How Do You Determine Parameters for a Non-Linear Friction Model?

[maxpower2008]

Hey all, I'm cross-posting this in the materials and mechanical engineering section because I feel like this might be a good question for both places.

I'm trying to develop a physical model of a mechanical system in MapleSim, and have the questions about the friction model used. This isn't a software question, but more trying to understand the math of a non-linear friction model.
The model itself is a sum of the Coulomb friction (the familiar F= uN component), as well as Stribeck and viscous effects.
As a result, the model requires input parameters such as breakaway friction force, viscous friction coeff., and transition approx. coeff.
My question is: How can I get numbers for these values? I have some performance data for my system but what do I need to know to find numbers for those input parameters? Can they only be determined experimentally?

Thanks in advance,
-Max

 

[Achy47]

Hi Max,

Great question! Friction is a complex phenomenon and there are various models that can be used to describe it. In your case, it seems like you are using a combination of Coulomb, Stribeck, and viscous models to describe the friction in your mechanical system.

To answer your question, the values for the input parameters can be determined experimentally, but there are also some theoretical methods that can be used to estimate them. The breakaway friction force, for example, can be estimated by measuring the force required to initially move the system from rest. The viscous friction coefficient can be determined by measuring the velocity of the system and the resulting force. The transition approximation coefficient can be estimated using theoretical models or by comparing the performance data of your system to similar systems with known coefficients.

It's important to note that these values may not be completely accurate, as friction is affected by many factors such as surface roughness, temperature, and lubrication. Therefore, it's always best to validate your model with experimental data to ensure accuracy.

I hope this helps and good luck with your model!

 

[oswaler]

I can provide some insight into the non-linear friction model you are working with. Non-linear friction models are commonly used in mechanical systems to account for the complex behavior of friction, which is not always a constant force and can vary with factors such as velocity and surface conditions. The model you are using, which includes Coulomb, Stribeck, and viscous effects, is a good representation of real-world friction.

To answer your question about obtaining values for the input parameters, experimentation is often the best approach. This involves conducting physical tests on your system and measuring the friction at different velocities and surface conditions. This data can then be used to determine the values for breakaway friction force, viscous friction coefficient, and transition approximation coefficient.

Another approach is to use existing data from similar systems or materials. This can provide a starting point for your model, but it is important to keep in mind that these values may not be directly applicable to your specific system.

It is also worth mentioning that these parameters may not be constant and can change over time due to wear and other factors. Therefore, it is important to regularly monitor and update these values as needed.

In conclusion, obtaining values for the input parameters of a non-linear friction model often requires experimentation or using existing data. It is important to regularly monitor and update these values to ensure the accuracy of your model.