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In this paper we present the results of a project that concentrates on the design of distributed embedded systems for control-related applications. The OPTMAP (Optimal Mapping of Virtual Control Functions to a Distributed Architecture) framework supports the function allocation based on given constrains involving a feasible solution. The control systems we will consider use a time-triggered paradigm for sensor reading and event-driven behavior for inter-processor communication. Sensor values are read at fixed periods in time and data processing occurs after the control unit receives the proper message. The aim of the project is to get an optimized mapping which minimizes information traffic on the network and guarantees that all processing units are able to handle the distributed control functions in real time.

One goal of modern power train control systems in heavy trucks is to damp driveline oscillations using appropriate controllers. Modern control algorithms like state-space controllers are based on a state-space model, which should accurately characterize the real process behavior. Otherwise, optimal control can not be guaranteed. These state-space models include a huge number of parameters, which have to be identified by an identification process. However, existing driveline models contain two serious problems: an increasing offset over time between measured and simulated data and an inadequate detection of the longitudinal dynamics of the truck. Therefore, this article deals with two goals: to optimize the offline identification process for the special use in driveline systems and to establish an online adaptation of the model parameters to guarantee an optimal model fit.

The new aerial communication protocol “Controller Area Network” (CAN) efficiently supports distributed realtime control in automotive applications. In order to unload CPUs from high-speed message transfer, dedicated CAN hardware handles messages up to the communication object level. In multiplex wiring message rates are one to two orders of magnitude lower, allowing to implement the upper communication level more cost-effectively in software. This reduces CAN interface hardware to bitwise protocol handling only. It may be incorporated even into low-end microcontrollers without significantly increasing chip size. Thus the same CAN protocol supports the entire range of serial automotive communication, matching implementation costs to requirements at each performance level.

Today, in many passenger cars and light trucks, the conventional driveline is extended by a dual mass flywheel (DMF). The DMF reduces driveline oscillations by mechanically decoupling the crankshaft and the transmission. Existing engine control systems are designed for conventional single mass flywheel (SMF) systems. In the future, to facilitate the optimal control of engines equipped with advanced DMF systems, such conventional control systems may require adaptation, modification or even replacement. The design and testing of appropriate new control systems has required the development of various types of engine models. In this paper, various engine modeling techniques are introduced and compared in respect to their capabilities for both driveline simulation and control system development.

The formulation of software tasks as parallel processes allows their implementation within distributed microcontrollers. The requirements for Automotive Networks to support these applications are discussed. By introduction of a locality measure, a classification of networks can be made either into interactive distributed realtime processing or into classical communication. Given a sufficiantly small locality, the physical network extension does not have an impact on the implementation. A concept i presented how to integrate process dispachting and synchronization. Based upon this concept, functions may be formulated independant of their location in a specific microcontroller.

As future drive-by-wire systems have no mechanical fallback level, the increased safety requirements need to be met by software-based solutions. The task of the software is to provide services in the field of fault detection and compensation as well as control of redundant hardware structures. Particularly the implementation of fault detection and error correction avoids fatal output of drive-by-wire control units caused by erroneous input signals. This article describes the implementation of a module compensating faults in the input signals of a vehicle function, which controls the longitudinal dynamics of a truck. The error correction is achieved by means of data fusion. Sensing units consisting of the sensor as well as the preprocessing unit often are provided by external suppliers. In some cases information regarding the characteristics of their output data written on the CAN bus is not available.

In this paper an approach is presented to determine an adequate number of clusters automatically in case of clustering a distributed automotive electronic system. Hereby, this approach is based on the ISODATA clustering algorithm. Its advantages are its flexibility and less computational effort in comparison to normally used partitioning algorithms. In order to cluster a distributed automotive electronic system with respect to a reduced external communication the input data normally used for partitioning algorithms has to be adapted. Besides, a new overall quality criterion is introduced to validate the results of clustering in reference to the busload before test stage.

Today, in many passenger cars and light trucks, the conventional driveline is extended by a dual mass flywheel (DMF). The DMF reduces driveline oscillations by mechanically decoupling the crankshaft and the transmission. Existing engine control systems are general designed for use with conventional single mass flywheel (SMF) systems. In the future, to facilitate the optimal control of engines equipped with advanced DMF systems, these conventional control systems may require adaptation, modification or even replacement. In the past, misfire detection has been done by expensive dedicated sensors; seismic, ion current measurement at the spark plugs or even by measuring in-cylinder pressures directly. Typically misfire detection is performed using signals derived from the crankshaft position sensor, which works well for engines with a limited number of cylinders and which are connected to relatively simply drivelines.

In this approach a nonlinear controller for the lateral vehicle dynamics is designed. The basis for the design is a nonlinear model of the lateral vehicle dynamics in state space representation consisting of three states: The vehicle velocity, the yaw rate as well as the vehicle body sideslip angle (VBSSA). As control variables the yaw rate and the VBSSA are chosen. To assure the vehicle follows the driver's directional intent, the yaw rate is adapted to a desired reference value determined by means of a linear single track model. The second control variable -the VBSSA- is utilized to reduce the lateral forces. Incorporating the VBSSA, the controller's behavior can be significantly improved. Thus, a nonlinear controller is designed which is capable to stabilize the vehicle in critical driving situations. This nonlinear controller is based on an adaptation of a quality function for the nonlinear model to the one for a linear reference system.

In this paper two new approaches are presented how to partition an amount of functions distributed in automotive electronic systems. In contrast to common partitioning algorithms as Kernighan-Lin, Best-Gain-First, Simulated-Annealing, a.s.o., these algorithms are real multi-partitioning ones. With respect to ECU (electronic control unit) characteristics, the software functions to be partitioned will be allocated automatically onto the available hardware. Main motivation is the reduction of the resulting bus-load which is provoked by the communication between such functions. Moreover these algorithms optimize the final partitioning solution to achieve a reduced number of ECUs. Reducing bus-load and the number of ECUs can lead to significant cost reduction. In order to validate partitioning results, a CAN as well as a FlexRay model was developed in Matlab/Simulink determining the bus-load over time.

The aim of OSEK/VDX is an industry standard for open architectures in vehicles. Originally founded as a Franco - German joint project, OSEK/VDX is now drawing worldwide attention. In the project, services and protocols are specified to standardize Communication, Network Management and a real-time Operating System. Its architecture offers a network-independent interface while taking into account the constraints of automotive applications in terms of size and cost. A structured and modular software implementation based on standardized interfaces and protocols as proposed by OSEK/VDX is a necessary condition for portability and extendibility, and thus reusability of existing software. An overview of the current status of OSEK/VDX is presented.