“Can ADVANCED Motion Controls servo drives operate at pressures equaling 6000m below the sea?”
Our application support team received this inquiry from a trusted partner and we had to take a realistic view on the scope of the project.
The Unknowns of the project
First, we’ve never designed and tested a servo drive at those levels before.
Second, how would we test it? We had no way to test at those pressures.
Third, we had to understand the advantages and disadvantages if the drive itself had to experience the pressure vs. being placed in a sealed container.
Testing & Validation
Our partnering company decided they would test the drive at the 6000m below sea level pressure.
We determined a pressure proof container was unrealistic. The pressure proof container was a design obstacle in itself due to the high pressure. We determined we would be end up spending more time designing a container that would likely fail to withstand the pressures presented at 6000m below the sea.
A more straight forward solution presented itself. We decided to submerge the electronics in an oil bath (with non-conducting oil). This allowed the container to equalize the pressure between the inside and outside while keeping the electronics safe from contacting any salt water.
The first test proved our theory correct; the standard servo drive model failed to survive the high pressure.
After analysis we determined a few parts had failed and we found suitable replacements. For example the housing on an electrolytical capacitor was crushed under the intense pressure. As a result we were able to replace it with a different type of capacitor able to withstand more pressure.
After a few rounds of testing, we made minor modifications to our drive which allowed the product to work at the required depths.
Once we established we could operate at the required depths, we designed a custom solution for our servo drives to operate at pressures equaling 6000m below the sea.
First, we incorporated a rotary magnetic module to replace the traditional Hall sensors and encoder feedback.
Second, we configured the controls for the drive to operate in velocity mode with the host controller closing the position loop.
Third, we set up RS-232 as the main communication between the drive and the host.
And the final custom design element we incorporated was to reduce the mounting footprint to fit within the motor enclosure.