Hello,
I was wondering how the Mitochondrik calculates RPM feedback of the motor since I read that the Mitochondrik is sensorless and doesn’t include a sensor for RPM feedback. Is there a document available which explains the RPM sensorless feedback calculation? Does Telega handle the RPM calculation or is this specific to the Mitochondrik?
Thanks!
Hi Matt,
Yes, Telega handles the RPM calculation in the motor state observer. In addition to the speed, the current position of the motor rotor is also calculated in the observer.
Thanks Dmitry! Have the RPM calculations been compared to a sensor’s feedback such as an optical RPM sensor? So the RPM calculation is based off Telega’s control feedback loop in real time?
In synchronous machines, RPM is not an estimated quantity but rather an effected quantity. It is derived by the Telega core based on the current angle which is estimated every ~13 microseconds. The angle estimation error is typically under 15 electrical degrees, excepting rapid transients where it may temporarily exceed this limit.
Hi Dmitry and Pavel,
Thank you for the information clarifying this.
We are performing wind tunnel testing using Telega v0 based ESCs, and I wanted to confirm my thoughts about how the sensorless RPM effecting may behave in certain situations. Our test setup is a Komar ESC running Telega v0 driving a propeller facing into the direction of the wind (such as in forward flight) in current control mode. The wind blowing over the propeller adds energy to the propeller to spin it (the propeller starts to behave like a windmill). If the ESC isn’t commanded (0 current setpoint) and the wind is on in the tunnel, then the propeller starts to windmill. In this situation with a sensorless RPM calculation in the motor controller, would the RPM due to windmilling be accounted for or would the ESC state 0 RPM since it isn’t commanding motor current?
On a similar note, if the propeller is in a forward flight configuration, would the additional RPM due to the windmilling effect be included in the RPM calculation? Say you gave the a current command with no free-stream velocity and the same command with some free stream velocity. Since current commands motor torque, the situation with no free-stream velocity will have a lower RPM than with some free-stream velocity since the free-stream velocity would be spinning the propeller as well as the ESC. Would the ESC’s calculated RPM be the actual RPM of the propeller in both cases?
Thanks!
In Telega v0, if the ESC is not receiving commands, it will enter the idle state and report zero RPM regardless of the state of the motor. If the ESC is actually receiving commands and the drive resides in the active state, it will report the true RPM of the motor, regardless of the source of power that drives the motor (whether it’s the motor controller or the external airflow).
Yes.
Yes.
More on this and related topics here:
This Telega v1 Reference Manual does not directly apply to Telega v0 that you’re using, but the fundamental principles are the same.