Electronic control unit

Control equipment (English ECU = electronic control unit or ECM = Electronic Control Modules ) are electronic modules that are mostly installed in places where something needs to be controlled or regulated. Control devices are used in the automotive sector in every imaginable electronic areas, as well as for the control of machines, plants and other industrial processes. They belong to the embedded systems.

Basics

At the start of the electronic motor control, they have been used mainly for ignition, since 1987, they are also used for the electronic control of diesel engines. Since about the mid-nineties mechanical control concepts in internal combustion engines were almost completely replaced by electronic control devices.

Today, the speedometer in its new form for the user-visible control devices as the instrument cluster along with tachometer and various other ads. Sensors such as tank level gauge and oil pressure gauge are now connected with their own control devices that implement, inter alia, a long-term monitoring and constantly monitor its functional ability in the sensor itself by plausibility check of its output values.

Function

Control devices generally operate according to the IPO - principle. EVA stands for input - processing - output. For the input sensors are available. These determine a physical characteristic such as speed, pressure, temperature, etc. This value is compared with an entered or calculated in the controller setpoint variable. If this does not match the measured value with the value stored in memory, the control unit by means of actuators controlled by the physical process, so that the measured actual values ​​again correspond to the desired sizes. The actuators draw so corrective action in a running process.

While " electronic ignition " of the early years were still composed of discrete, analog electronic circuits, current control devices are usually equipped with " integrated intelligence ", ie they consist of a stand-alone computer in the form of an embedded system. The size of this computer varies considerably depending on the complexity of its tasks, ranging from a single-chip solution with a microcontroller ( with built-in RAM and ROM memory ) to multi-processor systems with dedicated graphics output system. Programming is fixed by the use of ROM memory usually, but some systems allow by use of reprogrammable flash memory ( EEPROM) to update the software through the workshop.

Networking

In current vehicles, control units about different system buses (CAN, LIN, MOST, FlexRay, Ethernet) are interconnected. The devices swap over system-wide information about the operating conditions and other relevant data in the vehicle. It also connected the on- board diagnostics and a vehicle diagnostic system on such buses (and possibly the K-line ). It can be (alternatively with normal personal computers or notebooks plus a matching interface) communicates with the controllers from the outside with so-called diagnostic equipment. Here is queried especially if the control unit when the continuous self-test has detected any errors by yourself or with the sensors connected to it and registered. Thus it can be spared much investigative work of a workshop with a message such as " short to ground in the fuel sender unit ". Frequently, diagnostic protocols such as KWP2000 or UDS are used.

Due to the increasing complexity and software requirements and the need for communication between control units OSEK OS has established itself as a real- time operating system and communication standard in Germany. Another measure is the increasing standardization of the control device architectures, such as in the AUTOSAR development partnership.

In the meantime, are in a normal car more than ten control units throughout the vehicle distributed. Modern luxury sedans have installed some cases more than 70 ECUs. The range of microcontrollers used ranges from 8 - to 32 -bit machine.

Development and software

Control devices are rarely developed and manufactured by the automobile manufacturers themselves. Mostly these are developed by automotive suppliers on behalf of the automobile manufacturer.

To ensure interoperability of the various control devices in the different variants of different car models, automobile manufacturers usually prescribe a particular software equipment that the supplier has to use. The aim of this unified software equipment trouble-free networking and integration of all control units into an overall system.

This basic software features is generally referred to as a standard core of each manufacturer.

A design goal is always to respond correctly to predictable extreme situations. This mainly includes the undervoltage, as a special case of this, the starting voltage pulse, and temperature extremes in both directions.