Between 2015 and 2021, every manufacturer must cut the fuel consumption of its fleet of new vehicles offered in Europe by an average of 27 %.

Transcription

1

2 Between 2015 and 2021, every manufacturer must cut the fuel consumption of its fleet of new vehicles offered in Europe by an average of 27 %. Tobias Eckl, Dr. Eckhard Kirchner, Start-Stop: Yesterday, Today and Tomorrow, Schaeffler Technologies GmbH & Co. KG

3 KAVRAMSAL OLARAK START-STOP SİSTEMİ Microhybrids (idling start/stop) Soft hybrids (stop and go) Full hybrids (power assist HEVs) Example of existing HEV battery systems: NiMH batteries Example of incoming HEV battery systems: Li-ion batteries Plug-in hybrids Li ion batteries for PHEVs Electric vehicles Examples of recent EV battery systems: Li ion Examples of recent EV battery systems: lithium metal polymer Examples of recent EV battery systems: sodium/nickel chloride (ZEBRA) Fuel Cell Hybrid Vehicles Electric and Hybrid Vehicles - Power Sources, Models, Sustainability, Infrastructure and the Market by Pistoia 2010

4 KAVRAMSAL OLARAK START-STOP SİSTEMİ Mike Duoba, Electric Vehicles, Sizing and Operation in Hybrid, ERC 2011 Symposium, June 8, 2011

5 START-STOP SİSTEMİNDE MUHTEMEL TREND By 2017, about 90% of new vehicles will be equipped with start/stop systems in Europe. This means workshops can expect an increasing demand for the corresponding spare parts and services. Benefit from extensive start/stop system expertise: Parts, Diagnostic and Services from Bosch

6 KAVRAMSAL OLARAK START-STOP SİSTEMİ Microhybrids (Idling Start/Stop) In these cars, the combustion engine is stopped as soon as the car stops. The starter alternator is only used to start the engine. No regenerative energy is recovered on breaking, and a few hundred watt-hours of energy is required (with a power of kw). Therefore 12 V SLI lead acid batteries of the largest size can supply the required power. The same battery provides the energy for onboard equipment and starting. The battery is usually maintained at full SOC, but much more frequently and more deeply discharged than the conventional SLI. Therefore, battery aging is the challenge, the projected lifetime being generally about 1 2 years less than SLI batteries in conventional cars. As a consequence, the battery cost has to be as low as possible, and the replacement cost should be compensated by increased fuel economy. This fuel consumption reduction is obviously very dependent on the driving mode; in true urban configuration, with many stops, fuel saving can be more than 15%. The valve-regulated adsorbed glass mat (AGM) technology is the most appropriate and offers the best cost/performance ratio, because of an improved cycle life [15]. Flooded type batteries with improved cycle life are also being developed. Electric and Hybrid Vehicles - Power Sources, Models, Sustainability, Infrastructure and the Market by Pistoia 2010

7 START STOP (MIKRO HIBRIT) TEKNOLOJİSİ Start-Stop teknolojisi ihtiyaç duyulmadığı sürece içten yanmalı motorun (İYM) çalıştırılmaması prensibine dayanır. Böylece içten yanmalı motorun boşta çalıştığı süre minimuma indirilerek yakıt tasarrufu ve CO2 emisyonunda azalma sağlanır. Günümüzde modern bir benzinli içten yanmalı motorun çalıştırılması için gerekli enerji o motorun 0,7 saniyede boşta çalışarak tüketeceği enerjiye denktir. Dolayısıyla 0,7 saniye üstündeki her duruş süresinde içten yanmalı motoru kapatmak yakıt tasarrufu sağlamaktadır. Start-Stop (s-s) araçlar kendi içinde farklılaşmaktadır. Bazı araçlar geri kazanımlı frenleme yaparak araç kinetik enerjisinin aküde depolanmasını sağlarken, bazı araçlar ise geri kazanımlı frenleme özelliğini yapısında bulundurmuyor. Geri kazanımlı frenleme özelliğine sahip olmayan araçlarda yakıt tüketiminde ve CO2 emisyonlarında %5 azalma sağlanırken, bu özelliğe sahip araçlarda bu oran %10 lara ulaşabilmektedir (Avrupa şehir içi çevrim testleri sonucunda ulaşılmış değerlerdir). Her geçen yıl sıkılaşan emisyon standartları nedeniyle önümüzdeki yıllarda üretilecek araçlarının çok büyük kısmının start-stop özelliğine sahip olması beklenmektedir. - See more at:

8 KAVRAMSAL OLARAK START-STOP SİSTEMİ Soft Hybrids (Stop and Go) The main difference with the former concept is that some energy is saved by regenerative electric power produced on braking (50 60% braking energy is converted to electricity), and more electric energy is used on starting because the car starts in an electric mode, while the ICE is being started. Compared to stop and start, the gain in fuel consumption can be almost doubled in the same driving conditions (from 5 to 25%). There is a strong impact on the energy storage system that must be able to sustain high charge peak power, and provide more power and energy during the starting phase. The average power required during car start and average regeneration power is 6 kw. The lead acid battery provides the energy required during start, and all onboard electric energy needs. Because the battery provides more energy, the SOC will vary more than in the stop and start, and typical depth of cycling range is 20% DOD, between 100 and 80% SOC, for a battery of similar size to the stop and start hybrid. The conventional lead acid battery design with flat plates is not well suited for this working mode and lifetime is reduced. The solution would be to increase the battery size, but volume and weight would become a burden. A better technical solution is the advanced high-power lead acid technology of spirally wound design. Another solution considered today is an association of conventional SLI lead acid battery and supercapacitors. The role of the capacitors is to accommodate and store the high peaks of regenerative power and help on starting, while the battery provides energy. High-power Li ion batteries possess both power and energy requirements and can be considered as a future longer life solution as soon as the cost becomes compatible. Electric and Hybrid Vehicles - Power Sources, Models, Sustainability, Infrastructure and the Market by Pistoia 2010

9 START-STOP SİSTEMİ NEDİR? Start-stop teknolojisi ihtiyaç duyulmadığı sürece içten yanmalı motorun (İYM) çalıştırılmaması prensibine dayanır. Böylece içten yanmalı motorun boşta çalıştığı süre minimuma indirilerek yakıt tasarrufu ve egzoz emisyonlarında azalma sağlanır.

10 START-STOP SİSTEMİ NASIL ÇALIŞIR? Start-Stop sistemi, aracınızı durakta, kırmızı ışıkta ya da trafik sebebiyle durdurduğunuzda motoru otomatik olarak durdurur ve böylece aracınız sadece çalışması gerektiği zamanlarda çalışır.

11 START-STOP SİSTEMİ NASIL ÇALIŞIR? Manuel şanzımanlı araçlarda araç durdurulup, ayak debriyajdan çekildiğinde, Otomatik şanzımanlı araçlarda ise araç durur pozisyona getirildikten sonra sürücünün ayağı frene basıldığı süre boyunca sistem otomatik olarak motoru geçici olarak durdurur. Bu sırada gösterge panelinde ise "Start Stop" yazısı belirir. Aracı tekrar hareket ettirmek için manuel araçlarda debriyaja basılır basılmaz, otomatik araçlarda ise ayak frenden çekilir çekilmez sistem, motoru otomatik olarak yeniden çalıştırır. Start-stop sistemi opsiyonel olarak kontrol butonu yardımıyla devre dışı bırakılabilir.

12

13

14 START-STOP SİSTEMİNİN YAPISAL UNSURLARI 1. Engine control unit with software option start/stop 2. DC / DC converter 12 volts 3. Deep-cycle resistant battery (EFB, AGM) and battery sensor 4. Start/stop starter 5. Neutral gear sensor 6. Wheel-speed sensor 7. Crankshaft sensor 8. Alternator Benefit from extensive start/stop system expertise: Parts, Diagnostic and Services from Bosch

15 START-STOP SİSTEMİNİN YAPISAL UNSURLARI 1. Engine ECU: Manages the Start & Stop system. 2. Car Acces System 3. Start-up motor: It is responsible for starting the internal combustion engine. 4. Instruments panel: Informs the driver about the status of the Start & Stop system: activated/deactivated. 5. MSA Centre console switching centre 6. Speed sensor: Informs, normally through the ABS unit, of the vehicle s speed. 7. Battery sensor: Informs the engine unit about the current entering and leaving the battery in order to estimate charge level. 8. Bonnet switch: Warns the engine unit of bonnet opening. 9. Seat belt switch: Indicates to the engine unit whether the seat belt is fastened or not. Start & Stop System - EureTechNews_Dec_2012_GB

16 START-STOP SİSTEMİNİN YAPISAL UNSURLARI 10. Clutch pedal position sensor: Signals the pedal s position. If the lever is slightly shifted (a hand is resting on it), the motor starts after pressing the pedal by 90%. 11. Clutch pedal position sensor: Signals the pedal s position. If the gear lever is in neutral position, the motor starts after pressing the pedal by 10%. 12. Brake servo vacuum sensor: Located on the servo brake, sends a signal proportional to the brake s vacuum. 13. Neutral position sensor: Located on the gear box, signals the gear lever position. Normally, after replacement, calibration needs to be carried out using diagnosis equipment. 14. Automatic Heat and A/C integrated system (IHKA) / Heat and A/C integrated regulator (IHKR). Climate control unit: Requests start up of the engine when it needs thermal units (A/C compressor) or calories (heating radiator) to reach the temperature selected by the driver. Start & Stop System - EureTechNews_Dec_2012_GB

17 START-STOP SİSTEMİNİN YAPISAL UNSURLARI Coordination: Energy management (1 and 3) The engine control unit with integrated start/stop coordinator and the battery sensor are the principal components of the energy management system. Additional items include a deep-cycle resistant battery with EFB or AGM technology and a DC/DC converter. Direct current: DC/DC converters (2) The voltage level in the vehicle electrical system drops briefly when operating the starter. This can impair the operation of electronic devices in the form of interrupted radio reception or the loss of navigation function. The DC/DC converter prevents this from happening by stabilizing the electrical system when starting the engine. Monitoring: Electronic battery sensor [EBS] (3) The Electronic Battery Sensor EBS, located in the pole recess of the battery, accurately and dynamically records the operating values such as current, voltage and temperature. It uses the measured values to monitor the capability of the battery and determine the energy input and output capacity. Benefit from extensive start/stop system expertise: Parts, Diagnostic and Services from Bosch, 2014.

18 START-STOP SİSTEMİNİN YAPISAL UNSURLARI Reading Text Constant voltage level: DC/DC converter The DC/DC converter stabilizes the vehicle electronic system and prevents problems with, or the failure of electronic equipment, such as the radio or navigation system on starting. Maintains the voltage level on starting: DC/DC converter Accurate measurement results: Sensors A network of different vehicle sensors provides the control unit with the latest status data to achieve optimum control of the start/stop function. The neutral gear sensor indicates whether a gear is engaged. The wheel speed sensor detects the direction of wheel rotation and whether the wheel is at a standstill. The intelligent crankshaft sensor signals the engine activity. The brake booster differential pressure sensor monitors the pressure in the brake booster during the stop phase in order to start the engine when the pressure drops. This protects the brake booster. The electronic battery sensor (EBS) monitors the battery power status. Benefit from extensive start/stop system expertise : Parts, Diagnostic and Services from Bosch, 2014

19 START-STOP SİSTEMİNİN YAPISAL UNSURLARI Especially more powerful: Start/stop starters (4) By strengthening of the bearings, using an improved planetary gear, strengthened pinion-engaging mechanics and optimization of the commutator for longer service life, the starter has been optimized for frequent startings. Information managers: Sensors (5, 6 and 7) The sensors provide the control system with up-to-date information to help optimize the starting process. Whilst the neutral position sensor indicates whether a gear is engaged, the wheel speed sensor measures whether the vehicle has actually come to a standstill. The crankshaft sensor accordingly signals the engine activity. Reliable power source: Alternator (8) Even in the low speed range and immediately after starting, the highly efficient alternators generate a surplus of energy to supply the vehicle electrical system. In conjunction with the powerful battery they increase the availability of the start/stop Function. Benefit from extensive start/stop system expertise: Parts, Diagnostic and Services from Bosch, 2014.

20 START-STOP SİSTEMİNİN YAPISAL UNSURLARI Starters for Start/Stop Systems The number of starting sequences that are carried out with the starter motor, i.e. its service life, has been considerably increased so that the starter motor is able to withstand the frequent starts made over the lifetime of the vehicle. The following measures have thus been implemented: 1. Strengthening of the bearings which come under severe strain 2. Further improvement of the planetary gear 3. Use of a stronger starter pinion drive. 4. Optimization of the commutator for longer service life Alternators for Start/Stop Systems Alternators for start/stop systems create more electrical energy for the on-board diagnostics, even at low speeds and directly after the vehicle has been started. Together with the high-performance battery, they increase the availability of the start/stop function. Improved electrical design and optimized materials Particularly efficient at low speeds High efficiency diode technology (HED) Greater efficiency of up to 77% Greater fuel savings of up to 2% Noise-optimized Start & Stop System - EureTechNews_Dec_2012_GB

21 START-STOP SİSTEMİNİN YAPISAL UNSURLARI Filters for Start/Stop Systems Vehicles with start/stop systems start approximately six times more often than conventional vehicles. Due to the increased number of engine starts, the fuel filter is exposed more often to strong pressure pulsations. A particularly sturdy fuel filter with stronger housing, gasket seals and cover should thus be used to prevent bursting. Start & Stop System - EureTechNews_Dec_2012_GB Schaeffler Technologies GmbH & Co. KG Technology & Engineering

22 Tobias Eckl, Dr. Eckhard Kirchner, Start-Stop: Yesterday, Today and Tomorrow, Schaeffler Technologies GmbH & Co. KG While a conventional vehicle is designed for only about 36,000 starts, basic start-stop systems are designed to endure between 300,000 and 500,000 such cycles. The specifications for a vehicle with sailing function are based on an average 1.2 million starts. This means: During the 300,000 kilometers of the vehicle s expected lifetime, the motor is switched off and on again every 250 meters. For comparison: Today s hybrid vehicles arrive at approximately 600,000 start cycles (Figure 1). However, a decrease in the total required start cycles is emerging in vehicles with sailing function. This is due to the limited number of starts due to the operating strategy (reduced sailing speed range, latency). The following aspects also have to be taken into consideration: The crank and the valve train are subjected to prolonged periods without oil pressure and are therefore frequently operated under conditions of mixed friction. The systems for exhaust gas after-treatment go through a temporary, shortterm cooling phase much more often. The accessory units in the belt drive pass through the start process more frequently (resonances, rotational irregularities). The elements of the air intake system (throttle valve, fuel injection system, turbocharger) pass through the start process more frequently (mixed friction, thermal stresses, pressure fluctuations). The dual mass flywheel often passes through the resonant vibration range. Safety-critical auxiliary units (brake servo unit, power steering pump) must be supported using electric drives under certain circumstances.

23 The length of the delay depends largely on the technology used. With a conventional starter pinion, the time between the CoM ( Change of Mind ) event and reaching idle speed once again lasts up to 1200 ms. Development of start-stop technologies and functions by 2020 Tobias Eckl, Dr. Eckhard Kirchner, Start-Stop: Yesterday, Today and Tomorrow, Schaeffler Technologies GmbH & Co. KG In sailing mode, when the car is off throttle or going down an incline, the engine can turn off and the electric motor can either provide occasional power or act as a generator. Ref.:

24 Tobias Eckl, Dr. Eckhard Kirchner, Start-Stop: Yesterday, Today and Tomorrow, Schaeffler Technologies GmbH & Co. KG The starter-generator can then drive the air conditioning compressor when the engine is switched off. Two-speed starter with planetary gear

25 The starter can then translate the lower friction of the warm engine into higher starting speeds using the same power input. This not only reduces the start time, but also the noise and vibration levels. First gear is used for cold starts only, so that the customer perceives a noticeable difference between cold start and restart. This gain in comfort compares favorably to the relatively low outlay required for the mechanical integration. Tobias Eckl, Dr. Eckhard Kirchner, Start-Stop: Yesterday, Today and Tomorrow, Schaeffler Technologies GmbH & Co. KG

26 Tobias Eckl, Dr. Eckhard Kirchner, Start-Stop: Yesterday, Today and Tomorrow, Schaeffler Technologies GmbH & Co. KG Power split concept for the electrification of the air-conditioning compressor The existing belt drive remains unchanged. Instead of a rigidly connected or magnetically separable pulley, a planetary gear set is used for the airconditioning compressor.

27 EATON - Hydraulic Launch Assist POCLAIN HYDRAULICS CleanStart NAVISTAR IRISBUS HYNOVIS EPA HYDRAULIC POWER-TRAINS

28 Michael Conrad, Hydraulic Hybrid Vehicle Technologies, Bosch Rexroth Corporation, Clean Technologies Forum, September 09, 2008

29 HYDRAULIC LAUNCH ASSIST These hydraulic hybrids have been demonstrated to have higher power capabilities for start and stop duty cycles. Fuel efficiency gains due to regenerated braking energy in heavy duty hydraulic hybrid vehicles were up to 70% for series hybrids, and up to 30% in parallel drivetrains. Background, Research Needs, Stakeholder and Expert Input, Research Recommendations, and Research and Technology (R&T) Roadmaps, DECEMBER 2010 /

30 HATIRLATMA Michael Conrad, Hydraulic Hybrid Vehicle Technologies, Bosch Rexroth Corporation, Clean Technologies Forum, September 09, 2008

31 Michael Conrad, Hydraulic Hybrid Vehicle Technologies, Bosch Rexroth Corporation, Clean Technologies Forum, September 09, 2008

32 HYDRAULIC LAUNCH ASSIST Figure a Eaton Parallel Hydraulic Hybrid Schematic Background, Research Needs, Stakeholder and Expert Input, Research Recommendations, and Research and Technology (R&T) Roadmaps, DECEMBER 2010 /

33 HYDRAULIC LAUNCH ASSIST Figure b - The Eaton series hydraulic hybrid drive schematic Background, Research Needs, Stakeholder and Expert Input, Research Recommendations, and Research and Technology (R&T) Roadmaps, DECEMBER 2010 /

34 HYDRAULIC LAUNCH ASSIST - EATON

35 HYDRAULIC LAUNCH ASSIST - EATON

36 HYDRAULIC LAUNCH ASSIST - EATON Parallel Hydraulic Hybrid Architecture Maximum rated pressure bar psi Eaton Hydraulic Launch Assist (HLA) TRSM1200 / June 2012

37 HYDRAULIC LAUNCH ASSIST - EATON HLA Hybrid Components and Connector Locations Eaton Hydraulic Launch Assist (HLA) TRSM1200 / June 2012

38 HİDROLİK HİBRİDLERDE START-STOP SİSTEMİ Hydraulic starter (1) Hydraulic pump (2) Sequence valve (3) Hydraulic accumulator (4) Tank (5) Electronic control unit (6) CleanStart System, 2014

39 HİDROLİK HİBRİDLERDE START-STOP SİSTEMİ CleanStart consists of a hydraulic starter (1), which directly drives the engine crankshaft. Its function is to provide instant torque higher than the resisting torque of the engine (inertia and compression ratio), that is a maximum torque of 550 Nm. The compactness of this starter allows for an original positioning, directly into the engine pulley. The power density of the hydraulic starter enables greater responsiveness and a start-up in less than 0.5 seconds, while reducing energy losses. The hydraulic pump (2) pressurises the accumulator in preparation for the next engine start-up. A sequence valve (3) directs the pump flow for the time required to pressurise the accumulator. The stored energy (volume of oil under pressure) is sufficient to power the hydraulic starter for at least one start-up sequence. The hydraulic accumulator (4) stores the hydraulic energy necessary for starting up the engine. Since the batteries are not needed at every start-up, their life span is conserved. Fully recyclable, it furthermore presents a weight/power ratio that is very favourable when compared with batteries. The tank (5), which holds the oil. The electronic control unit (6) ensures the accumulator filling and draining sequences, provides system status updates and sends diagnostics. CleanStart System, 2014

40 HİDROLİK HİBRİDLERDE START-STOP SİSTEMİ

41 HİDROLİK HİBRİDLERDE START-STOP SİSTEMİ Contributes to urban transportations and city attractiveness When bus engine is stopped: Silence and absence of vibrations for passengers, driver and surroundings No emissions while the bus is stopped helps keep cleaner and safer air Environmentally friendly: Typical annual CO2 reduction for a 100 bus fleet : 540 ton CO2/year (1) Silence during 30% of bus operation time Recyclable hydraulic components No specific battery dedicated to engine restarts Savings and operating costs: Typical annual fuel savings for a 100 bus fleet : liters/year (~ 10%) (2) Transparent in bus maintenance programs 3 years engine operation saved after 10 years (2) (1) Calculation based on fuel savings measurement on a bus equipped with CleanStart in real operation (2) According to experimentation and measurement on a bus equipped with CleanStart in real operation

42 HYDRAULIC ENERGY STORAGE SYSTEM Energy can also be stored by using a hydraulic system, where it is stored in the form of a compressed fluid or gas in a cylinder or similar means, known as an accumulator. To pressurize a compressible fluid, one needs mechanical power and energy, which can come from an IC engine or any other engine used to activate a hydraulic pump. Of course, in this case the original source of energy which drives the engine is chemical energy of the gasoline or diesel. While extracting the energy back from the hydraulic storage, one can use a hydraulic motor. The system-level scheme for realizing a hydraulic energy storage and extraction mechanism is shown in Figure X. In this figure, the dashed lines indicate the fluid flow path. In Figure X, chemical energy of the gasoline or diesel will drive an IC engine. The engine will drive a hydraulic pump which will basically draw an incompressible fluid from a low-pressure reservoir and increase its pressure. The high-pressure incompressible fluid can be used to drive a hydraulic motor which can drive some mechanical load. In the hydraulic motor, the mechanical fluid enters at high pressure and exits at low pressure, doing mechanical work in the process. Upon exiting the hydraulic motor, the low-pressure fluid flows to the lowpressure reservoir and the fluid flow circuit is completed. The high pressure reservoir fluid can also move a piston or similar mechanism which in turn can push against a compressible gas. This compression will cause energy to be stored in the gas. Once some predefined pressure has been achieved, a valve can be used to prevent further pressurization of the gas. While extracting energy from the accumulator, an appropriate valve can be opened and the compressed gas will work against some piston and pressurize the incompressible fluid in the high-pressure reservoir, which in turn will drive a hydraulic motor. Chris Mi, M. Abul Masrur, David Wenzhong Gao, Hybrid Electric Vehicles - Principles And Applications With Practical Perspectives, ISBN , 2011.

43 HYDRAULIC ENERGY STORAGE SYSTEM Figure X: Generic scheme for hydraulic energy storage and extraction In Figure X, it can be seen that the dashed fluid flow path forms a closed loop system. It can also be seen that the fluid path can be bidirectional between the accumulator and the high-pressure fluid reservoir. Note that energy itself is stored in the compressible gas or fluid. The incompressible fluid (liquid) provides a flexible path or actuator, which replaces any mechanical linkage which otherwise would have been used for actuation. Note also that an accumulator by itself is not of much use without the peripheral equipment or subsystems shown in Figure X, since ultimately the goal is to be able to use the stored energy in a beneficial manner when needed, or, when extra energy is available, to store it in the accumulator. All the above items shown in Figure X together form the overall hydraulic energy extraction and storage system mechanism. Chris Mi, M. Abul Masrur, David Wenzhong Gao, Hybrid Electric Vehicles - Principles And Applications With Practical Perspectives, ISBN , 2011.

44 HYDRAULIC ENERGY STORAGE SYSTEM The accumulator includes a highpressure (HP) accumulator containing some benign gas like nitrogen. The pressure in this cylinder can be as high as psi (21 35 MPa), whereas the low-pressure (LP) cylinder pressure can be very low, on the order of a few hundred psi. The IC engine drives a pump, which takes the fluid from the LP cylinder side, pumps it to a very high pressure, and then delivers it to the HP cylinder side and the mechanical energy can be ultimately stored in the form of HP gas. To drive the vehicle s wheels, the HP fluid from the HP cylinder side passes through a hydraulic motor drive assembly. The hydraulic motor takes in the HP fluid, converts it to mechanical power at the wheels, and when the fluid has passed through the hydraulic motor, its pressure drops and it is transferred to the LP cylinder. Note that the amount of energy storage in the hydraulic accumulator system is rather low in terms of kilowatt hours per kilogram. For example, the energy storage density in a hydraulic accumulator can be about 1.9 Wh/kg [2], whereas a battery can have an energy density of Wh/kg. However, the power density of a hydraulic system can be 2500 W/kg, whereas the electrical system power density can be about 650 W/kg. It is therefore apparent that the hydraulic hybrid system is very suitable for a high-power and relatively low-energy system, particularly where short bursts of high-power acceleration and deceleration are involved. Chris Mi, M. Abul Masrur, David Wenzhong Gao, Hybrid Electric Vehicles - Principles And Applications With Practical Perspectives, ISBN , 2011.

45 Chris Mi, M. Abul Masrur, David Wenzhong Gao, Hybrid Electric Vehicles - Principles And Applications With Practical Perspectives, ISBN , 2011.

46 HYDRAULIC ENERGY STORAGE SYSTEM HHVs offer the benefit of regeneration when a vehicle is slowing down, and the ability to use the captured energy to accelerate again thereafter. As noted earlier, the specific energy of the hydraulic system or watt hours per kilogram is relatively low compared to a battery. However, it can still be good enough for braking applications, since, during braking, in general the power is high but the energy involved is typically low. Hence hydraulic storage can be quite adequate for the purpose. The regeneration process is shown in Figure. In this diagram it can be seen that the efficiencies of the hydraulic pump and motor are both a little over 90%. The efficiency of the accumulator (HP and LP together) is about 98%. Hence the efficiency of the whole regeneration process is about 82%. In another situation for a hybrid truck, the regenerative efficiency was shown to be 61%, which is still quite good. One advantage of the hybrid hydraulic system is that the technology is very mature and has been around for many years. Components used in a hydraulic system, like the ones indicated in Figure, have a very high efficiency. Chris Mi, M. Abul Masrur, David Wenzhong Gao, Hybrid Electric Vehicles - Principles And Applications With Practical Perspectives, ISBN , 2011.

47 HYDRAULIC ENERGY STORAGE SYSTEM Chris Mi, M. Abul Masrur, David Wenzhong Gao, Hybrid Electric Vehicles - Principles And Applications With Practical Perspectives, ISBN , 2011.

48

49 Michael Conrad, Hydraulic Hybrid Vehicle Technologies, Bosch Rexroth Corporation, Clean Technologies Forum, September 09, 2008

50 START-STOP STRATEJİSİ

51 24 V Sistemde Tahmini Yükler Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

52 START-STOP DÖNÜŞÜMÜ İÇİN GEREKLİ OLAN PARAMETRELER Engine and Auxiliary Systems Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

53 START-STOP DÖNÜŞÜMÜ İÇİN GEREKLİ OLAN PARAMETRELER Table: Minimum stop time, calculation inputs and results. s/s performed by means of the conventional starter motor. Idle fuel consumption [g/s] 0,77 Engine off power consumption [kw] 4,0 Engine off power consumption, equivalent fuel consumption [g/s] 0,50 Start fuel consumption [g] 0,7 Start battery energy consumption [Wh] 2,1 Start battery energy consumption, equivalent fuel [g] 0,94 Fuel saved at stop [g/s] 0,27 Total fuel needed for start [g] 1,64 Minimal stop time to break even [s] 6,1 Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

54 START-STOP STRATEJİSİ The strategy for controlling the engine stop and restart operation consists of four main tasks; 1. Detect when the engine can be turned off 2. Control the shut down process 3. Detect when the engine shall be restarted 4. Control the restart process A flow chart for the process of executing the strategy can be seen in Figure Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

55 START-STOP STRATEJİSİ 1. Conditions for engine stop 1.1 Triggers To carry out this strategy multiple conditions needs to be checked to enable engine stop. The triggers are used to detect when a stop is possible and to make the s/s function entirely automatic. These are presented here and explained. Bus stop brake request: As the bus stops and opens the doors to let passengers on and off the bus stop brake is engaged which applies the service brakes without the driver presses the brake pedal. Since this function uses the opening of doors as input using the bus stop brake request as trigger is equivalent to check the status of the doors. Bus stop brake request also implies zero vehicle speed. Parking Brake: Once the parking brake is set it is assumed that the bus will be at standstill most likely long enough to make the stop beneficial. Using the parking brake is an alternate way to detect vehicle stop compared to the bus stop brake. This condition will get hold of stops outside regular traffic. It should be pointed out that using the parking brake as trigger for shut down and restart might give a delay at restart if the driver intends to take off directly after releasing the parking brake. This is however still included because a delay is considered acceptable at occasions where the parking brake is used. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

56 START-STOP STRATEJİSİ 1. Conditions for engine stop (cont.) 1.2 Conditions The following conditions must be fulfilled to enable engine off. Vehicle speed: This condition is checked for redundancy since the triggers themselves implies zero vehicle speed but should be checked for security purposes. Regardless of the status of other signals the engine may not be turned off if the vehicle is in motion. This is an important condition if the functionality would be extended to include traffic stops such as stops at red lights or stop signs. Engine speed: This condition is motivated by the fact that if the engine speed exceeds idling speed the engine performs some kind of work and can not be turned off. Engine speed must be at normal idle speed to enable engine off. Battery status: A positive average battery charge rate must be assured during stop and go driving with start/stop functionality. This can be done by an external or internal function that provides a battery status indication. If the battery charge trend is positive an engine shut off is possible from a battery point of view. This information is not present in the bus today but will most likely be required to guarantee the service life of the batteries and the reliability of the vehicle. Future work is highly recommended in this area. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

57 START-STOP STRATEJİSİ 1. Conditions for engine stop (cont.) 1.2 Conditions Air supply pressure: To ensure that the pressure in the air tanks does not decline under 9 bar the pressure in the air tanks must be at a sufficient level. At 9 bar pressure regulation states that the air compressor must be activated to supply the air tanks with air. If the supply pressure is greater than a predefined limit it would be possible to open the doors as well as kneeling the bus without the pressure decreasing to 9 bar. Air compressor status: If the air compressor is active the engine can not be turned off. This is an alternative to looking at the air pressure since compressor active also is an indication of low pressure. To ensure sufficient air pressure, the compressor should be allowed to work until its cut-off pressure level. Super capacitors SOC: The SOC in the ESS must be at or above the SOC target value to be able to provide sufficient electrical power to both start the engine with the generator and accelerate the vehicle with the propulsion motor. Engine temperature: The engine temperature is estimated by checking the engine coolant temperature. The temperature should be within an acceptable range. The lower limit is set to ensure that the following restart can be considered warm. This is due to increased emissions and engine wear at cold restarts. The temperature should not be to hot either due to risk of damaging the coolant system. Therefore an upper temperature limit should also be set. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

58 START-STOP STRATEJİSİ 1. Conditions for engine stop (cont.) 1.2 Conditions Brake resistor temperature: The coolant system can take damage if the temperature is too high in the BR when the coolant flow ceases. If the brake resistor is hot and in need of coolant flow after braking the engine can not be turned off. Cab interior temperature: The cab interior temperature should be monitored to see how it s influenced by start/stop. There is no heating or cooling capacity during a stop so changes in temperature are inevitable. The temperature shall thus be monitored over time to ensure that the temperature is not decreasing or increasing from the target value e.g. the temperature value set by the climate control. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

59 START-STOP STRATEJİSİ 2. Engine Shut Down An approach is to utilize the generator to make the stop as smooth and comfortable as possible. By adding a braking torque a quick engine stop can be achieved where the natural frequencies quickly are passed. Normally, engine shut down is made by simply cutting off the fuel supply and letting the engine slow down to rest by means of its own internal friction. The tumbling movement occurs when the crankshaft momentum is decreased to a level where it no longer can overcome the resistance from the compression pressure alternately acting on the pistons. This causes the crankshaft to shift rotational direction and rotate backwards a little bit until it is meets the compression pulse from another cylinder where it changes direction again. Consequentially, the crankshaft changes direction a few times before it is settling to rest, resulting in a tumbling movement of the engine. These tumbles can be prevented by braking the engine by means of the generator and aim for a crankshaft position that is right in between the peak of two compression pulses. This calls for the controller to have the exact angular position of the crankshaft as input as well as a design based on a very accurate engine model in order to follow a specific trajectory. However, this information is not distributed on the CAN network today and will require software changes in the engine control ECU. Due to this and the time limitation of this thesis a position-based control of the enginegenerator unit was not further investigated. This is however an area for future research to further minimize noise and vibrations during shut down. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

60 START-STOP STRATEJİSİ 3. Triggers for engine restart One of the most important aspects to consider when to trigger an engine restart is to maintain full driver control of the vehicle. As mentioned earlier, the engine must have been restarted as the vehicle takes off. A restart is also initialized if an auxiliary system requires the engine to be restarted. Door status: The status of the doors would be a better way to predict an upcoming take-off from a bus stop than the bus stop brake. As the doors need a few seconds to close, it would be beneficial to perform a restart of the engine at the same moment as the driver closes the last door. The engine would then be up and running when the bus stop brake is released and the driver intend to accelerate. Kneeling: The request of bus level increase after kneeling would also be a god indication of that the engine should be restarted and since automatic kneeling at bus stops soon might be required. This would be an alternative way to predict bus take off. In addition, the raise of the bus is the most air-consuming event of the bus stop procedure. Meaning that a restart of the engine and the air compressor at this moment could be necessary in order to be able to raise the bus correctly and prevent far too low air pressure. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

61 START-STOP STRATEJİSİ 3. Triggers for engine restart (cont.) Parking brake: If s/s is performed in another situation than at a bus stop, where applying the parking brake is trigger for engine stop, the release of the parking brake would be a simple and obvious indication of that the driver intends to take off. Battery status: An indication of that the 24 V battery SOC has reached a minimum level should trig the engine to restart and thereby enable the use of the alternators in order to prevent battery discharge. Air supply pressure low: If the air supply pressure reaches the low limit a restart of the engine is necessary in order to maintain functionality of the pneumatically controlled systems such as the brakes. Air compressor status: This indicates that there is a need for compressing air into the air tanks and thereby engine restart. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

62 START-STOP STRATEJİSİ 3. Triggers for engine restart (cont.) Super capacitor SOC low: As the super capacitors might suffer from a leakage in form a slow discharge, it would be necessary to trig a restart of the engine if the SOC reaches a certain low level. As the engine is restarted, the SOC decrease would be stopped and the upcoming acceleration would not be negatively affected. Accelerator pedal position: An applied accelerator pedal is a good indication of that the driver within short intends to take off. Many bus drivers applies the accelerator pedal prior to or while closing the doors, meaning that the bus takes off as soon as the bus stop brake is automatically disengaged. This could give a trigger early enough to have the engine up and running so that the bus can take off without any delay. However, using the accelerator pedal position as a trigger could on the other hand contribute to a reduction in the s/s utilisation as some drivers might apply the pedal far too early. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

63 Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009 START-STOP STRATEJİSİ 4. Engine restart The engine start should be quiet and vibration-less in order to make the s/s function go by as unnoticed as possible. It should not have a negative impact on passenger and driver comfort as well as exterior noise. In order to fulfill this demand, the strategy utilizes the generator to crank the engine to an as large extent as possible. As a suggestion the engine also should be cranked to a speed higher than normal cranking speed. This would reduce the amount of fuel needed for the start as well as engine wear and high emission-transients. The standard starter motor should be kept and used during conditions where the generator-start function is not optimized, e.g. for cold starts. The starter motor also would serve as a back-up in case of generator-start control malfunction or if the generator at the moment can not be used due to low SOC in the super capacitors. The strategy is to accelerate the engine to idle speed by means of the generator and then hand the control over to the idle speed regulator as if it was a drag start. The engine installation and the chassis have many natural frequencies in the low (0 to idle) engine speed domain. Therefore, in order to prevent vibrations and noise, the engine should be cranked to the idle speed as quickly as possible. Also when considering take-off response, a quick start is desirable. However, an upper limit on applied torque would need to be implemented in order not to strain the components to a too large extent.

64 START-STOP - ECU VE CAN YAPISI Scania uses the CAN standard SAE J1939 [23]. CAN is a serial bus communication protocol developed by Bosch and is designed for efficient, robust and failsafe communication. The CAN message frame is divided into several fields according to Figure. Figure: CAN message frame. The SOF, Start Of Frame, bit indicates the start of the message. The identifier and the RTR, Remote Transmission Request, make up the arbitration field which is used by the CAN protocol to avoid collisions. The control field indicates how many bytes of data the data field includes. This can be anything from zero to eight bytes. The CRC, Cyclic Redundant Checksum, enables the receiver to check if the message has been corrupted. To acknowledge that a valid frame has been received the transmitter uses the ACK, ACKnowledge, field. The message ends with an EOF, End Of Frame, field [22]. The CAN protocol is widely used in the automotive industry. The major benefits come from the embedded error handling and the ability to connect multiple nodes to one bus. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

65 START-STOP - ECU VE CAN YAPISI Figure: Use case diagram of the start/stop logic and involved ECU s. The coordinator, COO, node is a gateway linking messages between the red, yellow and green CAN buses. Air processing system, APS Bus chassis system, BCS Interaction with the instrument cluster (ICL) Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

66 START-STOP - ECU VE CAN YAPISI Air processing system The air processing system, APS, unit holds information of the pneumatic system. To ensure that the tanks have sufficient pressure to permit an engine stop the compressor activity or pressure levels should be monitored. Bus chassis system The bus chassis system, BCS, holds information about the bus chassis and also works as a gateway towards the add-on systems that the bus bodybuilder provides. From the BCS information about kneeling, status of doors and ambient as well cab interior temperature can be obtained. Bus stop brake request is sent by the BCS when one or more doors are opened. When the request is sent the EBS applies the service brakes. The bus stop brake is released as the doors are closed again and the Bus Stop Brake Request message is in not requested status. Instrument cluster system Interaction with the instrument cluster (ICL) would be necessary to provide relevant information to the driver. The ICL should be notified when the engine is turned off perhaps with an engine status message. The ICL shall provide consistent information to the driver. To make the start/stop function transparent to the driver changes in the ICL system is necessary. For example battery lamp should not be high lightened during an automatic engine stop. Coordinator The coordinator, COO, node is a gateway linking messages between the red, yellow and green CAN buses. Enabling a red node to receive a message send by a yellow or green node. All messages or signals are not linked by the gateway. Hence a software update is required to decode the necessary messages and signals to enable the start/stop function. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

67 START-STOP - ECU VE CAN YAPISI Engine management system From the engine control, EMS, ECU the engine coolant temperature is obtained. This is to ensure warm engine operation temperature. Information about the engine speed can also be provided by the engine ECU but in this case this information is acquired from the HCS. Hybrid components system The hybrid components are controlled by a group of separate ECU s, here referred to as Hybrid Component System (HCS). From the HCS information is obtained concerning the generator, propulsion motor, super capacitors and resistor unit. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

68

69 İLERİ ARAŞTIRMALAR New APS strategy: To adapt the use of the air compressors would result in a more optimal use of the start/stop strategy Electrical auxiliaries: Introduction of electrical auxiliaries would ease an implementation of a start/stop function. The major reason why the engine stop is restricted to bus stops is that the power steering action is lost. Electrical power steering would eliminate this restriction and give room for more freedom in choosing when the engine can be turned off. To replace the pneumatically controlled opening of doors with an electrical system will reduce the load on the air process system. Electrical AC compressor is another possibility. This however needs future investigation both on electrical component performance, such as long term reliability, and the extensive need for battery supply. Battery surveillance: This thesis has brought to attention the problem concerning a positive charge trend to the batteries. Battery surveillance is a necessity to guarantee battery performance during engine start/stop. Alternatively the s/s frequency has to be restricted to only a certain amount of stops per kilometre. Interior climate: Further studies on what impact a start/stop strategy would have on the interior climate is advised. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009

70 İLERİ ARAŞTIRMALAR Impact on noise: Further studies on how the noise from the transient behaviour of the engine is perceived are advised. This shall be done to identify where the stop and restart process needs enhancements. Impact on fuel economy: Tests needs to be carried out to verify the fuel consumption calculations made in this thesis. Impact on emissions: How the start stop function with generator has positive effect on emissions needs to be further investigated. Strategy realization Engine position control: To minimize vibration during shut down the engine can be manoeuvred into a specified position. The generator can be used to brake the engine into that position. This requires information about the crankshaft position and a control algorithm for the generator torque demand. Optimization of generator start: The engine restart process can be further optimized. Robin Rockström, An engine start/stop strategy for a hybrid city bus, Master of Science Thesis Stockholm, Sweden 2009