Installation manual

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Epsilon EP-B Base Drive Reference Manual
+/- Travel Limits
The + and - Travel Limit input functions will stop motion in the direction indicated by the input function using the Travel
Limit Deceleration ramp. This feature is active in all modes. When an axis is stopped by a Travel Limit function, it will
maintain position until it receives a command that moves it in the opposite direction of the active Travel Limit.
For example, the + Travel Limit will stop motion only if the motor is moving + but allows - motion to move off the limit
switch. Conversely, the - Travel Limit will stop motion only if the motor is moving - but allows + motion to move off the
limit switch.
If both input functions are active at the same time, no motion in either direction will be possible until at least one of the
inputs is released.
When either + or - Travel Limit input function is activated, a fault will be logged into the Fault Log, and the drive will
display an “L” on the status/diagnostics display on the front of the drive. Once the axis is driven off the limit switch, the
fault will be cleared and the “L” will disappear.
If both Travel Limit input functions are activated simultaneously, the drive will respond as if the Stop input function has
been activated and will use the Stop Deceleration ramp.
Travel Limit Application Notes
Torque Mode
If you are operating in Torque mode, the drive must be tuned to the load to prevent instability when activating the Travel
Limit input functions.
Host Controller Travel Limits
If the host controller decelerates the drive faster than the Travel Limit Deceleration ramp, the drive allows the controller
to maintain full control of the axis during the deceleration. This results in no following error build up in the controller and
easier recovery.
Vertical Loads in Velocity Mode
In applications with horizontal, counterbalanced or un-counterbalanced vertical loads, the load will held in position when
motion is stopped due to a + or - Travel Limit. The position will be held until the controller commands motion in the
opposite direction of the activated Travel Limit.
Vertical Loads in Torque Mode
In applications with horizontal or counterbalanced vertical loads, the load will held in position when motion is stopped
due to a + or - Travel Limit. The position will be held until the controller commands motion in the opposite direction of
the activated Travel Limit.
When an axis is stopped by the upper Travel Limit with a vertical load, the controller must maintain a torque command
at a minimum level to hold the load or the load may drop.
In applications with un-counterbalanced vertical loads, you must be careful not to set the controller’s torque command
to zero when the upper Travel limit is activated. Setting the controllers analog torque command to zero in this situation
will command the axis to move off the limit switch causing the load to drop.
If your controller removes the torque command (zeroes the analog command output) when a Travel Limit is activated,
you have a number of choices to prevent the load from dropping. All of which require some external logic to determine
when the controller can actually take control again.
• Activate the opposite Travel Limit input function, then release it when the controller is operational again.
• Activate the Stop input function, then release it when the controller is operational again.
• Apply the axis brake, then release it when the controller is operational again
Vertical Loads in Pulse Mode
In applications with horizontal, counterbalanced or un-counterbalanced vertical loads, the load will be held in position
when motion is stopped due to a + or - Travel Limit. The position will be held until the controller commands motion in the
opposite direction of the activated Travel Limit.
When the travel limits are activated, the drive will decelerate at the Travel Limit Deceleration Ramp and will continue to
store all the command pulses received up to ±2
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counts. The stored pulses need to be cleared out before the axis will
move off the Travel Limit. This can be done if the controller generates command pulses in the direction opposite the
activated Travel limit. The stored command pulses can also be cleared by activating both Travel Limit input functions at
the same time, activating the Stop input function or disabling the drive for as little as 5 msec (plus any debounce time).