Why does uphill road terrain gives negative speed??

I have made a vehicle system with 6 gears, and have imported some drive cycle data with throttle and gear shifts as input. It works perfectly fine for flat road and downhill terrain data, but when I give uphill terrain, say 15 degree inclination, output shows negative speed. Can anyone help me out?

I have attached pictures of flat road, uphill and downhill.

Input is given in terms of degrees. Spikes in the output speed signal is nothing but gear shifts.

[Adam Danz]

Is the vehicle rolling backwards?

Does the actual velocity start at 0 at time 0? I see that the line starts at 0 but is there a calibration issue and have your verfied that the velocity is indeed 0 at time 0?

You also have negative RPMs at the end of the time series data, too.

[Nithin k]

How to check if the vehicle is rolling backwards??

yes, vehicle is starting at 0 at time 0. I don't think there might be calibration issue as I am getting exact results for flat road and also for downhill. Results are perfect, but for uphill it doesnt work.

Yes, even the rpm goes on the negative side. Do you know the reason??

[Adam Danz]

I'm unfamiliar with your system so I'm thinking at a big picture level. Is the velocity signal something your measuring directly, is it something you're conrolling, or is it being computed from position or acceleration?

Is there any way to pause the system just before the point where velocity and/or RPM goes negative?

What are the gears doing when these signals go negative?

[Adam Danz]

It looks like velocity goes negative right when RPM peaks. I don't know.... but it seems like something isn't being computed correctly.

Are you sure the velocity signal isn't acceleration?

[Shubham Gupta]

Check the driving froce for the vehicle & compare it gravitational force. I am sure you will find that gravitation force is greater than the driving force which is causing vehicle to decelerate from the start and once vehicle reaches 0 vehcile it starts rolling backward. Road angle of 15 degree is a very large slope reduce the angle I am sure it should work without a problem.

[Adam Danz]

Ah! So my initial inclination was correct! Good job looking into the data and confirming it!

Answer 1

[Nithin k]

I was just checking my model. What i was trying to do is to simulate the flat road drive cycle data in an uphill/downhill road terrain conditions. But the main point I missed is to see at what gear its travelling the uphill. As I can see from the uphill speed output, the speed is increasing from 1st to 2nd and then to 3rd. Then at higher gears the speed starts to reduce. Because of the lower torque it starts rolling down as 15 degree is too steep.

Thanks for the help!!