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Cartronic System Architecture for Energy and Powertrain Management
Copyright @ lFAC Advances in Automotive Control, Karlsruhe, Gennany, 2001
CARTRONIC SYSTEM ARCHITECTURE FOR ENERGY AND POWERTRAIN MANAGEMENT
Jiirgen Loffler, HoJger Hiilser*, Karsten Schiller, Manfred Schmitt
Robert Bosch GmbH, Postfach 300240, D- 70442 Stuttgart •asset GmbH, Raiffeisenstr. 3, D-71696 Mbglingen [email protected]
Abstract: Networking mechatronic components and sub-systems in a vehicle necessitates a concept of order to organize the controlling and regulating systems. One such concept, called CARTRONIC®, has been developed by Robert Bosch GmbH. This article describes the CARTRONIC system architecture for integrating systems in powertrain management as well as for electrical and thermal energy management. The modules and functions of each control system are shown. The physical relationships between the flows of mechanical, thermal and electrical energy in the vehicle are derived, and it is shown how this can be optimized by a system architecture designed for the whole vehicle. Copyright © 20011FAC Keywords: Automotive control, electronic architecture, energy management systems, powertrain management, electrical supply system, thermal management, climate control
I. INTRODUCTION
goals are: - Advanced torque-based engine management systems with automatic engine shut-off, - High-efficiency automated transmissions, - Efficient electric machines (e.g. starter-alternators) integrated in the powertrain that boost propUlsion and re-generate kinetic energy during braking and overrun (Schafer, 2001), - High-performance electrical power supply systems and batteries, - Advanced cooling and cabin-climate control systems, - Integrated control systems (BUrger, et al., 2000; LoGrasso, Kidston, Fehr 2000).
In order to improve fuel consumption and emissions while enhancing comfort and safety, it takes an holistic approach to optimize the efficiency of generating and utilizing the mechanical, electrical and thermal energy in the car. In an effort to improve the sustainability of transportation, the European automotive industry (ACEA = Association des Constructeurs Europeens d'Automobile) is committed to reduce the average CO 2 -emissions - and hence the fuel consumption - to 140 g!km by the year 2008 (VDA 2000). With the Partnership for a New Generation Vehicle (PNGV) program, the US carmakers took up the challenge of developing an 80 miles per gallon (gasoline equivalent) five-passenger vehicle (PNGV, 2000). These efficiency targets must comply with the lower emission limits to be introduced in the future, like e.g. EURO IV (Kolke, 2000) and SULEV (CARB, 1998).
Ultra-efficient vehicles, such as Volkswagen's Lupo 31 (Jelden, 2000), Honda's Insight (Nakano and Ochiai, 2000), Toyota's Prius (Abe, 2000) and PNGV demonstrator vehicles (PNGV, 2000), show that coordinated powertrain and energy management strategies are the key to optimizing efficiency and performance.
Major technologies to enable attainment of these
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Three forms of energy flowing here can be distinguished: mechanical, electrical and thermal energy. Mechanical energy is transferred by means of rotating shafts, toothed-wheel connections or belt drives. Electrical energy is transmitted by means of the wiring harness; this can take place at different voltage levels (e.g. 14 V or 42 V). Thermal energy is transported by the mass of flowing coolant, exhaust gas or air. This energy network supplies: - Mechanical power to the wheels for vehicle propulsion (1). When braking or during overrun, mechanical energy can also be returned to the network through the wheels (2). Also, mechanical energy might be supplied to such auxiliary units external to the network, like the power-steering pump for example (3). - Electrical power to consumers that are not part of the network (4). - Thermal power for heating or cooling the passenger compartriient (5).
This article presents control strategies and system architectures for the management of mechanical, electrical and thermal power. It focuses on vehicles with automated transmissions where a 42 V starteralternator is integrated in the powertrain. Chapter 2 describes the requirements for energy and powertrain control systems and derives the physical relationships in the flows of mechanical, thermal and electrical energy. Chapter 3 presents the CARTRONIC system architecture that integrates the control systems. The functionality of powertrain management, electrical energy management as well as thermal and climate management is presented in chapter 4. A summary is given in chapter 5.
2. REQUIREMENTS FOR ENERGY AND POWERTRAIN MANAGEMENT With its auxiliary systems, the thermal supply system and the electrical supply system, the powertrain constitutes a network of energy conversion, transport and storage devices (Fig. 1). The arrows in this diagram represent the energy flows; the corresponding numbers will be referred to in the description subsequently given. ;----
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.
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The powertrain supplies mechanical energy to the electrical supply system to drive an alternator, or an electric machine operated in the alternator mode (6). The powertrain also supplies mechanical energy to the thermal supply system in order to drive a climate compressor or a mechanically driven water pump (7).
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The electrical supply system might also provide electrical power to the powertrain to operate an electric machine in the motor mode (8). The motor may boost the vehicle in addition to the combustion engine or it may move the vehicle while the engine is turned off. The latter is advantageous in stop-and-go situations or to launch the vehicle. The electrical supply system also supplies electrically-driven auxiliaries in the powertrain, such as electromechanical actuators for throttle control, valve-train actuation or gearbox operation (8). It also supplies electrically-driven components in the thermal supply system such as the water pump and the radiator fan (9). The battery within the electrical supply system may be charged or discharged. Charging can take place during normal driving operation, when the
Thermal supply system
• 13
5 Passenger cabin Energy flows :
•
Mechanical
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------+
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The powertrain encompasses the combustion engine and the transmission with their corresponding control systems. An electric machine operated as a motor to drive the vehicle is also considered to be part of the powertrain. The electrical supply system encompasses one or more batteries as well as devices for managing the distribution of electric energy, like DCIDC converter and power distribution units (PDU). An alternator and an electric machine operated in the alternator mode are also considered to be part of the electrical supply system. The thermal supply system comprises the cooling system for engine and assemblies, as well as the Heating Ventilation and Air Conditioning (HVAC) for cabinclimate control.
----_._.--_..-. Thermal
Fig. 1. Energy network, formed by the powertain, the electrical and the thermal supply systems
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engine is idling and during braking maneuvers in order to re-generate braking energy. In particular the battery is discharged when the engine is turned off and when an electric machine in the powertrain is operated in motor mode.
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Thermal energy is transferred from the powertrain to the thermal supply system for cooling the engine and assemblies (10). Thermal energy can also be transferred by means of an exhaust heat exchanger. The thermal supply system also cools components of the electrical supply system such as an alternator or the inverter of an electric machine (11). Surplus thermal energy is released to the ambient air over a radiator (13). After a cold start, the electrical supply system can also provide heat to the powertrain to support warming-up by powering an auxiliary heater (12).
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Shared state
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Fig. 2. Hierarchical CARTRONIC functional architecture In the functional architecture, the various sub-systems send physically based "requests" (---» to the coordinator of the entire system. The coordinator knows the resources within the system, prioritizes the requests according to an algorithm which is generally customer-specific, and subsequently assigns "orders" ( - -» to suitable sub-systems in order to fulfil the requests with the highest priority or according to the resources momentarily available. Each sub-system relies on shared state information as shown on the far right in Fig. 2, as well as on specific information from other sub-systems ("" ">?), as shown in one example.
The goal of an energy and powertrain management system for the whole vehicle is to optimize fuel consumption, emissions, comfort and driveabilty. The components and sub-systems in the energy network must be controlled such that the mechanical power desired by the driver for vehicle propulsion is generated and that both electrical as well as thermal power is supplied. The limiting conditions such as max. engine speed, permissible voltage range for the electrical supply system or max. temperatures must be respected here. A further requirement is that the energy and powertrain management system adapts to the vehicle user as well as to surrounding conditions like e.g. the current driving situation and the ambient temperature. The architecture of the system must be designed to support different propulsion system architectures and must be adaptive to the systems that are installed in a particular vehicle.
Implementation of CARTRONIC is based on a modular, object-oriented software architecture with defined interfaces between higher-level vehicle functions and core functions of the engine, transmission or alternator. This is shown in Fig. 3.
3. CARTRONIC SYSTEM ARCHITECTURE
"Vehicle functions" : Customer and vehicle speCific
The requirements for energy and powertrain management lead to highly complex networks of vehicle sub-systems. To manage those, Bosch has developed a universal architecture called CARTRONIC® for the system design, function representation, software implementation and hardware partitioning (Hlilser, et al., 1998). The Bosch CARTRONIC system architecture constitutes the technical basis on which a system network can be universally implemented in the vehicle. CARTRONIC is based on a hierarchically clearly structured functional architecture with vehicle topological orientation. This is depicted in Fig. 2. Each sub-system coordinates its own sub-sub-systems whereas coordination between sub-systems is handled by higher-level function modules (or "coordinators"). Each sub-system can in itself be structured in a similar manner.
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+ Driver Software Standard operating system
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Fig. 3. CARTRONIC software architecture. Examples for higher-level vehicle functions are Electrical Energy Management (EEM) and Thermal Management (ThM).
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In a holistic system structured according to CARTRONIC, the functional structure can be assigned to the physical components of the vehicle, i.e. the hardware architecture and independent to a large extent of the functional and software architecture. Coordinators can principally be implemented in a decentralized manner in existing control devices, or the coordination functions can be assigned to central vehicle computers. The actual implementation is normally realized on a projectspecific basis whereby the major criteria for this include the resources available in bus systems and control devices as well as any specific requirements relating to monitoring and error response.
in section 4.2. Particular emphasis is given to the management of electrical consumers. It is shown how the corresponding algorithms can be integrated in the CARTRONIC architecture for the whole vehicle. Thermal power and climate management is discussed in chapter 4.3. A description of the major components of the thermal supply system is also given here. These are controlled within the CARTRONIC system architecture. The control approach and its interaction with powertrain and electrical energy management is derived here.
The basic step in implementing a CARTRONIC powertrain and energy management was to implement a CARTRONIC-compatible interface in higher-level vehicle functions for engine and electrical energy management controllers. With regard to the engine controller, this interface permits the distinction between engine-dependent and engineindependent requirements. When implementing their requirements therefore, the higher-level management functions do not have to consider any engine-specific selection of actuator paths. This is why these functions can be designed to be the same for both gasoline and diesel engines. This also applies for electrical energy management controllers. Moreover, the CARTRONIC functional and software architecture supports distribution of high-level management functions to any controller in the vehicle. The result of thoroughly applying the CARTRONIC system architecture is an open and modular energy and powertrain management system that guarantees long-term expandability even for new electronic sub-systems.
The task of the powertrain management system is to realize the driver's demand for propUlsion torque at a given vehicle speed. For this purpose, it determines the optimum operating points for the combustion engine, transmission and - optionally - an electric machine integrated in the powertrain. The objective is to achieve optimum vehicle operation with respect to fuel consumption, dynamic driving behavior and emissions for all driving situations and operating conditions. The powertrain management system computes the control signals for the lower-level control modules like engine management, transmission management and electric machine control. Standardized interfaces to these sub-systems support a unified approach for gasoline and diesel engines as well as for different types of transmission: automated shift transmissions (AST) with automated clutch control, hydraulic automatic transmissions (AT) and continuously variable transmissions (CVT).
4. J Powertrain Management
The major powertrain components and their corresponding control modules for a drive line with crankshaft-mounted starter-alternator and automated shift transmission are shown in Fig. 4: - The combustion engine is controlled by the engine management unit (EMU). It has a torque-based structure. Electronic throttle control (ETC) for gasoline engines and electronic diesel control (EDC) realize the electronic power control for the combustion engine. The accelerator pedal position is monitored by the EMU and interpreted as a demand for propulsion torque at the transmission output shaft. - The electric machine (starter-alternator) is managed by the electric machine control (EMC) module. This features a liquid-cooled inverter with torque control. - The transmission management unit (TMU) controls the transmission actuators for shifting operations and an automated clutch. It monitors the gearshift panel (not depicted in Fig. 4). It may also control a second automated clutch which can decouple the starter-alternator from the crankshaft. - The control modules are inter-linked within a CAN network. The powertrain management functionality
CARTRONIC makes implementation possible of an integrated energy and powertrain management system for vehicles. Based on the torque structure of the Bosch engine and alternator control systems, it permits new functionalities and flexibility in adding future automotive systems and components.
4. ENERGY AND POWERTRAIN MANAGEMENT FUNCTIONALITY The CARTRONIC system architecture and the functionality of energy and powertrain management will be discussed in the following sections. Section 4.1 describes how a powertrain management system can achieve optimum powertrain operation and provide mechanical power for the propulsion desired by the driver. An example of a powertrain with crankshaft-mounted starter-alternator and an automated shift transmission is also given here. The architecture of a 14 V /42 V electrical power supply system with integrated starter-alternator is presented
176
is implemented in a decentralized manner within this network of control units.
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Table I provides an overview of the functionalities of the main function modules for powertrain management.
Fig. 4. Powertrain with crankshaft-mounted starteralternator and automated transmission. Powertrain control modules: EMU (Engine Management Unit), EMC (Electric Machine Control), TMU (Transmission Management Unit)
Table I Powertrain management functionality Function Module Vehicle Coordinator
Functionality -Coordination of requests for power and torque -Selection ofpowertrain operating modes Powertrain Coordinator -Coordinated control of drive assemblies -Torque / speed control Engine -Torque I speed control Electric Machine -Power-boost -Braking-energy regeneration -Engine start-up -Ratio / gear control Transmission -Control clutch(es) or torque converter
The CARTRONIC system architecture for powertrain management is shown in Fig. 5. The pedal position is interpreted in the Vehicle Motion subsystem as a torque demand and is coordinated with the torque demands from vehicle dynamics control (VDC) and adaptive cruise control (ACC). The request for propulsion torque is transmitted to the Powertrain via the Vehicle Coordinator. The Vehicle Coordinator also manages requests for mechanical power by any auxiliary systems in the Electrical Supply System and in the Thermal Supply System. The Powertrain Coordinator determines the optimum operating state for the powertrain. The appropriate algorithms consider the efficiency of the combustion engine and that of the transmission, the emission characteristics as well as the surplus dynamic power prevailing in anyone operating state (LOffler and Hiilser, 1998). The operating state is dynamically adapted to the current driving situation, as well as to the driver's style and the operating conditions. The Powertrain Coordinator determines the command values for the combustion engine and the electric machine such that the desired propulsion torque is realized. The optimum gear for geared transmissions (the optimum speed ratio for continuously variable transmissions) is also determined. Moreover, the control signals for automatic clutch management are evaluated.
4.2 Electrical Energy Management The use of electrical energy for vehicle propulsion functions and the need to power safety and comfort systems of the future require management of the el~ctrical energy. Electrical power supply systems WIth ~2 V system voltage will efficiently supply electncal consumers and ensure a high degree of availability and reliability (Schottle and Threin 2000). Fig. 6 shows the architecture of the vehicle'~ electrical power supply system with centralized 42 V generation of power by a 42 V starter-alternator. The 14 V power is generated by a central DCIDC converter. All components are inter-linked on the CAN b~s . Such an architecture for the electrical system will be used in vehicles in which there will still ramain a large number of electrical consumers that are powered by 14 V.
Diffe~ent operating modes such as engine start-stop, electrIC power boost or regenerative braking are selected within the Vehicle Coordinator and realized by the Powertrain Coordinator.
177
examples of this: - Battery status (detection of SOC, SOH), - Synchronization of switching on consumers (Ioadleveling), - Consumer management, - Increasing the engine's idling speed, - Assigning target voltage values for alternator and DCIDC converter. The CARTRONIC architecture for electrical energy management is shown in Fig. 7 using consumer management as an example. The individual CARTRONIC sub-systems of Powertrain, Vehicle Motion, Body and Interior, Thermal Supply System and Electrical Supply System contain the consumers (Vx) assigned to the respective module as well as a consumer coordinator (VK). The CARTRONIC function modules are inter-linked by the Vehicle Coordinator. This is also where the actual consumer management (VM) and the electrical system management (BM) are located. The management systems communicate with the coordinators in the respective sub-systems. The coordinator for the Electrical Supply System consists of a Coordinator Electrical Supply System (KBN) besides the consumer coordinator. This constitutes the link between the resources of the electrical supply system (battery and alternator) and the electrical supply system management. The distribution of electrical power and consumer coordination requires that the consumers be classified according to priorities. This prioritization is made by the consumer coordination in the form of a consumer matrix.
PM: Power Module PDU: Power Distribution Unit S/A: Starter-Alternator (Alternative: Starter and Alternator)
Fig. 6. Architecture of the electrical power supply system with central generation of 14 V power (Schottle and Threin, 2000) The power is distributed by power distribution units (PDU). Such functions like: - Centralized reverse-polarity protection for the battery, - Data acquisition of the values measured for the battery parameters of voltage U, current I, temperature T, to determine the battery' s condition, - Switching and safeguarding individual supply paths, - Battery safety fuse are realized by power modules (PM) located close to the 36 V and 12 V batteries. Many of the growing requirements on the electrical system can no longer be met either technically or economically simply by appropriately designing system components like the alternator, battery, DCIDC converter and the cable harness, and introducing control and management functions from an energy management system will become inevitable. The major tasks of an Electrical Energy Management (EEM) system are therefore to: - Reduce peak loads, - Assure the battery' s state of charge, - Maintain the electrical system' s voltage within the specified range (dynamic and static), - Improve the dynamic interaction between the vehicle's electrical system and the powertrain, - Extend the service life of the battery.
Vehicle Coordinator
Powertrain, Vehicle Motion, Body and Interior, Thermal Supply System
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The key element of an efficient EEM is the efficiency of the algorithm detecting the battery's condition. This algorithm determines the battery's state of charge (SOC) and the state of health (SOH) from the battery parameters of current, temperature and voltage. Processing the sensors signals needed to do this is carried out by a power module located near to the battery.
5 6. 7. 8
Inquire potential electrical power available Order to provide electrical power Order to consume electrical power
Fig. 7. CARTRONIC architecture for electrical energy management for electrical consumers
4.3 Thermal Power and Climate Management To achieve even greater savings in the fuel consumption, not only the mechanical and electrical energy flows in the vehicle, but also the thermal energies and in particular the energy flows necessary
Status information and interventions in controlling participating components are indispensable in the capability to coordinate generation and use of the electrical power. Several function are listed here as
178
for engine cooling and cabin climate control, need specific control and mutual coordination (Hesse, et al., 1999). A thennal management system on the engine side coordinated with the powertrain, using controllable valves and an electric main water pump, can achieve a reduction in the fuel consumption of up to 5 % in NEDC (Melzer, et al., 1999). This is possible by higher engine temperature at partial load, faster engine heat-up and a lower coolant flow. An optimized control of all components emitting or dissipating thennal power can on the other hand, considerably enhance the comfort for passengers by providing a higher and more consistent heating power. Fig. 8 shows the main components being controlled by the thennal supply system.
corresponding coolant flow. Table 2 provides a summary of the functional modules, the main functionalities and the components that are controlled directly. temperature request,
cool."t flow request t
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Fig. 9. CARTRONIC architecture for thennal power and climate management
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Table 2 Thennal power and climate management functionality
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Functionality Function Module -Management of cooling the Thermal Supply System Coordinator engine and accessories -Management of the passenger-compartment climate -Coordination of resources with the vehicle coordinator -Control of the engine' s Engine Thermal cooling system Management -Control of the electrical water pump, valve(s) and fan(s) HVAC -Control of the passengercompartment climate -Control of the climate compressor, heaters, valves and fans
Fig. 8. Components of the thennal supply system The major components for engine cooling are the controllable main water pump generating an adequate flow of coolant, the electrically operated valves to regulate coolant flow through the components to be cooled and a radiator with fan to dissipate the excess thennal energy. A cabin heater, climate compressor and control valves are necessary for cabin-climate control. Several other components, such as exhaust heat exchanger, latent heat accumulator, transmission fluid heat exchanger (Holzer and Lenz, 2000) and others can be integrated as well. Fig. 9 shows the CARTRONIC architecture of the Thennal Supply System as well as the major signals that are exchanged with other vehicle functions . The Thennal Supply System consists of two functional modules, the Engine Thennal Management (EThM) for cooling the engine and accessories and the Heating Ventilation and Air Conditioning (HVAC) for controlling the climate in the cabin. The Vehicle Coordinator manages requests for heat, thennal power, etc., and coordinates requests for powering components used by both function modules, like the radiator fan for example. Communication with the other vehicle functions includes the necessary electrical power to operate the electric components such as main water pump, the necessary torque to operate the climate compressor and thennal power for heating, engine wann-up, etc. The components to be cooled request a temperature that is best suited for the prevailing operating conditions and the
5. SUMMARY A control system architecture for the whole vehicle with several layers of abstraction and high-level function modules coordinating the allocation of resources to sub-systems has been developed for integrated energy and powertrain management. The article presents control strategies and system architectures for the management of mechanical, electrical and thermal power. The system optimizes fuel consumption, emission control, comfort and driveabilty, and adapts both to the vehicle user and to the environment such as the driving situation or the ambient temperature. The system architecure is
179
Procedures for 1998 and Subsequent Model Passenger Cars, Light-duty Trucks, and Mediurnduty Vehicles. California Air Resources Board Hesse, V ., Hohl R., Schrnitt, M. (1999). Thermal Management. VDI Report No. 1505, VDI Verlag, Dusseldorf Holzer, H., Lenz, H.P. (2000). Der Antriebsstrang 2000 - Entwicklung einer Warmlaufstrategie fur Motor und Automatikgetriegbe durch gezieltes Warmemanagement. VDI Report No. 1565, pp. 83-107. VDI Verlag, DUsseldorf HUlser, H., Benninger, K., Gerhardt, J., Glas, H.J. (1998). CARTRONIC - Das Ordnungskonzept zur flexiblen Konfigurierung der elektronischen Sub-systeme im Kraftfahrzeug. A VL "Engine and Environment" Congress Jelden, H. (2000). VW Lupo, the world's first 3-liter car. SAE Convergence Proceedings, paper 200001-C044 Kolke, R. (2000). Alternative Antriebe aus Umweltsicht: Vision oder Illusion? Alternative Antriebssysteme im Automobilbau. Haus der Technik e.V. Essen Loffler, J., Htilser, H. (1998). Koordinierte Antriebstrangsteuerung fur Fahrzeuge mit automatisiertem Schaltgetriebe. VDI Report No. 1418, pp. 463-483 . VDI Verlag, DUsseldorf LoGrasso, J., Kidston, K., Fehr, W. (2000). Low Power Flexible Control Architecture for a New Generation (PNGV) Precept Vehicle. SAE Convergence Proceedings, paper 2000-01-C060 Melzer, F., Hesse, V ., Rocklage, G., Schrnitt, M. (1999). Thermomanagement. SAE Paper 199901-0238, Detroit Nakano, K., Ochiai, S. (2000). Development of the Motor Assist System for the Hybrid Automobile -- the Insight. SAE Convergence Proceedings, paper 2000-0 I-C079 PNGV (2000). http://www.ta.doc.gov/pngv Schlifer, H. (200 I). Integrierter Starter-Generator (lSG). Expert verlag, Renningen. Schottle, R., Threin, G. (2000). Electrical power supply systems: present and future. VDI Report No . 1547, pp. 449-497. VDI Veriag, Dusseldorf VDA (2000). Auto 2000. lahresbericht Verband der Automobilindustrie e.V. (VDA). Frankfurt am Main, 2000. ISSN 0171-4317
designed to support different propulsion system architectures. With its auxiliary systems, the thermal supply system and the electrical supply system, the powertrain is considered as a network of coupled energy conversion, transport and storage devices (Fig. 1). The control system architecture is oriented on the topology of this network and its physical interfaces. A universal architecture for the system design, function representation, software implementation and hardware partitioning, called CARTRONIC®, is presented in chapter 2. The implementation of CARTRONIC is based on a modular, object-oriented software architecture with defined interfaces between higher-level vehicle functions and core functions (Fig. 3). The powertrain management system determines the optimum operating state of the powertrain and achieves optimum powertrain operation with respect to fuel efficiency and dynamic driving behavior. The operating state is dynamically adapted to the driving situation, as well as to the driver's style and operating conditions. Its application to a powertrain with a crankshaft-mounted 42 V starter-alternator and an automated shift transmission is described (see Fig. 4). The electrical energy management system optimizes the supply to electrical consumers, interaction of the powertrain with the electrical supply system and extends the service of the battery. The architecture of a 14 V /42 V electrical supply system with integrated starter-alternator and functionality for management of electrical consumers is presented in section 4.2. Integration of the thermal power and climate management system in the CARTRONIC architecture is straightforward. The control approach improves fuel efficiency and comfort for the passengers considerably. The major components and the system architecture are described in section 4.3. The CARTRONIC system architecture provides a framework for the realization of advanced vehicle functions such as engine start-stop, electric power boost and regenerative braking. It thus exploits the potential for the improvement of effi.ciency, environmental compatibility and comfort.
REFERENCES Abe, S. (2000). Development of the Hybrid Vehicle and its Future Expectation. SAE Convergence Proceedings, paper 2000-01-C042 BUrger, K.G ., Harms, K., Kallenbach, R. (2000). Elektronische Systeme im Kraftfahrzeug Perspektiven fur das nachste Jahrzehnt. Special Edition "Automotive ATZIMTZ Electronics", January 2000 CARB (1998). Exhaust Emission Standards and Test
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CARTRONIC SYSTEM ARCHITECTURE FOR ENERGY AND POWERTRAIN MANAGEMENT
Jiirgen Loffler, HoJger Hiilser*, Karsten Schiller, Manfred Schmitt
Robert Bosch GmbH, Postfach 300240, D- 70442 Stuttgart •asset GmbH, Raiffeisenstr. 3, D-71696 Mbglingen [email protected]
Abstract: Networking mechatronic components and sub-systems in a vehicle necessitates a concept of order to organize the controlling and regulating systems. One such concept, called CARTRONIC®, has been developed by Robert Bosch GmbH. This article describes the CARTRONIC system architecture for integrating systems in powertrain management as well as for electrical and thermal energy management. The modules and functions of each control system are shown. The physical relationships between the flows of mechanical, thermal and electrical energy in the vehicle are derived, and it is shown how this can be optimized by a system architecture designed for the whole vehicle. Copyright © 20011FAC Keywords: Automotive control, electronic architecture, energy management systems, powertrain management, electrical supply system, thermal management, climate control
I. INTRODUCTION
goals are: - Advanced torque-based engine management systems with automatic engine shut-off, - High-efficiency automated transmissions, - Efficient electric machines (e.g. starter-alternators) integrated in the powertrain that boost propUlsion and re-generate kinetic energy during braking and overrun (Schafer, 2001), - High-performance electrical power supply systems and batteries, - Advanced cooling and cabin-climate control systems, - Integrated control systems (BUrger, et al., 2000; LoGrasso, Kidston, Fehr 2000).
In order to improve fuel consumption and emissions while enhancing comfort and safety, it takes an holistic approach to optimize the efficiency of generating and utilizing the mechanical, electrical and thermal energy in the car. In an effort to improve the sustainability of transportation, the European automotive industry (ACEA = Association des Constructeurs Europeens d'Automobile) is committed to reduce the average CO 2 -emissions - and hence the fuel consumption - to 140 g!km by the year 2008 (VDA 2000). With the Partnership for a New Generation Vehicle (PNGV) program, the US carmakers took up the challenge of developing an 80 miles per gallon (gasoline equivalent) five-passenger vehicle (PNGV, 2000). These efficiency targets must comply with the lower emission limits to be introduced in the future, like e.g. EURO IV (Kolke, 2000) and SULEV (CARB, 1998).
Ultra-efficient vehicles, such as Volkswagen's Lupo 31 (Jelden, 2000), Honda's Insight (Nakano and Ochiai, 2000), Toyota's Prius (Abe, 2000) and PNGV demonstrator vehicles (PNGV, 2000), show that coordinated powertrain and energy management strategies are the key to optimizing efficiency and performance.
Major technologies to enable attainment of these
173
Three forms of energy flowing here can be distinguished: mechanical, electrical and thermal energy. Mechanical energy is transferred by means of rotating shafts, toothed-wheel connections or belt drives. Electrical energy is transmitted by means of the wiring harness; this can take place at different voltage levels (e.g. 14 V or 42 V). Thermal energy is transported by the mass of flowing coolant, exhaust gas or air. This energy network supplies: - Mechanical power to the wheels for vehicle propulsion (1). When braking or during overrun, mechanical energy can also be returned to the network through the wheels (2). Also, mechanical energy might be supplied to such auxiliary units external to the network, like the power-steering pump for example (3). - Electrical power to consumers that are not part of the network (4). - Thermal power for heating or cooling the passenger compartriient (5).
This article presents control strategies and system architectures for the management of mechanical, electrical and thermal power. It focuses on vehicles with automated transmissions where a 42 V starteralternator is integrated in the powertrain. Chapter 2 describes the requirements for energy and powertrain control systems and derives the physical relationships in the flows of mechanical, thermal and electrical energy. Chapter 3 presents the CARTRONIC system architecture that integrates the control systems. The functionality of powertrain management, electrical energy management as well as thermal and climate management is presented in chapter 4. A summary is given in chapter 5.
2. REQUIREMENTS FOR ENERGY AND POWERTRAIN MANAGEMENT With its auxiliary systems, the thermal supply system and the electrical supply system, the powertrain constitutes a network of energy conversion, transport and storage devices (Fig. 1). The arrows in this diagram represent the energy flows; the corresponding numbers will be referred to in the description subsequently given. ;----
8
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~~
1
3
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2
~
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6
.
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The powertrain supplies mechanical energy to the electrical supply system to drive an alternator, or an electric machine operated in the alternator mode (6). The powertrain also supplies mechanical energy to the thermal supply system in order to drive a climate compressor or a mechanically driven water pump (7).
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The electrical supply system might also provide electrical power to the powertrain to operate an electric machine in the motor mode (8). The motor may boost the vehicle in addition to the combustion engine or it may move the vehicle while the engine is turned off. The latter is advantageous in stop-and-go situations or to launch the vehicle. The electrical supply system also supplies electrically-driven auxiliaries in the powertrain, such as electromechanical actuators for throttle control, valve-train actuation or gearbox operation (8). It also supplies electrically-driven components in the thermal supply system such as the water pump and the radiator fan (9). The battery within the electrical supply system may be charged or discharged. Charging can take place during normal driving operation, when the
Thermal supply system
• 13
5 Passenger cabin Energy flows :
•
Mechanical
Radiator
------+
Electrical
The powertrain encompasses the combustion engine and the transmission with their corresponding control systems. An electric machine operated as a motor to drive the vehicle is also considered to be part of the powertrain. The electrical supply system encompasses one or more batteries as well as devices for managing the distribution of electric energy, like DCIDC converter and power distribution units (PDU). An alternator and an electric machine operated in the alternator mode are also considered to be part of the electrical supply system. The thermal supply system comprises the cooling system for engine and assemblies, as well as the Heating Ventilation and Air Conditioning (HVAC) for cabinclimate control.
----_._.--_..-. Thermal
Fig. 1. Energy network, formed by the powertain, the electrical and the thermal supply systems
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engine is idling and during braking maneuvers in order to re-generate braking energy. In particular the battery is discharged when the engine is turned off and when an electric machine in the powertrain is operated in motor mode.
......
~.~I~~ Data
- ....?
Physica l "orders" and "requests"
-~
~
.. .
as interfaces
~_ .c:~Io~
"'~""
Thermal energy is transferred from the powertrain to the thermal supply system for cooling the engine and assemblies (10). Thermal energy can also be transferred by means of an exhaust heat exchanger. The thermal supply system also cools components of the electrical supply system such as an alternator or the inverter of an electric machine (11). Surplus thermal energy is released to the ambient air over a radiator (13). After a cold start, the electrical supply system can also provide heat to the powertrain to support warming-up by powering an auxiliary heater (12).
~
Shared state
information
Fig. 2. Hierarchical CARTRONIC functional architecture In the functional architecture, the various sub-systems send physically based "requests" (---» to the coordinator of the entire system. The coordinator knows the resources within the system, prioritizes the requests according to an algorithm which is generally customer-specific, and subsequently assigns "orders" ( - -» to suitable sub-systems in order to fulfil the requests with the highest priority or according to the resources momentarily available. Each sub-system relies on shared state information as shown on the far right in Fig. 2, as well as on specific information from other sub-systems ("" ">?), as shown in one example.
The goal of an energy and powertrain management system for the whole vehicle is to optimize fuel consumption, emissions, comfort and driveabilty. The components and sub-systems in the energy network must be controlled such that the mechanical power desired by the driver for vehicle propulsion is generated and that both electrical as well as thermal power is supplied. The limiting conditions such as max. engine speed, permissible voltage range for the electrical supply system or max. temperatures must be respected here. A further requirement is that the energy and powertrain management system adapts to the vehicle user as well as to surrounding conditions like e.g. the current driving situation and the ambient temperature. The architecture of the system must be designed to support different propulsion system architectures and must be adaptive to the systems that are installed in a particular vehicle.
Implementation of CARTRONIC is based on a modular, object-oriented software architecture with defined interfaces between higher-level vehicle functions and core functions of the engine, transmission or alternator. This is shown in Fig. 3.
3. CARTRONIC SYSTEM ARCHITECTURE
"Vehicle functions" : Customer and vehicle speCific
The requirements for energy and powertrain management lead to highly complex networks of vehicle sub-systems. To manage those, Bosch has developed a universal architecture called CARTRONIC® for the system design, function representation, software implementation and hardware partitioning (Hlilser, et al., 1998). The Bosch CARTRONIC system architecture constitutes the technical basis on which a system network can be universally implemented in the vehicle. CARTRONIC is based on a hierarchically clearly structured functional architecture with vehicle topological orientation. This is depicted in Fig. 2. Each sub-system coordinates its own sub-sub-systems whereas coordination between sub-systems is handled by higher-level function modules (or "coordinators"). Each sub-system can in itself be structured in a similar manner.
Modular Re-usable
~ ~
11
~::gn:~~:ace~ B-.-,~J Foo~+~l F_~; "Embedded software": Proprietary ECU-specific
CARTRONIC layer: Function . interfaces + Coordinators + Monitoring ~ Base system functionality + Core functions
+ Driver Software Standard operating system
Operating system ERCOS
Fig. 3. CARTRONIC software architecture. Examples for higher-level vehicle functions are Electrical Energy Management (EEM) and Thermal Management (ThM).
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In a holistic system structured according to CARTRONIC, the functional structure can be assigned to the physical components of the vehicle, i.e. the hardware architecture and independent to a large extent of the functional and software architecture. Coordinators can principally be implemented in a decentralized manner in existing control devices, or the coordination functions can be assigned to central vehicle computers. The actual implementation is normally realized on a projectspecific basis whereby the major criteria for this include the resources available in bus systems and control devices as well as any specific requirements relating to monitoring and error response.
in section 4.2. Particular emphasis is given to the management of electrical consumers. It is shown how the corresponding algorithms can be integrated in the CARTRONIC architecture for the whole vehicle. Thermal power and climate management is discussed in chapter 4.3. A description of the major components of the thermal supply system is also given here. These are controlled within the CARTRONIC system architecture. The control approach and its interaction with powertrain and electrical energy management is derived here.
The basic step in implementing a CARTRONIC powertrain and energy management was to implement a CARTRONIC-compatible interface in higher-level vehicle functions for engine and electrical energy management controllers. With regard to the engine controller, this interface permits the distinction between engine-dependent and engineindependent requirements. When implementing their requirements therefore, the higher-level management functions do not have to consider any engine-specific selection of actuator paths. This is why these functions can be designed to be the same for both gasoline and diesel engines. This also applies for electrical energy management controllers. Moreover, the CARTRONIC functional and software architecture supports distribution of high-level management functions to any controller in the vehicle. The result of thoroughly applying the CARTRONIC system architecture is an open and modular energy and powertrain management system that guarantees long-term expandability even for new electronic sub-systems.
The task of the powertrain management system is to realize the driver's demand for propUlsion torque at a given vehicle speed. For this purpose, it determines the optimum operating points for the combustion engine, transmission and - optionally - an electric machine integrated in the powertrain. The objective is to achieve optimum vehicle operation with respect to fuel consumption, dynamic driving behavior and emissions for all driving situations and operating conditions. The powertrain management system computes the control signals for the lower-level control modules like engine management, transmission management and electric machine control. Standardized interfaces to these sub-systems support a unified approach for gasoline and diesel engines as well as for different types of transmission: automated shift transmissions (AST) with automated clutch control, hydraulic automatic transmissions (AT) and continuously variable transmissions (CVT).
4. J Powertrain Management
The major powertrain components and their corresponding control modules for a drive line with crankshaft-mounted starter-alternator and automated shift transmission are shown in Fig. 4: - The combustion engine is controlled by the engine management unit (EMU). It has a torque-based structure. Electronic throttle control (ETC) for gasoline engines and electronic diesel control (EDC) realize the electronic power control for the combustion engine. The accelerator pedal position is monitored by the EMU and interpreted as a demand for propulsion torque at the transmission output shaft. - The electric machine (starter-alternator) is managed by the electric machine control (EMC) module. This features a liquid-cooled inverter with torque control. - The transmission management unit (TMU) controls the transmission actuators for shifting operations and an automated clutch. It monitors the gearshift panel (not depicted in Fig. 4). It may also control a second automated clutch which can decouple the starter-alternator from the crankshaft. - The control modules are inter-linked within a CAN network. The powertrain management functionality
CARTRONIC makes implementation possible of an integrated energy and powertrain management system for vehicles. Based on the torque structure of the Bosch engine and alternator control systems, it permits new functionalities and flexibility in adding future automotive systems and components.
4. ENERGY AND POWERTRAIN MANAGEMENT FUNCTIONALITY The CARTRONIC system architecture and the functionality of energy and powertrain management will be discussed in the following sections. Section 4.1 describes how a powertrain management system can achieve optimum powertrain operation and provide mechanical power for the propulsion desired by the driver. An example of a powertrain with crankshaft-mounted starter-alternator and an automated shift transmission is also given here. The architecture of a 14 V /42 V electrical power supply system with integrated starter-alternator is presented
176
is implemented in a decentralized manner within this network of control units.
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~
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Transmission
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Table I provides an overview of the functionalities of the main function modules for powertrain management.
Fig. 4. Powertrain with crankshaft-mounted starteralternator and automated transmission. Powertrain control modules: EMU (Engine Management Unit), EMC (Electric Machine Control), TMU (Transmission Management Unit)
Table I Powertrain management functionality Function Module Vehicle Coordinator
Functionality -Coordination of requests for power and torque -Selection ofpowertrain operating modes Powertrain Coordinator -Coordinated control of drive assemblies -Torque / speed control Engine -Torque I speed control Electric Machine -Power-boost -Braking-energy regeneration -Engine start-up -Ratio / gear control Transmission -Control clutch(es) or torque converter
The CARTRONIC system architecture for powertrain management is shown in Fig. 5. The pedal position is interpreted in the Vehicle Motion subsystem as a torque demand and is coordinated with the torque demands from vehicle dynamics control (VDC) and adaptive cruise control (ACC). The request for propulsion torque is transmitted to the Powertrain via the Vehicle Coordinator. The Vehicle Coordinator also manages requests for mechanical power by any auxiliary systems in the Electrical Supply System and in the Thermal Supply System. The Powertrain Coordinator determines the optimum operating state for the powertrain. The appropriate algorithms consider the efficiency of the combustion engine and that of the transmission, the emission characteristics as well as the surplus dynamic power prevailing in anyone operating state (LOffler and Hiilser, 1998). The operating state is dynamically adapted to the current driving situation, as well as to the driver's style and the operating conditions. The Powertrain Coordinator determines the command values for the combustion engine and the electric machine such that the desired propulsion torque is realized. The optimum gear for geared transmissions (the optimum speed ratio for continuously variable transmissions) is also determined. Moreover, the control signals for automatic clutch management are evaluated.
4.2 Electrical Energy Management The use of electrical energy for vehicle propulsion functions and the need to power safety and comfort systems of the future require management of the el~ctrical energy. Electrical power supply systems WIth ~2 V system voltage will efficiently supply electncal consumers and ensure a high degree of availability and reliability (Schottle and Threin 2000). Fig. 6 shows the architecture of the vehicle'~ electrical power supply system with centralized 42 V generation of power by a 42 V starter-alternator. The 14 V power is generated by a central DCIDC converter. All components are inter-linked on the CAN b~s . Such an architecture for the electrical system will be used in vehicles in which there will still ramain a large number of electrical consumers that are powered by 14 V.
Diffe~ent operating modes such as engine start-stop, electrIC power boost or regenerative braking are selected within the Vehicle Coordinator and realized by the Powertrain Coordinator.
177
examples of this: - Battery status (detection of SOC, SOH), - Synchronization of switching on consumers (Ioadleveling), - Consumer management, - Increasing the engine's idling speed, - Assigning target voltage values for alternator and DCIDC converter. The CARTRONIC architecture for electrical energy management is shown in Fig. 7 using consumer management as an example. The individual CARTRONIC sub-systems of Powertrain, Vehicle Motion, Body and Interior, Thermal Supply System and Electrical Supply System contain the consumers (Vx) assigned to the respective module as well as a consumer coordinator (VK). The CARTRONIC function modules are inter-linked by the Vehicle Coordinator. This is also where the actual consumer management (VM) and the electrical system management (BM) are located. The management systems communicate with the coordinators in the respective sub-systems. The coordinator for the Electrical Supply System consists of a Coordinator Electrical Supply System (KBN) besides the consumer coordinator. This constitutes the link between the resources of the electrical supply system (battery and alternator) and the electrical supply system management. The distribution of electrical power and consumer coordination requires that the consumers be classified according to priorities. This prioritization is made by the consumer coordination in the form of a consumer matrix.
PM: Power Module PDU: Power Distribution Unit S/A: Starter-Alternator (Alternative: Starter and Alternator)
Fig. 6. Architecture of the electrical power supply system with central generation of 14 V power (Schottle and Threin, 2000) The power is distributed by power distribution units (PDU). Such functions like: - Centralized reverse-polarity protection for the battery, - Data acquisition of the values measured for the battery parameters of voltage U, current I, temperature T, to determine the battery' s condition, - Switching and safeguarding individual supply paths, - Battery safety fuse are realized by power modules (PM) located close to the 36 V and 12 V batteries. Many of the growing requirements on the electrical system can no longer be met either technically or economically simply by appropriately designing system components like the alternator, battery, DCIDC converter and the cable harness, and introducing control and management functions from an energy management system will become inevitable. The major tasks of an Electrical Energy Management (EEM) system are therefore to: - Reduce peak loads, - Assure the battery' s state of charge, - Maintain the electrical system' s voltage within the specified range (dynamic and static), - Improve the dynamic interaction between the vehicle's electrical system and the powertrain, - Extend the service life of the battery.
Vehicle Coordinator
Powertrain, Vehicle Motion, Body and Interior, Thermal Supply System
Electrical Supply Syatem
- - - -+- 1!, 2!, 3! Request for electrical power
.::-+ 4? -
The key element of an efficient EEM is the efficiency of the algorithm detecting the battery's condition. This algorithm determines the battery's state of charge (SOC) and the state of health (SOH) from the battery parameters of current, temperature and voltage. Processing the sensors signals needed to do this is carried out by a power module located near to the battery.
5 6. 7. 8
Inquire potential electrical power available Order to provide electrical power Order to consume electrical power
Fig. 7. CARTRONIC architecture for electrical energy management for electrical consumers
4.3 Thermal Power and Climate Management To achieve even greater savings in the fuel consumption, not only the mechanical and electrical energy flows in the vehicle, but also the thermal energies and in particular the energy flows necessary
Status information and interventions in controlling participating components are indispensable in the capability to coordinate generation and use of the electrical power. Several function are listed here as
178
for engine cooling and cabin climate control, need specific control and mutual coordination (Hesse, et al., 1999). A thennal management system on the engine side coordinated with the powertrain, using controllable valves and an electric main water pump, can achieve a reduction in the fuel consumption of up to 5 % in NEDC (Melzer, et al., 1999). This is possible by higher engine temperature at partial load, faster engine heat-up and a lower coolant flow. An optimized control of all components emitting or dissipating thennal power can on the other hand, considerably enhance the comfort for passengers by providing a higher and more consistent heating power. Fig. 8 shows the main components being controlled by the thennal supply system.
corresponding coolant flow. Table 2 provides a summary of the functional modules, the main functionalities and the components that are controlled directly. temperature request,
cool."t flow request t
Climate blo....r-----.. Supplem. waler pump
Fig. 9. CARTRONIC architecture for thennal power and climate management
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Radiator with fan Radialor shul~er---~"""::~"
Table 2 Thennal power and climate management functionality
Climate compressor ----::..~"-j _.....-'\. \ ' Main water pump
Functionality Function Module -Management of cooling the Thermal Supply System Coordinator engine and accessories -Management of the passenger-compartment climate -Coordination of resources with the vehicle coordinator -Control of the engine' s Engine Thermal cooling system Management -Control of the electrical water pump, valve(s) and fan(s) HVAC -Control of the passengercompartment climate -Control of the climate compressor, heaters, valves and fans
Fig. 8. Components of the thennal supply system The major components for engine cooling are the controllable main water pump generating an adequate flow of coolant, the electrically operated valves to regulate coolant flow through the components to be cooled and a radiator with fan to dissipate the excess thennal energy. A cabin heater, climate compressor and control valves are necessary for cabin-climate control. Several other components, such as exhaust heat exchanger, latent heat accumulator, transmission fluid heat exchanger (Holzer and Lenz, 2000) and others can be integrated as well. Fig. 9 shows the CARTRONIC architecture of the Thennal Supply System as well as the major signals that are exchanged with other vehicle functions . The Thennal Supply System consists of two functional modules, the Engine Thennal Management (EThM) for cooling the engine and accessories and the Heating Ventilation and Air Conditioning (HVAC) for controlling the climate in the cabin. The Vehicle Coordinator manages requests for heat, thennal power, etc., and coordinates requests for powering components used by both function modules, like the radiator fan for example. Communication with the other vehicle functions includes the necessary electrical power to operate the electric components such as main water pump, the necessary torque to operate the climate compressor and thennal power for heating, engine wann-up, etc. The components to be cooled request a temperature that is best suited for the prevailing operating conditions and the
5. SUMMARY A control system architecture for the whole vehicle with several layers of abstraction and high-level function modules coordinating the allocation of resources to sub-systems has been developed for integrated energy and powertrain management. The article presents control strategies and system architectures for the management of mechanical, electrical and thermal power. The system optimizes fuel consumption, emission control, comfort and driveabilty, and adapts both to the vehicle user and to the environment such as the driving situation or the ambient temperature. The system architecure is
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Procedures for 1998 and Subsequent Model Passenger Cars, Light-duty Trucks, and Mediurnduty Vehicles. California Air Resources Board Hesse, V ., Hohl R., Schrnitt, M. (1999). Thermal Management. VDI Report No. 1505, VDI Verlag, Dusseldorf Holzer, H., Lenz, H.P. (2000). Der Antriebsstrang 2000 - Entwicklung einer Warmlaufstrategie fur Motor und Automatikgetriegbe durch gezieltes Warmemanagement. VDI Report No. 1565, pp. 83-107. VDI Verlag, DUsseldorf HUlser, H., Benninger, K., Gerhardt, J., Glas, H.J. (1998). CARTRONIC - Das Ordnungskonzept zur flexiblen Konfigurierung der elektronischen Sub-systeme im Kraftfahrzeug. A VL "Engine and Environment" Congress Jelden, H. (2000). VW Lupo, the world's first 3-liter car. SAE Convergence Proceedings, paper 200001-C044 Kolke, R. (2000). Alternative Antriebe aus Umweltsicht: Vision oder Illusion? Alternative Antriebssysteme im Automobilbau. Haus der Technik e.V. Essen Loffler, J., Htilser, H. (1998). Koordinierte Antriebstrangsteuerung fur Fahrzeuge mit automatisiertem Schaltgetriebe. VDI Report No. 1418, pp. 463-483 . VDI Verlag, DUsseldorf LoGrasso, J., Kidston, K., Fehr, W. (2000). Low Power Flexible Control Architecture for a New Generation (PNGV) Precept Vehicle. SAE Convergence Proceedings, paper 2000-01-C060 Melzer, F., Hesse, V ., Rocklage, G., Schrnitt, M. (1999). Thermomanagement. SAE Paper 199901-0238, Detroit Nakano, K., Ochiai, S. (2000). Development of the Motor Assist System for the Hybrid Automobile -- the Insight. SAE Convergence Proceedings, paper 2000-0 I-C079 PNGV (2000). http://www.ta.doc.gov/pngv Schlifer, H. (200 I). Integrierter Starter-Generator (lSG). Expert verlag, Renningen. Schottle, R., Threin, G. (2000). Electrical power supply systems: present and future. VDI Report No . 1547, pp. 449-497. VDI Veriag, Dusseldorf VDA (2000). Auto 2000. lahresbericht Verband der Automobilindustrie e.V. (VDA). Frankfurt am Main, 2000. ISSN 0171-4317
designed to support different propulsion system architectures. With its auxiliary systems, the thermal supply system and the electrical supply system, the powertrain is considered as a network of coupled energy conversion, transport and storage devices (Fig. 1). The control system architecture is oriented on the topology of this network and its physical interfaces. A universal architecture for the system design, function representation, software implementation and hardware partitioning, called CARTRONIC®, is presented in chapter 2. The implementation of CARTRONIC is based on a modular, object-oriented software architecture with defined interfaces between higher-level vehicle functions and core functions (Fig. 3). The powertrain management system determines the optimum operating state of the powertrain and achieves optimum powertrain operation with respect to fuel efficiency and dynamic driving behavior. The operating state is dynamically adapted to the driving situation, as well as to the driver's style and operating conditions. Its application to a powertrain with a crankshaft-mounted 42 V starter-alternator and an automated shift transmission is described (see Fig. 4). The electrical energy management system optimizes the supply to electrical consumers, interaction of the powertrain with the electrical supply system and extends the service of the battery. The architecture of a 14 V /42 V electrical supply system with integrated starter-alternator and functionality for management of electrical consumers is presented in section 4.2. Integration of the thermal power and climate management system in the CARTRONIC architecture is straightforward. The control approach improves fuel efficiency and comfort for the passengers considerably. The major components and the system architecture are described in section 4.3. The CARTRONIC system architecture provides a framework for the realization of advanced vehicle functions such as engine start-stop, electric power boost and regenerative braking. It thus exploits the potential for the improvement of effi.ciency, environmental compatibility and comfort.
REFERENCES Abe, S. (2000). Development of the Hybrid Vehicle and its Future Expectation. SAE Convergence Proceedings, paper 2000-01-C042 BUrger, K.G ., Harms, K., Kallenbach, R. (2000). Elektronische Systeme im Kraftfahrzeug Perspektiven fur das nachste Jahrzehnt. Special Edition "Automotive ATZIMTZ Electronics", January 2000 CARB (1998). Exhaust Emission Standards and Test
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