Mass and Additional Parts

This section defines how to specify mass information for UAV components and track additional parts that are not captured in the geometry or propulsion systems.

Overview

The Setuav Standard uses a simple approach for mass management:

• Geometry Components: Fuselage and wings can have an optional mass parameter (in grams)
• Propulsion Components: Motors, ESCs, propellers, and batteries all include mass parameters
• Additional Parts: Components outside geometry and propulsion (electronics, landing gear, etc.) are specified separately with mass and placement

Geometry Mass

Geometry components (Fuselage, Wing) can specify mass directly:

airframe:
  fuselage:
    tag: "main_fuselage"
    mass: 250  # grams (optional)
    geometry:
      sections: ...

  wings:
    - tag: "main_wing"
      mass: 180  # grams per wing (optional)
      geometry:
        profiles: ...

Note: If a wing has mirror: true in its attachment, the total wing mass contribution will be 2 × mass.

Additional Parts

Parts not represented in geometry or propulsion systems are specified as additional parts:

additional_parts:
  - tag: "landing_gear"
    description: "Carbon fiber landing gear assembly"
    mass: 120  # grams
    placement:  # optional, for CG calculation
      position: {x: 500, y: 0, z: -50}

Additional Part Parameters

Parameter	Unit	Description
tag	str	Unique part identifier.
description	str	Human-readable part description (optional).
mass	g	Part mass.
placement	object	Part placement in SETUAV_BODY frame (optional).
placement.position	object	Position: {x, y, z} in mm.

Example Configuration

setuav: '1.0'

airframe:
  fuselage:
    tag: "main_fuselage"
    mass: 250
    geometry:
      sections: ...

  wings:
    - tag: "main_wing"
      mass: 180
      geometry:
        profiles: ...

propulsion:
  motors:
    - tag: "main_motor"
      mass: 28
      # ... other motor parameters

  batteries:
    - tag: "main_battery"
      mass: 185
      # ... other battery parameters

additional_parts:
  - tag: "motor_mount"
    description: "3D printed motor mount"
    mass: 12
    placement:
      position: {x: 0, y: 0, z: 0}

  - tag: "landing_gear"
    description: "Carbon fiber landing gear assembly"
    mass: 120
    placement:
      position: {x: 500, y: 0, z: -50}

  - tag: "electronics_bay"
    description: "Flight controller, receiver, GPS, wiring"
    mass: 85
    placement:
      position: {x: 400, y: 0, z: -10}

Center of Gravity Calculation

With placement information for all components, the overall center of gravity can be computed:

\[ \vec{r}_{\text{CG}} = \frac{\sum_{i} m_i \cdot \vec{r}_i}{\sum_{i} m_i} \]

Where:

• \(m_i\) is the mass of component \(i\)
• \(\vec{r}_i\) is the position vector of component \(i\) in SETUAV_BODY frame

Components contributing to CG:

• Fuselage (if mass specified)
• Wings (position from wing attachment, mass × 2 if mirrored)
• Motors (from placement)
• ESCs (from placement)
• Batteries (from placement)
• Additional parts (from placement)
• Propellers (mounted on motors, use motor position)

This calculation should be performed by analysis tools, not stored in the specification.