Motion platforms are categorized by their application and cost. While high-end systems like the Stewart platform provide full six-degree-of-freedom (6 DOF) movement for professional flight training, and mid-range systems serve the arcade and amusement park markets, a lower-cost segment exists for personal use.
These home-based systems typically fall into a price range between $1,000 and $9,000. During the 2000s, several individuals and business entities began developing these smaller, more affordable motion systems. Originally popular as do-it-yourself projects for flight simulation enthusiasts, these platforms have expanded into a larger market for generalized "craft-oriented" simulation and entertainment.
Consumer motion platforms provide full-body tactile feedback to the user. For example, motion gaming chairs can roll, pitch, and tilt to simulate turning corners, accelerations, and decelerations. Because physical space is limited, these systems cannot identically mimic large-scale real motion. Instead, they rely on "acceleration onset cueing" and "washout" techniques:
Initial Acceleration: The platform simulates the initial cue of an acceleration as closely as possible.
Washout Filters: To stay within physical limits, the system uses washout filters to return the platform to a neutral position. This reset occurs at a rate below the human motion threshold, so the occupant does not detect the movement.
Gravity Vector (G-Tilt): For sustained linear acceleration, such as a car accelerating forward, the simulator can tilt the subject backward. This uses gravity to create pressure against the seat, which the brain perceives as forward force.
The effectiveness of a motion platform depends on the synchronization of cues processed by the human brain. The body perceives motion through three primary sensory inputs:
Vestibular System: Located in the inner ear, this system uses semicircular canals to sense rotational accelerations (pitch, roll, and yaw) and otoliths to sense linear accelerations (heave, sway, and surge).
Proprioceptors: These receptors in the muscles, joints, and gut provide "seat of the pants" feedback regarding the body's position and pressure.
Visual Input: The eyes relay information about velocity and altitude relative to the outside-world (OTW) scene.
In a simulator, it is essential that motion cues are processed by the brain before or simultaneously with visual changes. If these cues do not correlate—for instance, if there is a delay or mismatch between the visual and motion systems—the user may experience "simulator sickness," characterized by symptoms such as nausea, headache, or eye strain.
While professional-grade hexapod platforms are used for civil aviation training under authorities such as the FAA and EASA, consumer platforms are primarily used for:
Driving Simulation: Using specialized controllers like steering wheels and pedals, motion platforms provide physical correlation to the sight and sound of racing games.
Flight Simulation: Personal platforms allow enthusiasts to experience rotational and translational movements (surge, heave, sway) during flight maneuvers.
Virtual Reality: Motion platforms enhance the immersion of VR by providing the physical sensations that match the virtual environment.
The use of motion in these environments is intended to increase realism and stimulation. Studies of pilot perceptions have indicated a strong preference for simulation environments that include motion, as it provides an inner control loop where the user responds to accelerations as they would in a real vehicle.