HIL test bench commissioned for motion control software

Inventra has commissioned a hardware-in-the-loop (HIL) test bench to verify the embedded software of its motor driver boards.

The bench was set up at the Integration and Test Centre in Ostim OSB, Ankara. It verifies the software of the driver boards used in gimbals, pan-tilt positioners and mast systems before the mechanical hardware is available.

Real-time plant model

At the core of the bench is a real-time plant model. It solves brushless DC (BLDC) and permanent magnet synchronous motor (PMSM) behaviour, including phase-current dynamics, friction, backlash and load inertia. The electrical part of the model is stepped at microsecond scale so that it can follow the driver’s pulse-width modulation (PWM) switching frequency, while the mechanical part runs at a lower loop rate.

That difference in step size is the reason the bench exists rather than a simulation running on a desk. Phase current under PWM is not a value but a waveform, and where in the switching period the driver samples it determines whether the current loop closes on the average or on the ripple.

A model that cannot resolve the switching period cannot show that error, and a simulation with an idealised measurement never shows it at all. The error appears only against a real power converter, a real interrupt controller and a plant that answers back in time.

Fault scenarios

Fault injection is the second purpose of the bench. Phase loss, encoder faults and supply dropouts can be introduced in a controlled, repeatable way. On real hardware these cases are either dangerous or impossible to repeat identically, so they tend to be tested once and remembered rather than tested continuously.

Automated regression testing

The infrastructure is set up to run alongside automated regression suites. The result of every software change reaches the team as a coverage and deviation report, so a fault-handling regression is found on the day it is introduced rather than during integration.

HIL simulation and control algorithm verification on the microprocessor are part of the work described on the Analysis page. How far a HIL result depends on the mechanism model is examined in the blog post Your Controller Passed HIL. Did the Model Hide the Fault?.

About Inventra

Inventra Mühendislik A.Ş., founded in 2015, designs, manufactures, integrates and qualifies reconnaissance and surveillance systems at its R&D Centre and its Integration and Test Centre in Ankara. Its product line covers multi-channel stabilised thermal imaging gimbals, single and dual axis positioners, masts, tripods and portable climatic rack cabins.

Media contact: infoinventras3.com