Moog CSA Engineering

Hexapods & Positioning Systems

How to Specify a Hexapod

Step 0: Determine if you need or would benefit from a hexapod for your application.
The primary consideration is whether the motion or vibration of interest is in more than one or possibly two axes. If it is not, a hexapod may not be appropriate. For positioning or vibration applications, consider whether the available space is suited for a hexapod.

Step 1: Determine what function the hexapod would perform.
Distinguishing between vibration isolation and positioning is important. A further distinction should be drawn between positioning where the hexapod is part of the main system of interest and motion simulation where the hexapod is used mainly to create a motion environment for testing another product.

Step 2: Start getting into details.
Consider the following as first steps for a hexapod that must perform in one of three different functions or applications.

For a precision positioning or pointing application, determine the following requirements:

  1. Range in each axis
  2. Resolution, accuracy and repeatability in each axis
  3. Payload size, shape, mass and inertia
  4. Bandwidth, velocity or acceleration in each axis
  5. Geometry constraints on hexapod and attachments to payload
  6. Type of interface (digital, analog, or built-in user interface)
  7. Any other constraints, including electromagnetic compatibility (EMC)

For a vibration isolation application, determine the following requirements:

  1. Does the base or the payload produce the undesired vibration?
  2. Payload size, shape and mass
  3. Geometry constraints on hexapod and attachments to payload
  4. Nature of the disturbance in each axis, perhaps as a frequency domain PSD
  5. Required performance in each axis, perhaps as rms vibration level
  6. Passive only, or can active system be considered?
  7. Any other constraints, including thermal environment

For a motion simulation application, determine the following requirements:

  1. Payload size, shape, mass and inertia
  2. Is phase or waveform important, or just magnitude?
  3. Range in each axis
  4. Bandwidth, velocity or acceleration in each axis
  5. Resolution, accuracy and repeatability in each axis
  6. Geometry constraints on hexapod and attachments to payload
  7. Type of interface (digital, analog, or built-in user interface)
  8. Any other constraints, including emergency shutdowns