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How GM engineers test electronics

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The General Motors Electrical Integration Laboratory at Warren Tech Center is struggling with the routine of testing many electronic devices in modern cars.

According to Gary Bandursky, executive director of global electrical components and subsystems at General Motors, there was a time when design and validation were part of the same organization.

This was before the catastrophic scandal with the GM ignition keys, when cars accidentally turned off while driving. Checking his work is like a fox guarding a chicken coop, Bandurski noted, so now GM has a separate global validation organization led by executive director Christine Simen, which checks the innovations of the engineering team.

“We are the conscience of the organization, as the last gate to the client,” said Simen.

They both dedicate their lives to GM. Simen proudly notes that she practically grew up at GM's Warren Tech Center with the intention of working there when she is old enough. Bandursky's father was a GM climate control engineer who made his family work, forcing everyone to report thermometers from across the cab while riding.

They oversee extensive engineering and inspection work at the Warren Tech Center, aimed at keeping GM on the cutting edge during striking changes in the automotive industry. According to Simen, in new cars an average of 70 computers.

Their programming and connection is a difficult task for a team of engineers, and their success is then evaluated by validation engineers who test all the equipment in their path.

Even the physical connection of so many electronic devices can be extremely difficult, especially for the new GM Digital Vehicle Platform, which appears in new and future models such as the Chevrolet Corvette, Tahoe and Suburban, as well as the Cadillac CT4 and CT5. The company has more than 100 patents for the technology of this system, which has improved cybersecurity. Among other things, this security is ensured by the ability to receive software updates over the air to add or improve the functionality of existing equipment.

It includes two network buses at 2 Mb / s and three more CAN buses at 500 Kbps for data transmission throughout the vehicle. Wiring alone includes two miles of wires and weighs 125 pounds.

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For comparison, the team stores a small bunch of wires needed for a 1950s Chevy pickup truck. A handful of light bulbs, a siren, a fuel gauge and a starter were the only electrical components of such a car.

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For a modern wiring system, GM uses a test bench that roughly matches the size and proportions of the car, so that the electronic system can be connected for testing before the manufacturer needs to figure out how to install it in real cars. This is a non-trivial detail, and connecting and checking all system circuits can take two days. Sometimes they make important discoveries, for example, once, they found that the wiring for the planned version of the right-hand drive car was too short and it was not enough to connect the moved steering column, said Mike Maxiomei, manager of the engineering group in the electrical integration laboratory.

Eliminating any problems during the assembly of the system at the control rack helps manufacturing engineers plan the assembly process at the plant, as well as avoid the inconvenience associated with the presence of components that cannot be assembled if the wiring is too short. “This is of paramount importance for the manufacture of our prototype cars,” said Maxiomei.

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The GM test stand includes components such as power seats and mirrors in addition to wiring.

All connected subsystems must exchange information and interact with each other in an orderly manner so that everything works as it should. Therefore, the inspection team has 100,000 square feet of office and laboratory testing facilities.

Starting and shutting down computers are particularly sensitive moments that require special attention from test engineers, Simen explained. “All the trouble happens when you turn it on and off,” she said. It is at these moments that the process of automatically determining the state of the car starts, which should ensure that everything happens in the correct order and is completed correctly. At the same time, it’s difficult to keep all computers in service, because “it is at this moment that they are all reporting something,” she said.

Also, a large amount of electricity goes to a high-current starter operating simultaneously with the processes described above, which leads to drawdowns that microprocessors hate. This, according to Simen, exacerbates the problem.

Disabling is also crucial. Simen points to a ten-year-old Cadillac SRX that had a battery drain problem when the car was parked. As a family that forgot to let the dog into the house before going to bed, the SRX system forgot to turn off one of the many computers when the machine turned off, which would drain the battery if the car stood for a while.

The prevention of such failures requires a large number of tests of all kinds of combinations and permutations to make sure that all systems work as intended. GM says that they are able to test between 80 and 90 percent of all possible event options for the system.

This can be incredibly tiring for engineers who have to constantly repeat the tests. One test that tests the operation of the rear view camera took six weeks of re-testing. This test was supposed to confirm that the camera image (required by law) appeared on the screen regardless of the driver’s actions when starting the car and reversing. As a result, engineers did what engineers usually do and implemented an innovative automated solution.

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The modest beige box shown here is GM's own development, a device called STORM, designed to automate testing of a rear view camera.

They called the resulting device "STORM", which stands for "Average time for the appearance of the image from the rear camera." This is an amateur metal electric box with homemade internals, parts of which cost $ 150 in total. Engineers put STORM in front of the rear view camera display, and its own camera looks at the screen while the system goes through test cycles. STORM automatically logs any cases where the expected image does not appear on the display. With STORM monitoring problems, the lab was able to run the same test cycle, which took six weeks in just 12 hours. And, of course, for the minds of engineers it was useful to get rid of the tedious viewing of cases of malfunctions in the display.

Another part of automation is a robotic manipulator equipped with a rubber probe, capable of checking all possible options for pressing the dashboard touch screen for remote control of mobile phones. The robot changes the places of clicks and the time between clicks on the virtual buttons, which allows you to make sure that the screen and phones react as they should.

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Integration Lab uses this robotic arm to test the phone’s on-screen interface.

Changing the time between taps and actions like opening and closing doors is the key to identifying any problems, according to the engineers. Every year, GM buys from 55 to 60 new smartphones to test the latest models as they are released, and tests different combinations of them. Even for a car such as the double Corvette, GM believes that four simultaneously connected phones are a normal burden for car computers. They suggest that many people have separate work and personal phones, so if there are two people on board, the Corvette must support the simultaneous connection of four phones.

Using a robot for phones is similar to using STORM for the rear camera. “We do not need to look for problems. He finds them for us, and we can focus on eliminating them, ”said the engineer.

The volume of work in the laboratory and the scale of their tasks show how difficult the development of a new machine has become and how easily a bug can slip into it. If this happens, GM will be ready for it - with a new air upgrade option with which the electronics architecture can be updated.


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