Modeling Multibody Systems

SimMechanics enables you to create libraries of components that can be reused in many different designs. You define bodies in terms of their mass, inertia, and connection points. To create complex shapes, you assemble sets of simple geometries, such as spheres, cylinders, and extrusions defined in MATLAB, and SimMechanics calculates the resulting mass and inertia automatically. The diagram that defines the body clearly indicates all connections to the body, making it easy to see your system’s topology. Parameters such as length and mass can be calculated using MATLAB scripts and assigned using MATLAB variables.

Parameterizing Bodies 5:42
Parameterize bodies with MATLAB® variables. Reuse components and mechanisms to build a scissor lift.

You connect bodies using joints and constraints. These define the degrees of freedom permitted between the bodies in your system, which dictate how your system can move. You can define and connect actuators to these joints to enable your system to move. Actuating these joints with electrical, hydraulic, pneumatic, or other physical systems modeled using Simscape enables you to model your entire multidomain physical system within the Simulink environment.

Actuating and Sensing Joints 4:49
Actuate joints and send measured values to Simulink® scopes. A hydraulic system modeled in Simscape™ actuates a scissor lift.

SimMechanics models can be connected to control systems modeled in Simulink and Stateflow®. You can measure quantities such as force, torque, and velocity, and pass this information to Simulink blocks. Motion, force, and other results calculated in Simulink can be used to control your mechanical system.

SimMechanics model of four-bar linkage components.
SimMechanics model of four-bar linkage components. Links are composed of connected solids (left) that are defined by a preselected shape (bottom) and MATLAB variables; components are connected by joints with specified state targets (right).
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Landing Gear Actuator Design with Simscape

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