Multibody dynamics is the study of the dynamic behaviors of mechanical systems that consist of rigid and/or flexible bodies connected by joints. The bodies undergo translational and rotational motions caused by applied forces, torques, and constraints. Simscape™ Multibody™ enables you to perform multibody dynamics simulations for complex systems, such as robots, vehicles, construction equipment, or aircraft landing gear. You can specify force, torque, and motion inputs to drive your model and simulate the dynamic responses of the model.
To specify the degrees of freedom between a pair of bodies, use blocks in the Joints and Constraints libraries. For example, you can use the Prismatic Joint block and Revolute Joint block to model the straight-line and rotary motions of a slider-crank mechanism. You can use the Point on Curve Constraint block to model the constraint between a roller coaster car and the track.
To model forces and torques that act on bodies, use blocks in the Forces and Torques library. For example, you can use the Magic Formula Tire Force and Torque block to model the tire forces and torques between a tire and ground surface. When modeling contact problems, such as robotic grasping, you can use the Spatial Contact Force block to simulate forces between a pair of bodies.
To measure the relative motions between bodies, you can use the Transform Sensor block. To measure forces and torques, you can use blocks in the Constraints, Joints, and Forces and Torques libraries. The loads on the bodies at the joints can be measured at the joint blocks, and a constraint block can sense the forces and torques that maintain the constraint between a pair of bodies. Each of these quantities help you answer important questions as you analyze the multibody dynamics of the mechanical system.
|Prismatic Joint||Joint with one prismatic primitive|
|Revolute Joint||Joint with one revolute primitive|
|Spherical Joint||Joint with one spherical primitive|
|Weld Joint||Joint with zero primitives|
|Bearing Joint||Joint with one prismatic and three revolute primitives|
|Bushing Joint||Joint with three prismatic and three revolute primitives|
|Cartesian Joint||Joint with three prismatic primitives|
|Cylindrical Joint||Joint with one prismatic and one revolute primitives possessing parallel motion axes|
|Gimbal Joint||Joint with three revolute primitives|
|Pin Slot Joint||Joint with one prismatic and one revolute primitives possessing mutually orthogonal motion axes|
|Planar Joint||Joint with one revolute and two prismatic primitives|
|Rectangular Joint||Joint with two prismatic primitives|
|6-DOF Joint||Joint with one spherical and three prismatic primitives|
|Telescoping Joint||Joint with one prismatic and one spherical joint primitive|
|Universal Joint||Joint with two revolute primitives|
|External Force and Torque||General force and torque arising outside the modeled system|
|Gravitational Field||Field of force due to point mass|
|Internal Force||General force acting reciprocally between two frame origins|
|Inverse Square Law Force||Force proportional to the inverse square distance between two frame origins|
|Magic Formula Tire Force and Torque||Apply steady-state tire force and torque by using Magic Formula tire equations|
|Spatial Contact Force||Apply contact forces between a pair of connected bodies|
|Spring and Damper Force||Force proportional to the distance and relative velocity between two frame origins|
Simulate a four-bar model at different coupler link lengths and plot the resulting coupler curves.
Dynamic variables that you can sense and blocks that you can use to sense them.
Use the Transform Sensor block to sense frame motion in a simple multibody model.
Use the sensing capability of a joint block to sense the internal forces acting on a mechanical link.
Use the sensing capability of joint blocks to measure the forces and torques acting at a joint.
Use the Spatial Contact Force block to model normal and frictional forces between solid blocks.
Use the Spatial Contact Force block to model the wheels of a car rolling down a ramp.
Assemble a system of gravitationally-bound free bodies using Cartesian Joint and Gravitational Field blocks.
Use the actuation capability of joint blocks to specify the trajectory of frame.
Use the actuation capability of a joint block to specify the actuation torque on a joint.
Use the actuation capability of joint blocks to specify the trajectory of a frame.
Use contact proxies to increase the speed and robustness of contact simulations.
Using physical signals to specify actuation inputs and obtain sensing outputs.
Restrictions and special considerations for models with motion actuation inputs in joint blocks.
Workflow steps for setting and sensing dynamic quantities such as force, torque, position, and more.
Modeling the effects of uniform gravity, gravitational fields, and individual gravitational forces. Software definition of body boundaries and its impact on gravitational torques.
Joint actuation modes, motion input handling, and key differences between model assembly and simulation.
Forces and torques that you can sense and the blocks that you can use to sense them.
Measurement frame definition and summary of measurement frame types.
Motion variables that you can sense and the blocks that you can use to sense them.
Rotational motion variables that you can sense and the blocks that you can use to sense them.
Translational variables that you can sense and the blocks that you can use to sense them.