A 6DOF motion platform is a complex system designed to simulate real motion and acceleration in a controlled environment. To simulate acceleration while moving forward, the platform must be able to independently control its motion along all six degrees of freedom: three translations (wave, heave, sway) and three rotations (roll, pitch, yaw).
We did a study before to test how to realistically simulate forward acceleration. Participants sat on a six-degree-of-freedom Stewart motion platform and viewed computer-generated visual scenes on a projection screen (54 × 40.5). The visual scene consists of a randomly structured ground plane and sky. Observers were told that eye height was always 2 m above the ground. Across 180 trials, participants experienced brief simulated forward acceleration (4 sec ramp followed by 2 sec constant acceleration) presented as platform motion and motion within the visual scene. After the acceleration ends, the screen dims and the platform returns to zero after 6 seconds. Participants used a joystick to indicate the reality of the forward acceleration experienced. They were explicitly told to give high scores to trials in which they were convinced that they were moving forward based on the visual stimulus and to give low scores to trials in which they noticed a conflict. In each trial, stimuli with all six different parameters were randomly selected at fixed intervals: visual forward acceleration (0–1.5 m/s^2), backward tilt of the platform (0–15), brief forward movement of the platform Translation (0–0.5 m in 4s), acceleration/deceleration duration ratio for translation (0.11-1.5), and up/down noise to simulate ground roughness (0 -7cm). Multiple hierarchical regression analysis performed for each subject showed that only two parameters had a significant impact on the ratings: higher platform spacing and higher visual acceleration resulted in a better impression of accelerating forward. Brief forward translations of platforms and bumps added credibility to some observers. Interestingly, in the sensory conflict between canal and visual/otolith cues, the latter dominates, as predicted by a Bayesian model that considers vision to be more reliable.
The key to simulating acceleration is the coordinated control of these six degrees of freedom. For example, the platform can combine pitch and pitch motion when simulating forward acceleration. The surge component provides forward linear acceleration, and the pitch component tilts the platform slightly to create the sensation of being pushed back into the seat.
Overall, precise control algorithms and motion cues are used to create a realistic and immersive experience, simulating acceleration, deceleration and various dynamic scenarios while ensuring the safety and comfort of the occupants.