Difference between vehicle_speed and wheel_speed sensors

#1

Hi! I was wondering how the vehicle_speed in the Vehicle Monitor is calculated and whether the formula takes into account the four wheel sensors: FL_wheel_speed, FR_wheel_speed, RL_wheel_speed and RR_wheel_speed? In other words, is vehicle_speed a separate independent sensor or is the value dependent on the four wheel outputs and tire radius?
Thanks in advance!

#2

@borce I’m not sure if vehicle_speed is calculated from the speeds of the four wheels, but the wheels speeds and vehicle speeds shouldn’t be too different from each other

Do see https://www.nuscenes.org/nuscenes?tutorial=can-bus for more details

#3

Hi @Whye_Kit_Fong! Many thanks for the prompt feedback. Yes, indeed I had already compared the speeds indicated by the vehicle_speed and wheel sensors and I can see the correspondence after unit conversions. However, I am specifically interested in any dependency between them. I presume vehicle_speed is something coming straight from the vehicle manufacturer and not calculated by the Motional team?

#4

That is right - the data we provide in the CAN bus expansion is raw

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#5

Thanks for the inputs and clarification @Whye_Kit_Fong. I will make further investigations regarding the dependency and calculation behind vehicle_speed