Inverse Dynamics - 2 Rigid Bodies connected with hinge

In summary, the conversation is about simulating and animating inverse dynamics and calculating torques. The speaker started by using a rotating rod and applying a torque, and then used \tau=I\alpha to ensure the same torque was applied. They then attached the rod to the ground with a hinge joint and used the parallel axis theorem to calculate the torque. The next step is to attach a second rod to the first one, but the speaker is unsure of how the two rods interact and how to calculate the torque. They are seeking insight and suggest looking into Lagrangian dynamics.
  • #1
leonj
1
0
I am trying to simulate and animate inverse dynamics. So I need to calculate torques. I started out by just taking a rod which rotates about its COM, applied a torque and then just used [itex]\tau=I\alpha[/itex] to make sure I get back the same torque I applied. Next, I attached the rod to the ground with a hinge joint. This time to get the torque I used the parallel axis theorem to get [itex]\tau=(I_{COM}+Mh^2)\alpha[/itex]. So my next step is to attach a second rod to the end of the one attached to the ground. What I am stuck on now is I am not sure how the two rods interact.

For example how do I calculate the torque on the rod connected to the ground? When it is just one rod I used the aforementioned [itex]\tau=(I_{COM}+Mh^2)\alpha[/itex], but now with the other rod attached to it, what else do I need to take into account? Is there a negative torque on the opposite side?

Note: For now I have disabled gravity.

I would appreciate any insight. Thanks
 
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  • #2
If you are not familiar with Lagrangian dynamics, this would be a good excuse to do so.
 

FAQ: Inverse Dynamics - 2 Rigid Bodies connected with hinge

1. What is inverse dynamics in the context of 2 rigid bodies connected with a hinge?

Inverse dynamics is a method used to calculate the forces and torques acting on a system of rigid bodies, given their motion and constraints. In the case of 2 rigid bodies connected with a hinge, inverse dynamics can be used to determine the forces and torques exerted on each body through the hinge.

2. How is inverse dynamics different from forward dynamics?

Forward dynamics calculates the motion of a system given the forces and torques acting on it, while inverse dynamics calculates the forces and torques given the motion of the system. Inverse dynamics is often used in situations where it is easier to measure the motion of a system than to directly measure the forces acting on it.

3. What information is needed to perform inverse dynamics on 2 rigid bodies connected with a hinge?

To perform inverse dynamics on 2 rigid bodies connected with a hinge, you will need to know the mass properties (such as mass, moment of inertia, and center of mass) of each body, the position, velocity, and acceleration of each body, and the constraints imposed by the hinge (such as the hinge axis and the type of motion allowed).

4. Can inverse dynamics be used to analyze non-rigid bodies?

No, inverse dynamics is only applicable to systems of rigid bodies. Non-rigid bodies, such as flexible structures or fluids, require different methods of analysis.

5. What are some practical applications of inverse dynamics on 2 rigid bodies connected with a hinge?

Inverse dynamics on 2 rigid bodies connected with a hinge can be used in various fields, such as biomechanics, robotics, and mechanical engineering. It can help in designing and optimizing the movement and stability of jointed structures, such as prosthetic limbs, robot arms, and human joints.

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