Automatic transmissions were a breakthrough for cars more than half a century ago. Now we have an automatic gear shifter for a bicycle. Colorado State University engineering students Ben Johnke, Bill Engelking, and Matthew Stout created a bike that shifts gears by itself based on several inputs: rear wheel speed, pedaling direction, and initial chain position.
The students used the factory derailleur cable system, but they added high-torque servo motors instead of hand-turned levers. The bike uses four PIC microcontrollers to process the inputs, control the shifting, and display data to the user.
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The Colorado State University engineering students who created the self-shifting smart bike (left to right): Ben Johnke, Bill Engelking, and Matthew Stout.
I like this idea a lot. It is a flaw in the current system that you must change speed in order to shift in some ways, because when climbing up a hill you may want to still be in a lower gear. It would also be cool to have more manual inputs in the system. For instance, ideally if you could push varying setting for normal, hill, racing...etc on the bicycle's control box that would be very useful. These setting could have different programming for gear changing and utilize different sensors. That way you could put in an sensor for incline without forcing the rider to utilize this if they just want to go up the hill slowly. I actually considered doing this as an input function, but the programming would have been much more longer and complicated for this application. If I was going to actually market this product, I think it would be a great idea.
I agree with you that our design would not be good for racing, because it is meant for a person who wants to just have a comfortable ride to school or to work. Many basic level riders do not shift enough or shift too much. And most people riding their bike to school or work do not need all of the 21 speeds (or whatever) the bike offers. So this system utilizes four gear sets that are spread out over possible gear ratios in order to select a good gear for the speed of the rider. I understand the concerns about smoothness and that is something we tried to address, but of course it is difficult to address every riding conditions. So the compromise here is that you don't have as many gears for a varied amount speeds, but you also don't have a bicycle that is shifting constantly. If you really get pedaling quickly (as I even tested), the bicycle will skip shift steps (due to the timing of the program) if needed. Also to address comfort, we made the upshift different from the downshift for each gear. So even with a lot of variation in speed close to a shifting point, you won't get redundant shifting. Also, the movement of the servo motors is very quick (and since it can move both gears at the same time) it is actually quickier and equally as smooth (since it uses the same derailuer of the manual shifting bike). And the shifitng only occurs when the pedaling is constant in order to get smooth shifts. More of the features in order to improve smoothness and the ride are in the paper. Thanks for your comments and interest.
Neat idea, but maybe in the abstract, not in a practical sense. As a long-time touring bike rider and trainer of the 1984 USCF National Womens Criterium Champion, an automatic shift is the last thing one wants for touring or racing. Quite often it is important to anticipate what gear one wants to be in for an expected situation. Typically, one selects a gear to suit the terrain, wind, and pedalling cadence a rider can maintain. Riding in a pack of other riders, whether racing or touring, also affects the choice of ratio desired. No thanks, but I think KISS is the best.
I think a sweet addition would be an inclinomter to measure the angle of the grade, so even if the rider doesn't slow down that much, it would still downshift to give the rider more torque to handle the hill.
I think, however, power output of the rider would be a better measure than speed, albeit more expensive to obtain. User selects an upper and lower output range, and tranny controller adjusts to maintain. There are cycle computers out there that measure output, so it's probably possible, although more complicated. Of course there is another complication to be handled. You don't want the bike to shift while the rider is cranking down hard on the pedals. The audible "tranny controller suggests a change" melody would be a signal to the cyclist to ease up for the shift. If the system senses the ease in pedal pressure, then the shift occurs.
Next challenge: a cyclist airbag system for falls and collisions. And it has to weigh under 3 pounds.
This one comes pretty close to reading the mind of the cyclist. Perhaps even closer than the automobile's automatic transmission. I wonder if this will make it easier to drink coffee while cycling. The automatic trans in the auto certainly helped me in that area.
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