Engineering
Controlling Motion Sickness in Autonomous Vehicles Through Active Suspension Tuning
Quick fact
Humans are most sensitive to accelerations below 1 Hz, and these low-frequency motions are exactly what active suspension systems are tuned to reduce, potentially cutting motion sickness incidence by up to 40% in simulated studies.
Why this is interesting
You’re riding in a self-driving car, reading a book, when suddenly you feel queasy. Why does the car’s smooth motion make you sick?
Read the full explanation
Understanding Controlling Motion Sickness in Autonomous Vehicles Through Active Suspension Tuning
Imagine you’re sitting in a parked car that’s gently rocking from side to side. After a few minutes, you might start to feel uneasy. Now imagine that rock is combined with forward and backward jolts—that’s what’s happening in an autonomous vehicle when you’re not focused on the road. The car’s suspension, which connects the wheels to the body, determines how much of the road’s bumps and the car’s own maneuvers reach you. Conventional suspensions use a spring and damper to smooth out bumps, but they can’t actively adapt to different driving conditions. An active suspension system, though, can change the stiffness and damping in real time. It uses sensors to detect the car’s motion and actuators to push or pull on the suspension to either stiffen it for precise handling or soften it for a comfortable ride. For an autonomous vehicle, the goal is often to prioritize passenger comfort, so the active suspension is tuned to keep the car’s body steady and level, even during turns or over rough roads, minimizing the accelerations that make you feel sick.
A deeper explanation
Motion sickness arises when your brain receives conflicting signals from your inner ear, eyes, and body about your position and movement. When you’re not driving, your inner ear senses the car’s accelerations—both linear and angular—while your eyes see a stationary interior. This mismatch triggers the symptoms. The severity depends on the frequency and magnitude of the accelerations. The vestibular system is most sensitive to movements below 1 Hz, which are common in road vehicles. Active suspension works by using a control system to apply forces that counteract these accelerations. The system consists of sensors (accelerometers and gyroscopes) to measure the body’s motion, a controller that determines the desired force, and actuators (hydraulic or electromagnetic) that push against the body. By varying the damping coefficient and stiffness, the system can raise the natural frequency of the vehicle body to a value where acceleration is less perceptible, or it can directly cancel out specific disturbance frequencies. For example, during a sharp lane change, the controller anticipates the sway and stiffens the anti-roll bar to keep the body flat, reducing the lateral acceleration experienced by passengers. By reducing the characteristic low-frequency sway, the active suspension minimizes the vestibular stimulus, thereby reducing the sensory conflict and, with it, the incidence of motion sickness. This makes active suspension tuning a powerful tool in the design of autonomous vehicles, where human drivers are absent and passenger comfort becomes paramount.