C12x Wheel Slip calculation

[quadcam]

It looks like the internal Wheel Slip calculation gives the Fast and Furious hectic version rather than what might be considered the usual value.

Wheel_Slip_internal_calc.jpg (189.95 KiB) Viewed 4185 times

In this config Ground Speed = GPS Speed and with the displayed values of 122, 122 & 52 the internal Wheel Slip calculation appears to be (122-52)/52 = 1.35, which is near enough to 140% given calculation propagation times. Which is really a measure of how much faster the drive wheels are going compared to the non-drive wheels.

What we were hoping for (as it is intended to be used both in the display and as signalling) was the (Drive speed - Ground speed) / Drive speed calculation as that gives values betwwen 0% and 100%, provided the drive speed is not zero (locked) or less than the Ground speed. This seems more realistic as 0 % indicates no slip while 100% indicates that no drive is moving the vehicle. The 122 / 52 scenario (as an i2 post-processed Maths calculation) gives 70 / 122 = 0.573 = 57% which is more meaningful than 140%.

Is this calculation live in the dash a possibility?
Thanks in advance

[MalcolmG]

A good option for simple linear calculations like this in a C12* dash (or C18* without advanced functions) is to use a 3D table. It's not perfect but it's about the only option. You can create the table in excel using the formula you want, then copy the calculated values to the table (except those #DIV/0! errors and negative values which you can just replace with "0").

E.g.:

motec 3d table sample.png (6.75 KiB) Viewed 4140 times

[quadcam]

Hi MalcolmG, thanks for the response. I was planning on combining Slip with Gear which would mean another 3D table. The ECU is User Maths / Functions capable (a Bosch MS6) so it will probably be easier to do everything there and send the result to the dash. I hadn't previously done that as the ECU requires either all wheel speeds directly connected or all via CAN, but it is not feasible to reliably connect front sensors. It would be possible to transmit the driven speeds to the dash and back again with the front being GPS but I was trying not to introduce more steps. I will use a dash output in frequency mode to output GPS speed to the ECU as the front wheel speeds, and the ECU can do the calculations.