Home Position for a Resolver's Axis - 1756-PLS

Three features determine a relative zero point, also called home position, for the resolver’s axis. These three features are located in the module’s Configuration tag. These features are located in the

AB:1756 PLS:C:0

module-defined data type Axis substructure. Use these features to synchronize (calibrate or home) the 1756-PLS module position measured from the resolver to the machine’s position.

ZeroOffset

Use this feature when you know the starting point in the resolver’s axis. For example, if the resolver’s zero position is at the machine’s 10-degree point, to match the 1756-PLS zero position to the machine zero position, you can configure the 1756-PLS module with a ZeroOffset value of 10 degrees.

The ZeroOffset value is limited to +/- the Rollover Position. For example, if you are using degrees as your engineering units, the maximum position is 359 degrees. In this case, the ZeroOffset can be configured for values between -359 and +359.

The 1756-PLS module does not save ZeroOffset values after power-down. You must save the value in the ControlLogix controller and download it to the 1756-PLS module with configuration data.

Preset

Use the Preset member to set the relative starting point for the resolver’s axis by the energizing of an input. For example, the 1756-PLS module can be configured so that when an input turns ON, the module changes the ZeroOffset so that the current position is 0 degrees. The 1756-PLS module replaces the current ZeroOffset value with this number.

When the Preset occurs, the 1756-PLS module changes the current Position to its Preset predefined value. The ZeroOffset value is recalculated by the 1756-PLS module. The new zero offset value is temporary and remains until the next occurrence of the Preset.

PresetInput informs the 1756-PLS module which input on the module signals the Preset event.

You must perform these steps to use Preset:

Nudge Up/Down

The Nudge Up/Down data types allow you to precisely adjust the 1756-PLS module’s setpoints to account for minor changes in the machine set-up.

For example, during a shift, a resolver may have changed its position by +5 degrees due to slippage. NudgeUp allows you to correct the setpoints by nudging up to the original position.

The NudgeUpOffset value determines the number of units that are added to the ZeroOffset when NudgeUpInput turns ON.

For example, if your application is using degrees for its position units, you can configure the NudgeUpOffset so that each time you energize the NudgeUpInput, the position change is +1 degree. Therefore, to move the zero offset 5 degrees, you select the NudgeUp button 5 times.

NudgeUpInput informs the 1756-PLS module which input is used to signal the NudgeDownOffset.

You must perform these steps to use the Nudge Up:

NudgeDownInput informs the 1756-PLS module which input on the module is adjusted when using the NudgeDownOffset. The NudgeDownOffset value determines the number of units, engineering or raw, that are added to the ZeroOffset when NudgeDownInput turns ON. This function works similarly to the NudgeUpOffset.