SimMechanics 3.1.1

Modeling Mechanical Systems

With SimMechanics you build a model of a three-dimensional mechanical system just as you would assemble a physical system. Using bodies, coordinate systems, joints, and force elements, you define a mechanical system that can be connected directly to other Simulink models. This approach lets you expand the capabilities of SimMechanics and reuse existing Simulink models. You can save models that combine Simulink and SimMechanics blocks as subsystems for reuse in many applications.

These subsystems can include:

• Nonlinear springs that use Simulink look-up tables
• Aerodynamic drag models that attach pressure distributions to aerospace components, such as ailerons and rudders
• Active vehicle suspension subsystems, such as stabilization mechanisms and controllers
• Tire models for aircraft and ground vehicles

Using the sensor blocks in SimMechanics, you can measure values for different physical quantities such as force, torque, and velocity, and then pass these signals into standard Simulink blocks. Actuator blocks enable Simulink signals to assign values to any of these variables and actuate your mechanical system. Sensor and actuator blocks let you connect a control algorithm developed in Simulink to a SimMechanics model.

You can design the controller using the nonlinear plant model developed in SimMechanics. Alternatively, you can extract a linear plant model from the nonlinear model using Simulink Control Design™, enabling you to use linear control theory to design your controller.

SimMechanics model of a Stewart platform connected to a controller (near left, top). All six legs of the Stewart platform reuse the leg model (near left, bottom). Plots (far left) show the angle of the platform and the force required of one actuator. Click on image to see enlarged view.