An Integration of Optimum Electric Drive Control Systems with Downsized ICE to Build an Efficient Parallel Hybrid Vehicle Architecture

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1 EngOpt rd International Conference on Engineering Optimization Rio de Janeiro, Brazil, July 2012 ABSTARCT An Integration of Optimum Electric Drive Control Systems with Downsized ICE to Build an Efficient Parallel Hybrid Vehicle Architecture S.S.Ramdasi, A.SenthilKumar, S.S.Thipse & N.V.Marathe Automotive Research Association of India, VIT University, Vellore (India) Sustainable mobility leading towards cleaner environment is imposing a revolutionary change in shifting from conventional power train technology to the mix of many engineering disciplines under one roof. This not only addressing air quality improvement but will care also for Depletion in fossil fuels and Global Warming issue in a great extent. This need along with coming stringent norms has already started trend towards extreme downsizing and down speeding of I.C. Engines. Definitely this has revamped engine design with incorporation of state of art technology such as third generation CRDI systems, twin turbo charging etc. to operate engine with very high BMEP levels leading to efficient combustion. However this is putting an additional load from strength, dynamics and NVH point of view. Now day s passenger cars are equipped with downsized diesel engines with specific power rating in the range of kw /lit meeting Euro-IV and CO2 emissions up to 120 g/km. In order to go beyond further than present fuel economy and CO2 emission landmarks achieved, one of the most promising technology emerging out is Hybrid Electric Vehicle (HEV).Hybridisation may be of two fold in nature. Putting present downsized diesel engine technology in coalition with modern electric motor control systems results in first level of hybridization. Integrating cleaner Fuel Cell System with electric motor control system launches a platform for Zero Emissions which is a second level of hybridization. While thinking of this technology, drivability so called Fun to Drive should not be compromised. Successful implementation of this technology will greatly lie in the final cost of product on mass scale and its financial impact against present available mobility options. For present and till near future first level of Hybridisation is having a large potential in the context of Indian scenario, since Fuel cell technology operating cost is still on higher side. By considering these facts and need of present and coming situation, an attempt is made to conceive a concept of Hybrid Electric Vehicle which will have minimum cost implications. This paper depicts a systematic approach followed to build parallel Hybrid vehicle architecture suitable for one of the passenger car vehicle which is already an outcome of High Power Density Trend meeting present Euro emission norms with a magnificent fuel economy. The base vehicle selected is a Diesel Engine Powered passenger car vehicle having 1.3 lit downsized engine with 5 speed manual transmission. An optimum Electric Drive Control Strategy is selected to improve overall efficiency of electrification. A control strategy is worked out in order to get best vehicle performance on different driving cycles in terms of CO2 emissions and fuel economy. INTRODUCTION The four key policy-relevant and consumer choice advantages of HEVs over conventional and comparably clean and efficient technology (clean diesel, CNG) are summarized as follows: l Emissions - Available HEV technology will decrease emissions of conventional air pollutants substantially as compared to a standard vehicle on the roads today. While similar emission reductions can be achieved with, e.g. CNG and clean diesel vehicles with advanced emission control technologies, the HEV combines both non-co2 and CO2 reductions. Part load emission reduction is a key parameter that can be obtained from HEV. Fig. 1 shows the tighter requirement of CO2 emissions need to meet. HEV attracts for achieving these stringent CO2 emission targets. 2 Fuel efficiency - HEVs decrease fuel consumption substantially compared to conventional vehicles used today and also compared to CNG and the new generation of cleaner diesel vehicles. Alarming depletion of fossil fuels, forcing to switch over HEV 3 Product Life Cycle Cost - While HEVs are more expensive initially, the fuel savings are recouped based on mileage and driving conditions. Analysis has shown that the HEV life cycle cost, including the cost of purchase, fuel and maintenance costs, is, in most cases, less than owning a conventional vehicle.

2 Figure 1 : CO 2 Emission Trend on NEDC 4 Strategic Stepping Stone Technology - HEVs, plug-in hybrids (PHEVs), full electric vehicles (EVs), and fuel cell vehicles (FCVs) share basic technologies such as electric motors, batteries, and power electronics. Making available these technologies at comparable prices with conventional technologies on mass production will lead to a strategic stepping stone towards cleaner and fuel efficient vehicle technologies. When used to improve fuel economy and reduce carbon emissions, rather than to increase vehicle power and size, hybrid technology compares favorably with existing; vehicle technology. Hence the present work is undertaken to explore the possibility of implementing HEV technology suitable to Indian scenario. At present most hybrid passenger vehicles have gasoline engines, although hybrid diesel electric passenger vehicles are in development. According to International Energy Agency (IEA) scenarios - by 2050 almost all (99%) passenger vehicles will be HEVS and 69% will use diesel. For the present work, a passenger vehicle fitted with diesel engine is taken under consideration for HEV development. After study of various architectures possible viz. mild, series, parallel and complex, parallel hybrid configuration is selected to begin with. Emphasis is given for designing the system within available space constraint and will have minimum impact on additional weight caused due to High Voltage Lithium Ion battery, inverters and controllers. Base vehicle performance in terms of chassis dynamometer cycle level emissions, fuel consumption along with acceleration levels in different gears and max velocity achieved is simulated using CRUISE algorithm. The simulated performance is compared with the tested vehicle performance as a part of road worthiness trails. The calibrated model is used as a base for designing various control strategies for electrification in order to get targeted performance. Complete optimization is done on EUDC, since base vehicle performance is validated on the same. Fuel economy of 2.77l / 100 km against 4.83 / 100 km while CO2 emissions have come down to 71.2 gm/km from gm / km which is a substantial reduction with the extent of electrification. Apart from emission as a goal, electrification is used a booster to improve acceleration performance in all gears. Subsequent simulation trails are carried out on NEDC, FTP 75 Urban and Highway Cycle to access importance of electrification at higher loads with electric motor assisting Mode. A robust control strategy is worked out with various optimization techniques which will have influence on various parameters viz. engine fuel consumption, CO2 emissions, battery SOC, motor efficient operating zones, compact motor etc. This has make vehicle operations with increased weight due to hybridization still meeting desired targets on various cycles mentioned. Once control strategy is fixed up, utmost attention is given on shaping of electric motor torque characteristics with precise control strategies. By taking Torque vs. speed operating points on different cycles as a duty cycle, motor characterization along with inverter switching frequency look up tables is worked out. Extensive use of MATLAB/SIMULINK motor performance models are used to work out optimum control strategies for three phase induction motor. Direct Torque Control and Field Oriented Control strategies are worked out to improve transient behavior of motor thus improving power factor. Developed control strategies are experimentally evaluated on scaled down performance motor and Microautobox for its transient behaviors. Finally to improve the torsional vibration behavior due to incorporation of Integrated Starter / Motor between gear box and flywheel, a rear drive timing chain drive is worked out for an engine. This has helped in transferring very negligible torsional vibration amplitudes from flywheel end against very high amplitudes from pulley end to FIP and Valve train mechanisms, thus not worsening original NVH characteristics of vehicle. Thus an integration of electric drive control system with downsized ICE is worked out to build an optimum and efficient parallel hybrid vehicle architecture.

3 CONCEIVING THE CONFIGURATION Present scenario for meeting Euro-IV and V emissions has forced downsizing and down speeding trend in case of diesel engines. For passenger car segments vehicles equipped with High Power Density Diesel Engines are becoming first choice due to better thermal efficiencies of Diesel engines over gasoline engines. After a comprehensive survey and available statistical information, a passenger car fitted with downsized engine meeting EURO-IV emission norms is selected for hybridization. The cleaner vehicle option considered in this work can meet future stricter regulations on emissions such as hydrocarbons, nitrogen oxides, and particulate matter using available, off the shelf emission control technologies. The main difference between the technologies considered is in fuel consumption and the resulting emissions of carbon dioxide (CO2). On average, hybrid passenger vehicles offer 30% better fuel economy, and switching from petrol to diesel vehicles gives a 20% reduction in fuel use, whereas CNG vehicles offer a 10% reduction (based on energy content in the fuel). However, the reduction in CO2 emissions from use of CNG is roughly 20% on a life cycle basis (compared to hybrids and diesel) due to the lower carbon content in natural gas. This substantiates decision for selecting diesel vehicle as a base vehicle. In addition to the technology and fuel used, reduction in fuel consumption is dependent on driving conditions (traffic management, infrastructure, etc.). The more stop-and-go traffic (e.g. city driving conditions), the greater the potential for fuel savings when using a hybrid as compared to an ordinary vehicle. This is especially relevant for city driving conditions where most of the time vehicle operates in part load conditions. Though the downsized engine will give superior performance under full load conditions or in normal cruising mode operations, one can t get rid off from in efficient operation zones which comes across during part load operations. Thus there is a great challenge to improve part load fuel economy and emissions while maintaining vehicles best performance under other operating conditions. Basics of HEV technology A conventional vehicle has a mechanical drive train that includes the combustion engine, the gear box, and the differential to the wheels. A HEV has two drive trains - one mechanical and one electric. The electric drive train includes a battery, an electric motor, and power electronics for control. Fig.2 shows the principal layout of a mechanical and an electrical drive train is shown Figure 2 : Basic Power Flow - Mechanical vs Electric Drive Train In principle, these two drive trains can be connected with each other, sharing some components such as clutch and gear box. The hybrid denotation refers to the fact that both electricity and conventional fuel can be used. Current hybrid models all use gear boxes, but in the future a single one-gear transmission might be a reality for series hybrid configurations as the electric drive train can handle a wide variety of speeds and loads without losing efficiency. HEV deal with recapturing various losses under different driving conditions. Following are different modes in which HEV helps in overcoming losses. Table 1 shows brief about different possible modes with hybridization.

4 Sr.No Technology Degree of hybridization 1 Avoiding energy losses during idling by shutting off the combustion engine 2 Recuperating energy from regenerative braking 3 4 Using the battery energy to assist the engine and enable downsizing the engine Running the combustion engine at its maximum load, where the engine efficiency maximizes 5 Driving without the combustion engine running 6 Enlarging the battery pack and recharging it with energy from a wall plug Table 1: Degree of Hybridization Mild HEV Full HEV Mode 1: The energy lost during idling can decrease substantially by allowing the combustion engine to shut down or run at maximum load to recharge the battery during this time. First feature will lead to great reduction in emissions as well as improving fuel economy by using Integrated Starter Generator (ISG) kind of technology. Second feature is mainly depend on State of Charge (SOC) of Battery and mainly used in case of serried hybrid vehicle architecture. Mode 2: The use of an electric drive train enables the HEV to recuperate part of the energy losses during braking. The electric drive train can then be used backwards as a generator to charge the battery. This considerably maintains SOC to desired levels. Only with sudden and hard braking will the conventional brake pads be used. An important secondary benefit of this system is the much longer life of the brake pads and the reduced cost for replacement. Mode 3: Hybridisation can be used as a power booster. This mainly adds electric power on top of Full Load Power of ICE, enabling improved accelerations as compared to base vehicle. Other way round, one can de-rate engine s full load power and gap can be filled with electrification. This may lead to use even smaller capacity engine to replace base engine. Mode 4: An ordinary combustion engine (diesel or petrol) operates at maximum engine efficiency close to its maximum power. As the engine is smaller and the excessive delivered power is used for recharging the batteries, the combustion engine can run in its efficient zone at most of the time. Mode 5: The possibility of driving without the combustion engine running, and thus zero emissions, can be especially advantageous when driving at low speed or in congestion in urban areas. The current limitation is that currently full HEVs have small battery packs, with battery-only mode viable for less than a mile at low speed. Larger battery capacity in the future will allow for longer battery-only operation. Mode 6: The next step in hybridization, plug-ins, rely on increased battery capacity to increase battery-only driving range - typically between km. Because of the larger capacity, it is worthwhile to charge the battery from a conventional power plug. FINAL HYBRID VEHICLE ARCHITECTURE Fig.3 shows various hybrid vehicle architectures studied for the work under consideration. Figure at location a depicts a typical series hybrid architecture. Here two electrical power sources are utilized in different possible modes to propel the vehicle. Primary source is a generator which driven by ICE supplying power input to an electric motor. Secondary source is a battery which supplies power via DC- DC converter and IGBT inverter to drive an electric motor. Battery SOC is always monitored and charged by ICE driven generator whenever SOC falls below the lower limit. Generally in this configuration, ICE acts as a range extender and a large battery can be used as a primary source. This kind of architecture calls for a complete new layout of a vehicle and can be implemented for Hybrid Vehicle design programs from scratch. PHEV

5 Figure 3 : Hybrid Vehicle Architectures Figure at location b shows a typical layout for parallel hybrid vehicle architecture. Here there is a coupling of Mechanical power with electric power in power converter. Depending upon the extent of modes of electrification, further classification can be obtained as mild hybrid and full parallel hybrid architecture. Implementation of any one of this two architectures are possible in vehicles already existing with major modifications in power train layout. However, as far as possible, Implementation of hybrid architecture at design stage itself when vehicle is need to build from scratch is always preferred to take advantage of other features of hybridization. This mainly includes use of light weight material chassis frame to compensate an additional weight occurred due to battery / super capacitors, DC-DC converters, IGBT inverters etc. Figure at location c shows the most complicated layout called as mix architecture. Use of planetary gear box simplifies the complexity of torque coupling up to great extent. For the work under consideration, option b as full parallel hybrid is considered for development purpose. Following are the major driving factors for conceiving the concept of full parallel hybrid architecture need to implement on a passenger car fitted with downsized,fuel efficient diesel engine. Driving Factors for Development of Hybrid Electric Vehicle Architecture for Passenger Car Application designed for : Best Possible CO2 reduction and Lowest Fuel Consumption with an integration of Downsized Diesel Engine Technology with Optimum Electric Drive Control Technology Retro fitment Possibility Minimum weight for increased electrical components Efficient controls for electric drive technology for transient operations Features for NVH control in Hybrid Mode / Engine traction mode Minimum Cost implication BASE VEHICLE- ENGINE SPECIFICATIONS / ENGINEERING TARGETS WITH HYBRIDISATION Table 2 shows the brief specifications of vehicle selected and the engineering targets need to achieve by means of hybridization. Base vehicle is a passenger car vehicle equipped with a 1.3 liter, 3 Cylinder, DI, Diesel engine complying EURO-IV emission norms on EUDC cycle. Sr No Parameter / Data Data / Engineering Targets Vehicle 01 Gross Vehicle Weight (GVW), kg Curb Weight, kg Reference Mass, kg Road Load Equation V dv/dt 05 Transport Capacity 5 Persons 06 EURO-III Compliance, g/km EUDC Cycle Fuel Consumption km/lit C0-0.24, HC-0.02, NOx -0.25, PM CO , F.C Free Acceleration Smoke HSU 07 Max Velocity, km/hr 147

6 Engine 01 No Cylinders / liter 3 / Rated Speed rpm 03 Max Speed rpm Engineering Targets 01 Max Velocity 160 km / hr 02 Acceleration (0-100 km / hr) 13 sec 03 Grad ability 30 deg 04 NEDC CO 2 Emissions < 80 g/ km Table 2 : Engineering Targets Need to Achieve with Base Vehicle Specifications SIMULATION OF BASE VEHICLE PERFORMANCE AND CALIBRATION CRUISE algorithm is used to simulate base vehicle performance in terms of driving cycle emissions, fuel consumption, acceleration in different gears and max velocity. Coast down values for friction and drag coefficient generated during coast down test on a flat test track are used in the coast down equation to calculate vehicle tractive effort requirement at time based load and speed conditions during negotiation of driving cycle. Other inputs such as full load characteristics of engine viz power and torque are generated by taking full load performance test on engine dynamometer. Steady state emission and bsfc maps for part load conditions are generated on steady state engine dyno. Other details such as polar moment of inertias of various drive line components are precisely made available using solid modeling techniques. Base vehicle is having 5 speed manual synchromesh gear box and the vehicle is having front wheel drive. Fig.4 shows mathematical model of vehicle for performance simulation. Figure 4 : Vehicle Performance Simulation Model Base vehicle is then subjected for its emission and fuel consumption measurement on chassis dynamometer to follow EUDC cycle with top speed of 90 km/hr. Table 3 shows comparison of simulated and experimental data for cycle fuel consumption, CO 2 emissions, accelerations in different gears and max velocity. Parameter Simulation Experimental Cycle Fuel Economy km / lit km / lit Cycle CO 2 Emissions gm / km gm / km Acceeration : I st Gear 4.54 m/sec 2 : II nd Gear 2.74 m/sec 2 : III rd Gear 1.76 m/sec 2 : IV th Gear 1.22 m/sec 2 : V th Gear 0.87 m/sec Max Velocity 153 km/hr 147 km/hr Table 3 : Calibration of Base Vehicle Simulation Model Fig. 5 shows cycle trace comparison of vehicle, gear shifting pattern and engine operating points along with weighted average time during cycle trace for base vehicle performance on EUDC. Simulated model has shown results which are in close agreement with experimental

7 results. It can be seen that most of the time engine is operated in part load conditions during cycle run. This mainly results to keep engine away from the optimum bsfc points which lies approximately around 75% of full load points. This has creates further impact on CO2 emissions. Though benchmark vehicle is fitted with a state of art downsized 4 cylinder engine, further reduction in fuel economy and CO2 emission reduction seems to be possible by means of electrification. Figure 5 : Base Vehicle Performance Results on EUDC After this calibration activity, base model is used to simulate hybrid vehicle performance with different control strategies. Steady state emission and fuel consumption maps are modified to get different electrification strategies.attempt is made that there should be a common control strategy which will result in optimum performance when the vehicle is subjected to different driving patterns. In order to this control strategies are tried out by assessing performance of vehicle on different driving cycles with GVW. Consideration of GVW pushes vehicle operating points close to optimum efficiency points. Fig. 6 shows the final optimized control strategy worked out to meet the target vehicle performance parameters on NEDC. This strategy is checked out for vehicle performance with GVW on NEDC,FTP 75 URBAN and FTP Highway cycle, Figure 6 : Final Control Strategy for Electrification

8 Motor Power (kw) Start-Stop feature is used so that idling fuel consumption and CO2 emissions can be reduced. For this purpose parallel hybrid architecture with motor in an Integrated Starter Generator mode is used. For any speed between rpm, upto 25 % load vehicle will operate in pure electric mode. This mainly improves part load performance. Between % of engine full load, vehicle will run only with ICE for complete speed range. Above 75 % of engine full load, ICE is restricted to operate at 75% of full load and remaining power is assisted with the help of electric motor. On top of this motor further adds 10% extra power as a booster over 100 % combined power of ICE and motor. This felicitates in improving accelerations in different gears as well as max vehicle speed. 30 Electric Motor Characteristics Motor Characteristics Motor Speed (rpm) Figure 7 : Desired Power vs Speed Characteristic of an Electric Motor Fig.7 shows desired Torque characteristic for the electric motor under consideration. This is a typical flat power characteristic which favors for hybrid vehicle applications. A light weight 3 phase induction motor which is connected with a variable voltage / frequency inverter source is used. HYBRID VEHICLE PERFORMANCE SIMULATION ON DIFFERENT DRIVING CYCLES Various driving cycles viz.eudc, NEDUC, FTP Urban and Highway Cycles are used to assess performance of vehicle to fine tune the control strategy worked out. Table 4 shows comparison of Hybrid vehicle performance with base vehicle for EUDC cycle run with reference mass. Great amount of reduction in fuel consumption as well as CO 2 emissions is obtained with the finalized control strategy. Sr No Parameter Base Vehicle EUDC (With Ref Mass KG) Hybrid Vehicle EUDC (With Ref Mass KG) Base Vehicle EUDC (With GVW KG 01 C0, gm/km HC, gm /km NO X, gm/km CO 2, gm/km FC / 100 km Table 4 : Hybrid Vehicle Performance with Reference Mass / GVW on EUDC Hybrid Vehicle EUDC (With GVW KG Fig. 8 shows comparison of acceleration performance in different gears for hybrid and base vehicles. It can be seen that accelerations are increased by 5-8 % in all gears with hybrid mode. Boosting the original base vehicle torque curve by 10 % by means of electrification has also resulted in max vehicle speed to 160 km / hr.

9 Figure 8 : Acceleration Performance : Base vs Hybrid Fig. 9 shows NEDC and FTP Highway cycles used for checking the hybrid control strategy. Comparison in driving cycle clearly shows shifting of engine operating zones near to engine optimum operating points with FTP Highway cycle. Figure 9 : NEDC and FTP Highway Cycles used for Control Strategy fixing Table 5 shows comparison of emission and fuel economy performance on NEDC and FTP-Highway cycle. Clearly we can see that a common optimum control strategy for all above mentioned cycles has helped in meeting closely CO2 emissions targets and getting considerable reduction in fuel consumption.

10 Sr No Parameter Base Vehicle (NEDC) Hybrid Vehicle (NEDC) Base Vehicle FTP (Highway) Base Vehicle FTP (Highway) 01 C0, gm/km HC, gm/km NO X, gm/km CO 2, gm /km FC / 100 km Table 5 : Hybrid Vehicle Performance with Reference Mass / GVW on NEDC and FTP Highway ELECTRIFICATION Figure 10 : Integration of Mechanical / Electrical System and CAN for ECU and TCU Fig. 10 portrays an efficient and compact integration of mechanical and electrical systems for the hybrid vehicle under consideration. A 25 kw motor is placed in between engine flywheel and proposed six speed Automated Transmission. This motor will act as ISG to offer dual advantage of Start / Stop feature and regenerative braking to assist in maintaining SOC. A 42 V ultra capacitor will supply enhanced DC input via DC/ DC converter integrated with rectifier and filter. MOSFET / IGBT inverter converts DC input into variable frequency 3 phase supply to a 3 phase 25 kw induction motor. A 12 V auxiliary battery as a power source for ECU/TCU. Master Hybrid Control unit along with Motor Control Unit and PPS management unit are under development. In order to improve electrification efficiency to minimize PPS weight and to enhance transient performance Direct Control Torque and Field Orientation Control Strategies for motor

11 operation are worked out with available MATLAB / SIMULINK models. In order to ascertain benefit of FOC over DTC a case study is performed with small capacity motor and giving transient Torque and Speed demands. OPTIMUM CONTROL STRATEGIES As EV and HEV propulsion, an induction motor drive is usually fed with a DC source (battery, fuel cell, etc.), which has approximately constant terminal voltage. Thus a variable frequency and variable voltage DC/AC inverter is needed to feed the induction motor. The general DC/AC inverter is constituted by power electronic switches and power diodes. Figure 11 : DC/AC Inverter Topology The commonly used topology of a DC/AC inverter is shown in Figure 11, which has three legs (S1 and S4, S3 and S6, and S5 and S2), feeding the phase a, phase b, and phase c of the induction motor. When switches S1, S3, and S5 are closed, S4, S6, and S2 are opened, and phases a, b, and c are supplied with a positive voltage (Vd/2).Similarly, when S1, S3, and S5 are opened and S4, S6, and S2 are closed, the phases a, b, and c is supplied with a negative voltage. Two separate methods are used to feed these voltages namely Direct Torque Control method and Field Orientation Control Method. Direct Torque Control (DTC) Fig. 12 shows schematic of available MATLAB/SIMULINK model along with Inverter Control Scheme for DTC. Figure 12 : MATLAB / SIMULINK model for DTC simulation and Inverter Control Scheme This is a constant volt/hertz control of an induction motor with sinusoidal pulse width modulation (PWM). Three-phase reference voltage Va,Vb and Vc of variable amplitude Aa,Ab, and Ac are compared with a common isosceles triangular carrier wave Vtr of a fixed amplitude

12 Am as shown in Fig.10 The outputs of comparators 1, 2, and 3 form the control signals for the three legs of the inverter. However this method have poor transient response, since both filed and armature fluxes are not orthogonal all the time as in case of DC motor. This is improved by using Field Orientation Control Technique. Field Orientation Control The aim of FOC is to maintain the stator field perpendicular to the rotor field so as to always produce the maximum torque as in DC motors. However, for induction motors, phase voltages are the only accesses for the purpose of control. control. For this control accurate knowledge of rotor flux information is required. This can be accomplished by putting Hall sensor which measures rotor flux orientation w.r.t Stator flux on real time method. Two kind of transformations are used on rotor flux information to convert into DC equivalent independent control of filed and rotor flux. First transformation is known as Clark Transformation which converts rotor frame reference quantities into stator frame reference. Second transformation is called as Park Transformation which converts AC quantities referred in stator frame into time independent quantities. This gives information about required Pulse Width and its frequency by which one can reorient rotor flux position orthogonal to stator flux position, thus improves power factor and hence transient performance. Fig.13 shows schematic for Field Orientation Control Method. Figure 13 : Field Orientation Control Scheme with Clark and Park Transformation MATLAB / SIMULINK MODELLING FOR DOC AND FOC In order to decide implementation of control strategy for Hardware in Loop Simulation (HiL) of an induction motor, MATLAB / SIMULINK model for DOC and FOC is used. Before using actual Torque and Speed real time data, 3 Hp motor performance is simulated with limited Torque / Speed demand data to check response and correctness of model. Table 6 shows a sample data used for this exercise. Time (sec) Torque (N-m) Speed (rpm) Table 6 : Real Time base Requirement of Torque and Speed : Case Study Fig.14 shows phase current requirement with DTC and FOC for real time Torque and Speed demand as shown in Table 6. It can be seen that with FOC there is a substantial reduction in phase current requirement for the same output.

13 Direct Torque Control Field Orientation Control Figure 14 : 3 Phase Current Simulation with DTC and FOC Strategy It is proposed to generate real time requirement of Torque vs Speed for the electric motor to deliver for EUDC, NEDC, FTP Urban and FTP Highway to access effectiveness of FOC over DTC. With this data and both control strategy algorithms, HiL testing of electric motor will be carried out by using dspace OR ETAS simulation models and either real time ECU or Rapid Pro Hardware SUMMARY An optimum Electric Drive Control Strategy with Downsized ICE is worked out to build efficient hybrid vehicle architecture. Use of advance simulation algorithms have helped in formulating and testing control variables more precisely. Developed electrification strategy has resulted in ISG based parallel hybrid vehicle architecture which can be implemented with least modifications in present vehicle packaging. A common strategy will take care of operation of vehicle on different driving cycles viz. EUDC, NEDC, FTP Urban and FTP Highway. Use of super capacitor is proposed along with IGBT inverter running with DTC and FOC both control strategies till actual vehicle trails gets proved. HiL testing of electric motor on simulators is proposed before integrating electrification system with ICE for test bed trails. ACKNOWLEDGEMENT The Authors would like to acknowledge The Director, Automotive Research Association of India, Pune for his support and granting permission to publish this paper. Authors would like to extend thanks to Mr. Mohammad Jamadar and Mr.R.V.Mulik for their technical support during carrying out this work. REFERNCES 1. C. C. Chan and K. T. Chau, Modern Electric Vehicle Technology, Oxford University Press, New York, Y. Gao, H. Maghbelli, M. Ehsani, G. Frazier, J. Kajs, and S. Bayne, Investigation of proper motor drive characteristics for military vehicle propulsion, Society of Automotive Engineers (SAE) Journal, Paper No ,Warrendale, PA, Z. Rahman, M. Ehsani, and K. Butler, An investigation of electric motor drive characteristics for EV and HEV propulsion systems, Society of Automotive Engineers (SAE) Journal, Paper No , Warrendale, PA, Z. Rahman, M. Ehsani, and K. Butler, Effect of extended-speed, constant-power operation of electric drives on the design and performance of EV-HEV propulsion system, Society of Automotive Engineers (SAE) Journal, Paper No , Warrendale, PA, K. M. Rahman and M. Ehsani, Performance analysis of electric motor drives for electric and hybrid electric vehicle application, IEEE Power Electronic in Transportation, 49 56, ISBN X, M. Ehsani, Y. Gao, and J. M. Miller, Hybrid electric vehicles: Architecture and motor drives, Proceedings of the IEEE, Special issue on Electric, Hybrid Electric and Fuel Cells Vehicle, Vol. 95, No. 4, April M.Ehsani, K. L. Butler,Y. Gao, and K.M.Rahman, Next generation passenger cars with better range, performance, and emissions: The ELPH car concept, Horizon in Engineering Symposium, Texas A&M University Engineering Program Office, College Station, Texas, September M. Ehsani, The Electrically Peaking Hybrid System and Method, US Patent No. 5,586,613, December CONTACT Sushil S. Ramdasi Asst Director Powertrain Engineering Automotive Research Association of India ramdasi.edl@araiindia.com