Motion Platform

Motion platform

Library

Environment and Target

phasedenvlib

• 

Description

The Motion Platform block models the motion of multiple platforms such as airplanes, ground vehicles, and/or receiving and transmitting sensors arrays, determining their positions and velocities. The platforms move along trajectories determined by initial positions and velocities, according to which motion model you choose — the velocity or acceleration model. The platform positions and velocities are updated at each simulation step. In addition, you can specify initial orientations for the platforms and obtain orientation updates.

Parameters

Model of object motion

Object motion model, specified as Velocity, Acceleration, or Custom. When you set this parameter to Velocity, the platform follows a constant velocity trajectory during each simulation step. When you set this parameter to Acceleration, the platform follows a constant acceleration trajectory during each simulation step. When you set the parameter to Custom, the platform motion follows a sequence of waypoints specified by the Custom trajectory waypoints parameter. The object performs a piecewise cubic interpolation on the waypoints to derive the position and velocity at each time step.

Initial position (m)

Specify the initial position of the platform in meters as a 3-by-N matrix where each column represents the initial position of a platform in the form [x;y;z]. The quantity N is the number of platforms.

Initial velocity (m/s)

Specify the initial velocity of the platform in m/s as a 3-by-N matrix where each column represents the initial velocity of a platform in the form [vx;vy;vz]. The quantity N is the number of platforms. This parameter appears only when you set the Source of velocity or the Source of acceleration parameters to Input port.

Source of velocity

This parameter appears only when you set the Model of object motion parameter to Velocity. Then, you must supply velocity data for the model. Specify the Source of velocity data as either coming from a Property or an Input port.

Source of velocity	Use these model parameters or ports
Property	Initial position (m) parameter Velocity (m/s) parameter
Input port	Initial position (m) parameter Initial velocity (m/s) parameter Vel input port

Velocity (m/s)

Specify the current velocity of the platforms in m/s as a 3-by-N matrix where each column represents the current velocity of a platform in the form [vx;vy;vz]. This parameter appears only when you set the Model of object motion parameter to Velocity and set the Source of velocity parameter to Property.

Source of acceleration

This parameter appears only when you set the Model of object motion parameter to Acceleration. Then, you must supply acceleration values for the model. Specify the Source of acceleration data as either coming from a Property or an Input port.

Source of acceleration	Use these model parameters or ports
Property	Initial Position (m) parameter Initial Velocity (m/s) parameter Acceleration (m/s^2) parameter
Input port	Initial Position (m) parameter Initial Velocity (m/s) parameter Acl input port

Acceleration (m/s^2)

Specify the current acceleration of the platforms in m/s^2 as a 3-by-N matrix where each column represents the current acceleration of a platform in the form [ax;ay;az]. This parameter appears when you set the Model of object motion parameter to Acceleration and set the Source of acceleration parameter to Property.

Custom trajectory waypoints

Custom trajectory waypoints, specified as a real-valued M-by-L matrix, or M-by-L-by-N array. M is the number of waypoints. L is either 4 or 7.

• When L is 4, the first column indicates the times at which the platform position is measured. The 2^nd through 4^th columns are position measurements in x, y, and z coordinates. The velocity is derived from the position measurements.

• When L is 7, the 5th through seven^th columns in the matrix are velocity measurements in x, y, and z coordinates.

When you set the Custom trajectory waypoints parameter to a three-dimensional array, the number of pages, N, represent the number of platforms. Time units are in seconds, position units are in meters, and velocity units are in meters per second.

To enable this property, set the Model of object motion property to Custom.

Mechanical scanning mode

Mechanical scan mode for platform, specified as None, Circular, or Sector, where None is the default. When you set the Mechanical scanning mode parameter to Circular, the platform scan clockwise 360 degrees continuously in the azimuthal direction of the platform orientation axes. When you set the Mechanical scanning mode parameter to Sector, the platform scans clockwise in the azimuthal direction in the platform orientation axes within a range specified by the Azimuth scan angle span (deg) parameter. When the platform scan reaches the span limits, the scan reverses direction and scans back to the other scan limit. Scanning happens within the orientation axes of the platform.

Initial scan angle (deg)

Initial scan angle of platform, specified as a 1-by-N vector where N is the number of platforms. The scanning occurs in the local coordinate system of the platform. The Initial orientation axes parameter specifies the original local coordinate system. At the start of the simulation, the orientation axes specified by the Initial orientation axes are rotated by the angle specified in the InitialScanAngle Initial scan angle (deg) parameter. The default value is zero. Units are in degrees. This parameter applies when you set the Mechanical scanning mode parameter to Circular or Sector.

Azimuth scan angle span (deg)

The azimuth angle span, specified as an N-by-2 matrix where N is the number of platforms. Each row of the matrix specifies the scan range of the corresponding platform in the form [ScanAngleLowerBound ScanAngleHigherBound]. The default value is [-60 60]. Units are in degrees. To enable this parameter, set the Mechanical scanning mode parameter to Sector.

Azimuth scan rate (deg/s)

Azimuth scan rate, specified as a 1-by-N vector where N is the number of platforms. Each entry in the vector is the azimuth scan rate for the corresponding platform. The default value is 10 degrees/second. Units are in degrees/second. To enable this parameter, set the Mechanical scanning mode parameter to Circular or Sector.

Initial orientation axes

Specify the three axes that define the initial local (x,y,z) coordinate system at the platform as a 3-by-3-by-N matrix. Each column of the matrix represents an axis of the local coordinate system. The three axes must be orthonormal.

Enable orientation axes output

Select this check box to obtain the instantaneous orientation axes of the platform via the output port LAxes. The port appears only when the check box is selected.

Source of elapsed simulation time

Specify the source for elapsed simulation time as Auto or Derive from reference input port. When you choose Auto, the block computes the elapsed time. When you choose Derive from reference input port, the block uses the time duration of a reference signal passed into the Ref input port.

Inherit sample rate

Select this check box to inherit the sample rate from upstream blocks. Otherwise, specify the sample rate using the Sample rate (Hz) parameter.

Sample rate (Hz)

Specify the signal sampling rate (in hertz) as a positive scalar. This parameter appears only when the Inherit sample rate parameter is not selected.

Simulate using

Block simulation method, specified as Interpreted Execution or Code Generation. If you want your block to use the MATLAB^® interpreter, choose Interpreted Execution. If you want your block to run as compiled code, choose Code Generation. Compiled code requires time to compile but usually runs faster.

Interpreted execution is useful when you are developing and tuning a model. The block runs the underlying System object™ in MATLAB. You can change and execute your model quickly. When you are satisfied with your results, you can then run the block using Code Generation. Long simulations run faster than they would in interpreted execution. You can run repeated executions without recompiling. However, if you change any block parameters, then the block automatically recompiles before execution.

When setting this parameter, you must take into account the overall model simulation mode. The table shows how the Simulate using parameter interacts with the overall simulation mode.

When the Simulink^® model is in Accelerator mode, the block mode specified using Simulate using overrides the simulation mode.

Acceleration Modes

Block Simulation	Simulation Behavior
	Normal	Accelerator	Rapid Accelerator
Interpreted Execution	The block executes using the MATLAB interpreter.	The block executes using the MATLAB interpreter.	Creates a standalone executable from the model.
Code Generation	The block is compiled.	All blocks in the model are compiled.

For more information, see Choosing a Simulation Mode (Simulink).

Ports

Note

The block input and output ports correspond to the input and output parameters described in the step method of the underlying System object. See link at the bottom of this page.

Port	Description	Supported Data Types
Vel	Platform velocity input	Double-precision floating point
Acl	Platform acceleration input	Double-precision floating point
Ref	Reference signal input	Double-precision floating point
Pos	Platform position output	Double-precision floating point
Vel	Platform velocity output	Double-precision floating point
LAxes	Platform orientation output	Double-precision floating point