicle using AVL Cruise Simulation Techniques, SAE Technical Paper, , IPG CarMaker Quick Start Guide Ver , IPG Automotive, Karlsruhe, Germany, Edition IPG CarMaker User s Guide Version 4.5.2, IPG Automotive, Karlsruhe, Germany, Bogdan Ovidiu Varga Department of Automotive Engineering and Transports, Technical University of Cluj-Napoca Cluj-Napoca, Romania bogdan.varga@auto.utcluj.ro Călin Iclodean Department of Automotive Engineering and Transports, Technical University of Cluj-Napoca Cluj-Napoca, Romania calin.iclodean@auto.utcluj.ro

ROAD VEHICLE SIMULATION USING AVL CRUISE

UNIVERSITY OF PITESTI SCIENTIFIC BULLETIN Faculty Of Mechanics And Technology AUTOMOTIVE series, year XXI, no. 25 Adrian IORGA University of Pitesti ROAD VEHICLE SIMULATION USING AVL CRUISE Article history: