How do I resolve the issue with steering controller?

Pramod Mallipudi

Hello,

I've been trying to build a vehicle model to run constant radius turn. When I run the model, the solver throws an error as shown:

"<< ALTAIR DRIVER :: Steering Controller : Computed predicted path error > allowed path error of 1 mm.
Proceeding with the best approximation."

when the results button is clicked and observed in hyperview, the vehicle deviates from the path described, Kindly help me resolve this issue.

Thank you.

AnanthK

This is the precise reason why, in my previous post, I advised the use of K&C analysis to setup your suspension correctly first, before running any vehicle dynamics events. It appears the model doesn't have the spring preloads (ride height) set correctly - your vehicle mass is only 200kg, but the spring preloads are way higher.

 

Here is a rough process to setup any vehicle model, regardless of architecture: 

1) Build the corner/half-car models first, and add a Kinematics & Compliance event, making sure to set the vehicle & event parameters carefully. 

2) Calibrate the spring preloads, and component mass properties so the ground reaction forces (corner weights) are in the ballpark. 

3) Assemble the full vehicle model from the corner/half-car models, double-checking to make sure all tire properties are correct for the type of vehicle (esp tire radius and vertical stiffness).

4) Start with simple straight line events at steady state (ie Ax=0). Calibrate the vehicle mass and payload properties so that the ride height is correct. You may have to re-visit the spring preloads to ensure correct ride height. 

4) Now the model is ready for cornering and other vehicle dynamics events. 

 

Also, a quick note about sharing models on this forum: Please export your model using the following options in the File->Export Model menu. This will ensure all externally referenced files are zipped up in the same package, and allow another user to open and run the model without making any changes. 

 

AnanthK

For issues with specific models, we would need to either see log files, or the mdl itself before any useful diagnosis can be provided. The error suggests the vehicle model has not been setup correctly. The best path forward for you is to create a support ticket, and not the forum. Someone on our end will be able to give you personalized attention at that point. 

 

Thanks,

Ananth 

Pramod Mallipudi

Okay sir, I have attached the log file below. On contacting the support, I was told to continue the discussion in the forums. Please let me know if the mdl file is required.

AnanthK

From your log file. 

ERRMES:USER [337001]
<< ALTAIR DRIVER :: Steering Controller : Computed predicted path error > allowed path error of 1 mm.
Proceeding with the best approximation.
Possible Reasons:
1. Vehicle has spun out.
2. Path is not smooth
3. Steering wheel angle has reached saturation

It appears that there maybe kinematic issues with your steering system that is causing the driver to lose control and not follow the path. From your other posts and tickets it appears you're simulating a non-standard vehicle architecture. Have you first run it through a K&C analysis first and ensured a physically realistic steering system? This is a prerequisite to any kind of vehicle dynamics simulation effort. Properties such as steering ratio, column U-joint phasing, full lock etc. can affect the robustness in full vehicle simulations. Please check these using the K&C analysis, and correct any issues before continuing. 

AnanthK

This is the precise reason why, in my previous post, I advised the use of K&C analysis to setup your suspension correctly first, before running any vehicle dynamics events. It appears the model doesn't have the spring preloads (ride height) set correctly - your vehicle mass is only 200kg, but the spring preloads are way higher.

 

Here is a rough process to setup any vehicle model, regardless of architecture: 

1) Build the corner/half-car models first, and add a Kinematics & Compliance event, making sure to set the vehicle & event parameters carefully. 

2) Calibrate the spring preloads, and component mass properties so the ground reaction forces (corner weights) are in the ballpark. 

3) Assemble the full vehicle model from the corner/half-car models, double-checking to make sure all tire properties are correct for the type of vehicle (esp tire radius and vertical stiffness).

4) Start with simple straight line events at steady state (ie Ax=0). Calibrate the vehicle mass and payload properties so that the ride height is correct. You may have to re-visit the spring preloads to ensure correct ride height. 

4) Now the model is ready for cornering and other vehicle dynamics events. 

 

Also, a quick note about sharing models on this forum: Please export your model using the following options in the File->Export Model menu. This will ensure all externally referenced files are zipped up in the same package, and allow another user to open and run the model without making any changes. 

 

Pramod Mallipudi

Okay sir, Thank you for the support. Will make the following changes.