Multibody Dynamics Module
Multibody Dynamics Module
Software for Analyzing Assemblies of Rigid and Flexible Bodies
Tools for Designing and Optimizing Multibody Systems
The Multibody Dynamics Module is an expansion of the Structural Mechanics Module that provides an advanced set of tools for designing and optimizing multibody structural mechanics systems using finite element analysis (FEA). The module enables you to simulate mixed systems of flexible and rigid bodies, where each body may be subjected to large rotational or translational displacements. Such analyses help identify critical points in your multibody systems, thus enabling you to perform more detailed component-level structural analyses. The Multibody Dynamics Module also gives you the freedom to analyze forces experienced by segments of the structure, and stresses generated in flexible components that may lead to failure due to large deformation or fatigue.
Utilize a Library of Joints
A library of predefined joints is included in the module so that you can easily and robustly specify the relationships between different components of a multibody system, where the components are interconnected such that only a certain type of motion is allowed between them. Joints connect two components through attachments, where one component moves independently in space while the other is constrained to follow a particular motion, depending on the joint type. The joint types in the Multibody Dynamics Module are generic to the extent that they can model any type of connection. Researchers and engineers can thereby design accurate multibody structural mechanics models, using the following joint types:
- Prismatic (3D, 2D)
- Hinge (3D, 2D)
- Cylindrical (3D)
- Screw (3D)
- Planar (3D)
- Ball (3D)
- Slot (3D)
- Reduced Slot (3D, 2D)
- Fixed Joint (2D,3D)
- Distance Joint (2D,3D)
- Universal Joint (3D)
- Orientation of movement for the prismatic, hinge, cylindrical, and screw joints.
- Orientation of movement for the planar, ball, slot, and reduced slot joints.
- Model of a truck crane used for handling large loads. The simulation analyzes rigid body movement and predicts forces on the crane's axles and hydraulic cylinders. Results are used to optimize the position of link mechanisms in the base.
- A swashplate mechanism is used to control the orientation of helicopter rotor blades. This example shows an application derived from the model where only the pitch of the blades can be changed, but where both transient and eigenfrequency analyses can be presented.
- Model of a three-cylinder reciprocating engine, having both rigid and flexible parts, is used for maximizing the engine power and the design of structural components.
Complete Flexibility in Analyzing Multibodies
Components of a system that undergo deformations can be modeled as flexible, while other components, or even parts of these components, can be specified as rigid. You can also provide your multibody dynamics design and analyses with nonlinear material properties by combining models in the Multibody Dynamics Module with either the Nonlinear Structural Materials Module or the Geomechanics Module. At the same time, the rest of the physics that you can model with COMSOL Multiphysics and the suite of application-specific modules, can be coupled to the physics described by the Multibody Dynamics Module, such as the effects of heat transfer or electrical phenomena.
Transient, frequency-domain, eigenfrequency, and stationary multibody dynamics analyses can be performed. Joints can be assigned linear/torsional springs with damping properties, applied forces and moments, and prescribed motion as a function of time. Analysis and postprocessing capabilities include:
- Relative displacement/rotation between two components and their velocities
- Reaction forces and moments at a joint
- Local and global coordinate system frames of reference
- Stresses and deformations in flexible bodies
- Fatigue analysis of critical flexible bodies by combining with the Fatigue Module
Often, motion between two components is restricted due to the presence or functions of other physical objects. Limiting and conditionally locking the relative motion can be specified for the joints in order to fully define and model these complex systems. In robotics, for example, the relative motion between two arms can be defined as a pre-defined function of time. Joints can also be spring-loaded and appropriate damping factors can be included in the Multibody Dynamics Module.
Keeping Cool: SRON Develops Thermal Calibration System for Deep-Space Telescope
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Differential Gear Mechanism
This model simulates the mechanism of a differential gear used in cars and other wheeled vehicles. A differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn. This is necessary when a vehicle turns in order to allow the wheel that is traveling along the outside of the turning curve to roll faster and to ...
Vibrations in a Compound Gear Train
This model simulates vibrations in a compound gear train. Spur gears, used to model the gear train, are mounted on rigid shafts. The shafts are supported by an elastic housing at both ends. The gear mesh is assumed to be elastic with varying stiffness, which is the source of vibration. A transient analysis is performed to compute the dynamics of ...
Helical Gear Pair
This model illustrates the dynamics of helical gears. It is built using the gears functionality in the Multibody Dynamics interface in COMSOL Multiphysics. A transient study is performed to analyze the effect of constant gear mesh stiffness, varying gear mesh stiffness, and the transmission error on the angular velocity of driven gear and the ...
Dynamics of a Gyroscope
Gyroscopes are used for measuring the orientation or maintaining the stability of airplanes, spacecraft, and submarines vehicles in general. They are also used as sensors in inertial guidance systems. This model demonstrates the modeling of a mechanical gyroscope. It analyzes the response of the spinning disc to an external torque coming on the ...
Simulation of Shock Absorber in Landing Gear
This model simulates the dynamics of the shock absorber used in a landing gear mechanism of an aircraft. It analyses the stresses, as well as the heat generated in the landing gear components due to the energy dissipated in the shock absorber. A prismatic joint, with spring and damper, is used to model the shock absorber assembly.
Three Cylinder Reciprocating Engine
In this example, a dynamic analysis of a three-cylinder reciprocating engine is performed to investigate stresses generated during operation, thereby permitting identification of the critical components. Demand for high power output relative to the weight of the engine requires careful design of its components. This model of a reciprocating ...
Forces and Moments on Bevel Gears
This tutorial model simulates a pair of straight conical bevel gears. The gears are modeled as rigid, but one of the gears is fixed while the other is hinged on a rigid bar. The rigid bar is also hinged at a point lying on the axis of the fixed gear. A transient analysis is performed to compute the forces and moments at the center of the fixed ...
Shift into gear
This model demonstrates the ability to simulate Multibody Dynamics in COMSOL. It comprises a multilink mechanism that is used in an antique automobile as a gearshift lever. It was created out of curiosity to find out how large forces are on the individual components. The model uses flexible parts, i.e. the Structural Mechanics Module was used ...
Spring Loaded Centrifugal Governor
A centrifugal governor is used to control the speed of rotating machinery. One of the most common applications is in controlling the RPM of an engine by regulating the fuel supply. This model illustrates the functioning of a spring loaded centrifugal governor. The dynamics of the governor are analyzed under the influence of a centrifugal ...
Assembly with a Hinge Joint
This example illustrates how to model a barrel hinge connecting two solid objects in an assembly. In this model, the details of the connection are not the focus of the analysis, therefore, the hinge joint is modeled using a Joint feature in the Multibody Dynamics Module. The connected parts can be either rigid or flexible or a combination as ...