Servo motor and drive · Lesson 6 of 12

Control modes

A servo can run in position, speed or torque mode, or execute positions stored inside it. In this lesson you will try each mode yourself on a simulator and learn to read the pulse formats.

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14 basic modes

Mode	Where the command comes from	Loops the drive closes	Example
Position	Pulses from the PLC, or a network	Position + speed + current	Cut-to-length, CNC axis
Speed	Analogue ±10 V, or internal speeds	Speed + current	Synchronised conveyors, spindle
Torque	Analogue ±10 V, or an internal value	Current only	Winding material at constant tension, pressing
Internal positions (PR / indexer)	A table inside the drive + digital inputs	Position + speed + current	A table that stops at 4 stations

The mode is set by a parameter (and sometimes you can switch between two modes with an input). The names differ: Delta, for example, calls them PT, PR, S and T, and other manufacturers use other names, but the idea is the same.

2Try the four modes

Mode simulator

Notice: in torque mode the motor does not control the speed. If the load is suddenly removed (the material breaks) it will run up to the speed limit, so you must always set it.

3Pulse formats

Pulse + Direction: one wire for the pulses and one for the direction (high = forward, for example). The most common with a PLC.
CW / CCW: one pulse wire for each direction.
A / B (quadrature): like an encoder, 90° apart. Used when a servo follows the encoder of another machine.

The drive must be set to the same format the PLC outputs (the pulse format and logic parameter). If it is not set correctly, the motor may turn in one direction only, not turn at all, or move half the distance.

Drill: read the pulses

?Lesson quiz

Answer at least 5 of 6 correctly so the lesson is marked complete.

The numbers and values in this lesson (voltages, frequencies, gains, limits) are approximate training values based on general field experience, and they differ from brand to brand and model to model: your drive's manual is the reference before any setup on a real machine. Alarm and parameter names also differ from one manufacturer to another. Your progress is saved on this device.
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