CAN Bus Based Automotive Test Solution
With the rapid development of the Chinese automotive market and the rapid increase in the value of automotive electronics, test technologies for automotive electronics have also become increasingly complex. Under the trend of global automotive design and production, local engineers in China increasingly feel that The difficulties faced by automotive electronics testing include:
• It is unable to meet the ever-changing demand of the product line, and hopes to reduce the cycle of launching the product.
(1) The increasing renewal of automotive electronic products requires test systems to meet new demands as quickly as possible. At present, the special test systems introduced by foreign countries often have a long upgrade cycle and cannot meet the rapidly changing product testing requirements of the local market.
(2) Professional automotive electronics manufacturers often produce many different types of similar products, and their production schedules often change according to the conditions of orders and logistics. If different types of products use different test equipments, it will lead to low test equipment reuse rate and greatly reduce investment efficiency.
· Current automotive electronics testing lacks solutions for general-purpose instruments. For example, car audio and instrument panel testing often requires specially-customized instruments, and these instruments are very expensive.
· Local after-sales service and timely response to faults. In the test production line, the continuous operation of the production line is the highest goal. When Chinese engineers cannot master comprehensive fault diagnosis and repair techniques, they can only seek assistance from engineers abroad. This easily leads to slow response and is costly.
Complex automotive test systems often require multiple measurements and control tasks to work together. An integrated hardware and software synchronization platform is especially important.
Flexible test equipment supporting CAN protocol
In the 1980s Bosch developed the CAN bus standard to solve the communication problems between various electronic units in automotive systems. This serial bus connects two electronic devices in the car with two wires or one wire and can transfer information to each other. Using CAN bus to avoid a large number of complex wiring between electronic modules, such as the dashboard speed, engine speed, fuel and engine temperature indicators do not need to connect different cables to the corresponding sensor, but only need to access the CAN bus , you can get the corresponding information from the bus. The outstanding performance of CAN has led car manufacturers to develop and use test systems based on CAN and data acquisition equipment. The International Standard Organization has accepted the CAN bus as an ISO 11898 standard. National Instruments introduced the CAN controller family on its standard virtual instrument test platform, supporting multiple CAN bus protocols, including high-speed CAN, low-speed fault-tolerant CAN, and single-wire CAN. In particular, the new PXI-8464 software-selectable CAN controller allows you to adapt to various CAN communication protocols without changing the hardware connection. At the same time, it can be used as a bus controller or a bus communication analyzer. Test equipment can be flexibly adapted to flexible production.
PXI+TestStand Automotive Test Platform
In the field of automotive electronic measurement based on CAN bus, the most successful test platform is a virtual instrument platform based on PXI bus and TestStand software.
PXI is an industry-standard test platform built on a high-speed CompactPCI bus and incorporates timing, triggering, and synchronization features similar to those of VXI. For ease of integration, PXI uses open software standards that include common operating systems, plug-and-play drivers, and networking technologies. PXI-based modular instruments not only have standardized hardware profiles and interfaces, plug-and-play installations, but also support higher-level, higher-compatibility software protocols such as the Interchangeable Virtual Instrument Standard (IVI) and Virtual Instrument Software Architecture Standard (VISA) and more. This allows any test to be standardized into the same hierarchy mode.
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| Figure 1: Test system based on PXI+TestStand platform. |
The physical signal of the unit under test is connected to the test and measurement hardware through sensors and signal conditioning. These modular instruments are plugged into the PXI chassis and connected to the PXI bus interface. The driver exchanges measurement and control data through PXI underlying communications and modular instruments. The measurement and control software package implements universal data acquisition, instrumentation and unit under test control through the driver. The signal processing software package calls signal processing tools to implement common signal analysis functions. The test and measurement module calls the measurement and control software package and the signal processing software package to realize the test and measurement related to the specific unit under test. These test measurement modules constitute a single step of the entire test and are called by the test software platform. NI's TestStand software is an internationally widely used test management software. It provides everything common to each test, such as test flow management, results archiving and reporting, user rights management, operator interface, and more. With this software as a platform, each test module can be called down to form a standard test procedure. Upward data can be recorded to the database, which together with the hardware system constitutes a complete test and measurement system (Figure 1).
success case
Shanghai Juxing Instrument Co., Ltd., as the system alliance provider authorized by NI China, is one of the proponents of applying the PXI+TestStand platform technology to the automotive system test based on CAN bus, and has provided several internationally renowned automotive electronics manufacturers with Ten sets of test systems based on this technology. For example, based on the CAN bus-based car audio test system developed by Juxing, which is used for the testing of fully automated car radio pipelines, each automatic assembly line is equipped with 6 PXI test stations, which automatically tests different functions of different audio assembly stages. . When the assembly line undertook another brand new car radio project and requested the production plan of the assembly line to be deployed according to the order, due to adopting the PXI+TestStand platform technology, the pipeline modification did not require the purchase of new test instruments. The software program can be quickly put into the test of new products. It took the manufacturer more than a month to retrofit the test system for the new radio, and it would take at least 4-6 months if the test equipment was imported from a foreign system integration company. The introduction of new products three months in advance not only means early earnings, but also preemptively occupying market share.
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Figure 2: Radio test connection diagram. |
The PXI+TestStand Platform Advantage
For customers, this test system based on PXI+TestStand software and hardware platform has the advantages of high integration, good reliability, convenient upgrade and maintenance, and openness and thoroughness.
First of all, you can use a standard 3U PXI chassis to plug in a variety of modules to replace a number of traditional instruments stuffing the entire cabinet; for the CAN bus based unit under test, it often requires a variety of test modules to work together to test The various properties of the unit are tested. For example, a functional test of a car dashboard requires a CAN controller, analog voltage and current acquisition, light switch control, night lighting PWM acquisition, LED video detection, etc. All of these test instruments can be integrated in a PXI chassis. in. In this way, while reducing the equipment volume and the area, it greatly simplifies the complexity of the testing equipment and the complexity of the wiring, thereby improving the reliability of the equipment.
Secondly, due to the standardized platform structure, the overhaul and upgrade of equipment are greatly simplified. For example, if a factory wants to replace an existing oscilloscope or upgrade to a PXI oscilloscope, since the PXI oscilloscope supports the GPIB and IVI standards as well as these traditional oscilloscopes, you only need to configure the corresponding system resource name in the IVI driver. Need to change any test code, you can easily complete the replacement and upgrade. In this way, you can save investment while greatly reducing the cost of maintenance and upgrades, especially to reduce production line interruptions. In addition, from the software point of view, since all tests use the same TestStand platform software, when the production process changes or the test product upgrade needs to change the test flow or settings, the production and maintenance engineer only needs to master a software TestStand, ie It is easy to maintain all inspection stations.
Finally, what may be most important to Chinese engineers is a completely open test system. It needs to open up all test and control information to the test engineer, so that engineers have the opportunity to master the core technology of automatic test and measurement. Such a test system architecture opens up the data acquisition, signal analysis, test flow, and data management hierarchically, allowing engineers to easily obtain raw signals, adjust analysis methods and pre-processing parameters, optimize test procedures, and define data report structure formats. For example, in a CAN bus-based test, you can use another CAN control card to monitor the communication timing between the UUT and the outside world, and analyze whether the bus logic meets the specifications. For another example, you can obtain the audio output of a problematic car stereo and do a detailed post-mortem analysis to find out where the problem lies. Once there was a car radio with a low signal-to-noise ratio, it was impossible to diagnose the cause of the problem with standard detection methods. After a slight modification of the SNR test program, the test engineer recorded the original audio, and then used the FFT function for spectrum analysis. It was found that there was an unusual peak at a frequency exceeding 20 kHz, and the fault was immediately eliminated after the design was improved.
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