Automotive electronics test: A functional test perspective

Electronics in automobiles serve three major functions: to ensure safety, provide comfort, and optimize driving experience. Automotive electronics can be categorized into four major segments:

• Powertrain—where the electronic system provides optimal driving experience by managing fuel injection and drive power, reducing emissions, as well as controlling braking and traction;

• Body electronics—where the electrical functions of the automobile such as lights, ignition, and electrical appliances are managed;

• Safety—in which life-saving systems such as air bags, tire pressure monitoring, and antiskid measures are managed; and, • Infotainment and telematics— where navigation, communications, and entertainment systems are integrated into automobiles.
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The key functional unit to enable all these is the electronics control module (ECM). The ECM is fundamentally a computer with one or several processors to read information from different sensors and provide the appropriate controls to the powertrain. Because much of the data from sensors is analog, the ECM incorporates microcontrollers and processes information in near realtime. Since the ECM is able to gather a lot of ambient information (temperature, air pressure, etc.), it is able to control the ignition system more efficiently resulting in better fuel efficiency, reduced emissions, and better power control and responsiveness.

ECMs today are more sophisticated than ever and have the ability to read more sensors, manage more automobile resources and systems, and therefore provide more dynamic controls. As a result, more systems such as braking and traction controls that were traditionally mechanical now have greater degrees of electronic actuation and control. The result is a safer, more efficient and more comfortable driving experience.

The automotive electronics industry is growing at a fast pace. It faces the pressure of meeting timeto- market demands, as well as technological challenges. While sophisticated designs can be rigorously validated in R&D, manufacturers need to ensure that they produce cost-effective, high quality products.

TEST CONSIDERATIONS
Given the complexity of ECM, several stages of tests are performed on the ECU, starting from assembly to complete functional test at the end of the line. Inspection of the ECU board before and after assembly is performed using automatic optical inspection (AOI) and automatic Xray inspection (AXI), where defects arising from the assembly process are prevented, followed by incircuit test (ICT). Finally, the ECU is put through a rigorous functional test.

Figure 1 illustrates a typical SMT assembly line with various tests at different stages (with examples of test solutions from Agilent)

Given the complexity of today’s ECMs, manufacturing functional test typically uses automated measurement systems comprising multiple measurement and control channels. Developing a test requires a balance of the three key manufacturing challenges:

• Time : Test deployment, development, and execution time,
• Cost : Capital investment cost, integration, and maintenance, and
• Scope : Throughput, accuracy, and flexible capabilities.

With the TS-5000 family of automotive functional test systems, a balance can be achieved in producing a standard test system that is reusable, scalable, and meets the evolving test requirements of electronic control modules and smart sensors.

Three approaches to creating a functional test system:
• Using the in-house test department to develop a custom system,
• Outsourcing the development of the entire system, and
• Using a commercial off-the-shelf platform as the basis for the test system to be deployed.

Whatever the approach chosen, the right platform must be versatile and scalable, allowing for optimum test coverage, exposing it to the reusability of multiple types of ECMs without trading off measurement accuracy. The robustness of a system minimizes the system downtime, and lowers maintenance costs. Test systems should also have high throughput, operate 24 hours a day, seven days a week, and be fast enough to prevent bottlenecks in the manufacturing line.

AGILENT TS-5000
An example of such a test system is the Agilent TS-5000 family of automotive electronic functional test systems. This family is not limited to a particular ECM test, but is scaled to the required test requirements of the ECM. These systems come equipped with the Agilent TestExec SL test executive software that combines with the TS-5400 application software to provide a development environment and a library of over 400 test routines specifically tuned for automotive ECM tests.

The TS-5000 family systems have been successfully deployed to test engine management, automatic transmission, body control, airbag, ABS/TC, and security control modules.

Take a typical engine control ECM test as an example. The ECM requires fast switching for routing of multiple signals and loads, and this is provided for in the system via the E6198A Switch/Load Unit (SLU). Complimenting the SLU are multiple load cards with fast relays, pull-up and pull-down capabilities, as well as bridge load capabilities.

An engine control ECM also requires high-current and highvoltage response handling, and these systems provide f ly-back voltage and current handling with voltages and current of up to 500V and 30A respectively. Measurement capability includes period, frequency, timing, and duration measurement capabilities.

With the engine control ECM, as in most other ECMs, there is also a requirement for serial communications. In a test, this is the essential part of a DUT (deviceunder- test)-assisted test, where the DUT must be able to communicate with the test system to allow it to manipulate and verify the ECM via a serial link. Serial communication is available for most automotive protocol such as ISO-9141, J1850 and fault-tolerant CAN.

Targeting at no specific ECM test, these highly scalable systems allow ECM manufacturers to standardize their systems for easier supportability, and the streamlining of engineering time and support required. The approach of the Agilent TS-5000 family functional test systems is to reduce customers’ overall test development time, to enable them to re-prioritize their efforts in more important areas such as test coverage and optimization, product quality, and manufacturing process improvements.

The Agilent TS-5000 family comprises of the TS-5400, TS-5410, TS-5020 Automotive Functional Test Systems and the TS-5020 TPMS (tire pressure monitoring systems).