Gyroscopes and accelerometers provide information about orientation, movement, and balance of an object. Human body has sensory structures that function similarly to these two.
When automating human tasks such as automatic driving, it is important to know how a person's own sensors work. Before talking about self-driving technology and computer vision, let’s check out what happens in the human ear.
Semicircular Canals
There are three semicircular canals located in each ear, oriented in three different planes. The membranous labyrinth of the inner ear is filled with a fluid called endolymph. These canals detect angular motion or rotation of the head in three dimensions; pitch (nodding), yaw (turning left or right) and roll (tilting the head). When the head rotates, the fluid inside the canal moves, bending hair cells. This bending generates nerve signals that are sent to the brain, indicating the direction and speed of rotation.
– The sensors and control in the automatic operations can do the same function as what the eye does when a person turns their head. This is called the vestibulo-ocular reflex, explains Jussi Collin, the CEO of Nordic Inertial.
Saccule and Utricle
The otolith organs, saccule and utricle, are located in the vestibule of the inner ear, next to the semicircular canals. They contain hair cells embedded in a gel-like substance with otoconia (calcium carbonate crystals) on top. These organs are our accelerometers. The saccule is more sensitive to vertical movements, and the utricle to horizontal movements.
When you move straight, stop quickly, or change your head's orientation relative to gravity, the otoconia shifts, causing the gel to move and the hair cells to bend. This bending converts into nerve signals sent to the brain, providing information about linear movement and head position.
– Canals are gyroscopes, Saccule and Utricle accelerometers. At Nordic Inertial, we know that processing inertial sensor data is not straightforward (non-commutativity, etc..). Can brain perfom non-commutativity calculations? Some physicists argue that our perception of time is due to non-commutativity! Quite interesting topic to research and improve human-technology interactions and assistive technologies, Collin explains furthermore.
Leading with Science
The brain integrates signals from these gyroscope and accelerometer-like sensors with information from the proprioceptive and visual systems. This integration helps maintain balance, coordinate movements, and understand our position in our surroundings.
When there's a mismatch of information among these systems, it can lead to the familiar sensations like dizziness or vertigo. The unique feelings experienced on a roller coaster, including the sensation in your stomach, arise from the complex interplay of these sensory systems responding to rapid changes in motion and orientation.
– One can use Einstein's equivalence principle, think that there we are accelerating upwards instead of being pulled down by the gravitational force. And that’s what our mechanical instruments, accelerometers show. Working at NI may change your worldview, Collin smiles.
– We have inertial sensors not only in the inner ear, but also intuitive feeling in the bottom of one’s gut. We utilize these genuine functions of the human body in the development of our own measuring devices.
Curious to learn more about the inertial sensors? Check out more on our website here or contact Jussi Collin at jussi.collin@nordicinertial.com.