Motion fault limit paremeter

The parameter called motion fault limit controls a safety faulting mechanism of GD servo drives.

Usage

Motion fault attempts to detect incorrect motor behavior and sets drive in fault state (and stop driving motor) in case of abnormal motion condition. The motion fault will help to detect following fault scenarios:

• DC motor runaway when feedback is lost
• Motion blocked by obstacle (can react faster than following/tracking error fault)
• Detect stall of stepping motor

How it works

Motion fault monitors three variables to determine fault:

• Actual velocity
• Time
• Output torque/current

Drive activates fault if output current is greater than set threshold value for over 0.2 second period and simultaneously velocity stays below a fixed threshold.

Parameters

Motion fault has only one changeable parameter: threshold. The threshold value controls the current level which must be exceeded to activate 0.2 second timer and velocity monitor.

Finding correct value

Correct value can be found by experimenting.

1. Set threshold to low starting value such as 500
2. Give settings a try and observe if motion fault occurs in normal use
3. If unwanted fault occurs, increase threshold and go to step 2
4. Add some safety headroom (10-50%) to the threshold to increase margin for rare errors
5. Simulate some fault cases to ensure that fault triggers properly (such as disconnect feedback or block motion). If fault doesn't occur reliably, decrease threshold.

Disabling motion fault

If motion fault is not needed or can't be configured to operate properly, one can disable it by setting threshold value to 0.

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