Reinventing manufacturing tests for automotive electronics

 Ram Mohan Ramakrishnan

Ram Mohan Ramakrishnan

Automotive electronics has been making steady gains in percentage cost of the total vehicle cost world-wide. Consequently, it has been facing some of the same challenges that were faced earlier (and mostly solved by automated tests) in other areas of automobile mass-manufacturing – fabrication, mechanical assembly, electrical components and hydraulic systems.

A typical example is the Electronic Control Unit (ECU) that has become the heart (or brain!) of the modern automobile. An ECU receives inputs from various sensors and sends outputs to multiple actuators, in addition to communicating with other ECUs of related subsystems in the vehicle. Some ECUs implement performance critical functions such as fuel injection, ignition timing etc., whereas others control safety critical systems such as Anti-skid Braking (ABS), Electronic Stability Control (ESC) etc. Therefore an automated manufacturing test station for the ECU is significantly complex in design, involving several pieces of instrumentation, simulation of sensors and multiple automotive communication protocols.

Let’s see if some real-world figures could lend a quantitative perspective to this mass-manufacturing challenge. For instance let’s take the case of a mid-size automotive OEM that sells over a 100,000 vehicles annually, with production in 2 plants of identical capacity. That would mean at least (taking Engine Control) an equal number of ECUs supplied annually by their Tier-1 ECU Manufacturer who needs to manufacture around 8 ECUs in an hour, assuming full 3-shift operations. Assuming 4 parallel assembly-lines, it gives less than 30 minutes to manufacture an ECU! The time available practically for testing ECUs at the End-of-Line (EoL) is even shorter. Assuming 2 parallel test stations, the operator typically would have less than a minute to test an ECU – to load it on the test station, execute the automated tests, to know if it passed or failed, print a bar code and affix it to the passed piece (or dump the failed piece into the reject bin) and unload the ECU, and ready to load the next one! Added is the complexity of different versions of the same ECU that are simultaneously in production. Since batches having different versions of ECU come to the same test station, the operator would need to reconfigure the station for a different set of tests each time. The reconfiguration must be completed typically within 4 to 5 minutes before loading the next ECU type.

Now let’s review how this challenge applies (or doesn’t apply!) to different segments in the automotive industry. It’s a no-brainer that any Tier-1 Manufacturer (or OEM) in the business would have all of this covered in their factory floors already, if not they would hardly be selling! However it is no longer the steady-state in the case of a newly introduced ECU design, be it part of a new brand of vehicle the OEMs plan to introduce to the market, or be it related to an additional feature, like adaptive cruise control, that’s being introduced for a new model variant. Does the Tier-1 Manufacturer have the required engineering bandwidth to design the test station themselves? In the case of technology transfer for ECU design from a global principal, does the Tier-1 Manufacturer have in-house expertise in the early stages to develop a test station on time before pilot production starts? In the case of in-house development of the ECU, does the Tier-1 Manufacturer really have the resources, bandwidth and simply the time to get the test station ready before the ECU design passes all type tests and hits production?

Alternatively, do existing test station vendors for other components, like starter motors, tiltable mirror assemblies or instrument clusters, have the necessary expertise to design such a complex test station? What about ECUs for Electric Vehicles (and hybrids) that are predicted to transform the entire motoring landscape forever! Not to forget the two-wheeler (and three-wheeler) segments, which under the rapidly closing time window of emission control regulations (Bharat Stage-VI in India although behind Euro-VI by a few years, has a 2020 deadline currently!) will be forced to switch to ECU based fuel-injection etc. in a few years’ time in order to legally sell in the market.

Here’s where a little foresight into accelerating the design of manufacturing test solutions could benefit the relevant stakeholders. At Deep Thought Systems, We have designed and developed a reliable, modular and generic platform called TestMate for building manufacturing test stations specifically for ECUs. We have successfully customized Testmate to supply EoL test stations for ECUs to Indian Tier-1 Manufacturers and OEMs in a very short turnaround.

The Human Machine Interface (HMI) of the Testmate, the main part that the operator sees and operates on a continuous basis, is a very generic requirement that consists of rugged enclosure, controls and indications for long years of reliable performance in an assembly floor. They say, and we’ve witnessed it ourselves, that routine use of test stations by the creed of factory operators indeed constitutes a really hash environment! The mounting, orientation, peripherals for viewing and printing, display properties etc. are all ergonomically designed, optimally for continuous usage by an operator over an 8-hour shift (or longer!). We have successfully installed the test station in factory floors where they are being used continuously for years, with zero support calls.

We work with the customer on the ECU connector type, to design a custom cable harness and test fixture that includes the mating connector, with locking arrangement. The fixture design ensures proper contact between the pins of the ECU connector and the mating connector over months of continuous loading and unloading. We equip the customer with spare cable harness to handle the unlikely event of damage due to exceedingly rough/careless usage by operators, which can be easily replaced onsite without having to depend on a service engineer.

Built on the same principles as our other automotive offerings for vehicle diagnostics, testing and simulation, Testmate is capable of communicating with various ECU designs over multiple automotive communication protocols like CAN, K-Line and LIN and messaging standards like J1979, J1939, UDS, KWP2000 etc. We work with the customer to customize it for the ECUs communication specification. Apart from testing continuous engine parameters, Diagnostic Trouble Codes defined for the ECU can also be tested. Containing many building blocks of an actual ECU, for many communication tests the test station appears to the ECU as a peer ECU (sometimes multiple) of the related sub-system(s)!

Testmate can reliably simulate inputs to the ECU, ranging from the simplest ignition key switch to the complex crankshaft position waveform that is a critical input for many engine control functions. It also measures the ECU’s outputs, ranging from the discrete voltages or timed pulses to PWM waveforms to actuators, and evaluates it against defined limits for pass or fail. In addition to functional tests, power supply and other electrical (negative) tests can be performed to test how well the ECU hardware responds to abnormal conditions, like reversed polarity of the power supply, under voltage etc. The I/O instrumentation is completely custom-designed as per the interface specification of the ECU.

The HMI software supports multiple levels of users, with differential permissions defined for each login level, like running tests, modifying test parameter limits, changing the sequence of tests, error message text, test calibration and troubleshooting. All tests are logged for later review by supervisors or managers. For failed tests clear troubleshooting assistance is displayed/logged as to which specific test failed and how exactly, so that the defective unit can be repaired. An ECU may come in twice for tests, once after bare assembly without the enclosure, and once again after the enclosure is fitted.

Finally it all comes together in the hands of the operator, who after loading an ECU has less than a minute to run the automated tests to know if it is a pass or a fail. Pass is good news always, the ECU gets a bar-coded label stuck on it and moves forward to the next stage. However a fail is hardly the end of the road because in order to keep the rejection costs low failed units need to be repaired, with the test station providing precise troubleshooting information to get it repaired quickly. In this context a few pertinent questions for relevant Tier-1 Manufacturers and OEMs are:

1) How much of ECU test station design could be generic, versus how much of it should essentially remain ECU design specific?

2) Does it justify to their business to completely reinvent a unique solution to their challenge in terms of engineering effort, cost or timelines? While large parts of the challenge retain a commonality, which a generic test platform such as Testmate has not only abstracted, but also been customized for specific ECUs and proven on the factory floor.

At Deep Thought Systems, we clearly understand the generic and reusable parts of the TestMate platform which help accelerate the design of EoL Test Stations. A high-performance hardware platform, powered by a real-time operating system and sound embedded firmware design practices ensures fast test execution and that all timing considerations in vehicle communication protocols are taken care of. Thanks to our expertise in digital and mixed signal hardware design, we are able to quickly customize other parts of the test station like I/O interfaces, ECU fixture and HMI software as per the customer’s specification and needs with total assurance of the customer’s Intellectual Property.

Another closely related area for production where we could work with customers to provide a quick solution is the design and supply of ECU Flashing units. Operators use the flashing units to flash the firmware into ECUs after assembly. The design of the ECU flashing unit is greatly accelerated by our generic ECU flashing framework, where the only input required from the customer is the seed generation algorithm for unlocking the ECU, which could be imported into our firmware as a library (in binary form) to protect the customer’s (or principal’s) confidentiality. In conclusion, our expertise and track record of supplying and installing EoL test stations on factory floors and supporting production personnel in the usage and fine-tuning of these systems will ensure an efficient and trouble-free operation for the customer for the entire production lifecycle.

Link to Linkedin article

Bringing home SAE J1939 Heavy-Duty Protocol Simulation

The J1939 standard for heavy-duty vehicles drafted by the SAE (Society of Automotive Engineers) in the mid-90s was driven originally by the “ECU trend” with the main objective of controlling exhaust gas emissions under increasingly tightening US and European regulations. Having gained wide acceptance ever since among diesel engine manufacturers, the SAE J1939 heavy-duty protocol has presently reached the stature of the de-facto standard for Truck and Bus manufacturers worldwide, for communication between various vehicle components and for diagnostics.

J1939 is a set of standards that includes a higher layer messaging protocol that works over CAN (Controller Area Network) protocol at the physical layer. The communication model supports both peer-to-peer and broadcast communication. The J1939 message format uses the Parameter Group Number (PGN) to label a group of related parameters, each of which may be represented by a Suspect Parameter Number (SPN). Continuously varying vehicle parameters (like Engine RPM etc.) are defined along with their valid range, offset, scaling etc. Besides, discrete (ON/OFF) parameters (like Brake Switch ON etc.) are defined separately. Commands to Enable/Disable specific vehicle functions (like Engine Fuel Actuator Control etc.) are defined.

Time based updates happen at 20 milliseconds (or lower) repetition rate, whereas the rate is significantly higher at higher Engine RPMs. Some periodic messages contain information that is of particular interest only when a specific state change occurs, and there is a defined range of repetition rates for these messages. Diagnostic messages (DMs) from various sub systems (like emission control etc.) are defined as per the Diagnostics Application Layer of the J1939 standard that includes services like periodic broadcasts of active DTCs (Diagnostic Trouble Codes), reading and clearing DTCs etc. Manufacturer specific parameter groups are supported that allow OEMs to define their proprietary message in addition to standard messages.

ECU design engineers of vehicle sub-systems at automotive OEMs, Tier-1 suppliers and R&D Service Companies routinely use J1939 Simulators for their product development, test and validation activities. In the early stages of development, a simulator comes handy for providing signals from other vehicle components exactly the same way as it would be in the real vehicle environment without the need for an actual vehicle in the lab. For instance a design engineer working on an ECU development program for Transmission Control would need signals from Engine Control system, Braking System etc. in order to validate his design functionality and performance. The ECU would get all these signals from the Simulator exactly as it would receive them in a vehicle environment, the physical connection provided by 2 CAN wires (CAN-HI and CAN-LO) and Ground (GND), taken out from the Simulator’s 16-pin OBD (or 9-pin D-Sub) connector using a custom wire harness to the mating connector of the ECU.

The J1939 simulator provides the design engineer with the ability to generate and vary individual parameters in order to check the response of the system under design/test. The required variations could be manually controlled using (rotary knob) potentiometers for continuously varying parameters. Some simulators automate the variation according to a pre-defined curve. A linear ramp that sweeps the full range (0-100%) of the given parameter, in increasing steps of 1%, is typical. Advanced simulators based on engine modeling data provide the ability to vary multiple parameters simultaneously in a specific relationship with reference to each other for better real-world simulation. A cost effective alternative to this would be to record multiple parameters of interest from the actual vehicle under standard test/driving conditions for the required duration, also known as the drive signature, and playing back the captured signature in the lab in the same time base, although with a lesser timing accuracy. Add on the simulation of actual vehicle hardware, like sensors, actuators etc. to create a fully Hardware-In-The-Loop (HIL) simulation and the full-extent of the simulation picture becomes complete.

Indian automotive R&D groups have traditionally banked on imported tools for J1939 simulation. Originating from USA, Canada, Germany etc. many of them come with pricey licenses although offering just an elementary 5-signal manual simulation. A few sophisticated ones with automatic ramp sweeps etc. are super-pricey, that even Indian R&D subsidiaries of multi-national OEMs have to contend with time-sharing the same simulator across multiple engineers/teams. It is in this context that a strong need is being felt for a high quality, cost effective J1939 Simulator that is indigenously designed and manufactured, that could provide many Indian customers the much-needed scalability for their R&D activities and reduce their dependence on imports.

Awareness on the availability of an indigenous product is the starting point however strict adherence to the standard is a hard requirement, including very strict timing considerations, in order to create a positive lean among automotive customers who always select and use only “proven technology”. Benchmarking data with reference to competing products could help customers get quantitative insights. Pilot trials could help them in familiarizing themselves with the indigenous product and to evaluate it against their experience with imported tools.

We at Deep Thought Systems design manufacture and supply J1939 simulators to Indian automotive customers, in addition to other offerings for CAN/J1939 logging, test/diagnostics, J1939 based displays and ECU manufacturing test automation. In our endeavors in bringing the above mentioned advantages to the Indian automotive R&D sector, we found that a customer’s need many a time is a highly customized simulator for their specific application. And thanks to our expertise in automotive protocols like CAN, OBD-II and J1939, and being fully in control of the hardware design, component sourcing and manufacturing as well as the embedded firmware and application development, we find ourselves well placed to deliver to these custom needs.

Post Scriptum:

A later industry development has been that all the major European heavy-duty OEMs came together in 2000 to co-develop the Fleet Management Standard (FMS) which is based on J1939 that incidentally opened up possibilities for manufacturer-agnostic telematics applications. The J1939 simulator, combined with suitable GPS simulation having the required levels of performance, offer telematics product designers a proven means to quickly test and validate their design well before going for in-vehicle tests.

 Link to article on Linkedin