Real-time simulation of multibody systems with applications for working mobile vehicles
Baharudin, Mohamad Ezral (2016-04-01)
Väitöskirja
Baharudin, Mohamad Ezral
01.04.2016
Lappeenranta University of Technology
Acta Universitatis Lappeenrantaensis
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-265-933-0
https://urn.fi/URN:ISBN:978-952-265-933-0
Tiivistelmä
This dissertation describes an approach for developing a real-time simulation for working
mobile vehicles based on multibody modeling. The use of multibody modeling allows
comprehensive description of the constrained motion of the mechanical systems involved
and permits real-time solving of the equations of motion. By carefully selecting the
multibody formulation method to be used, it is possible to increase the accuracy of the
multibody model while at the same time solving equations of motion in real-time.
In this study, a multibody procedure based on semi-recursive and augmented Lagrangian
methods for real-time dynamic simulation application is studied in detail. In the semirecursive
approach, a velocity transformation matrix is introduced to describe the
dependent coordinates into relative (joint) coordinates, which reduces the size of the
generalized coordinates. The augmented Lagrangian method is based on usage of global
coordinates and, in that method, constraints are accounted using an iterative process.
A multibody system can be modelled as either rigid or flexible bodies. When using
flexible bodies, the system can be described using a floating frame of reference
formulation. In this method, the deformation mode needed can be obtained from the finite
element model. As the finite element model typically involves large number of degrees
of freedom, reduced number of deformation modes can be obtained by employing model
order reduction method such as Guyan reduction, Craig-Bampton method and Krylov
subspace as shown in this study
The constrained motion of the working mobile vehicles is actuated by the force from the
hydraulic actuator. In this study, the hydraulic system is modeled using lumped fluid
theory, in which the hydraulic circuit is divided into volumes. In this approach, the
pressure wave propagation in the hoses and pipes is neglected. The contact modeling is
divided into two stages: contact detection and contact response. Contact detection
determines when and where the contact occurs, and contact response provides the force
acting at the collision point. The friction between tire and ground is modelled using the
LuGre friction model, which describes the frictional force between two surfaces.
Typically, the equations of motion are solved in the full matrices format, where the
sparsity of the matrices is not considered. Increasing the number of bodies and constraint
equations leads to the system matrices becoming large and sparse in structure. To increase
the computational efficiency, a technique for solution of sparse matrices is proposed in
this dissertation and its implementation demonstrated. To assess the computing
efficiency, augmented Lagrangian and semi-recursive methods are implemented
employing a sparse matrix technique. From the numerical example, the results show that
the proposed approach is applicable and produced appropriate results within the real-time
period.
mobile vehicles based on multibody modeling. The use of multibody modeling allows
comprehensive description of the constrained motion of the mechanical systems involved
and permits real-time solving of the equations of motion. By carefully selecting the
multibody formulation method to be used, it is possible to increase the accuracy of the
multibody model while at the same time solving equations of motion in real-time.
In this study, a multibody procedure based on semi-recursive and augmented Lagrangian
methods for real-time dynamic simulation application is studied in detail. In the semirecursive
approach, a velocity transformation matrix is introduced to describe the
dependent coordinates into relative (joint) coordinates, which reduces the size of the
generalized coordinates. The augmented Lagrangian method is based on usage of global
coordinates and, in that method, constraints are accounted using an iterative process.
A multibody system can be modelled as either rigid or flexible bodies. When using
flexible bodies, the system can be described using a floating frame of reference
formulation. In this method, the deformation mode needed can be obtained from the finite
element model. As the finite element model typically involves large number of degrees
of freedom, reduced number of deformation modes can be obtained by employing model
order reduction method such as Guyan reduction, Craig-Bampton method and Krylov
subspace as shown in this study
The constrained motion of the working mobile vehicles is actuated by the force from the
hydraulic actuator. In this study, the hydraulic system is modeled using lumped fluid
theory, in which the hydraulic circuit is divided into volumes. In this approach, the
pressure wave propagation in the hoses and pipes is neglected. The contact modeling is
divided into two stages: contact detection and contact response. Contact detection
determines when and where the contact occurs, and contact response provides the force
acting at the collision point. The friction between tire and ground is modelled using the
LuGre friction model, which describes the frictional force between two surfaces.
Typically, the equations of motion are solved in the full matrices format, where the
sparsity of the matrices is not considered. Increasing the number of bodies and constraint
equations leads to the system matrices becoming large and sparse in structure. To increase
the computational efficiency, a technique for solution of sparse matrices is proposed in
this dissertation and its implementation demonstrated. To assess the computing
efficiency, augmented Lagrangian and semi-recursive methods are implemented
employing a sparse matrix technique. From the numerical example, the results show that
the proposed approach is applicable and produced appropriate results within the real-time
period.
Kokoelmat
- Väitöskirjat [1099]