FAQ - Frequently Asked Questions

The purpose of this FAQ document is to answer questions you may have about the Motion Plus Coordinated Motion Feature.

What is Coordinated Motion?

Coordinated motion is time, position and speed synchronized motion between the robot’s six motorized axes and one or more external axes. The TCP motion of the robot and the external axes are controlled in sync to deliver motion of the TCP relative to a moving frame attached to an external axis. See here for more terminology and here for more coordinated motion details.

What is MotionPlus?

MotionPlus is an add-on software module that coordinates robot motion with external axes. This module currently consists of the functions of coordinated motion and will be extended in the future.

Which part of MotionPlus is licensed?

The license controls access to the MotionPlus URCap, which contains the EtherCAT master and controls the motor output. The World Model is open in PS 5.16.

Is it possible to test run MotionPlus without a license?

Not at this time. But for OEM partners and CSI we can provide a developer’s license at no charge.

Does MotionPlus come with hardware?

Coordinated Motion is a software solution that can work with third-party servo drives and actuators. It does not come with hardware?

What cobots does MotionPlus work with?

All e-series robots as well as UR20 and UR30 are supported.

What servo drives are supported?

See the list of tested EtherCAT servo drives here.

If I am a servo drive manufacturer, how do I get my servo drive tested for compatibility with Motion Plus.

Contact Universal Robots Support and ask to be put in touch with the MotionPlus product manager. We can guide you through validation of your servo drive with Coordinated Motion.

What happens to the servo drive if the robot experiences a protective stop?

If the robot enters a protective stop, the servo is instructed to halt.

What happens to the servo drive motion when the cobot enters reduced mode?

The servo drive speed will be scaled down when the cobot enters reduced mode to conserve the motion synchronization.

Will users be able to set homing, limits, motion profiles within the URCap, rather than in the servo drive?

While MotionPlus will include physical homing to limit switches, the EtherCAT configuration within MotionPlus allows you to set the max/min limits of the axis, as well as max acceleration and speed.

Is the Motion Plus URCap required to use the Coordinated Motion UR Script commands?

Yes. But the general World Model URScript commands do not require MotionPlus.

How many external axes are supported?

· The first release (MotionPlus 1.0) with Polyscope 5.16.0 supports a single rotary axis.

· The multi-axis version (MotionPlus 1.1), released in Q4 2024, has support up to four external rotary axes.

· The linear version (MotionPlus 1.2) is planned for Q1 2025, with support for up to six rotary and/or linear axes.

Is the external axis also collaborative?

No. The external axes motor system typically does not sense the presence of obstruction, collisions or push-back from the human operators. Proper safety systems must be put in place to protect the operator and the robot.

Does the motion of the external axis work with speed scaling?

Yes. Adjusting the speed scale on the teach pendant will also scale the speed of the external axes to maintain synchronization.

What happens to the robot motion if the external axis servo drive experiences a fault?

If the external axis servo faults, the robot motion will stop as well. The fault is detected through communication between the robot EtherCAT master and the EtherCAT servo drive.

What happens to the motion of the external axis if the robot protective stops while performing coordinated motion?

If the robot protective stops or e-stops, the axis is stopped. The converse is also true. If the axis faults, the robot will protective stop as well.

Does the log file indicate the root cause - either external axis stop / protective stop or the robot?

The log file contains all error messages/faults generated by the servo drive with the fault code.

What are the requirements for an EtherCAT servo to work with Motion Plus?

Servo drives that implement the EtherCAT standard with Cia402 motor control profile. In particular, the servo drive must support CSP model (cyclic synchronous profile) and DC (distributed clock). Here is a list of tested servo drives.

Can I use MotionPlus for indexed motion as well?

Yes – MotionPlus can control independent motion external axes to indexed positions.

What URScript commands can jog an external axis?

Jogging can be performed with axis_group_movej and axis_group_speedj. See here for more information.

What URScript commands are used for coordinated motion?

Coordinated motion typically uses combinations of movep_with_axis_group, movec_with_axis_group, movel_with_axis_group, and movej_with_axis_group, along with frame_tracking_enable and frame_tracking_disable for frame tracking. See here for more information.

What is the World Model and how does that work with coordinated motion?

The world model is a set of reference coordinated systems known as frames. In Polyscope 5.16 and later, the robot programmer can define a set of frames to represent kinematic chains of one or more external axes. The TCP motion of the robot can be defined to move with respect to a reference frame. See here for more information.

Do I need MotionPlus to use the World Model reference frames?

No – World Model is included with Polyscope 5.16. The URScript commands for movec, movep and movel have been updated to accept a struct of a pose relative to a frame. That makes it possible to specify TCP motion with a user-defined frame. See here for more information.

What does the World Model support?

The World Model supports multiple frames, but not axes. MotionPlus, which is separate, supports the creation of Axes and the driving of servo drives via EtherCAT. More information on the world model can be found here, and more information on MotionPlus can be found here.

What is frame tracking and how does it work?

Frame tracking sets the reference frame for the robot TCP motion. This frame could be attached to a moving external axis or some stationary position and orientation in the work spaced defined by a reference object. See here for more information.

What applications use coordinated motion?

Common applications are welding, surface treatment (sanding, polishing) and visual inspection. Coordinated motion can also be used to reduce cycle time for pick-and-place and palletizing applications.