Dual Feedback Overview

Feedback Connections

When you configure an axis with dual feedback, Machine Setup shows how feedback is connected between the mechanical and electrical device. It also shows the effective encoder resolution for each feedback device. You can use the Swap button to change the feedback connections if the default connections are not correct for your feedback cabling.

Machine Setup uses the rules that follow to select the default feedback connections for dual feedback:

1. If an absolute encoder feedback device with incremental signals is configured (for example, EnDat with Sine Wave Incremental), then Machine Setup connects it to Primary Feedback. On Automation1 drives, only the primary feedback connector supports this feedback type.

2. If an absolute encoder is configured and a Sine Wave encoder feedback device is also configured but the electrical device does not support an encoder multiplier on the auxiliary feedback input, then Machine Setup connects the incremental encoder to Primary Feedback, and connects the absolute encoder to Auxiliary Feedback.

3. Otherwise, if an absolute encoder is configured, Machine Setup connects it to Primary Feedback.

Parameter Configuration

Use Machine Setup to configure feedback connections for an axis with dual feedback. Then use the Checklist for that axis to complete the configuration.

Machine Setup configures your parameters as follows:

• The PrimaryFeedbackType Parameter specifies the type of feedback device that is connected to the primary feedback input on the drive. This is usually the feedback device for the motor encoder.

• The AuxiliaryFeedbackType Parameter specifies the type of feedback device that is connected to the auxiliary feedback input on the drive. This is usually the feedback device for the workpoint encoder / laser.

• The feedback device inputs on the drive are associated with the servo loop via the FeedbackInput0 Parameter and FeedbackInput1 Parameter. Refer to the servo loop block diagrams:

  • Servo Loop Block Diagram - Dual Feedback (Secondary PI)

  • Servo Loop Block Diagram - Dual Feedback (Secondary I Only)

• ServoLoopGainKv Parameter is usually set to the ratio of the resolution (for example, counts/mm) of Position Feedback Input 1 (usually the motor encoder) divided by the resolution of Position Feedback Input 0 (usually the workpoint encoder / laser).

Analog Encoders

You can use the Encoder Tuning module to tune either of the dual feedback devices with an analog encoder. Use the device selection drop-down box to select "Primary" or "Auxiliary”.

Absolute Encoders

You cannot use an absolute and incremental encoder on the same connector at the same time unless they are part of the same physical encoder (for example, EnDat with Sine Wave Incremental).