Sensor simulation Improving automotive test strategies

Bob Stasonis, Pickering Interfaces: “In most cases, programmable resistors result in a simpler test system that takes up less space, is faster, and is also more repeatable and accurate.”
Bob Stasonis, Pickering Interfaces: “In most cases, programmable resistors result in a simpler test system that takes up less space, is faster, and is also more repeatable and accurate.”

Pickering Interfaces expects that the demands for speed, repeatability and documentation will drive automation in automotive test practices massively. With this, sensor simulation becomes an important part of an automated test strategy, states Pickering's Technical Product Specialist Bob Stasonis,

“The worldwide automotive sensor market is predicted to be worth $36 billion market by 2023 (source: Research and Markets). If anything, this is likely to be an under-estimation, given the massive uptake in electric and hybrid electric vehicles and the rapid development of autonomous vehicles which require a significant environmental sensor capability, including high frequency devices such as radar and lidar. Another trend that we are seeing is that the proliferation of electrification in vehicles and transportation is driving the requirement for higher voltages and currents in test systems.

The use of sensors in many automotive functions will require extensive testing. This becomes increasingly complex as sensors proliferate not only because the test process must show a sensor to be known good, it must also determine the effect of a failure on the rest of the system. And every combination must be checked to understand the implication of any single or combinational fault. Of course, in automotive applications, failures cannot be tolerated – even more so when we are considering autonomous vehicles – so the test methodology must be extremely rigorous.

Because of the complexity of automotive systems and the absolute need for the ultimate safety, the three factors that influence the choice of test practice are repeatability, speed and the ability to document the process. These factors naturally lead to test automation.

In many cases it is not practical to use the end-product together with its integrated sensors as the test bed. For example, if an EMU (engine management unit) is being tested, it is not desirable to have the actual automobile as part of the test station. In order to test the EMU, the test methodology must simulate sensors for temperature, air flow, altitude and other conditions to make sure that the unit under test is operating properly. Therefore, sensor simulation is increasingly-likely to be part of an automated test strategy. 

Programmable resistor modules are used extensively in sensor simulation test systems, replacing the sensors in an automated test program. Such devices are controlled by a test program with the resistance values being changed using relays to short out a series of resistors. Programmable resistors are often plugged into a modular test format such as PXI, or they can be stand-alone, controlled via USB or Ethernet.

In most cases, programmable resistors result in a simpler test system that takes up less space, is faster, and is also more repeatable and accurate. Pickering Interfaces manufactures a broad range of programmable resistors available in both PXI and PCI formats, from standard resistor chains to precision resistors to specialized modules, covering diverse hi-rel applications including space, defence and automotive. For example, the company lists over 225 PXI programmable resistor modules, offering up to 18 channels in a single PXI/PCI slot with resistance ranges from 1 Ω to 22 MΩ and resolutions down to 2 mΩ with accuracies as precise as 0.03%. Pickering is also responding to the automotive industry’s need for increased switching speed to test Radar and Lidar systems with its series of programmable resistor modules which operate up to 65 GHz in the 40-7XX family, and also higher voltage and current test modules with up to 1,000 volts in the 40-33X family, and 40 A for emerging hybrid and electric vehicle applications (series 40-18X family).

Programmable resistors are often used together with Fault Insertion Unit (FIU) switching solutions for Hardware-in-the-Loop (HIL) simulation applications. FIU switching modules can be used to introduce electrical faults into a system, which typically duplicates various conditions that can occur because of corrosion, short/open circuits, and other electrical failures, inherited through age, damage or even faulty installation. Using fault insertion modules to automate the fault injection process, test departments can run more test cases in a shorter period of time, resulting not only in time savings, but also in the testing becoming more repeatable and comprehensive. Customers are also using this approach to find and fix problems earlier in the development cycle.”