parameter modification of Inverted robots

Yu I

Hello,

Do we need to modify parameters for Inverted robots in RS?
I have just turned robots and not modified any parameters so far.
I think floor and inverted robots have the same performance in cycle time.
I'd appreciate your infomation.

Yu

Henrik Berlin

Hi,

Other than the baseframe there are no other parameters. The exception to this rule are the 6620 and 6640 that have the "gravity-beta" angle that must be defined in the motion configuration parameters.

Floor and inverted robots have similar cycle time, although not exactly the same.

Yu I

Hi Henrik,

I didn't know the "gravity-beta" angle. Is there any reference for that? I don't know how to define.

Do you mean motion parameters would be modified for other robots when I change the baseframe parameter?   I have to know exact cycle time of inverted robots.

Yu

Henrik Berlin

Hi Yu,
Look at the information below regarding gravity beta that is taken from the product documentation.
From the IRB6620 Product Manual:
2.3.7. Suspended mounting
General
Initially the system is configured for mounting on the floor, without leaning. The method for
mounting the robot in a suspended position is basically the same as for floor mounting.
NOTE!
With suspended installation, make sure that the gantry or corresponding structure is rigid
enough to prevent unacceptable vibrations and deflections, so that optimum performance can
be achieved.
System parameters
If the robot is mounted at any other angle, the system parameter "gravity beta" must be
updated. Gravity beta specifies the robot's mounting angle expressed in radians.
NOTE!
It is very important to configure gravity beta correctly so that the robot system can control the
movements in the best possible way. Incorrect definition of mounting angle (gravity beta) will
result in:
Overloading the mechanical structure.
Lower path performance and path accuracy.
Some functions will not work properly: e.g Load Identification & Collision detection.
Mounting angles and values
The parameter "gravity beta" specifies the robot's mounting angle in radians. It is calculated
in the following way for a mounting angle of 15?.
Gravity beta = 15? x 3.141593/180 = 0.261799 radians.
Example of position Mounting angle Gravity Beta
Floor (A) 0? 0.000000 (Default)
Tilted (B) 15? 0.261799
Suspended (C) 180? 3.141593
From the System Parameter Reference Manual:
6.30.9. Gravity Beta
Parent
Gravity Beta belongs to the type Robot, in the topic Motion.
Cfg name
gravity_beta
Description
Gravity Beta defines the orientation of gravity with respect to the base frame.
Usage
The beta gravity is a positive rotation direction around the y-axis in the base frame. The value
is set in radians.
Allowed values
A value between -6.283186 and 6.283186 radians.
Default value is 0.Henrik Berlin2008-8-7 17:58:32

Henrik Berlin

The cycle time is not affected by the baseframe, but the Inverted models are optimized for mounting up-side-down.

Yu I

Hi Henrik,

I don't get what you mean. Do you mean inverted models like 140 and 2400 are optimized automatically when those are inverted?

Yu

Henrik Berlin

Hi Yu,

What I mean is that the control system has a dynamic model of the robot. The gravity influences the dynamics of the robot and is included in the dynamic model of the robot. When the robot is mounted upside down, the gravity points in the opposite direction (from the robot point of view). This is taken into account in the dynamic model of the Inverted variants.

Some robot models (6620 & 6640) also support mounting with an angle or on the wall, then this is configured in the control system with the gravity alpha and beta angles.

If there is a discrepancy between the dynamic model and the real world the robot may behave differently than expected. This will be the case if an Inverted robot is mounted on the floor, if a standard robot is mounted up-side-down or a 6620 is mounted on a wall without defining the gravity-beta angle.

Jetman

Yu,

 

in order words yes. You do have to set the Beta gravity to 3.14 (Rad) it's 180 degres if you are using a robot upside Down. Even if it's a IRB140.

 

If you don't ,youll endup with motion supervision errors and routine like LoadIdentify won't give you accurate values.

 

It's not in the manuals though.

 

Sorry it took so long, I was playing with that with an inverted IRB140 recently and had a couple chats with ABB support. Modifying Beta gravity fixed our problem.

 

Jet

kschmid

Is Gravity beta a parameter in station setup in robotstudio as well?

ah found it https://forums.robotstudio.com/discussion/comment/26137#Comment_26137