Configure parameters that are used when halting telescope axes.

Arguments:

Axes axes

The set of telescope axes to configure.

Double halt_speed

The speed below which the axes are deemed to have come to a halt (degrees).

Double timeout

The time (hours) to wait for the completion of a controlled halt, before concluding that it failed, and initiating an emergency stop.

Example:

The following example would tell the control system that it can consider the azimuth and elevations axes to have come to a halt once they have each slowed to speeds below 2 arcseconds per second. It also tells it that if either of these axes fails to come to a halt in 10 seconds of a halt being initiated, then it should initiate an emergency stop.

  halt_pars az+el, 0:0:2, 0:0:10

Context:

While axes are under servo control, they are always moving at some level, even when halted. When halted, although on average they stay centered on a single position, they move around this position a bit, due to wind perturbations etc. This command tells the control system how slowly specified axes should be moving before it should consider those axes to have come to a halt. Beware that if this is set too low, then the halt timeout will trigger.

If servo control of an axis is lost, say due to the analog output to the velocity servo controller having been disconnected, and floating at a voltage that causes it to continue moving the axes, then the servo can't bring the axis to a halt. To handle this possibility the control system implements a halt timeout for each axis. If it takes more than this time for an axis to come to a halt, then the control system asserts the digital I/O bits that turn on the brakes, and just in case these bits also aren't working, it also stops generating keep-alive pulses to the servo hardware, so that the servo hardware is alerted of the loss of computer control, and applies the brakes.