Head Specification

Overview

The head assembly serves as the primary sensory platform for the Salvius robot, housing vision, audio, and communication systems. While there are minimal functional requirements for a humanoid head design due to the lack of mandatory moving parts, the specification ensures proper proportions, sensor placement, and integration with the neck assembly.

Dimensional Requirements

Proportions

The head must maintain proportions relative to the body to ensure balanced appearance and proper weight distribution:

  • Height: 22-28 cm (approximately 1/7 of total robot height)
  • Width: 18-22 cm (shoulder width × 0.7)
  • Depth: 20-24 cm
  • Weight: Maximum 2.5 kg (to prevent excessive torque on neck servo)

Eye Position

Camera/sensor placement should follow human eye positioning for natural appearance:

  • Eye Height: Approximately 60% from bottom of head
  • Inter-pupillary Distance: 6-7 cm for stereo vision
  • Forward Offset: 4-6 cm from head rear surface
Note: These proportions are based on average human head dimensions. Variations may be necessary depending on available components and aesthetic preferences.

Required Subsystems

Visual Input System

The head must accommodate one or more cameras for vision processing:

  • Primary Camera: Minimum 720p resolution, 60° field of view
  • Recommended: Dual cameras for stereo vision and depth perception
  • Mounting: Adjustable brackets to allow camera alignment
  • Protection: Clear acrylic or glass lens covers

Audio Output System

Audio components for speech and sound generation:

  • Speaker: 8 ohm impedance, 3-5 watt power rating
  • Placement: Mouth area or front panel for clear audio projection
  • Speaker Wire: 12-18 gauge stranded core wire, twisted pair to reduce electromagnetic interference
  • Amplification: Integrated audio amplifier (PAM8403 or similar)

Audio Input System

Microphone array for voice recognition and sound localization:

  • Microphone: USB microphone or analog microphone with preamp
  • Array Configuration: 2-4 microphones for directional audio
  • Placement: Ear positions or forehead area

Materials and Construction

Structural Materials

  • Frame: Aluminum sheet metal (0.5-1mm thickness) or rigid plastic
  • Face Panel: Acrylic, 3D-printed material, or thin wood
  • Internal Supports: Aluminum angle stock or 3D-printed brackets
  • Fasteners: M3 or M4 machine screws with nuts

Construction Techniques

  • Salvaged Materials: Computer case panels, electronics enclosures
  • Cutting: Hand shears for thin metal, jigsaw for wood/plastic
  • Joining: Machine screws, rivets, or epoxy for permanent bonds
  • Finish: Optional paint for aesthetics

Interface Requirements

Neck Connection

The head must securely attach to the neck rotation mechanism:

  • Mounting Pattern: 4-bolt pattern, minimum M4 screws
  • Load Distribution: Mounting plate distributed across neck servo
  • Cable Routing: Minimum 20mm diameter passage for wiring
  • Balance Point: Center of mass should align with rotation axis

Electrical Connections

Standard wiring requirements for integration with main control system:

  • Camera: USB 2.0 or higher
  • Audio Output: 3.5mm stereo jack or direct amplifier connection
  • Audio Input: USB microphone or 3.5mm microphone input
  • Servo Control: PWM signal wires for any head-mounted servos
  • Power: 5V and/or 12V power rails

Optional Enhancements

  • LED Audio Visualizer: Visual feedback for audio output
  • Ultrasonic Sensors: Forehead-mounted distance sensors
  • Thermal Imaging: Infrared camera for heat sensing
  • Cooling System: Small fan for internal ventilation

Design Considerations

Weight Distribution

Heavy components (cameras, speakers) should be positioned close to the neck rotation point to minimize torque requirements. Use lightweight materials for areas far from the center.

Cable Management

Plan for wire routing from the beginning. Cables should:

  • Have sufficient slack for neck rotation (±90°)
  • Be secured to prevent interference with moving parts
  • Use strain relief at connection points
  • Follow paths that minimize electromagnetic interference

Modularity

Design the head with modular components that can be easily replaced or upgraded:

  • Quick-change face panels for different expressions or displays
  • Removable camera mounts for swapping it out or adding sensors
  • Accessible speaker and microphone mounting
  • Tool-free access panels for maintenance

Testing and Validation

Before final assembly, verify:

  • Weight: Total mass within servo torque capacity
  • Balance: Head doesn't tip when neck is stationary
  • Camera View: Clear, unobstructed field of view
  • Audio Quality: Clear speech output, minimal distortion
  • Cable Routing: No binding or tension during rotation
  • Structural Integrity: No vibration during movement
Tip: Start with a simple design and add complexity incrementally. A basic box-shaped or round head with mounted cameras and speakers is functional and can be enhanced with cosmetic improvements later.