The Sigma-7 servo throws a following error — position deviation exceeds the limit — and the axis stops, often with an alarm shown on the drive or the controller.
These are the failure paths we see most often on the Yaskawa Sigma-7 for a following error condition. A following error means the motor cannot keep up with the commanded position, and the cause is almost always tuning, load or feedback. Likelihood reflects field frequency; First Check is what you can do remotely before sharing logs.
| Cause | Likelihood | First Check |
|---|---|---|
| Gain / servo tuning too low for the load | High | Check the position-loop gain; a sluggish response lags the command |
| Mechanical load too high or binding | Medium | Move the axis by hand; a stiff coupling or overload causes following error |
| Encoder / feedback fault or misread | Medium | Check the encoder cable, connector and homing |
| Wrong inertia / load estimate in tuning | Low | Check the inertia ratio used in autotuning |
Work through these in order. Each step is something you can perform and report back on without opening the enclosure or swapping parts.
Capture the Sigma-7 alarm number and the deviation-counter value from the drive or controller. The alarm and the deviation are what we interpret.
Move the axis by hand with power off. A binding way, a stiff coupling or a real overload makes the motor fall behind the command — a load problem, not a tuning one.
Inspect the position-loop gain and the filter. If the response lags the command, a cautious gain increase often resolves it; too much gain causes oscillation, so we set it from the deviation.
Check the encoder cable, the connector and homing. A lost or noisy feedback reads as deviation and trips a following error even with a healthy motor.
Check the load/inertia estimate used in autotuning against the real axis. A wrong inertia ratio makes the loop soft and prone to following error under load.
A following error means the axis cannot track the command — tuning, load or feedback. The deviation value plus the alarm pin it: a large deviation with a smooth load points to gain, a deviation that appears only under load points to the mechanism, and a deviation with a feedback alarm points to the encoder. Cross-reference the broader collections: Servo following / tracking error · Servo & motion control.
When to escalate: if the encoder is confirmed dead, a cable or module is the physical part — but we confirm that from the alarm and the feedback test before you order anything. Most following errors we address are gain or load, corrected by tuning you apply on the Sigma-7.
Rarely. Following error is tuning, load or feedback; we address those first. Hardware is only suspected if the encoder is confirmed dead, and we verify that from the alarm.
Because the axis cannot track the command — low gain, a binding load or lost feedback. The alarm and the deviation value show which one it is.
Cautiously — too high causes oscillation and a new fault. We set the gain from the deviation and the load so the loop is stable, not just faster.
Possibly. A following error with a feedback alarm points there. We confirm it from the cable and the alarm before you replace the encoder.
Send the alarm number and the deviation value. We split tuning, load and feedback remotely so you avoid swapping a good servo.
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The other Sigma-7 fault in the same cluster.
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Full machinery controller troubleshooting collection.