What the C154 alarm means

The robot cannot move linearly through the commanded point because it is in (or too close to) a kinematic singularity. This fault ranks high in our Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) service records, and the first site inspection usually finds the source.

Most common causes

  • MoveL commanded straight through a wrist singularity
  • Wrist axes J4/J6 nearly parallel at the via point
  • Robot asked to keep TCP orientation while passing through the shoulder singularity
Field note: The first cause shows up most on real machines, so verify it before you go further.

Step-by-step field fix

  1. Use joint-space moves (MoveJ) through the singular region
  2. Reteach the via point slightly off the singularity
  3. Change the tool orientation to avoid wrist alignment
  4. Reduce speed when passing near singularities
  5. For long straight paths, split the move around the singular posture
Safety first: For Universal Robots c154, this alarm family points at arm motion control: after a reset the arm can move unexpectedly, and anyone inside the working envelope is at strike and pinch risk. The self-serviceable action is Use joint-space moves (MoveJ) through the singular region; anything past that falls under the arm working envelope and needs a certified engineer.

How we diagnose motion alarms on site

Universal Robots c154 belongs to the motion & path family. On Universal Robots c154 the failing stage is joint-integrated drives (motor, drive and harmonic reducer in one joint) on the UR control box (CB3 / e-Series) - the gap between command and execution: trajectory planning, joint limits, singularities, following error and mechanical resistance. We start reading Universal Robots c154 at the PolyScope event and alarm pages; codes carry a C prefix (C15x, C5x, C7x).

The chain involved in Universal Robots c154 runs: program command -> trajectory planner -> joint targets -> servo execution -> actual position feedback -> deviation compare.

The clearest field clue for Universal Robots c154 is MoveL commanded straight through a wrist singularity; the discriminator is this test: The most valuable judgement on motion alarms is separating software from mechanics. We take the fixture off and re-run the same path below 10% speed: if it is clean unloaded and slow, the problem is mechanical - over-heavy tooling, shifted centre of gravity, or a joint that already has drag; if it alarms even unloaded and slow, look at program points, frame calibration and whether the path crosses a singular region. No instruments needed, and it removes half the wrong turns.

Field notes on this page cover Universal Robots c154 (Protective Stop — Position in Singularity); written by the Henghuan repair team, updated 2026-10-01.

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Related Motion & Path alarms

C150 — Protective Stop — Position Close to Joint Limits C153 — Protective Stop — Position Deviates from Path C155 — Protective Stop — Robot Cannot Maintain Position C157 — Protective Stop — Collision Detected
Same family: this code belongs to the Motion & path alarms family - the page collects all Motion & path-family codes we have handled, with the common inspection order and spares.
Other brands: we also keep field-fix libraries for Kawasaki · Staubli · Epson and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Universal Robots c154 alarm mean?

The robot cannot move linearly through the commanded point because it is in (or too close to) a kinematic singularity. This fault ranks high in our Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) service records, and the first site inspection usually finds the source. Universal Robots c154 sits in the motion & path family; on our work orders the highest-frequency trigger for this code is "MoveL commanded straight through a wrist singularity".

QCan I clear a Universal Robots c154 alarm myself?

Whether Universal Robots c154 clears on its own depends on the outcome of "Use joint-space moves (MoveJ) through the singular region". Finish the flow with "For long straight paths, split the move around the singular posture" to confirm Universal Robots c154 - do not skip it. If that step is clean, the second most frequent cause on Universal Robots c154 is "Wrist axes J4/J6 nearly parallel at the via point". When Universal Robots c154 keeps coming back it is not a one-off trigger - especially if For long straight paths, split the move around the singular posture is where you get stuck. Do not keep producing through Universal Robots c154.

QFor motion alarms like Universal Robots c154, can you triage remotely first?

The commonest causes we see on Universal Robots c154 are "MoveL commanded straight through a wrist singularity, Wrist axes J4/J6 nearly parallel at the via point, Robot asked to keep TCP orientation while passing through the shoulder singularity", so we stock the van against those. For Universal Robots c154 specifically, we carry mechanical and configuration items: grease, limit switches, drag-chain segments, encoder cables and the parameter sheets for common reducers. For Universal Robots c154, motion alarms can often be narrowed remotely first, so an on-site visit is not always immediate. Before we roll, tell us what Universal Robots c154 shows on the PolyScope event and alarm pages; codes carry a C prefix (C15x, C5x, C7x) and what the machine was doing - phone or video triage is free.

This page on Universal Robots c154 was compiled from actual repair records of the Henghuan Robotics repair team. Alarm notes are our own summary for troubleshooting reference only and may vary with controller and software version — please consult Universal Robots documentation or contact us if in doubt. Henghuan is an independent service provider, not affiliated with or endorsed by Universal Robots.