PBP projects for R/C models

[Kenjones1935]

Today in the mail came two toy store Xmas catalogs. Both feature toy level R/C vehicles. All the more reason my autonomous car for introduction to STEM is a good idea. It may be that we need to teach-the-teachers first.

On the subject of cost. In Fitchburg well over 50% of our public school students come from families that fall below the poverty line. In Massachusetts that means they are eligible for free or reduced price school lunches. If we were to use my cars to teach STEM to middle school kids, it would be nice if they could keep what they build. (Maybe in the context of an after-school program.) If we use my cars to guide teachers toward this corner of STEM through a college supported Professional Development course, again it would be nice if the students could keep what they build.

Here's the question. What games can $50 1/10 scale TOY level cars play given the limitations of bang-bang controls and a 16F887 PIC. As a goal keep the total cost less than $100.

Ken

[Kenjones1935]

The point of my project is communicating "how things work" to pre-teens.

Examples of today's difficulties: My Mom's natural gas powered oven was obvious. Ever try to explain a micro-wave? Souping up a car in my day included high lift cams, carborator changes, tuned straight through pipes. Today the first thing you do to hop up a car is change a computer.

The dashboard on my 2004 GM car told me: "TIRE Pressure LR 23psi LOW". It also said, "TIRE Pressure RR 28psi OKAY". I pumped up my left rear tire. Then the car told me,"TIRE Pressure LR 23psi LOW" and "TIRE Pressure RR 33psi OKAY". WHAT??

The garage mechanic told me each tire valve contains a pressure gauge and enough of a computer to maintain a connection to the car's internal wireless network. A previous owner of my car had rotated the tires. The mechanic also told me that my car, depending of accessories, carries some twenty computers.

It seems to me that the first question in the mind of a future STEM professional is, "How does this thing work?"

Ken

[Kenjones1935]

Today at the gym I got two speed levels to negotiate the wall racing. I have divided my POT's full motion into six steps, 0 - 5. 0 is slowest. 5 is fastest.

Today speed 0 and 2 worked fine. Speed 5 crashed a bit. This evening I increased the proportionality multipliers relating POT position to distance thresholds.

If I can get this car up to speed, imagine racing with more than one on the track.

Ken

[Kenjones1935]

I've added a new video to youtube.



Check it out and please give me your advice. I think the car is not responding as fast as it can. I can list an abbreviated version on my code. I may have some fundamental incorrect.

Ken

[chuck]

Hi Ken
I've been watching and reading this thread with great interest and I've got to admire and take my hat off to you for your persistence. Don't give up your nearly there.
Have you used interrupt's in your code ?
If you have not may be the pic cannot proeccess the comamnds quick enough to repsoned. having watching some other video clips they seem to responed really quickly travelling at high speed.
I was thinking of trying my Nitro car but I think that would be to fast.

[Kenjones1935]

chuck et al,

My code has no interrupts. It loops through poling the sonars many times per second. They flash a red led when poled. This is visible.

I use HPWM to generate the controlling signals. This is a stretch. The spec calls for one pulse each 20 msec. With the standard oscillator the PIC can't go that slowly. I learned what works by trial and error.

When controlling the car using R/C I can make it behave at faster speeds than the PIC can. Why? It might be that the feed back loop through my eyes and fingers is inherently better. My PIC code only works with distances. My eyes and brain work with distance and rate (of closing speed and steering).

Want to see some code?

Ken

[Kenjones1935]

I have been wondering whether the HPWM code starts fresh each time it is called. My system calls it after every SONAR poling. This is many times per second. Could it be that each time HPWM is called it pulls the output pit down in order to create a new pulse stream and in so doing screws up the pulse stream it had been sending.

Ken