From in-vehicle communication to fuel efficiency and regulatory norms, every automotive innovation is becoming more complex and highly integrated. It implies that test and applications engineers must be innovative and resourceful in approaching every test for better design, shorter time-to-market and lower cost
SHWETA DHADIWAL BAID
When you build a system that integrates many small systems, the biggest challenge is effective communication between all the smaller systems to make the big integrated system work as one. Today’s automobiles consist of various interconnect buses to communicate between sub-systems. To test these systems, you need tools and solutions that support serial communication standards.
An evident change which the automotive industry has gone through over the years is the use of electronics in automobiles. “If you see a new-generation car, the use of electronics is conspicuous right from the security and vehicle access system to the driver interface, powertrain, safety and enticing infotainment and telematics,” says Asish Jain, applications engineer, Agilent Technologies.
Test and measurement tools have been used for many years now in the design and testing of engine control systems, entertainment systems and safety systems. “What is now emerging as a critical area is energy conservation and power management,” adds Evan Sun, technical marketing manager, Tektronix. Agreeing to this Prabhakaran P.V., business unit head-MDTS from TTL Technologies, shares, “With the increasing commercial and regulatory pressure for safer and environment-friendly vehicles, most of the automotive OEMs are looking for more efficient and green designs to position themselves on top.”
Rajesh Pathak, advanced specialist-technology, Delphi, explains, “An automotive controller has to undergo many tests in sub-systems as well as integrated environment. Some of the tests include vibration analysis, crash testing, accelerated tests, temperature test, EMI/EMC test, safety standard requirement, emission test and structural tests. Apart from these, there are non-electronics related tests like oil test, salt test, water test, soak test, sand test and drop test.”
“The test and measuring solutions have to be versatile, adaptable and exhibit excellent forward/reverse compatibility to cater to an extremely varied nature of testing requirements of the automotive industry without affecting the integrity of the test methods,” says Tapesh Gautam, assistant manager, product support & application, Rohde & Schwarz.
Commercial off-the-shelf equipment
Automobiles, though specialised applications, are basically an integration of many sub-systems. To test these systems, there are several commercial off-the-shelf (COTS) bench equipment available that fit the general requirements. However, “the difference may lie in the frequency ranges of the applications and implementation,” says Jain. Illustrating with an example, he says, “The radars used in aerospace and defence typically operate below 40 GHz and involve complex design and stringent tests. However, radars used in automobiles for collision prevention work in the 76-77GHz band with a relatively simpler set-up. The testing solutions vary to match these specifications.”
Digital and mixed-signal oscilloscopes, specialty probes, expert power measurement software, logic analysers, signal generators and real-time spectrum analysers are among the general-purpose equipment used in automotive design as well as production. “Switch-mode power supplies, electronic loads and data loggers are used in design and verification and life-cycle testing of any automotive component or system,” shares Prabhakaran.
“Equipment can be standalone box tester units with predefined test functionality or modular with I/O cards added based on the sub-system being tested,” says Rohit Panikkar, technical marketing manager, National Instruments. During R&D, dynamometers are used to study the effect of various conditions on engine, brake and chassis. Test systems to study the endurance of system components and noise, vibration and harshness (NVH), as well as safety test systems are also used at this stage. An RF signal generator and RF analyser with spectrum analysis capability are used to test remote keyless-entry modules.
Automotive vehicle power systems are very harsh electrical environments. “High-current motors, solenoids and other components on the power system often cause power system voltage transients and dropouts to occur. Successful operation of automotive electronics depends on adequate power transient immunity. These transients can be studied using a scope. However, a DC power analyser reduces the test time and improves ECU test coverage by allowing engineers to easily capture and re-play power system transients. Libraries of transient cases can be developed and archived for future use as well as for long-term support and ECU re-qualification,” explains Jain.
Data acquisition systems and highly accurate digital multimeters (DMMs) are also required in almost all the stages of design and development cycles. “There are specially designed loads and power supplies used for testing of fuel cells, batteries and charging of electrical vehicles,” adds Prabhakaran.
Automated test systems
In automobile production, typically, automated test equipment (ATE) are used to achieve high throughput and efficiency. ATE are built using COTS equipment like oscilloscopes, spectrum analysers, DC power analysers, data acquisition systems and switches with a difference that these are interconnected via LAN or GPIB and the software runs the required test routines and hence controls these equipment. A lot of T&M vendors provide modular or synthetic instrumentation, which can be combined to form an ATE depending on the specific requirement.
Jain shares that there are turn-key test solutions for engine control module (ECM) testing which are primarily used in a manufacturing set-up where time (test development, execution and system deployment), cost (capital and integration) and scope (throughput, accuracy and flexibility) are of utmost importance.
“T&M vendors also provide solutions based on the OpenChoice structure, which means customers can easily develop their own software or utilities script for an automation testing mechanism,” adds Sun. Also, “a small number of manufacturers use innovative processes by transmutation of communication technology for verification of mechanical parameters,” says Gautam.
Automotive communication test systems
Electronic control units communicate with each other using some protocol like controller area network (CAN), local interconnect network (LIN), FlexRay, and media-oriented systems transport (MOST) for multimedia and infotainment.
“Debugging and testing this type of network topology can be challenging and time-consuming,” says Sun. Pathak adds, “Due to huge in-vehicle communication and stringent emission norms, it necessitates data logging for a long duration along with the ability to replay the same.”
The popular usage of CAN in automobiles has also prompted the development of a variety of CAN interfacing tools. However, Gautam says, “after the design phase is over, a recursive approach is generally followed by using test and measurement instruments and going back to conduct modifications based on the actual test results until perfect values are physically achieved. No prototype can afford to proceed for further stages of design cycle by completely substituting actual measurements with simulation.”
Jain says, “To test these serial data protocols and hence the communication between various ECUs, an oscilloscope with CAN or LIN decoding and triggering capability is used. Also, one can use a logic analyser to perform timing and state analysis on the bitstreams and command execution.”
ECU: critical to test
The electronic control unit (ECU) is the heart of automotive electronics. It takes care of the engine control, transmission, airbags, antilock braking system, audio system, windows, doors, mirror adjustments, environment control and many other such systems and sub-systems. “It is difficult to prioritise the automotive assemblies in terms of their relative importance because the basic operation of an automobile is completely dependent on coherent operation of all the modules, big or small,” says Gautam.
“Using ECUs to control both essential and non-essential automotive systems is becoming the new industry standard. Based on digital technology, these ECUs require a deeper understanding of complex timing and signal integrity issues,” shares Sun.
Testing of automotive electronics relies heavily on being able to interact with a particular ECU responsible for a particular electronic sub-system. Panikkar says, “Initially, these test systems are used to test prototypes of the ECU in a rapid-control prototyping scenario, where they provide real-world signals to the prototype. They are used for fault insertion and studying the behaviour of the sub-system under varying conditions and limits.” With vehicles incorporating more and more electronics, testing of driver information systems, navigation as well as in-vehicle entertainment systems is also necessary and critical.
EMI/EMC: a rising concern
The staggering growth of electronics in automobiles has led to a rising concern about electromagnetic compatibility (EMC) and electromagnetic interference (EMI) issues. Telematics, electric power, use of electronic controls in place of mechanical, in-vehicle infotainment, wireless voice and digital communication, active suspension, antilock brake and satellite navigation are some of the functional units that give rise to EMI/EMC issues. T&M vendors are developing new methods, tools and standards for automotive EMC testing.
“For EMI/EMC testing, you require EMI receivers. Apart from this, T&M providers provide antennae, amplifiers, signal generators, power meters and other test transducers required for automotive EMC testing,” says Gautam.
Use of radio frequency (RF) interfaces within an automobile for communication, safety and security systems has created the need to develop and measure real-time RF systems that can efficiently monitor vehicle operation and status.
“Tyre pressure monitoring, keyless entry, infotainment and immobiliser systems are examples of technologies containing RF signals that are often triggered by external events which create profiles that are intermittent in nature—present one moment, absent the next—and variable over time,” informs Sun. These transient signals are difficult to measure using traditional spectrum analysis tools and require new instruments that can measure time-varying signals in the frequency domain.
“For RF testing, the test instruments used are vector/scalar signal generators, analysers and vector network analysers generally less than 6 GHz,” says Gautam. There are also handheld RF analysers with spectrum analyser capability which can be used to fulfil RF testing needs of the automotive industry.
Intensive tests to maximise safety
The most critical modules are those related to safety. “The automotive industry has always considered safety a critical engineering concern. Indeed, much of this (anti-lock brake systems and electronic control units) is implemented using a new software that has been introduced specifically to increase safety,” shares Sun. Safety is the most critical module in automobiles for which specialised testing is required.
Panikkar explains, “Crash testing is a very important test, and its results are fed back to the designers to offer as much protection to the driver as possible.”
The response of critical modules needs to be studied under different test scenarios and injection of faults. Data received from these tests needs to be analysed thoroughly to determine key conditions when drivers are at greater risk.
“Tools like DIAdem with its crash testing and analysis toolkit offer effective methods to analyse data obtained from such tests,” Panikkar adds. These need to be combined with data acquisition systems for measurement of vibration, impact and other parameters.
New technologies for automotive tests
Test and measurement instruments always work on future orientation. This means that all the latest trends in instrumentation technology reflect immediately on these solutions. All the innovations in automotive technology need innovative test and measurement solutions.
“Miniaturisation of the instruments is one such example. Tests that required an entire bench of instruments not long ago, can now be done with a single instrument. The architecture now also ensures that modifications can be carried out with minimum or no change in hardware,” says Gautam.
Implementation of technologies like ZigBee, Bluetooth, GPS and DVB has increased the diversity of T&M solutions used in the automotive industry now.
Today’s test systems rely heavily on reprogrammable field-programmable gate arrays (FPGAs), which offer flexibility to a great extent. Panikkar shares, “These FPGAs allow for system models to be downloaded onto them. Input/output (I/O) can then be fed directly to these boards and the FPGA mimics the system response. These systems use real-time operating systems in order to achieve deterministic performance and accurately control timing of signals and make synchronised measurements.”
More and more advanced technologies are being adopted in the automotive industry for developing an ecology-conscious, safe and comfortable car. Sun tells, “For example, last June when HDMI 1.4a was released, it was the first time that any advanced digital video and audio technology supported automobiles. There are solutions to test and support automotive HDMI (Type E) and unique direct synthesis capability.”
The convergence of technologies and capabilities inside an automobile has led to test equipment that combine multiple capabilities in a single unit.
“T&M offerings include a wide range of combined solutions that are easy to use and economical. One example is the DC power analyser which combines 1-4 DC power supplies, DMM, oscilloscope, arbitrary waveform generator and data logger in one integrated instrument. And most importantly, it is a modular instrument and hence provides the users flexibility in terms of expansion with need,” Jain says. Thus it ensures optimised initial investments.
Technologies like LXI (LAN eXtension for Instrumentation) have made it very easy and user-friendly to connect various test instruments to a PC and to each other. “The new power supplies and loads with advanced sequencing and high slew rate can help to simulate the charge/discharge conditions for hybrid cars’ charge controllers and electro-motors,” shares Prabhakaran. He adds, “Isolated analogue controls also help the user in testing of critical parameters.”
The ultimate goal
The ultimate goal of any T&M vendor is to provide solutions that reduce engineering costs and time to market while maximising flexibility and long-term investment. The automotive sector has challenging demands on either of the aforesaid parameters.
“Since the failure of the system can cost the human life, a very effective, robust and exhaustive testing is required,” cites Pathak. Agreeing to this, Gautam adds, “This emanates from the fact that vehicles (and their sub-assemblies) are expected to operate in completely uncorrelated scenarios demanding high ruggedisation.” Testing solutions are available that can be used in design, validation, certification, manufacturing as well as service of automotive electronics.
Measurement integrity and speed, test throughput, test system up-time, flexibility and reuse are the specific needs of this industry. Ever-changing market scenarios and increasing competition are leading to improvements in the existing products and testing of new products with almost the same test setup.
The author is a senior technology journalist at EFY