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Future of cycling and transportation

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Future of cycling and transportation

Old 07-13-11, 10:01 AM
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bluefoxicy
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Future of cycling and transportation

Over in the e-bike forum I posted some thoughts on the program loaded into the Bionx electric bicycle kit computer. After some thought on the matter, I've come to the following ever-evolving view.

Electric-assist bicycles are a part of the transportation infrastructure of the future; however, they are not the only part. Cars and motorcycles will play a large role. In fact, electric-assist bicycles are strikingly similar to future motorcycles. In the future, motorcycles will not use a chain, but rather an electrical cable: a 1 cylinder 2-stroke turbodiesel will efficiently produce a high power output from a small engine to drive a small dynamo. This dynamo will keep a small battery charged, which will drive a hub motor in the rear, also used as the back (regenerative) brake.

An electric-assist bicycle uses human power rather than diesel power. The human's pedaling power and regenerative braking can recharge the bike by turning the hub motor. As such, these provide more efficient and effective transportation for mid-sized out-of-city trips: a bicycle is good for 2-5 miles, and maybe 10-20 miles for those with the time investment and fitness; but in the 5-20 mile range, with hills, stop-and-go traffic, the need for higher speeds, and the desire for less effort, bicycles falter for the masses.

The motorcycle, as described, is overkill for these cases, as is a car. Such a motorcycle would still consume fuel, and would be fit for the task; however, other options are available. An electric-assist bicycle is particularly fit for these tasks. The electric assist takes load off the rider and allows for strategic use to avoid fatigue over long distances and when dealing with hills. This allows a rider to reach his destination faster and with less effort, while at the same time providing the enjoyment and physical benefit of biking a shorter distance.

The Assist Program

First, I would like to cover modern assistance programs. Bionx, in particular, used on Trek Ride+, is my primary concern; I am unconcerned with other programs in particular.

The Bionx assistance program, in simple terms, reads the power output to the ground supplied by the ride and applies a multiplier. The available modes are 25%, 50%, 100%, and 200%, giving multipliers of 1.25, 1.5, 2.0, and 3.0. The electric hub motor supplies the additional power. Thus a rider inputting 100W at 200% gets 200W from the motor, putting 300W into the rear wheel.

Further, the Bionx assistance program can be speed limited. Trek Ride+ bikes sold in the US are speed limited to 20mph. The bicycle itself can exceed this speed, but no assistance is provided.

The first error in this program is in the speed limiting: owners of Trek Ride+ bicycles often complain about sudden cut-off at 20mph. A proper speed limiting program would take power input, speed, and acceleration into account to predict the approach to 20mph and smoothly reduce the assistance, avoiding a jarring cut-off.

More fundamentally, I think that the biometrics of the program do not fit well for longer rides and more reasonable use. To the point, I believe that the electric motor is best used to raise the power ceiling of the rider, not the continuous power output. Riders most want power for climbing hills and for accelerating; multiplying continuous power output will multiply cruising speed, but this is unnecessary for most riders and costly for battery.

I therefor suggest multiple programs which can easily be combined to produce a customized behavioral profile for a bike, suited to the individual rider.

Sports Mode

The goal of Sports Mode is to supply increased output power when accelerating fast--either from a stop or while cruising--and fighting resistance such as climbing hills or rushing headwinds. This gives a rider a boost when demands are high, allowing quick take-offs and easier flow with traffic.

The Sports Mode program requires a rider to measure his cruising, accelerating, and peak outputs and determine the best goals for himself. This system could use a training mode, or it could allow the rider to fine-tune its settings.

Cruising Power is the power produced when cruising. Let's assume a certain rider outputs 170 watts when traveling on level ground at 14mph, and that this is his typical output and speed on level ground. This rider's cruising power is 170 watts.

Peak Power is the maximum power output. Again, let's assume this rider can output 350 watts when pedaling really, really hard. That's the rider's peak power.

(Hard) Accelerating Power is an abstract value, more so than Cruising Power. When a rider accelerates or climbs a hill, he may output 225-250 watts instead of 170 watts. This same rider may pedal hard to accelerate fast, and at those times deliver 275W, all the way up to peak power. The rider may chose his Accelerating Power as somewhere over 250 watts, then, but below 275W.

So let's say the rider puts into the computer C=170W, A=255W. He would then give the sports program a Sports Assist S=200% value for 200% added assistance. Now what?

When the rider rides normally, nothing happens. The motor doesn't do anything.

When the rider breaks 255W, however, the motor starts rolling on assistance. It quickly but smoothly rolls up from minimal assistance, ramping up quicker if the rider puts in more power. Thus the motor only kicks in to aid in hard acceleration or hard hill climbing.

As long as the rider stays above cruising power, the motor will continue to supply assistance. If the rider's power input drops, assistance is rolled off smoothly to meet the rider's power input relative to his cruising power. Thus the motor doesn't outrun the rider, but continues to supply input to maintain high speeds if resistance is great (i.e. cruising at 30mph is harder than cruising at 15mph, keeping 15mph up hill is hard, etc.).

The sports program overrides all other programs that dictate lower assistance. When Sports Mode kicks in, it ramps assistance up beyond what any other program dictates. When the sports program rolls down, it defers to any assistance program dictating higher levels of assistance than it has selected.


Base Assist

The Base Assist program does the exact same thing that the current Bionx program does: multiplies power input. The Base Assist program allows a rider to maintain the same speeds without as much effort, or to maintain higher speeds with the same effort.

The Base Assist program is overridden completely by the Sports Mode program if it supplies less assistance. Sports Mode will not roll back power below Base Assist's base level.

(Note: it may be better to let sports mode act as normal, and ADD to Base Assist, such that if the rider puts in i.e. 255W PLUS the 25% assist of 64W, Sports Mode multiplies the whole 319W by the Sports multiplier. Other options are to simply add the multiplers, or raise the multiplier to whatever is set for Sports Mode, both determined by the human power input and not the human+motor total power)


Hill Smoothing

The Hill Smoothing program uses an accelerometer in the unit to measure tilt and motion. It then smooths out the hills, making the ground more flat. The Hill Smoothing program has two parts that can activate separately: Uphill and Downhill.

The Uphill program makes hills less dramatic. The rider can configure the program to make the hills completely flat or just less steep. When climbing a hill, the electric motor applies a percentage of power assistance to reduce effort. The Uphill Program MUST add to the Base Assist program to produce the desired effect; interaction with Sports Mode is most likely best additive as well.

The Downhill program flattens out the downhill ride by regeneration. It completely overrides all assistance modes except Sports Mode, which it may optionally scale back rather than shutting completely down. The Downhill program shouldn't skid, as it's not a hard braking program but rather a flat land simulation and thus should only supply relatively weak braking.

Activating only the Downhill program gives an extension to battery life, at the expense of gaining speed down hills. Still, it only virtually levels the ground, so it wouldn't remove speed so much as it would remove free acceleration. Other assist modes uphill would avoid fatigue, making this manageable.


Conclusion

The above program description leaves a few interaction questions, mainly with the Sports Mode that supplies so much speed increase by giving more acceleration in stop and go traffic. In fact, the usefulness of the Base Assist mode could be questioned entirely given the Hill Smoothing and Sports Mode combination. All of this is by no means complete; it is simply conjecture, ideas for future improvement to be explored. Further improvements are likely possible over even a refined assist program based on the above; something completely different may prove much better.

Still, this program is customizable enough to take the load off out-of-shape riders for short and long commutes. The hilly commute to work I personally follow would be much faster and easier with Hill Smoothing or Sports Mode, and yet still be a ride: a perfectly flat 7 mile commute with Hill Smoothing. Long tours would go by exceedingly quickly for anyone with Sports Mode and Hill Smoothing combined due to the fast 0-20 acceleration and the ability to maintain 15mph easily up hills.

This kind of electric assistance is completely unnecessary for trips below 5 miles. Still, the minimal use of the electric motor coupled with the regenerative rear brake and the regenerative Downhill smoothing program should make bicycle trips for up of 20 miles quick and easy for non-dedicated cyclists, while still giving the physical health benefits of cycling (you are effectively riding 20 miles on flat land, instead of hills; and Sports Mode gives you nothing below your cruising output).



In short, I think the future of transportation is in classical bicycles for short trips, but nothing over 5-10 miles for any but the most serious and dedicated cyclists. Casual cyclists will find that they can efficiently and quickly move from one point to another via the use of an electric assist motor; but I believe the application of the current technology needs some tweaking before it can provide a truly effective method of getting people moving 10-20 miles regularly. Motorcycles will likely go towards hub motors on efficient, narrow-power-band diesel bikes, but the benefits of cycling will make electric assist bicycles more attractive for relatively short trips.

As for cars and motorcycles, they will be displaced only in part due to gas, traffic, and maintenance. Cars will probably move to diesel-electric as I've described motorcycles doing; but no amount of fuel efficiency will alleviate traffic congestion or maintenance costs.

Last edited by bluefoxicy; 07-13-11 at 10:05 AM.
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