Electronic Hand Throttle/Cruise Control (Nissan Versa)

[Rick Rae]

"Hybrid Hand Throttle/Cruise Control" would be a more accurate title, but I didn't want to imply hybrid vehicle involvement.

Basically, I'm contemplating a device that would primarily be an electronic hand throttle, but which would also have aspects of a cruise control. The intent is DWL with limits, so one's speed will stay above a set minimum for highway travel for example. It will not be a traditional cruise control; speed would be set by a control on the unit, not with the accelerator and a SET button.

Normally I wouldn't bring this up until I had something to show, but I wanted to gauge interest. That's because I'd typically do something like this in 8051 assembly language, or even on a PIC processor given sufficient horsepower. But it seems like Arduino is the preferred DIY platform these days, so I'm thinking maybe I should go that way. It doesn't matter to me which I use, but if open sourcing it on a common platform might give others a building block or starting point to work from, why not?

So: Would anyone be interested in such a thing? No promises: I have no idea how long this will take or if I'll even do it; I'm just evaluating right now. But to show it's not purely a mental exercise, here's a snapshot showing the VSS signal from the CARDIS at 55 MPH:


Image by Rick Rae on Flickr

Clearly, I'm at least serious enough about this to have found and tapped the VSS signal, rigged up my scope on an inverter, and done a quick test drive to gather some data. (Sorry for the blurry image; a cruddy cell phone camera plus taking photos while driving at speed rarely equals high quality! I was taking snapshots because mine isn't a storage scope, and pictures were faster than setting up the data acquisition system on the laptop. Sharing an image with fellow EMers was purely an afterthought.)

Thoughts invited, and thanks!

Rick

P.S. To any engineer types reading this, don't let the grungy waveform concern you. I was using a distant ground so the scope was showing all manner of noise that wasn't really there. All I cared about was getting the pulse timing for a few different speeds.

[JRMichler]

I will follow this project with interest, but most likely will not build one for myself.

I would REALLY be interested in a way to adjust the relationship between accelerator pedal position and throttle valve position so as to get a linear torque response to accelerator pedal position.

[Rick Rae]

Originally Posted by JRMichler

I would REALLY be interested in a way to adjust the relationship between accelerator pedal position and throttle valve position so as to get a linear torque response to accelerator pedal position.

If the Canyon has drive-by-wire, have you looked at any of the so-called "throttle controllers" ("APPS response warpers," more accurately) to see if they'll do what you need?

Rick

[skyl4rk]

I am interested in a digital cruise control. I'm not sure I would dare try it on my car, without a lot of track testing. I would like a regular cruise control, but also a special hypermiling pulse acceleration button for pulse and glide engine off coasting.

When the pulse button is depressed, the motor accelerates at a TPS calculated to find sweet spot for efficiency, which changes with rpm and LOD. When released, the motor is shut down.

The pulse acceleration TPS (throttle position) is set using an algorithm with inputs from RPM and LOD and kept in the most efficient range for those values. The user should be able to input an acceleration level (slow, medium, fast) for the pulse. The appropriate TPS would be found either from a calculation or an array that holds rpm values, LOD values and the most efficient TPS for each data pair of rpm and LOD.

[Rick Rae]

Originally Posted by skyl4rk

I would like a regular cruise control, but also a special hypermiling pulse acceleration button for pulse and glide engine off coasting.

When the pulse button is depressed, the motor accelerates at a TPS calculated to find sweet spot for efficiency, which changes with rpm and LOD. When released, the motor is shut down.

I'm pretty sure I've read of someone working on (or having worked on) that or something very similar. Trying some creative search terms here and on some of the other FE-oriented forums might be worth a shot. (And if I happen across it again I'll certainly pass the info along.)

What I'm planning is much more rudimentary; while it could be used as a stepping stone to your goal, you might be better off with an OBD II or CAN connected device, since that would give you a wealth of data without a lot of wiring and conditioning.

Speaking of rudimentary, I'm also considering an "old school" fully analog approach. It shouldn't really take any smarts for a device to do this job.

Cheers,
Rick

[skyl4rk]

What are you planning to do, adjust the voltage?

[Rick Rae]

Originally Posted by skyl4rk

What are you planning to do, adjust the voltage?

More like substitute a voltage but basically, yes. When engaged, the hand throttle's outputs will replace or override the outputs from the APPS.

Rick

[JRMichler]

Originally Posted by Rick Rae

If the Canyon has drive-by-wire, have you looked at any of the so-called "throttle controllers" ("APPS response warpers," more accurately) to see if they'll do what you need?

Rick

I hadn't realized that such gadgets existed until you mentioned it. I found a couple with an "Eco" mode that is a step closer to what I'm looking for, but nothing that gets all the way there.

Most of my driving is between 700 and 1900 RPM. In that range, I want the torque to be linear to accelerator pedal position. This is tricky because the relationship between accelerator pedal position and throttle blade position is a function of engine RPM. At low RPM, you get 90% torque with the throttle open less than 20%, while at high RPM the throttle might need to open over 80% to get 90% torque.

Maybe it's time for me to learn how to work with an Arduino....