Implement three-axis inertial measurement unit (IMU)
GNC/Navigation
The Three-Axis Inertial Measurement Unit block implements an inertial measurement unit (IMU) containing a three-axis accelerometer and a three-axis gyroscope.
For a description of the equations and application of errors, see the Three-Axis Accelerometer block and the Three-Axis Gyroscope block reference pages.
Specifies the input and output units:
Units | Acceleration | Length |
---|---|---|
Metric (MKS) | Meters per second squared | Meters |
English | Feet per second squared | Feet |
The location of the IMU, which is also the accelerometer group location, is measured from the zero datum (typically the nose) to aft, to the right of the vertical centerline and above the horizontal centerline. This measurement reference is the same for the center of gravity input. The units are in selected length units.
Specify the update rate of the accelerometer and gyroscope. An update rate of 0 will create a continuous accelerometer and continuous gyroscope. If noise is selected and the update rate is 0, then the noise will be updated at the rate of 0.1. The units of update rate are seconds.
If you:
Update this parameter value to 0 (continuous)
Configure a fixed-step solver for the model
Do not have a Control System Toolbox™ license
you must also select the Automatically handle rate transition for data transfer check box in the Solver pane. This check box enables the software to handle rate transitions correctly.
Select to apply second-order dynamics to acceleration readings.
The natural frequency of the accelerometer. The units of natural frequency are radians per second.
The damping ratio of the accelerometer. A dimensionless parameter.
The 3-by-3 matrix used to skew the accelerometer from body-axis and to scale accelerations along body-axis.
The three-element vector containing long-term biases along the accelerometer axes. The units are in selected acceleration units.
The six-element vector containing three minimum values and three maximum values of acceleration in each of the accelerometer axes. The units are in selected acceleration units.
Select to apply second-order dynamics to gyroscope readings.
The natural frequency of the gyroscope. The units of natural frequency are radians per second.
The damping ratio of the gyroscope. A dimensionless parameter.
The 3-by-3 matrix used to skew the gyroscope from body axes and to scale angular rates along body axes.
The three-element vector containing long-term biases along the gyroscope axes. The units are in radians per second.
The three-element vector contains the maximum change in rates due to linear acceleration. The units are in radians per second per g-unit.
The six-element vector containing three minimum values and three maximum values of angular rates in each of the gyroscope axes. The units are in radians per second.
Select to apply white noise to acceleration and gyroscope readings.
The scalar seeds for the Gaussian noise generator for each axis of the accelerometer and gyroscope.
The height of the PSD of the white noise for each axis of the accelerometer and gyroscope.
Input | Dimension Type | Description |
---|---|---|
First | Three-element vector | Contains the actual accelerations in body-fixed axes, in selected units. |
Second | Three-element vector | Contains the angular rates in body-fixed axes, in radians per second. |
Third | Three-element vector | Contains the angular accelerations in body-fixed axes, in radians per second squared. |
Fourth | Three-element vector | Contains the location of the center of gravity, in selected units. |
Fifth | Three-element vector | Contains the gravity in body axis, in selected units. |
Output | Dimension Type | Description |
---|---|---|
First | Three-element vector | Contains the measured accelerations from the accelerometer, in selected units. |
Second | Three-element vector | Contains the measured angular rates from the gyroscope, in radians per second. |
Vibropendulous error, hysteresis affects, anisoelastic bias and anisoinertial bias are not accounted for in this block. Additionally, this block is not intended to model the internal dynamics of different forms of the instrument.
Note: This block requires the Control System Toolbox product for discrete operation (nonzero sample time). |
See asbhl20
for
an example of this block.
Rogers, R. M., Applied Mathematics in Integrated Navigation Systems, AIAA Education Series, 2000.