Inertia Sensor

Sensor to measure the inertial properties of body groups or mechanisms

Libraries:
Simscape / Multibody / Body Elements

Description

Use the Inertia Sensor block to measure the inertial properties for collections of body elements in the Simscape Multibody model. Parameters that the Inertia Sensor block can measure include:

Mass
Center of mass
Inertia matrix
Centered inertia matrix
Principal inertia matrix
Orientation of principal inertia frame

A body group is the set of all body elements that are connected to each other directly or through rigid transforms. The body group may include solid blocks, inertia blocks, variable mass blocks, or flexible body blocks. By default, two body elements that are connected by a joint block are not considered to be a part of the same body group.

A mechanism is the set of all connected body elements within the model. With mechanisms, you can choose to exclude grounded bodies by enabling the Exclude Grounded Bodies parameter. A grounded body is any rigid body that is rigidly connected to a World Frame block.

Ports

Input

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S — Sensor port
frame

Sensor port to attach to a frame in the model. Use this port to determine which body group or mechanism is measured.

M — Custom measurement frame port
frame

When Custom is selected, a second port, M, appears on the Inertia Sensor block. The Inertia Sensor block measures inertial properties relative to the frame connected to the M port.

Dependencies

To enable this port, set the Measurement Frame parameter to Custom.

Output

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m — Mass
scalar

Total mass for the collection of body elements.

Dependencies

To enable this port, select the Mass check box.

com — Center of Mass
vector

The center of mass for the collection of body elements.

Dependencies

To enable this port, select the Center of Mass check box.

I — Inertia Matrix
matrix

The inertia matrix for the collection of body elements.

Dependencies

To enable this port, select the Inertia Matrix check box.

Ic — Centered Inertia Matrix
matrix

The centered inertia matrix for the collection of body elements.

Dependencies

To enable this port, select the Centered Inertia Matrix check box.

Ip — Principal Inertia Matrix
matrix

The principal inertia matrix for the collection of body elements.

Dependencies

To enable this port, select the Principal Inertia Matrix check box.

R — Rotation Matrix
matrix

The rotation matrix for orientation of principal inertia frame relative to measurement frame.

Dependencies

To enable this port, select the Rotation Matrix check box.

Parameters

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Sensor Extent

Sensor Extent — Determine the extent that the Inertia Sensor block measures
`Body Group` (default) | `Mechanism`

Extent that the Inertia Sensor block measures, defined as Body Group or Mechanism.

Body Group: When Body Group is selected, the Inertia Sensor block measures inertial properties for the collection of body elements that are connected to each other directly or through rigid transforms. This includes solid, inertia, variable mass, or flexible bodies.
Mechanism: When Mechanism is selected, the Inertia Sensor block measures inertial properties for all connected body elements within the model.

Sensor Extent: Span Weld Joints — Include bodies connected by weld joints in a body group
`cleared` (default) | checked

If selected, this option causes body groups to include body elements that are connected via a weld joint.

Dependencies

To enable this option, set Sensor Extent to Body Group.

Sensor Extent: Exclude Grounded Bodies — Do not measure inertial properties of grounded bodies
`cleared` (default) | checked

If selected, this option causes the Inertia Sensor block to measure inertial properties for the collection of body elements connected to the same mechanism as the Inertia Sensor block excluding any grounded bodies.

Dependencies

To enable this option, set Sensor Extent to Mechanism.

Measurement Frame — Determine the frame that the Inertia Sensor block uses for measurements
`Attached` (default) | `World` | `Custom`

The measurement frame specifies the frame the sensor uses to measure the center of mass, inertia matrix, and centered inertia matrix.

Attached: When Attached is selected, the Inertia Sensor block measures inertial properties relative to the same frame that is connected to the S port.
World: When World is selected, the Inertia Sensor block measures inertial properties relative to the World Frame.
Custom: When Custom is selected, the M port is exposed. The Inertia Sensor block measures inertial properties relative to the frame connected to the M port.

Mass — Total mass of measured bodies
`cleared` (default) | checked

Select the Mass check box to measure the mass of the collection of body elements.

Center of Mass — Center of mass coordinates
`cleared` (default) | checked

Select the Center of Mass check box to measure the center of mass of the collection of body elements, output as a 3-by-1 vector relative to the measurement frame. If the mass of the measured body group or mechanism is zero, the center of mass is undefined and a runtime error occurs.

Inertia Matrix — Measurement of the inertia tensor
`cleared` (default) | checked

Select the Inertia Matrix check box to measure the inertia tensor of the collection of body elements, output as a 3-by-3 matrix relative to the measurement frame.

Centered Inertia Matrix — Measurement of the inertia tensor relative to the centered frame
`cleared` (default) | checked

Select the Centered Inertia Matrix check box to measure the inertia tensor of the collection of body elements, output as a 3-by-3 matrix relative to the centered frame. The centered frame is a frame whose origin coincides with the center of mass and whose axes are aligned with those of the measurement frame. If the mass of the measured body group or mechanism is zero, the centered inertia matrix is undefined and a runtime error occurs.

Principal Inertia Matrix — Measurement of the inertia tensor with respect to the principal inertia frame
`cleared` (default) | checked

Select the Principal Inertia Matrix check box to measure the inertia tensor of the collection of body elements, output as a 3-by-3 matrix with respect to the principal inertia frame. The principal inertia matrix is a diagonal matrix.

The principal inertia frame is a frame with an origin that coincides with the center of mass and axes that are aligned with the principal axes of inertia. If the mass of the measured body group or mechanism is zero, the principal inertia matrix is undefined and a runtime error occurs.

Rotation Matrix — Orientation of the principal inertia frame
`cleared` (default) | checked

Select the Rotation Matrix check box to measure the orientation of the principal axes of inertia with respect to the measurement frame as a 3-by-3 matrix. In other words, the rotation matrix maps vectors in the principal inertia frame to the vectors in the measurement frame.

If the mass of the measured body group or mechanism is zero, the rotation matrix is undefined and a runtime error occurs.

Graphic

Type — Sensor visualization setting
`Principal Inertia Frame` (default) | `Equivalent Inertia Ellipsoid` | `None`

Display of the inertial properties for the sensed collection of body elements, specified as Principal Inertia Frame, Equivalent Inertia Ellipsoid, or None.

Set the parameter to Principal Inertia Frame to represent the sensed inertial properties as the principal inertia frame. The principal inertia frame is a frame with an origin that coincides with the center of mass and axes that are aligned with the principal axes of inertia.

Set the parameter to Equivalent Inertia Ellipsoid to represent the inertia properties as an ellipsoid that has the same mass, moments, and products of inertia as the group of bodies being sensed.

Set the parameter to None to hide the visualization of the sensed inertia properties.

Size — Display size for the principal inertia frame
20 `pixels` (default) | positive scalar

Display size for the principal inertia frame, specified as a positive scalar.

Dependencies

To enable this parameter, set Type to Principal Inertia Frame.

Visual Properties — Parameterizations for color and opacity
`Simple` (default) | `Advanced`

Parameterizations for specifying visual properties. Select Simple to specify Diffuse Color and Opacity. Select Advanced to specify more visual properties, such as Specular Color, Ambient Color, Emissive Color, and Shininess.

Dependencies

To enable this parameter, set Type to Principal Inertia Frame or Equivalent Inertia Ellipsoid.

Diffuse Color — Color of light due to diffuse reflection
[0.5 0.5 0.5] (default) | 3-by-1 or 1-by-3 vector with values in the range of 0 to 1 | 4-by-1 or 1-by-4 vector with values in the range of 0 to 1

Color of the light due to diffuse reflection, specified as an [R,G,B] or [R,G,B,A] vector with values in the range of 0 to 1. The vector can be a row or column vector. The optional fourth element specifies the color opacity. Omitting the opacity element is equivalent to specifying a value of 1.

The diffuse color reflects the main color of the graphic and provides shading that gives the rendered object a three-dimensional appearance.

Dependencies

To enable this parameter, set Type to Principal Inertia Frame or Equivalent Inertia Ellipsoid.

Opacity — Graphic opacity
1.0 (default) | scalar in the range of 0 to 1

Graphic opacity, specified as a scalar in the range of 0 to 1. A scalar of 0 corresponds to completely transparent, and a scalar of 1 corresponds to completely opaque.