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Motec M150 groundspeed (vehicle speed) through GPS

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Hello,Any way to use gps speed ( 50hz high speed and acuracy GPS, through CAN and C125) on a M150 GPRP as vehicle speed on a 4wd aplication to be able to calculate slip? And also for launch rpm vs speed table? Or ecu already calculates vehicle speed through gps if this is the lowest speed?

thank you

You can send the GPS information from your dash through to the M1 ECU via CAN. There's information on how to do this in this thread - https://www.hpacademy.com/forum/webinar-questions/show/114-setting-up-dash-comms-sending-a-can-message-to-m1-from-dash

As for using the GPS speed for vehicle ground speed, with the default packages this won't be possible. You would need to have some custom firmware written to allow the GPS speed to be used for your traction control strategy.

Thank you for answer, I suspected it is not possible in the normal GPRP, I will try and see if it is really needed

best regards

Hi Claudiu,

You can use GPS Speed over CAN as the Vehicle Speed in the M150 and GPRP, it will fall back to this once the GPS Speed is over 10km/h and the Wheel Speeds are zero for longer than the Wheel Speed Diagnostic Delay is set to.

I would not recommend using GPS for any Launch/Traction control functions, as it just doesn't refresh fast enough. It also doesn't provide any feedback to what the wheels are actually doing.

I know the standard 5hz and 10hz from Motec is a bit slow for this but the 50hz is quite reactive , and would seem apropriate to be used for slip calculation, but i gus loggin it would be enough

When you talk about slip, are you meaning wheel slip or vehicle slip? Either way, GPS is not going to give you a clean representation of what is occurring compared to wheel speed sensors or a dedicated yaw/slip sensor.

The M1 will calculate wheel speed as an estimate based on engine speed and gearing, if the wheel speed sensors and GPS are unavailable, but it is just an estimate, meaning that it will only be as good as the way that it is setup, and the information available to it.

@BlackRex I think the problem Claudiu is trying to resolve is traction control on a 4WD platform where (within reason) all four wheels will break traction simultaneously. I've had the discussion previously with Jamie (@MoTeC Australia) about 10 Hz GPS for traction control and I understand the problems with a 10 Hz sensor. I'm also aware however of some people using a 50 Hz GPS to perform traction control on 4WD chassis with apparently good results so I'm personally interested to try this and gather some data.

Can you clarify what you're talking about with a yaw/slip sensor though? Obviously if we can directly measure slip this is going to be the best way for a traction control strategy - As far as I've seen though this is usually a ground speed vs wheel speed calc which isn't feasible in a 4WD platform.

Apologies for putting you wrong Claudiu on the GPS for vehicle speed too!

Hello Andre, you have nailed perfect, i just wanted a wheel vs groundspeed slip ( i have all 4 wheel abs sensor connected, i have speed imput from gearbox, and i thought we could yuse the gps as true ground speed) than you could set launch as in a 2wd aplication with slop between driven and non driven wheels. For vehicle slip a IMU is required i guess, but a strategy to implement it would be a head ache :))

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