I have a gas-powered UTV (utility "golf cart") that I've modified to be quite fast. After I get the brakes and suspension up to the task, I intend to further modify it to be able to reach highway speeds. For no good reason (just because I want to), I am slowly turning it into something more like a car. I'll be putting a PLC in the buggy with a touchscreen HMI in the dashboard. This will allow me to have an infinitely configurable dashboard so that I don't have to drill a bunch of holes in the dash to mount gauges and switches, and then be forever unsatisfied with the way I laid everything out.
I would like to have a way to slow it down, in 2 or more steps, so that my kids can enjoy using it without me having to worry about them being involved in a 50mph rollover. I envision a login screen where, depending on the password you enter, one or another profile is loaded, and max speed is a part of the profile. If my 8 y/o logs in, her speed will be limited to 10mph or so. For my 13 y/o, maybe 20. For me, none.
So I'm after some means of an adjustable ground speed governor. This buggy employs a CVT (Continuously Variable Transmission), which I don't fully understand the operation of, but I think that engine RPM is not always directly correlated to vehicle ground speed. Therefore the governor will need to be a closed loop with wheel RPM as feedback. I have tossed around many ideas about how to do it, and can't settle on one. I feel like there is a better solution I'm not thinking of. Thought I would bounce it off you fine folk.
Here are my ideas so far:
I am leaning towards option #3, but it doesn't feel as elegant of a solution as it could be. Surely there is a better idea? What say you?
I would like to have a way to slow it down, in 2 or more steps, so that my kids can enjoy using it without me having to worry about them being involved in a 50mph rollover. I envision a login screen where, depending on the password you enter, one or another profile is loaded, and max speed is a part of the profile. If my 8 y/o logs in, her speed will be limited to 10mph or so. For my 13 y/o, maybe 20. For me, none.
So I'm after some means of an adjustable ground speed governor. This buggy employs a CVT (Continuously Variable Transmission), which I don't fully understand the operation of, but I think that engine RPM is not always directly correlated to vehicle ground speed. Therefore the governor will need to be a closed loop with wheel RPM as feedback. I have tossed around many ideas about how to do it, and can't settle on one. I feel like there is a better solution I'm not thinking of. Thought I would bounce it off you fine folk.
Here are my ideas so far:
- When max speed reached, Cut spark to spark plugs. Simplest solution but this won't stop fuel being dumped into the cylinders, and could result in something nasty.
- Complete drive-by-wire. Potentiometer on accelerator pedal, servo on throttle lever at engine. This offers the highest level of control with the easiest implementation, but also introduces the most opportunity for catastrophic failure. Any number of failure modes could result in runaway operation. Not willing to take the risk.
- A servo linked by spring to the throttle lever on the engine, in opposition to the accelerator pedal cable (also linked to throttle lever by spring). A PID loop monitors speed, and as max speed is approaching, begins a game of tug-of-war with the operator's foot. The result would hopefully be a gradual settling in at max speed, no abrupt drop-off, and the only failure modes would still leave the operator in control (able to achieve max speed or able to achieve zero speed, but no runaway operation).
- Replace the carburetor and magneto with fuel injection and electronic ignition. This would be cool, and offer a great level of control, but it's a bit more advanced than I would like to go for now, or maybe ever.
- An array of solenoids with springs connected in opposition to the accelerator pedal, same concept as option #3, but one spring & solenoid for each speed profile. Depending on individual spring tension, the engine throttle lever only moves at some ratio of accelerator pedal travel.
I am leaning towards option #3, but it doesn't feel as elegant of a solution as it could be. Surely there is a better idea? What say you?