{{ post.title }} 글 편집 Author {{ post.author.name }} Posted on

RecurDyn/DriveTrain

RecurDyn/DriveTrain is a solution that enables to model and simulate the components of a drivetrain consisting of gears, bearings, shaft, and other components. It consists of 3 toolkits: GearKS, BearingKS, and Shaft. Users can easily simulate and analyze drivetrain systems with specialized modelers that can easily create gears, bearings, and shafts, a specialized solver, and dedicated post-processing.

In particular, GearKS and BearingKS have been developed through the technical partnership with Gleason’s KISSsoft. This allows users to accurately calculate a variety of results including Transmission Error for noise and vibration evaluation by using RecurDyn's dynamic solver, KISSsoft's Gear Analytic Contact and tens of thousands of bearing libraries.

Contact elements in RecurDyn/DriveTrain

This article will cover the contact elements which are used for GearKS of RecurDyn/DriveTrain.

Among the contact elements for GearKS, GMM (Gear Meta Model) will be explained in detail. (If you use RecurDyn/DriveTrain, you may use GMM most.)

In case of Gear simulation, the contact between the gears in the gear pair is very important. So GearKS supports various gear contact elements. In GearKS dialog, you can find 3 Gear Force Types (This determines how RecurDyn calculates the gear contact.)

3 Types of the Gear Force

1. Inactivate

• If this type is selected, GearKS doesn’t calculate the gear contact.
• Instead, other contact such as Gear Involute Contact or Geo Contact must be defined.

2. KISSsoft Force

• The gear contact is calculated by the Direct Co-simulation between RecurDyn and embedded KISSsoft solver.
• Each time step, RecurDyn transfers the updated location/orientation of the gears to KISSsoft, then KISSsoft solver embedded in RecurDyn calculates the gear contact. And the reaction force/torque is transferred from KISSsoft to RecurDyn

3. KISSsoft Force (Meta Model) *Recommended*

• Unlike KISSsoft Force (Direct Co-Simulation), KISSsoft Force (Meta Model) uses the pre-calculated Gear Meta Model and use it for the simulation. So the calculation speed is very fast.
• Gear Meta Model (*.gmm file) must be created using 6 parameters which are related to the location/orientation of the gear pair before simulation.
• Generating Gear Meta Model takes several minutes ~ hours
• Gear Meta Model is reusable
• If the same gear pair is used for another model.
• One Gear Meta Model can be used for the several gear pairs in one model.
  

What is Gear Meta Model?

*Meta Model is also known as Surrogate Model, or approximation model.

Meta model is an engineering method to predict the outputs which were not calculated/measured by a model which was generated by the pre-calculated/measured results as a function of several design variables.

KISSsoft Force (Meta Model) which is used in RecurDyn/DriveTrain can reduce the simulation time dramatically. RecurDyn/DriveTrain generates the meta model (Gear Meta Model) using the pre-calculated gear forces (including gear contact) as a function of 2~6 design variables, then uses the meta model to predict the gear force during simulation.

6 Parameters (Design variables) for Gear Meta Model generation

• Rotational Angle, Penetration, Distance Error, Axial Offset, Twist, Tilt
• Default setting uses only 2 parameters
• Rotational Angle, Penetration
• If the gears are constrained by revolution joints, Distance Error, Twist, Tilt can be ignored. And Axial Offset can be ignored in many cases
• For more accurate result, it is recommended to use all 6 parameters
• Generation time of Gear Meta Model (this varies depending on the system)
• 2 parameters are used: several minutes
• 6 parameters are used: several hours 

How to use Gear Meta Model?

Comparison of 3 types of Gear Contact

Guide to choosing the right Contact Type

1. In most of the cases, KISSsoft Force (Meta Model) is recommended

Usually, KISSsoft Force (Meta Model) is recommended over KISSsoft Force (Direct)

• KISSsoft Force (Direct) is a little more accurate, the benefit of the much faster simulation speed compensates for the slight loss of the accuracy.
• Simulation speed which includes the simple gear pair
• Direct: tens of minutes ~ hours
• Meta Model seconds ~ tens of seconds

If you run just 1 or 2 simulations, KISSsoft Force (Direct) can be a good choice. But generally, more runs are needed. So KISSsoft Force (Meta Model) is recommended.

Even if it takes time to generate Gear Meta Model, Gear Meta Model is reusable.

• If the same gear is used, Gear Meta Model can be used for another gear pair or in other RecurDyn model.
• Start the generation of Gear Meta Model before leaving the office and use it from next morning

If you must consider the following factors, you must use KISSsoft Force (Meta Model), not Gear Involute Contact

• You need the accurate transmission error
• The effect of the micro-geometry of the gear should be considered
• Deformation of the gear teeth affects the system.

KISSsoft Force (Meta Model) is more accurate than Gear Involute contact

2. Gear Involute Contact is useful in the following cases

• - If you care more about the macro system behavior than the micro behavior such as the transmission error or the effect of the micro geometry of the gear, it is recommended to use Gear Involute Contact.
• Gear Involute Contact is fast and accurate enough if the effect of the micro geometry can be ignored
• If you are interested in the overall behavior of the system rather than the detailed result of the gears
• Gear Involute Contact is very convenient because this doesn’t need any pre-calculation
• But if the gear specification is already fixed, then it is recommended to use KISSsoft Force (Meta Model)
• To use Gear Involute Contact, Gear Force Type must be set to Inactivate first, then Gear Involute Contact needs to be created instead
• Gear Toolkit is required – it is different from GearKS

3. Other cases

If you need to use the flexible gear, you should use Geo Surface Contact.

• KISSsoft Force and Gear Involute Contact don’t support the flexible body