# How is the speed and acceleration related in movej?

**URL:** <https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325>\
**Category:** Technical Questions\
**Created:** [May 21, 2024, 6:50am UTC](https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325 "2024-05-21T06:50:38Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![sayank](https://avatars.discourse-cdn.com/v4/letter/s/db5fbb/32.png) [@sayank](https://forum.universal-robots.com/u/sayank)\
**Post date:** [May 21, 2024, 6:50am UTC](https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325/1 "2024-05-21T06:50:38Z")

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Hi ,  
I have a doubt on how the speed and the acceleration related when used in movej arguments. Is the speed provided as an argument the final speed when the robot reaches the destination accelerating from initial waypoint with 0 speed ?  
Regards,  
Sayan

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**Author:** ![Ebbe](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/ebbe/32/1413_2.png) [@Ebbe](https://forum.universal-robots.com/u/Ebbe)\
**Post date:** [May 21, 2024, 11:06am UTC](https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325/2 "2024-05-21T11:06:38Z")

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Hi @sayank,

Welcome to the UR Forum!

Per default the robot will stop at the target waypoint. So the acceleration will give the acceleration and deceleration in this figure. While the speed argument will give the cruise speed. For the joint the have the longest travel.

 ![image](https://us1.discourse-cdn.com/flex020/uploads/universal_robots/original/2X/e/eafb3ae11e6d2332b7403fa4567cd751b011f8a8.png)

If you would like not to stop you should make use of the blend parameter and maybe the _movep()_ function

Best regards  
Ebbe

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<div class="post-metadata">

**Author:** ![sayank](https://avatars.discourse-cdn.com/v4/letter/s/db5fbb/32.png) [@sayank](https://forum.universal-robots.com/u/sayank)\
**Post date:** [May 22, 2024, 8:56am UTC](https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325/3 "2024-05-22T08:56:10Z")

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Hi @Ebbe ,  
I have query regarding this

> [@Ebbe](#):
>
> If you would like not to stop you should make use of the blend parameter and maybe the _movep()_ function

Do you mean using blend parameter or movep() will maintain the robot speed to cruise speed after reaching the destination waypoint?

Thanks,  
Sayan

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**Author:** ![robin\_gdwl](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/robin_gdwl/32/2676_2.png) [@robin\_gdwl](https://forum.universal-robots.com/u/robin_gdwl)\
**Post date:** [May 22, 2024, 8:50pm UTC](https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325/4 "2024-05-22T20:50:43Z")

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how is the “starting speed” for each motion determined?  
If I have multiple points with small blend radii, is there a way for me to calculate myself what the exact speed at each point is and how much the individual joints will decelerate before the direction changes?

If I have a series of waypoints, speed settings and blend radii how can I determine how long the toolpath will take precisely?

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**Author:** ![Ebbe](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/ebbe/32/1413_2.png) [@Ebbe](https://forum.universal-robots.com/u/Ebbe)\
**Post date:** [May 23, 2024, 1:03pm UTC](https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325/5 "2024-05-23T13:03:35Z")

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Hi @sayank,

The most important if you would like a initial speed \> 0 is to add a blend. In PolyScope a movep waypoint will by default have a blend radius. Whether the move should be J or P depends on your need.

Ebbe

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<div class="post-metadata">

**Author:** ![Ebbe](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/ebbe/32/1413_2.png) [@Ebbe](https://forum.universal-robots.com/u/Ebbe)\
**Post date:** [May 23, 2024, 1:16pm UTC](https://forum.universal-robots.com/t/how-is-the-speed-and-acceleration-related-in-movej/34325/6 "2024-05-23T13:16:41Z")

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Hi @robin_gdwl,

Each move will follow its speed trapezoid before/after entering/exiting the blend sphere  
So if I extend the plot from earlier with the next movement and a blend:

 ![image](https://us1.discourse-cdn.com/flex020/uploads/universal_robots/original/2X/0/0fad6987e1fb1b0a68bb2e6e7cf22ea55ecf19cd.png)  
The marked blend section the controller will find a solution to the boundary conditions. Pleas note that the blend section is the geometric sphere measure. So first movement will impact the time fore the robot exit the sphere going towards next pose.

Ebbe