ModalysObjects > Object Reference > Rectangular Membrane - Fixed
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Rectangular Membrane - Fixed

Description

A rectangular membrane with a thickness of zero, fixed at the edges.

(make-object 'rect-membrane ... )

Lisp Syntax and Default Values

A 'rect-membrane can be created using the following Lisp syntax (the default values are shown for each of the physical parameters):

(make-object 'rect-membrane

(modes 80)

(length0 .5)

(length1 .5)

(tension 1000)

(surface-density .1)

(freq-loss 10)

(const-loss 10))

Parameters

The arguments for the physical parameters can be either numerical values or Modalys controllers (either dynamic or constant). If a given parameter is not supplied when using the Lisp syntax, the default parameter value will be used.

• modes: number of modes.
• length0: length along the x-axis in meters.
• length1: length along the y-axis in meters.
• tension: in Newtons.
• surface-density: surface density in kg. NB: was named "mass" in older versions of Modalys.
• freq-loss, const-loss: loss coefficients. See General object information.

Note that, unlike other objects, the values for freq-loss and const-loss default to 10 for this object.

Accesses

A rectangular membrane can be accessed in its z-direction ('normal) from any point on its surface.

(make-access my-membrane my-2D-controller 'normal)

This makes an up-and-down access (in the z direction) at a point on the surface of my-membrane. The point is defined by my-2D-controller where the first dimension is x and the second is y (the membrane's corners being the points (0, 0), (0, 1), (1, 0) and (1, 1)). For example, in order to access the center of the plate we can say:

(make-access my-membrane (const 0.5 0.5) 'normal)

Options

Tuning

A rect-membrane can be tuned to a specific pitch, using the (set-pitch ...) function, by adjusting one of the following physical parameters:

• 'size
• 'tension
• 'mass

Note that for 'size, both the x and y dimensions are scaled together proportionally in order to preserve the harmonic relationships the membrane's mode frequencies.

(setq my-membrane (make-object 'rect-membrane))

(set-pitch my-membrane 'size (const 110))

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