BY T . J . KROB

As humans , we are bombarded with fancy words and acronyms that are tossed around to class-up a product and make it more appealing .

Some buzz words these days in the transportation sector include adaptive cruise control , Super Cruise / Bluecruise , active aerodynamics , active or semi-active suspension , automatic parking assistant , pro-trailer backup assist , lane keeping assistant , dynamic bending headlamps , displacement on demand , collision avoidance system , variable nozzle geometry turbo system … need I continue ?

Each of these instills a proudness factor of how cool one ’ s chosen vehicle may become if equipped with such nifty tech , but the technology also creates immense functionality .

We ’ ve seen similar buzz words propagate into the snowmobile realm as well – from variable exhaust control , tuned pipes and silent track tech in the “ good old days ” to more recent integration of adjustable ride modes , TFT digital display , inertial measurement unit ( IMU ) and more .

The latter will be our focus in this column as we examine the roots of an inertial measurement unit . It was formally introduced to many snowmobilers on the Polaris Dynamix suspension system , but the vast majority of people have been utilizing IMU capabilities for years through other consumer products .

First up , let ’ s pull out the physics book to analyze the first word – inertia . Inertia is defined by Newton ’ s first law of motion where “ A body at rest remains at rest , and a body in motion continues moving at a constant velocity in a straight line unless acted upon by a net external force ” ( which could include friction , aerodynamic drag , etc .). A few examples include the usage of a seatbelt in a car ; if the driver stops suddenly , the human body attempts to remain moving forward in the direction the car moved , but the application of brakes made the body lurch forward only being acted on by the external force of the seatbelt to hold the body .

Measurement is the act or process of measuring . This can be quantifying attributes of an object such as size , color , location , etc . Measures outside of physical properties also include time , distance , price , rate , etc .

Unit has a myriad of definitions depending on the application . It can refer to the first and least natural number ( one ) or be a single quantity regarded as a whole in calculation . It can be a determinate quantity ( as of length , time , heat or value ) adopted as a standard of measurement , or an area in a medical facility that is specially staffed and equipped to provide a particular type of care ( i . e ., the intensive care unit ). It can be a single thing , person or group that is a constituent of a whole ( we ’ re getting closer ) or a piece of complex apparatus serving to perform one particular function . That ’ s the one we ’ re after !

So , our IMU is a complex apparatus that performs measurements of an object ’ s resistance to change in motion . Sounds neat .

An inertial measurement unit works by detecting linear acceleration using one or more accelerometers , plus rotational rate using one or more gyroscopes .

The history of this device roots largely in military development where spacecraft , missiles , UAVs , submarines , satellites and more require the unit to be paired with a Global Positioning System ( GPS ) to stay on course , land and be controlled . This usage evolves into the inertial navigation system , which uses the data collected by the unit to calculate relative position , linear velocity , angular rate of turn , attitude and more .

Once IMUs became cheaper and less cumbersome to create and integrate , applications beyond military and navigational usage grew . Now IMUs are present in a plethora of consumer devices – many of which you may use daily but you may not realize the IMU ’ s presence . MEMS gyroscopes are popular in consumer electronics , such as smartphones or tablets . When lifting a phone off the nightstand , it senses the change in motion by turning on the screen , or can rotate the screen when positioned in landscape mode vs . up / down portrait mode .

Rewind to the mid-2000s and the unveiling of the Nintendo Wii , the remote

system derived its abilities to interact and manipulate items on a screen via accelerometer and optical sensor integration . Remember how amazing it first seemed to bowl , play imaginary tennis or drive a Mario Kart without being wired into the base ? Now virtual reality already makes that all seem rather low-tech .

Spinning back into transportation land for the vehicles we all enjoy , IMUs measure acceleration in the forward-backward , up-down and right-left directions and the angular velocity in the machine ’ s pitch , roll and yaw directions similar to the navigational devices .

Coupling this data with inputs from wheel speed sensors now creates the ability to adjust allowed driver inputs ( such as antilock brake activation , throttle blade closure or steering wheel correction ) to reduce accidents .

The racing world has benefited from IMU integration for years , whether on four wheels or two . The exotic and expensive world of Formula 1 racing installs hundreds of sensors on a race car , picking up data such as driver inputs ( throttle , brake , steering ), ride heights , suspension actuation , brake temperature , engine temperature , longitudinal and lateral forces ( from the IMU ), individual wheel speeds and more . The information from these sensors and the IMU are collected , stored and analyzed to allow engineers to make assumptions about the behavior of the car at any period of time to make changes and

40 / JANUARY 2025 / SNOWGOER . COM