Driving test towards the right balance
05 July 2007
Automotive electronics is in a rock and a hard place situation – it requires the volumes and therefore cost pressures of high volume, yet needs the quality and reliability of aerospace. The test regime must therefore play an important role in automotive electronics manufacture, as Antonio Grassino, President of Seica, discusses
There is no shortage of challenges for the testing of automotive electronics. Meeting quality and safety standards like AVSQ, VDA6, EAQF, QS9000, etc. demands strict test and validation procedures generally only seen in the aerospace industry. However, unlike the aerospace industry, automotive products are produced in large volumes, which brings with it the cost demands and constraints of a high volume operation. Every manufacturing operation, including test, has a cost that has to be justified. Getting this balance between quality and cost is the biggest test in automotive electronics.
Today’s cars make large usage of a variety of Electronic Control Modules (ECM) also called Electronic Control Units (ECU). ECMs consist of a CPU and associated logic to convey input/output signals that control different components of the car. Some ECMs are responsible for delicate functions of the car, like the Antilock Brake System (ABS), while others can control simpler utilities like the windscreen wipers and the electric windows (i.e. the Trunk Door Module, TDM). The ECM body computer, the Dash-Board and the Remote Controller implement most electronic functions on a modern car. Communication with the Body Computer is done via two main types of specific busses with associated protocols, the Controller Area Network (CAN) and the Local Interconnect Network (LIN). The first is the most popular standard to date, but in some applications it might be too costly and it is increasingly being substituted by the less complex LIN solution. A LIN master node can connect the LIN network to higher-level CAN network, extending the benefits of networking all the way to the individual sensors and actuators. Lower cost solutions might also deploy the K Bus, an RS232-like with levels 0 to 12V. Sensors and actuators can carry high currents, which pose specific challenges to signal switching and reproduction of the appropriate test conditions. Some of the functions in the car are remote controlled, which involves availability in the test equipment of the appropriate RF resources.
Additional challenges are brought in by the different scenarios on which test should be performed. Initially the test platform is used in engineering, where quick changes and high interaction are required. Once in manufacturing, we can identify at least two different scenarios: the End-Of-Line stage and the Run-In stage. In the first one, final functional test of the body computer working with special firmware (instead of real loads) is executed, to optimise speed and measurement accuracy. The Run-In executes instead the final functional test of the body computer with real firmware and real car loads (often involving high currents up to 35A and more). The Run-In test is often imposed by the extremely high quality requirements demanded by the car manufacturers for some modules. Additionally, some stages might require On-Board-Programming (OBP) of the microcontroller and additional operations. Remote controls require smaller tester configurations, but availability of RF functional capabilities.
Flexible and scaleable-
While intended to respond to a variety of applications, conventional ATE are rarely suitable to combine the variety of requirements of ECM test at acceptable cost levels. On the other hand, dedicated lower cost solutions, built around PCI or PXI standard instruments, fail to adequately respond to all of the requirements and do not offer the advantages of a well documented and supported common platform. Closely working with major automotive manufacturers, SEICA has developed a flexible, scalable and reconfigurable test platform, the STRATEGY VL, capable of addressing all the requirements of comprehensive, high quality and high throughput test with careful cost control. Easily reconfigured in function of the application, the platform becomes a point solution at each stage of test, while maintaining the commonality of software, hardware and operating functionalities.
The test platform is controlled by a PC, running under Windows/XP. Digital communication with the Unit Under Test (UUT) is assured via two CAN channels (programmable as Low Speed or High Speed), one LIN channel, PCI Bus and a K Bus.
The core of the system is architected around a 40 slots Test Backplane with embedded 8 lines analog bus routing. All instruments and channel cards that configure the Test Backplane are controlled via proprietary optical link connection, which allows zero-noise test environment.
Most stimulus/measurements functionalities are assured by a DSP-controlled multi-instrument subsystem, the ACL. This instrument-card includes 3 independent Arbitrary Waveform Generators (AWG), Multi-Meter, Timer-Counter, and features signal analysis capabilities and digital scope functionalities. ACL is used both for structural, power-off and active In-circuit test and for functional test applications. Signal routing to the DUT is performed via configurable switching cards (64x2, 32x4 or 16x8) capable to serve up to 544 channels. Additionally, special High Current modules have been designed, offering 20A switching current on multiples of 32x2 channels. To avoid costly fixture add-ons, the Test Backplane is configurable with an optional dedicated module including 40 general purpose automotive outputs, loads, voltage references and opto-couplers, another module with 20 automotive relays and service LEDs, another module with resistive loads, and emulation for lights and other loads. The system can also easily integrate external instrumentation (GPIB, VXI, PXI or PCI), like Agilent programmable electronic loads or RF generator (1.16GHz) for remote control test.
A number of DUT power supplies can equip the system, including a high power (28V/35A) programmable unit. The variety of signal routing requirements to the UUT (including High Voltage, High Current, Low Levels, RF) demands special attention to the connectivity with the fixture. To best assure quality, the STRATEGY VL platform uses the well proven ODU-MAC connectors on its receiver.
Test program generation, debug and run time software are usually controlled on all SEICA Test Systems by the proprietary VIVA environment. VIVA offers an efficient development environment, with connection to most CAE/CAD tools, test generation algorithms, graphical edit and display tools, interactive debug and run-time environment, accurate diagnostics and paperless repair station. Given the need to extend utilisation of the test platform up into engineering and development, where National Instruments tools are very popular, STRATEGY VL can also (preferably) be equipped with a comprehensive LabView and TestStand environment that allows full control of the system’s operations under a potentially more familiar software.
Reconfigurable to suit the application, the STRATEGY VL platform will typically adopt a one-bay configuration, with edge connector access, for engineering/development positioning. In manufacturing, the EOL stage can be configured with twin fixture and pneumatic and motorised tools to assure high throughput and low cost of operation. The Run-In configuration is arranged instead to provide direct access to DUT connectors. During Run-In test all loads are active simultaneously as in real conditions, with the result of sometimes finding previously undetected faults. Point solutions for remote control Test Radio Frequency (TRF) carry minimal, cost controlled configurations, but add the RF generator and a Spectrum Analyzer.
The solution has the ability to provide dedicated stations working in parallel, all part of the same family and all easily transformed (EOL to Run-In or TRF and vice-versa). And as automotive requirements evolve, STRATEGY VL will maintain its value thanks to its expandable, open system, standards-base architecture.
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