Status: In Progress
Fix Version/s: None
Team:Telescope and Site
As part of the hexapod overheating investigation, we need to make sure the hexapod does not command tiny moves when it is supposed to be stationary. Part of this is to make sure neither the CSC nor the low-level controller sends move commands all the time, which is addressed in separate tickets.
This ticket is for making sure that the Copley software doesn't have a closed-loop mechanism trying to fight against fluctuations in encoders readings, such as those fluctuations due to environmental factors or reading noise.
This is a continuation of the investigation as recorded in
DM-30168. (see the latest comment by Te-Wei Tsai)
DM-30168 confirm that the hexapod low-level controller doesn't command moves when it is supposed to be stationary
If this correction of error is by the physical movement, can we say this is the tiny movement we are looking for? Or it is just to adjust the linear encoder reading value?
Felipe Daruich - at what frequency is the encoder being read?
- at time t0, we read L0;
- at time t0+dt, we read L0+dL
both dt and dL are very small, are we still commanding the motor to move to L0+dL?
If so, I think this is what Doug Neill has been worrying about. The correct behavior should be that, once it is in position, the motor should not attempt to move until the next move or offset command.
In other words, a change in the encoder reading alone, without a move or offset command, should not cause it to move.
ts_xml 9.1 will have motor current and voltage in the telemetry and those fields will be set once we are using the appropriate versions of the low-level controller and CSC. Until then it will be hard to know just how much power is being dissipated while idle. I would expect it to be low even if the motors are enabled because it should not require much torque to maintain a position. But we will see.
My understanding is that the Copley drive is actually closing the position using the linear encoder.
If the linear encoder reading change by any reason other than actual motion, the drive will correct the error.