Understanding Motion Cueing: Two Sides of Newton’s Second Law

Motion cues are one of the most challenging aspects of human-in-the-loop vehicle simulators. The real vehicle cues can only be presented in a highly distorted way, so it is important to understand what these cues look like and which aspects are important for the human controlling the vehicle. This paper describes two complementary ways of assessing (translational) motion cues: accelerations plus gravity, and specific forces. These perceived cues can be constructed from different components of Newton’s Second Law and are fundamentally equivalent. The paper shows how the situation heavily favors one representation or the other in understanding the motion cues to be presented. When assessing the cues in flight, the specific force formulation is superior as it leverages flight dynamics knowledge and intuition to predict and explain the form of the cues. The paper gives a number of examples to illustrate this claim, supported both by analysis and by measurements in an instrumented business jet and a motion-based flight simulator.