Invalid Control Command Generated

When error [2.1908] occurs, the robot stops with the error message below.

• The robot stops during a program, during jogging, or at the moment of servo on.
• It often happens at the same program line or the same kind of motion — for example a blend between two motions, a motion close to a singular posture, or palletizing mode.
• Sometimes servo on is not possible afterwards, especially when a joint has moved past its limit.

[2.1908] Control algorithm category

An invalid control command was generated.
Param 1: Detailed cause

The robot's control algorithm calculates a command for every joint in every control cycle. This error means the calculated command was outside what the robot can physically do, or could not be calculated at all. The robot stops rather than execute it.

• A software issue fixed in a later version — several motions that caused this error have been corrected in software updates.
• The motion itself — a large blend between very different motions, high speed near a singular posture, or a target the robot cannot reach smoothly.
• A joint beyond its limit — when a joint is outside its allowed range (often shown together with 4.1019), the robot cannot calculate a valid command until it is moved back.
• A problem in a joint — less often, a fault in one joint makes its position or torque unreliable.

• Note exactly what the robot was doing: which program line, which motion command, and whether it was jogging or running.
• Check the controller software version. If a newer version is available, update — several causes of this error have been fixed in updates. The release notes list what each version fixed.
• If 4.1019 appears with 2.1908, or servo on is not possible, use recovery mode on the teach pendant to move the joint back inside its range, then try servo on again.
• If the error happens at the same motion every time, try a smaller blend radius, a lower speed, or a slightly different waypoint that keeps the robot away from a singular posture.
• Check that the tool and payload settings match the real tool and workpiece.

If the error continues after updating and adjusting the motion, contact your distributor.

Prepare the following so the problem can be diagnosed quickly:

• Robot model and serial number
• Software version of the controller
• The error code with its Param value, all codes shown with it, and the date and time
• The program (or the part of it) and the line where the robot stopped
• The controller log exported right after the error
• A video of the motion, if the error can be reproduced

• 4.1019 Software Position Limit Error
• 4.1025 Position Following Error
• 5.7025 Motion Controller data sequence number error occurred
• 5.7057 Current joint position exceeds user limit in at least one joint
• 2.3509 Commanded motion can be unstable in the vicinity of singular configuration