ERL

Requests/sets the error limit for the specified axis.

Mnemonic:

ERror Limit.

Syntax:

ERL $<$n$>$[, limit]

n: Axis number (0:azimuth, 1:elevation).

limit: New error limit, in encoder counts (0 - 25000).

Return values:

Success:

ERL 1, n, limit

Failure:

ERL 0[, n], err_msg

n: Axis number.

limit: New or current error limit

err_msg: Should the command fail, this value will be an error message string, explaining the cause of failure. ERL may fail if:

• The wrong number of parameters were supplied.
• A non-numeric value is provided for any of the parameters.
• The axis number in n is not `0' or `1'.
• The new error limit supplied in limit is less than 0 or greater than 25000.

Remarks:

For the LM628 servo controller chip, the position error is defined as the difference between the actual position and the desired position. ERL sets the maximum tolerable error. If this is exceeded, the servo controller will shut of the servo motor. The cause of the error can be static, i.e. something is physically preventing the servo from moving, or dynamic, where the servo motor cannot keep up with the computed trajectory. The latter is an indication of a mis-tuned servo system or an amplifier failure. A command to move to a new destination, if possible, will re-enable the servo motor.

Example:

     send: ERL 0, 5000
  receive: ERL 1, 0, 5000

     send: ERL 0
  receive: ERL 1, 5000

See also:

ACP, AXS, DSP, RDS, STS, STW