3DOF Acceleration

R2026b

Compute acceleration of body in three-degrees-of-freedom motion

Since R2025a

• 

3DOF Acceleration block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Aerospace Blockset / Equations of Motion / 3DOF

Description

The 3DOF Acceleration block computes the acceleration of a body in three-degrees-of-freedom motion with respect to body-fixed coordinate frame and inertial (flat Earth) coordinate frame.

To compute the acceleration for equations of motions blocks:

• Select Output mass properties for acceleration computation.

• Feed signals from the matching output ports of the associated 3DOF equation of motion block into the associated input ports of 3DOF Acceleration.

Tip

Match all the parameter values for 3DOF Acceleration and the 3DOF equations of motion blocks.

Ports

Input

θ — Pitch altitude

scalar

Pitch attitude, within ±pi, specified as a scalar, in radians.

Dependencies

To enable this port, set Axes to Body.

Data Types: double

γ — Flight path angle

scalar

Flight path angle, within ±pi, specified as a scalar, in radians.

Dependencies

To enable this port, set Axes to Wind.

Data Types: double

q — Pitch angular rate

scalar

Pitch angular rate, specified as a scalar, in radians per second.

Data Types: double

V_w — Velocity in wind-fixed frame

two-element vector

Velocity of the body resolved into the wind-fixed coordinate frame, (V, 0), returned as a two-element vector, in the units selected in Units.

Dependencies

To enable this port, set Axes to Wind.

Data Types: double

U w — Velocity of body

two-element vector

Velocity of the body resolved into the body-fixed coordinate frame, (u, w), specified as a two-element vector, in the units selected in Units.

Dependencies

To enable this port, set Axes to Body.

Data Types: double

α — Angle of attack

scalar

Angle of attack, returned as a scalar, in radians.

Dependencies

To enable this port, set Axes to Wind.

Data Types: double

g — Gravity

scalar

Gravity, specified as a scalar, in the units selected in Units.

Data Types: double

Fuel — Fuel tank status

scalar

Fuel tank status, specified as:

• 1 — Tank is full.

• 0 — Tank is neither full nor empty.

• -1 — Tank is empty.

Dependencies

To enable this port, set Mass type to Simple Variable.

Data Types: double

m — Mass

scalar

Mass, specified as a scalar, in the units selected in Units.

Data Types: double

F_x — Applied force along x-axis

scalar

Applied force along the body x-axis, specified as a scalar, in the units selected in Units.

Data Types: double

F_z — Applied force along z-axis

scalar

Applied force along the body z-axis, specified as a scalar, in the units selected in Units.

Data Types: double

dm/dt — Rate of change of mass

scalar

Rate of change of mass (positive if accreted, negative if ablated), specified as a scalar, in the units selected in Units.

Dependencies

To enable this port:

• Set Mass type to Simple Variable or Custom Variable.

• Select Include mass flow relative velocity.

Data Types: double

I — Inertia tensor

scalar

Inertia tensor, specified as a scalar, in the units selected in Units.

Dependencies

To enable this port, set Mass type to Custom Variable.

Data Types: double

V_re — Relative velocity

two-element vector

Relative velocity at which mass is accreted to or ablated from the body in body-fixed axes, specified as a two-element vector, in the units selected in Units.

Dependencies

To enable this port:

• Set Mass type to Simple Variable or Custom Variable.

• Select Include mass flow relative velocity.

Data Types: double

Output

A_xbA_zb — Acceleration of body

two-element vector

Acceleration of the body with respect to the body-fixed coordinate frame, (Ax, Az), returned as a two-element vector, in the units selected in Units.

Data Types: double

A_xeA_ze — Acceleration of body

two-element vector

Accelerations of the body with respect to the inertial (flat Earth) coordinate frame, returned as a two-element vector, in the units selected in Units. You typically connect this signal to the accelerometer.

Data Types: double

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Units — Input and output units

Metric (MKS) (default) | English (Velocity in ft/s) | English (Velocity in kts)

Input and output units, specified as Metric (MKS), English (Velocity in ft/s), or English (Velocity in kts).

Units	Forces	Moment	Acceleration	Velocity	Position	Mass	Inertia
Metric (MKS)	Newton	Newton-meter	Meters per second squared	Meters per second	Meters	Kilogram	Kilogram meter squared
English (Velocity in ft/s)	Pound	Foot-pound	Feet per second squared	Feet per second	Feet	Slug	Slug foot squared
English (Velocity in kts)	Pound	Foot-pound	Feet per second squared	Knots	Feet	Slug	Slug foot squared

Programmatic Use

Block Parameter: units

Type: character vector

Values: Metric (MKS) | English (Velocity in ft/s) | English (Velocity in kts)

Default: Metric (MKS)

Mass type — Mass type

Fixed (default) | Simple Variable | Custom Variable

Mass type, specified according to the following table.

Mass Type	Description	Default for
Fixed	Mass is constant throughout the simulation.	3DOF (Body Axes) 3DOF (Wind Axes)
Simple Variable	Mass and inertia vary linearly as a function of mass rate.	Simple Variable Mass 3DOF (Body Axes) Simple Variable Mass 3DOF (Wind Axes)
Custom Variable	Mass and inertia variations are customizable.	Custom Variable Mass 3DOF (Body Axes) Custom Variable Mass 3DOF (Wind Axes)

Programmatic Use

Block Parameter: mtype

Type: character vector

Values: Fixed | Simple Variable | Custom Variable

Default: 'Fixed'

Axes — Body or wind axes

Body (default) | Wind

Body or wind axes, specified as Wind or Body.

Programmatic Use

Block Parameter: axes

Type: character vector

Values: Wind | Body

Default: Body

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"aerolib3dof2/3DOF Acceleration"

Example: add_block("aerolib3dof2/3DOF Acceleration","myModel/myBlock",MakeNameUnique="on")

Version History

Introduced in R2025a