How to calculate the common center of mass position of multiple rigid bodies in Simscape Multibody？

How to calculate the common center of mass position of multiple rigid bodies in Simscape Multibody？

I think it is possible to get the position of the center of mass of each rigid body and then calculate the overall center of mass by weighting, but this is very complicated. Is there a more convenient method?

[Vasco Lenzi]

Hi there

have you taken a look at the inertia sensor block?

it was introduced in 2019b

https://www.mathworks.com/help/releases/R2020b/physmod/sm/ref/inertiasensor.html

this should provide a fairly straightforward way to get center of mass, as well as:

• Mass
• Center of mass
• Inertia matrix
• Centered inertia matrix
• Principal inertia matrix
• Orientation of principal inertia frame

[Juan Sagarduy]

Good insight Vasco,

Indeed the Inertia Sensor works well for Jingchiao's query. I attach an example with two masses. When density of one is very high, the centre of mass is in the centre of the heavy body. And viceversa.

Br Juan

Answer 1

[Steve Miller]

As Vasco mentioned above, the Inertia Sensor block was created for this purpose.

From Vasco's Comment above:

Hi there

have you taken a look at the inertia sensor block?

it was introduced in 2019b

https://www.mathworks.com/help/releases/R2020b/physmod/sm/ref/inertiasensor.html

this should provide a fairly straightforward way to get center of mass, as well as:

• Mass
• Center of mass
• Inertia matrix
• Centered inertia matrix
• Principal inertia matrix
• Orientation of principal inertia frame

Answer 2

[Moritz Ischebeck]

another example, of a double pendulum

important property to change when recreating: Inertia Sensor > properties > Sensor Extent > "mechanism"

connect sensor port (input) with world frame