PHM 6DOF Block Documentation

Toolbox: RflySim PHM

Overview

Summary: This block connects the PHM fault-model bus to a quaternion-based six-degree-of-freedom rigid-body model, enabling the calculation of vehicle position, attitude, velocity, and environmental states in fault injection and health assessment simulations.

The PHM 6DOF block contains an environment model and a quaternion-based rigid-body six-degree-of-freedom model. The environment model simulates the effects of gravity, atmospheric pressure, and the GPS origin on flight states; the rigid-body model describes the translational and rotational motion of the unmanned vehicle in the body frame and the Earth coordinate system.

Compared with the basic 6DOF block in the RflySim Model library, this block additionally provides a Fail Model Bus input for receiving mass, inertia, payload, environmental disturbance, or other fault-related quantities generated by the PHM fault injection chain, allowing the dynamic states to reflect the impact of faults on vehicle motion.

Ports

Inputs

Port	Data type	Dimension	Description
Force and Moment Model Bus	Bus	-	Force and moment model bus that provides the resultant body-frame force and torque
Fail Model Bus	Bus	-	PHM fault-model bus carrying fault quantities that affect dynamics after injection
fColi	double	1x6	Collision and friction force/torque vector in the body frame; typically connected to a zero vector when no collision model is used
Wind	double	1x3	Wind disturbance vector in the Earth or NED frame; typically connected to a zero vector when no wind model is used

Outputs

Port	Data type	Dimension	Description
6DOF Bus	Bus	-	Six-degree-of-freedom state bus encapsulating body velocity and acceleration, Earth-frame velocity, position, Euler angles, direction cosine matrix, angular rate, angular acceleration, and GPS/environment quantities

Parameters

The following parameters can be configured in the Mask dialog opened by double-clicking the block:

Parameter	Default value	Description
Init_PosE	ModelInit_PosE	Initial position in the Earth or NED frame
Init_VelB	ModelInit_VelB	Initial velocity in the body frame
Init_AngEuler	ModelInit_AngEuler	Initial Euler angles
Init_RateB	ModelInit_RateB	Initial angular rate in the body frame
Param_uavMass	ModelParam_uavMass	Vehicle mass
Param_uavJ	ModelParam_uavJ	Vehicle inertia matrix
Param_GPSLatLong	ModelParam_GPSLatLong	GPS origin latitude and longitude
Param_envAltitude	ModelParam_envAltitude	GPS origin altitude

Block Characteristics

Item	Value
Block type	Masked Subsystem
Mask Type	6DOF API
Direct feedthrough	No
Data communication protocol	No network communication involved

Usage

1. Initialize the ModelInit_* and ModelParam_* variables in the MATLAB workspace.
2. Connect the force and moment model output to Force and Moment Model Bus.
3. Connect the PHM fault injection chain output to Fail Model Bus.
4. If no collision or wind model is used, connect zero vectors to fColi and Wind respectively.
5. Connect the 6DOF Bus output to sensor, visualization, flight-controller interface, or health-assessment modules.

Notes and Frequently Asked Questions

• Bus structure consistency: Force and Moment Model Bus and Fail Model Bus must match the bus structures defined in the library; otherwise, simulation initialization will fail.
• Parameter initialization: The default parameter values reference MATLAB workspace variables, which must be assigned in the model initialization script before use.
• Closed fault chain: When using payload, inertia, or wind disturbance faults, ensure the corresponding fault quantities correctly enter Fail Model Bus; otherwise, the faults will not be reflected in the dynamic states.
• Frame convention: Inputs and outputs follow the body-frame and NED/Earth-frame conventions commonly used by RflySim. Coordinate consistency must be maintained when connecting custom external modules.

Changelog

• v4.10 (2026-05-07): Added the PHM 6DOF block help document and connected it to the Simulink Help button index.