Analog Feedback Control

Standard software for analog feedback control makes it easy to control motion based on an analog input signal, and effectively control web tension, dancer position, pressure, force and more. Typical applications include:

• Web control for tensioning/nip, unwind and rewind applications
• Press applications
• Crane applications
• Servo valve control: flow & pressure

Simplifies Programming

Using the SMLC for analog feedback control eliminates the need for users to develop their own application code. Once configured using the setup screen in ServoWire Pro, operation takes place in the background. Analog feedback can be based on multiple inputs that can be shared among axes and scaled based on user-supplied algorithms.

The SMLC also provides flexibility for using a variety of analog input options. Supported I/O modules from WAGO include 12, 14 and 16-bit analog inputs offering a variety of signal types (+10V, 0 to 10V, RTD, 4-20 mAmps, thermocouples) plus an SSI interface for Temposonics transducers. A digital encoder can measure dancer position.

Implementing Analog Feedback

The ability to configure individual axes in an SMLC system and actively control tension by closing the servo loops around a tension transducer eliminates complicated programming and simplifies setup and operation.

Axis properties can be easily configured one time in the ServoWire Pro development software to specify limits, optimal loop gains, feedback source and optional low pass filter and correction direction (speeding up or slowing down). User units make it simple to define the ratio or raw tension transducer units to tension user units.

How It Works

In an analog feedback application, the application program reads the analog feedback transducer and stores the value in the appropriate value during the I/O scan. In the background, the SMLC sends the feedback value to the drive during the next isochronous loop update. The ServoWire SM drive then compares the feedback value to the command value, and adjusts motor motion to compensate for any difference.