Actuator in a System Simulation with Simulink®
Modeling an electromagnetic actuator in a systems context is sometimes required to accurately simulate the dynamic interaction between drive circuit, actuator, and load. Co-simulation, where a systems simulator and MagNet run parallel transient solves, is one method that can be used. An alternative approach, Response Surface Modeling (RSM), creates a functionally equivalent model of the actuator by performing a large number of static analyses at different currents and positions. Presented here is an example of an RSM is used in conjunction with the Simulink® system simulator from The MathWorks, Inc.. The procedure is automated with Infolytica's Actuator RSM Wizard, which drives MagNet to execute its static solver and generates a file containing the RSM data. A special plug-in to Simulink, the Actuator RSM Plug-in, reads this file and provides a system block that can be connected to the rest of the system.
Results:
|
| Click image to see full size version |
Shown here is the Simulink system diagram of the actuator and drive circuit. In this example, the coil is driven by a capacitor charged to 12 V. A spring holds the plunger against the upper stop. At time t=0, a switch closes to connect the charged capacitor to the coil. The RSM block has inputs for coil voltage (top) and external plunger force (bottom), and outputs for coil current (top), plunger position and velocity (center), and electromagnetic force (bottom). On the electrical side an integrator models the charged capacitor which discharges through the actuator's coil. On the mechanical side the spring, viscous damper, and upper and lower stops are modeled using appropriate Simulink blocks.
|
| Click image to see full size version |
The actuator model is shown at right in a cutaway view. Since this device has axial symmetry, the MagNet Static 2d solver is used to calculate force and flux-linkage at different positions and currents. (Note - This solver is also available in the
MagNet Trial Edition, which is a free download.) The solution setup to create the Response Surface Model (RSM) is automated with the use of the
Actuator RSM Wizard.
|
| Click image to see full size version |
The RSM of the force as a function of coil current and plunger position is shows at right. The response surface models for both flux and force were created using Infolytica's
Actuator RSM Wizard and required a total of 460 Magnetostatic 2d solutions.
|
| Click image to see full size version |
This graph shows the position of the plunger as a function of time. The complicated behaviour arises from the transfer of energy between the potential energy of the capacitor, the energy stored in the magnetic field, the potential energy in the spring, and the kinetic energy of the plunger.
|
| Click image to see full size version |
This system can be modeled directly in MagNet's Transient with Motion solver, as shown at right. The position is slightly different because MagNet can simulate an ideal bounce (instant velocity reversal), whereas a very large spring constant was used in Simulink. The small error at each bounce is amplified over time. Although the transient solution time is comparable to the time required to generate the RSM, the RSM allows changes in the drive circuit to be made and the result simulated almost instantly in Simulink.
Number of time steps: 600
Transient solution time: 6 minutes 12 seconds
Number of static solutions in RSM: 460
Static solution time (total): 5 minutes 10 seconds
Simulink simulation time: 0.2 seconds
Modeling an electromagnetic actuator in a systems context is sometimes required to accurately simulate the dynamic interaction between drive circuit, actuator, and load. Co-simulation, where a systems simulator and MagNet run parallel transient solves, is one method that can be used. An alternative approach, )
)
)
)
)