Optimal Hybrid Vehicle, embedded data acquisition ...

Optimal Hybrid Vehicle, embedded data acquisition and tracking L. BAGHLI 1,2, A. MOUSSAOUI 1, K. BENMANSOUR 3, S. DELPRAT 4, M. DJEMAI 4

1 LAT, Laboratoire d'Automatique de Tlemcen, Université de Tlemcen, Algeria Université de Lorraine, GREEN, EA 4366, Vandoeuvre-lès-Nancy, F-54500, France ([email protected]) 3 Laboratoire de Recherche en Electrotechnique et en Automatique, Université de Médéa, Algeria 4 Univ. Lille Nord de France,F- 59000 Lille, France, UVHC, LAMIH, F-59313 Valenciennes, France, CNRS, UMR 8201, F-59313 Valenciennes, France 2

The paper is about the first part of a PNR (National Research Program). The study is divided into numerous parts. The first one concerns the collect of operating points of a conventional (engine) vehicle to know the energy consumption and instantaneous power needed on a driving path, in a suburban and urban everyday use of the vehicle. This paper presents the hybrid, electrical and conventional vehicle technology followed by the first part of the PNR study. It shows how the acquisition system is build, based on OBD-II CAN interface. PIDs and GPS data are recorded and displayed using 2D and 3D maps and tables. The preliminary results are presented and commented. Keywords— Hybrid vehicle, Electrical vehicle, OBD-II, Energy, PNR.

I.

INTRODUCTION

The oil crisis lead to petrol and gasoline price increase. Difference in prices on both sides of countries borders can lead to gasoline trafficking and results in local crisis and people being under pressure. Pollution, crowded city centers and oil dependency are all over factors that naturally promote the research for an alternative transport solution that can get rid of these fossil fuels. Electrical power source is naturally the awaited solution for this problem because of the different parts of the solution it can furnish. Electric motors are now a mature solution to drive a car thanks to power electronics and microcontrollers. They allow a powerful and efficient control of the driving motor and the whole car, even by using the drive by wire concept. Hybrid vehicles (HV) and plug-in hybrid electric vehicles (PHEV) are smooth transitions to the fully electrical vehicle (EV). Electrical energy storage is still a problem and the electrical vehicle has not enough autonomy for long distances. EV can only operate in urban and suburban zones, whereas HV is designed for long distances as well as a zero emission vehicle, in the city center or in residential parking. The Nissan Leaf [1][2] is the first mass diffused EV on the market. Launched in 2011 on European markets, it was awarded as the car of the year. This car succeeded the HEV Toyota Prius which had and still has a great impact on the HEV and PHEV market. Many studies, nowadays, deal with different technical solutions for HEV and EV [3]. If political considerations in USA slowed down research in HEV solution in the past 15years, we can notice that the Japanese car industry is leading the market in term of mass diffused HEV and EV. EV solution relies on the implementation of fast charging stations and/or battery-exchange stations along the roads and in the cities. The city centers are the main area to use the EV where pollution and noise must be reduced. The primary energy production for these EV cars is another problem that must find

its solution considering the new development of smart grids where customers share energy consumption in an intelligent sharing decision mode. In Algeria, the HEV has not diffused the market; through renewable energy is a great concern of the research ministry and university laboratories. Under a wide National Research Program (PNR), we decided to carry a study on the HEV. We associate two national universities (Tlemcen and Médéa) and a French one (Valenciennes) that deals with this theme. The study is divided in different parts. The first one, that belongs to the Tlemcen team, is to build an acquisition system and collect vehicle trip data in a specified database and make it available to other teams of the PNR, under graphical and table views. Afterwards, we must develop a suitable model of HEV and identify its parameters in order to prepare an optimal control algorithm based on filtering and estimation techniques. The final step is to build an experimental bench, with hardware in the loop (HIL). We will use an induction motor as the electrical motor, whereas the engine and the road will be simulated by HIL thanks to a DC motor driven by a chopper and the dSPACE DS1104 board. The study is scheduled over two years, with regular reports and exchanges between the working teams. Our partner SNVI, which is a local manufacturer of industrial vehicles, is interested in hybrid technology and we plan to log the vehicle and engine data of their buses, thank to this system tracking. This paper deals with the first part of the PNR study, which is the development of the tracking system. We will first present the hybrid scheme within a HEV vehicle and the technology found on modern cars, traditional and HEV/PHEV/EV that allows the data acquisition. Then we will focus on the OBD-II interface and the protocol used by nowadays car manufacturers. The physical interface is presented; the embedded software and the server side part are also presented.

Preliminary results are discussed in the last section of the paper. II. HYBRID, ELECTRICAL AND CONVENTIONAL VEHICLE TECHNOLOGY

We will review some achievements and technical solutions that are used in HEV, PHEV and EV. A. Motors To build an optimized HEV, one must first consider to whom it is targeted for use. If it is a city vehicle then an electric car suits well the application. Whereas, if it must go from city to city with a large range, then a hybrid vehicle is more suitable because of its large autonomy. HEV uses conventional motor named Internal Combustion Engine (ICE) as well as the electrical motor(s) (EM) to drive the car. The power requirement varies from a car manufacturer to another one because of the control strategy they implement in respect to the car usage it is designated for. ICE in HEV is often downsized, in comparison to ICE of conventional vehicles, to reduce the fuel consumption. The required nominal power of the vehicle is given by the additional EM. The latter is a Permanent Magnet Synchronous Motor (PMSM) [1] [4] (Fig. 1) or less often an Induction Motor (IM). The PMSM has an excellent efficiency and a unity power factor allowing the conversion of energy in both ways (driving / regenerating) nearly without losses. The IM is more robust than the PMSM and is naturally protected against short circuits. Indeed, there are no induced currents in the rotor if the stator is in short-circuit and the rotor is still driven by the wheels. Whereas, for the PMSM, if it is still in rotation, we will get a copper melting… because the emf is still generated in the stator, as the rotor with Permanent Magnets (PM) is driven by the car wheels. However, because the IM has a lower efficiency and is somehow heavier than the PMSM, the latter is preferred.

Fig. 1. 10kW PMSM of Honda Insight HEV[4] B. Motor control ICE is controlled through the ECU with achievement technology (common rail or TDI, piezoelectric injectors,

turbo,..) in order to reduce and event nullify the heating-up time. These allow for greater engine efficiency, and therefore greater power outputs. For electric motors, the control method can be vector control for sinusoidal m.m.f. (magnetomotive) motors or 6-sectors BLDC for trapezoidal m.m.f. synchronous motors. The vector control allows a better control and a smoother torque. Flux weakening is made obvious. Furthermore, for special structures like IPM SM (Inner Permanent Magnet), where there is a reluctance torque that can be used, a shifted control angle instead of the Park d-axis angle can be used in order to increase the overall torque [5]. C. Power electronics and energy sources Power electronics are necessary to convert the electrical energy from a DC storable form in the batteries to an AC one to drive the EM. The inverters use IGBTs and MOSFETs. The IGBT offers high voltage and current ranges in comparison to the MOSFET, but has more losses. However, the losses in the inverter are negligible in comparison with those of the motor or other elements of the power chain. The main problem of EV is the energy storage system. It is insufficient, bulky and expensive. Nowadays, the Li-Ion battery is taking the advantage over the NiMH one. The latter is present in old EV like the Prius. Li-Ion batteries are used in new vehicles like the Nissan Leaf but are very expensive (18 k USD for the battery pack). HEV and EV car manufacturers often add a DC-DC booster [6][7]. This DC-DC converter raises the battery voltage from 200 V to 500V. This choice reduces the size and the currents of the electrical machines in comparison of machines powered from a 200 V bus. There are also alternative power sources under investigation like fuel cells, but the technology is still not mature. The required drive power excludes the use of solar cells as main power source. It can only be used to charge the auxiliary 12V lead battery or to power on the A/C compressor drive while the car is parked. New concept of alternative buffers using supercapcitors with power electronics instead of traditional capacitors are investigated and implemented. Battery charge balancing and State Of Charge (SOC) estimation are the main problems that can reduce the optimal use of the battery pack in a normal use of a EV. A new concept of smart grid called Vehicle to Grid (V2G) technology is studied for PHEV while they are parked and connected to the grid. They can be used to re-inject power to the grid, on demand, in order to smooth out fluctuations. Of course, the idea is not to furnish power for long periods, but to get a damping power station of up to 1 MW, composed by about 1000 PHEV or 100 EV [8]. D. Power split device A hybrid car has to manage energy split between the ICE, the electrical motor(s) (EM) and the drive train. Thus, the power split device is the keystone of the hybrid drive system particularly in the case of a series/parallel hybrid scheme. The power ratio between the ICE and the EM depends on the control strategy but for a series/parallel hybrid scheme it could

be viewed as in Fig. 2 [9], where the total power of the electrical motors is higher than that of the ICE. The example given in Fig. 3 [9], is the one of the well known Toyota Prius. In this configuration, the vehicle can be driven by the ICE, the EM or a combination of both of them with a variable ratio allowing an optimum use of the primary energy, guaranteeing the maximum efficiency of the overall system. This system, previously named "Toyota Hybrid System (THS)" is licensed to Lexus and Nissan under the name of "Hybrid Synergy Drive (HSD)" [9][10]. Thanks to it, they achieved a high end-user HV [6][7].

gear will only slip on the next pole's pair. On the contrary, the mechanical gear will break. The transmitted torque is higher for the same size, whereas the manufacturing is a little more complex [19][20]. We can also consider including the SM within the inner rotor (Sun gear) as in to get an active magnetic planetary gear [12] and even the two EM as in [13].

Outer rotor

Airgaps

Ω3 Ω1

Fig. 2. The Ratio of engine and motor operation in hybrid systems

Ω4

Permanent magnets

Ferromagnetic pole-pieces

Inner rotor Back iron Fig. 5. Schematic of the magnetic planetary gear E. Driving strategy

Fig. 3. Series/parallel hybrid scheme The heart of the HSD is the power split device. It consists of a planetary gear box (Fig. 4) [9][10][18]with three inputs/outputs: The Internal Combustion Engine (ICE) named engine, the generator that is a permanent magnet synchronous machine (PMSM) called MG1 and a PMSM called MG2 that is connected to the wheel through reduction gears.

The HSD manages all the operating modes, involving the hybridation of the car. In the scheme presented in (Fig. 3), it combines the series hybrid system with the parallel hybrid one in order to maximize the benefits of both systems. It has two motors, and depending on the driving conditions, uses only the electric motor or the driving power from both the electric motor and the engine, in order to achieve the highest efficiency level. Furthermore, when necessary, the system drives the wheels while simultaneously generating electricity using a generator. We can distinguish 6 driving mode for this example (Fig. 3): • Start and low-speed driving: The ICE stops when in an inefficient range,the vehicle runs on the EM alone. • Cruising: ICE power is divided by the power split device. Some of the power turns the generator, which drives the EM. The rest of the power drives the wheels directly. Power allocation is controlled to maximize efficiency. • Accelerating: When strong acceleration is called, extra power is supplied from the battery to EM, over cruising scheme. This way, the HSD delivers power comparable to cars having one class larger engine. • Battery recharging: Battery level is managed to maintain sufficient reserves. The ICE drives the generator to recharge the battery when necessary at standstill or when running.

Fig. 4. Planetary gear box of the power split device A new structure is under test in laboratories based on magnetic. The replacement by a magnetic planetary gear has some advantages; [11] The magnetic gear is unbreakable because if the allowed transmitted torque is overtaken, the

• Decelerating: Under braking or when the accelerator is lifted, the HSD uses the kinetic energy of the car to recharge the battery through the EM, which works as a generator.

• At rest: The ICE, generator and EM are stopped immediately. No energy is wasted by idling. However, if the battery voltage is low, the battery recharging mode is activated. Switching between different modes depends on the battery state, the driver action and the optimization of the energy consumption. Therefore, an optimal control strategy requires an accurate estimation of the energy consumption. Moreover, if the trajectory of the vehicle is know in advance, like for regular urban and suburban buses, then the control strategy can be somehow different and could increase the autonomy by taking advantage of kinetic and potential energy along the path. F. More Electronics Modern cars requires air conditioning (A/C), GPS driving assistance, Bluetooth in order to make and receive calls handfree using car's audio speakers and to stream music from mobile phones with the A2DP profile. All these technologies are now very cheap and can be included by car manufacturers without excessive cost. They all use electric power sources, apart from the A/C which needs a compressor. The idea is to use an electric motor instead of taking the mechanical power from the ICE. At this condition, one can activate the A/C from a wireless phone while connecting to his EV car, minutes ago from getting into his car to get a cool atmosphere directly while seated without waiting, as in traditional cars. This remote functionality can be used to pre-heat or pre-cool the car prior to use while it is still charging, so that less energy from the battery is used for climate control, example for the Nissan Leaf [1][2].

coolant temperature, throttle position… but also occurred faults and engine malfunctions. Laws obliged car manufacturers to implement a standard interface, named OBD II, to support on-board diagnostis. These law applied to light duty vehicles (sold in North America since 1996), as well as medium duty vehicles (2005) and heavy duty vehicles (2010) [14]. The OBD-II PIDs (On-board diagnostics Parameter IDs) are codes used to request data from a vehicle following the SAE J1979/ / ISO 15031-5 standard [15]. However, manufacturers also define many more PIDs specific to their vehicles. An automotive technician will use a scanning device connected to OBD-II plug in order to get data according to a particular PID. The scanning device will send the PID to the through the OBD-II and the vehicle's bus (CAN, VPW, PWM, ISO, KWP. After 2008, CAN only). The corresponding device recognizes the PID as the one it is responsible for, and answers by giving the related data. The scanning tool displays the data to the technician. Going through standardization avoids having all manufacturing particular scanning tools. It is fast and reliable. The diagnosis can be made very fast and gives the history of the vehicle in term of faults. Table 1 presents the first standard PIDs of mode 01 which represent actual data. Whereas other modes (2 to 10) represents the freeze frame data, stored Diagnostic Trouble Codes (DTC),… Table 1. First standard PIDs of Mode 1 (current data) Bold represent the accessible data of the vehicle used PID Description

(hex)

Diagnosis and car maintenance are processed with M2M communications facilities through automatic calls to manufacturer data centers to redirect to nearest help / facilities.

2 3 4 5 6 7 8 9 0A 0B 0C 0D

PIDs supported [01 - 20] Monitor status since DTCs cleared. (Includes malfunction indicator lamp (MIL) status and number of DTCs.) Freeze DTC (Diagnostic Trouble Code) Fuel system status Calculated engine load value Engine coolant temperature Short term fuel % trim—Bank 1 Long term fuel % trim—Bank 1 Short term fuel % trim—Bank 2 Long term fuel % trim—Bank 2 Fuel pressure Intake manifold absolute pressure Engine RPM Vehicle speed

III. CAN BUS AND OBD-II PROTOCOL

0E

Timing advance

Modern vehicles are all equipped with ECU (Engine Control Unit) that controls the engine under the conductor demand of acceleration, deceleration, braking and the road path. Thus, these vehicles are equipped with many sensors that deliver the necessary information to control the vehicle. Other variables are calculated by the ECU and made available on the CAN bus (Control Area Network). Among these, we find: engine load, rpm, intake manifold absolute pressure, engine

0F 10 11 12 13

Intake air temperature MAF air flow rate Throttle position Commanded secondary air status Oxygen sensors present Bank 1, Sensor 1: Oxygen sensor voltage, Short term fuel trim

GPS maps and power monitoring are used on PHEV and EV to indicate the nearest power charging station by calculating the remaining distance for the EV in function of the State Of Charge (SOC). A security system produces a special audible tone by a loud speaker in the front of the EV car to warn pedestrians. Indeed, the EV does not produce the motor noise that people are used to. This ability is switched of when the vehicle is at high speed and supposed being on a highway.

0 1

14

Units

% °C % % % % kPa kPa rpm km/h ° relative to #1 cylinder °C g/s %

Volts %

IV.

INTERFACING OBD-II

We first built a CAN interface (Fig. 6) with Bluetooth capabilities around the dspic 33FJ128MC802 and BT LMX9838, but we found a much cheaper, reliable and integrated component (Fig. 7) based on the standard controller ELM327 [16]. The device interfaces to the car through a standard OBD-II plug and to the computer or WM phone through a Bluetooth interface under the Serial Port Profile (SPP). We developed a software "VHO PNR" running on Windows Mobile 6.x phone (Fig. 8), in order to get PID data through OBD-II CAN bus and also vehicle position, speed and direction through the embedded GPS.

The data are acquired from the GPS at a rate of 1 Hz and from the OBD-II at 1 Hz per PID, so for 5 data, the refreshing frequency is about 0.2 Hz in case of steady acquisition. One can see from the Table 2, that all the data are not significant. This relies on which data the car manufacturer lets available. Table 2. GPS data and OBD-II PID data collected by the developed software "VHO PNR" ID

DateTime

N. Sat

Latitude (°)

Longitude (°)

Altitude (m)

Direction (°)

VitGPS (km/h)

72 54

2012-04-01 16:01:59

9

34.879

-1.34085

785.3

95.5

35.7436

Coolant T (°C) 93

Throttle (%) 0

VitMoy (km/h) 36

GEAR 0

MAP (kPa) 0

MAF (g/s) 30.58

Load (%) 39.2157

RPM 2381

We used a local and a remote hosted server MySQL data base (DB) in order to collect the data. Since the data do not require real time processing, we prepare the SQL sentence of the insert data into the DB on a log file, updated at the fastest varying variable: 1s. The DB is updated once, after the whole campaign data set is ready. V. EXPERIMENTAL RESULTS

ELM327

Fig. 6. OBD-II CAN (lower board) and Bluetooth (upper board) interface on a programmable device

Preliminary tests are carried on a conventional (ICE) vehicle. We collected data for suburban and urban paths thanks to the "VHO PNR" acquisition system. We setup a web server interface that allows the selection of the considered path. When the page is loaded or the path is changed, the web client performs a jQuery asynchronous HTTP (Ajax) request, to get the corresponding records (Table 2); the data issued from the GPS and OBD-II PIDs. They are displayed on a table and on 2D - Google maps (Fig. 9). Enhanced features allow displaying a popup window with local data as the mouse cursor follows the path of records.

Fig. 7. OBD-II plug with ELM327 interface

Fig. 9. Map of the path and information on a particular point (urban track)

Fig. 8. WM6 Embedded software for tracking real time engine and vehicle signals

Several itineraries, around the university and the city center are tested. We present, in the associated website [17] some results of two of them; a suburban and an urban path. Using Matlab we also process data to build a 3D map with altitude and speed thanks to regularly spaced green vertical lines (Fig. 10, Fig. 11).

It is hard to obtain readable 3D figures of the paths. We project the itinerary on the ground, on a 2D Google map, to match with the previous 2D representation. The altitude and the speed give a precise idea of the kinetic and potential energies of the vehicle, at a given position. One can observe the lack of precision of GPS data on Fig. 11, when the vehicle comeback on its trajectory, at the same points, we have an error in altitude of (8 to 10 m). This is not due to earth rotation, between the records, but rather to the precision of GSPS signals which are not greater than 15 m for civil applications. Further analyses are carried out to compute the variations of kinetic and potential energies in order to get a physical estimation of energy consumption. It will be compared to the estimation of energy consumption given by the board computer through the ECU.

Fig. 10. Latitude, longitude and altitude 3D plot of the tested suburban track

Fig. 11. Latitude, longitude and altitude 3D plot of the tested urban track VI. CONCLUSION AND PERSPECTIVE We presented an overview of the techniques used nowadays and in the near future, in HEV, PHEV, EV. The study is the first part of a large research project and focuses on the development of an acquisition system based on embedded GPS and OBD-II PIDs data. Early results show the effectiveness of the system. These data will be used by a second team to elaborate an estimation of the energy used and setup an optimal control strategy, particularly for regular itineraries of suburban and urban buses.

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