MEMS+ System Simulation in Simulink

Control engineers and system Architects commonly use Simulink from Mathworks to design MEMS control loops and signal processing circuits. In order to succeed, they require a fast and accurate model of the MEMS device in the Simulink simulation environment. MEMS system simulations are essential for controller and filter design and to predict yield sensitivity to manufacturing variations.

system-simulation

MEMS+ for Simulink lets you create the required device model by simply importing a 3-D model from MEMS+ Innovator. MEMS+ created models can be inserted into larger systems made of components from the standard Simulink library or user defined components. MEMS+ created models are based on Coventor’s powerful MEMS+ model library and go far beyond first order approximations. MEMS+ in Simulink give you real world answers to real world problems: What if other modes of motion interfere with the measurement of the desired mode to control or sense? Is the device control loop able to recover from severe shock? What if the device hits the stops? What if the device topology changes, or the dimensions change considerably?

All MEMS+ created Simulink models are inherently parametric. Any number of material, process or geometrical variables set as “exposed” in the Innovator schematic are preserved in the created Simulink symbol:

simulink-parameters

In addition, Innovator’s MEMS modeling environment gives the user the full control over the number and names of the symbol pins created during the MEMS+ model import. MEMS+ for Simulink supports voltage, force, torque, pressure load, acceleration and angular rate input pins and capacitance, resistance, position and angle output pins:

In the example above, the user has exposed as inputs for system simulation: the x and y acceleration of the reference frame (this is a 2-axis accelerometer) and the voltage for the separate stator combs and the proof mass (V_Rotors). And for outputs the user has exposed the 4 capacitances between the proof mass and four stator combs. For purely diagnostic purposes, a point on the model has been exposed for direct application of a force input and a position output (M1x, M1y)

Description
Once the 3-D model is created in MEMS+, it is ready for simulation. MEMS+ automatically creates the symbol for system simulation in Simulink. The models can be parameterized for materials, process and geometry, which means you never have to recreate the model in case of changes . MEMS+ for Simulink expands the analysis capabilities available in Simulink from pure transient simulations to DC, DC transfer, Modal and AC analysis without requiring an additional tool box from MathWorks. MATLAB or Simulink simulation results can be loaded back into the MEMS+ Scene3D module for 3-D viewing.

 

Features of MEMS+ for Simulink

  • MEMS+ GUI in the Simulink for automatic parametric model creation
  • User defined number of symbol pins and parameters
  • Fast system simulations
  • Accurate multi-physics modeling
  • Enables DC, DC Transfer, modal, AC in addition to transient simulations

 

MEMS+ Simulink Design Flow

The MEMS+ for Simulink design flow includes the following steps:

  1. Identical to the MEMS+ Cadence workflow, first construct the high order finite elements in the MEMS+ 3-D user interface by selecting building blocks from the library of parameterized MEMS components. As part of this process, the MEMS designer can specify which parameters will be exposed in the MATLAB Simulink environment.
  2. After completion, import the MEMS+ designs into Simulink by simply selecting the created MEMS+ design in the Simulink menu. MEMS+ automatically generates a symbol and places it into the Simulink model editor window.
  3. Incorporate the MEMS+ generated symbols into a larger system of user-defined components or components from the standard Simulink library. For the MEMS designer, there may be only a few other components in the schematic necessary to provide electrical or mechanical excitation. For the system architect, however, the schematic will include complete feedback loops or designs for MEMS signal processing.
  4. Run a simulation or co-simulation using Simulink’s build-in transition solvers. The simulator will connect, via Simulink’s S-function interface, with the MEMS+ component library to evaluate the MEMS high order finite elements at each time step. In addition to standard transient simulations, MEMS+ provides additional analysis such as DC, DC transfer, Modal and AC analysis.
  5. On completion of a simulation, view the simulation results in MEMS+ Scene3D (shown in the diagram as a separate window, but in fact one and the same as the MEMS+ design view above). With Scene3D, simulation results can be visualized as 2-D graphs or as fully contoured three-dimensional animations.

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