Vehicle diagnostic system
Vehicle diagnostic systems are applications that are used during the entire service life of control units in vehicles to diagnose them . The service life includes development, production and later servicing of the control units in the specialist workshops. Vehicle diagnostic systems use, among other things, the on-board diagnostic functionalities of the individual control units. In connection with the evaluation of the data bus communication, this enables a detailed error analysis.
Concept and definition
A vehicle diagnostic system is an analysis tool consisting of hardware and software , which generally offers functionality for reading out control unit data and for recording data bus communication (tracing). Vehicle diagnostic systems are used in test drives and in workshops for quick error detection and error analysis. Ideally, the data from the data bus communication ( CAN , LIN , MOST , Flexray , K-Line ) and the data from the error memory of the control units are brought into connection and evaluated. The key word protocol 2000 (KWP2000) or increasingly UDS is used as the protocol for communication between the diagnostic computer and control units .
meaning
The early detection, analysis and elimination of errors is a decisive success factor in the development of new vehicle generations. Shorter development times as well as increasing complexity make it more difficult to guarantee high quality standards at the start of series production. The increasing number of new functions, which are increasingly being implemented across multiple control units, creates a complicated network of dependencies between the software on the individual control units. Furthermore, dynamic dependencies (such as processing sequences or time conditions) between the software of different control units and the insufficiently realistic simulation of sensors and actuators, despite extensive tests of the individual components in laboratory setups, lead to errors that are only detected on test drives with the help of vehicle diagnostic systems and analysis tools can.
Functionality and examples
Many diagnostic systems limit themselves to the hardware-based recording of the onboard communication, which generates relatively large amounts of data that are difficult to analyze. These vehicle diagnostic tools are also called data loggers. Some examples based on embedded hardware are MultiLOG (GiN, Vector Informatik ), UniCAN 2 Professional (CSM GmbH), MC Log (IHR GmbH), CCO DLIII (Condalo GmbH), M-LOG (IPETRONIK GmbH & Co. KG). With these systems there is no software-based support for the analysis of the data .
Another group of systems offers this functionality purely software-based (can therefore be operated on laptops or industrial PCs in the car) and also primarily offers data logger functionality, such as B. CANalyzer , CANoe , X-Analyzer, canAnalyzer, CANcorder, EDICmobil, TraceRunner, IPEmotion and others. Some of these vehicle diagnostic tools offer additional functionalities such as B. Remaining bus simulation (CANalyzer, CANoe). In addition to the pure acquisition of CAN messages, many classic systems offer error memory analysis and evaluations of diagnostic protocols such as UDS. There are also vehicle diagnostic systems that support both main functionalities of fault memory analysis and recording of the data bus communication. Examples are CANape ( Vector Informatik ), DiagRA MCD (RA Consulting) and Tedradis (IT designers). These create a temporal relationship between the recorded CAN messages and the read out control unit error memories and in this way facilitate the analysis. The Tedradis tool supports the user with further options for data reduction (such as triggers), visual processing of the relevant data, reading out and recording of vehicle information such as B. ECU coding, etc. Also manufacturers of embedded devices such as Telemotive (blue PiraT) and Condalo GmbH (CCO DLII) are currently working on functions that support the user in analyzing the data.
Technically, most of the problems of simply recording data have already been overcome today. In the future, the trend will be towards intelligent analysis, for example with the help of data mining and artificial intelligence methods .
Vehicle diagnostic systems in production
A vehicle diagnostic system for production is closely linked to the plant logistics to ensure that the vehicle is built according to the customer's order. For each individual vehicle there is a data record that describes which vehicle is built with which engine, country variant and additional special equipment. In addition, further data such as the chassis number, part numbers of the control units to be installed and the associated coding can be taken from the data record. Test results and read data such as serial numbers are written back to a database.
The requirements for vehicle diagnostic systems in the manufacturers' production processes are as diverse as their areas of application:
Pre-assembly areas
In the pre-assembly, individual vehicle modules such as seats, doors or instrument panels are set up separately, checked and then installed in the entire vehicle. A diagnostic system used for this requires in addition to the actual diagnostic communication:
- Remaining bus simulation for the missing entire vehicle in order to be able to test the functionality;
- Electrical measuring devices to ensure the correct functioning of the actuators , e.g. B. window regulators or lamps to be able to evaluate;
- additional test equipment, e.g. B. for pneumatics .
Vehicle assembly
In vehicle assembly, the entire vehicle is assembled and its functionality checked statically (with the engine stopped). The diagnostic system first checks whether the correct variant of the control unit is installed. This is followed by the coding according to the engine and country variant as well as special equipment, followed by a functional test, including measuring devices for electricity, e.g. B. can be used via clamp meter (so-called ECOS), which are integrated in the diagnostic system.
Entry area
In the run-in area, test stands are used for chassis adjustment and roller test stands , which are controlled by the vehicle diagnostic system. This dynamic function test with the engine running is partly controlled directly via diagnostics, in that actuators are controlled via diagnostics. For example, during the ESP function test by braking individual wheels, activating the suspension struts of an active chassis or simulating the accelerator pedal.
Operating area
Vehicle technology
In vehicle technology, in addition to diagnostic testers and data loggers , vehicle diagnostic systems are also used for fault diagnosis. See also: Error memory
Aircraft technology
Automatic vehicle diagnostic systems are used in aircraft technology and rail technology, which compare the function of a device with a redundant device. The results are transmitted to the operator by radio.
Vehicle diagnostic systems in the workshop
The major automobile manufacturers have vehicle diagnostic systems specifically produced for their authorized workshops that are tailored to the needs of the bus systems installed in the vehicle. The mechanic is guided to the solution of the problem with a decision tree or also called guided troubleshooting. It all starts with a symptom that the customer complains about and makes this known to the workshop. In the decision tree, various tests are carried out with which possible causes can be checked so that the defect can be found quickly and the necessary repair instructions can be given. The tests use individual diagnostic commands for this purpose. In addition to the guided troubleshooting, an expert mode is also available; this allows more direct access to the diagnosis and thus a quick solution.
The vehicle diagnostic systems for workshops provide numerous other functions in addition to vehicle diagnostics:
- Software update of the control units with direct access to download the appropriate software
- Circuit diagram directory
- Repair guides
- Parts catalog
- Connection to accounting for invoicing
- as well as a customer database
Programming of control units
Control units that are reprogrammable ( flashable ) can be sent a new program version in this way. To do this, there must be an extra program in the control unit called a flash loader . This program receives the diagnostic messages for reprogramming the remaining software from the diagnostic device and executes the commands received, such as B. deleting or writing to the flash memory.
The essential components of a control device for reprogramming are the transport protocol - proxies ( CAN -TP proxy MOST -TP proxy), optionally a KWP2000 component and the flashware Reprogramming controller. The TP proxies offer the KWP2000 component a uniform interface for sending messages and make the necessary adjustments to send transport messages to the respective subnets. If a new vehicle subnet (e.g. Flexray or TT-CAN) is used, a corresponding TP proxy only needs to be added in order to be able to flash control units on these vehicle subnets.
The flashware proxies represent the flashware modules installed on the control units. If a flashware module is to be updated in a control unit, a new flashware proxy, which contains the new flashware and associated configuration information for the control unit, is loaded into the vehicle from the download server in the infrastructure. The flashware proxy loaded into the vehicle contacts the components of the installation and configuration monitoring and, after positive feedback, initiates the installation of the flashware. For this purpose, the flashware and the configuration information are transferred from the flashware proxy to the flashware reprogramming controller, which interprets the configuration data, compiles the parameters for the KWP2000 messages and sends them in the correct sequence to the control unit to be programmed. The configuration data provide information, for example, on the structure of the flashware or on specifics during the download process into a special control unit. After a successful installation, the flashware proxy deletes the flashware and configuration data it contains and continues to be used in the vehicle as part of configuration monitoring.
Efforts towards standardization
In the early days of vehicle diagnostics, the individual automobile manufacturers developed proprietary systems themselves or through system partners, e.g. Some even independently for vehicle development, production purposes and for their own trade organization. These in-house developments became more and more cost-intensive in ongoing maintenance, tied the manufacturers to individual suppliers and prevented the simple data exchange in cross-manufacturer cooperation. The prohibition of discrimination against independent workshops and dealers (keyword block exemption regulation GVO) also required a standardized data format. These legal requirements and the realization that the basic diagnostic techniques are not relevant to competition therefore led to the willingness of the automotive groups to cooperate. The problem of standardization was dealt with at ASAM in the Automotive Electronics ( ASAM-AE ) working group and several standards were developed that are internationally standardized in the ISO 22900 group. As a result of the work, the ODX standard (also MCD-2D) for the data description and with MCD-3D an object model of a diagnostic kernel were designed. A third standard, MCD-1D or PDU-API, has been published for operating the communication hardware. MCD-1D takes existing standard tools into account, such as B. Pass-Thru adapter for flashing control units.
With these three standards, a diagnostic kernel is specified which has three interfaces:
- Communication hardware
- Diagnostic description
- Diagnostic application
With the adoption of the standards, new products based on them were created or existing products were adapted to the new standards.
literature
- Christoph Marscholik, Peter Subke: Data communication in automobiles: basics, bus systems, protocols and applications. Hüthig, Heidelberg 2007, ISBN 978-3-7785-2969-0 .
- Matthias Becker: Diagnostic work in the automotive trade as a human-machine problem. Consequences of the use of computer-aided diagnostic systems for specialist work. W. Bertelsmann Verlag, Bielefeld 2003, ISBN 3-7639-3145-7 .
- Werner Zimmermann and Ralf Schmidgall: Bus systems in vehicle technology - protocols, standards and software architecture. 5th edition, Springer Vieweg, 2014, ISBN 978-3-658-02418-5 .