How is purely torque-sensing PAS actually implemented?

[Jeremy McCreary]

Jeremy, just as an FYI, there is another option to the torque sensing systems and some of the less expensive PAS only systems that surge to 12 mph or so as soon as you start pedaling in PAS 1 (those are PAS "speed based" systems). The aftermarket KT systems controllers have an option for what they call "imitation torque control". What it amounts to is a "power based" system where a predetermined amount of power (established by you) is supplied to the motor for each PAS level. Speed has no effect on this amount of power, so it is truly based on how much assist you want to use. This ability enables awesome low speed control down into the areas so slow the bike is difficult to balance. 6 mph for instance, is easily maintained while using less than 100w of power in PAS 1. When this power based low speed control is compared to Bafang's torque sensing at the same speeds (using both the M600 and Ultra/M620), you can actually see the difference on the watt meter. Where the KT has a nice relatively smooth draw, the Bafang meters are surging with each power stroke - and yes, you can feel that surging. Nothing terrible, but you can feel it....

Interesting approach. So many ways to skin this motor control cat.

BTW, totally impressed by the experience and skill sets I see on display on this forum. Definitely the place for a guy who likes to understand his ebike.

 

[Jeremy McCreary]

I have ridden ebikes for two years and I have enjoyed it to the fullest. Trying to figure out how it works is not what I want to dig into.
Just ride it.
For example I have a gang load of Festool and Hilti battery and corded hand tools
I like them because they are smooth and precise, light weight and wrist friendly.

You do you.

 

[mschwett]

Thanks! Aside from a little surging under certain uncommon conditions, I'd rate my Rook's power delivery as quite smooth and natural-feeling. Certainly way more so than 5 bikes we tested with cadence sensors alone.

I think I read somewhere that my torque sensor just measures distortion in its own rear drop-out. Could you get crude but useful cadence info from the ripple in such a sensor's signal?

i assume the bike cuts off power at 20 or 28mph, so it must know how fast you’re going. it would not be difficult to use that info in combination with the torque sensor output to get a pretty smooth ride.

 

[Jeremy McCreary]

good one. I did way to many lego till I started riding more could not afford both. lego cost more then e bikes.

If I sold off all the LEGO that's not gonna fit in our new house -- which is most of it -- I could commission NASA to build me a custom ebike made of unobtainium from the ground up. With inertial guidance, a 1,000 kW mid-drive motor from the X-57 Maxwell, full rover-grade suspension, and a miniature 14-year MMRTG (multimission radionuclide thermoelectric generator) instead of a battery. It'd weigh 3 lbs.

X-57 Maxwell

Then I'd be a player in the "my bike's better than your bike" game.

 

[Jeremy McCreary]

i assume the bike cuts off power at 20 or 28mph, so it must know how fast you’re going. it would not be difficult to use that info in combination with the torque sensor output to get a pretty smooth ride.

I was thinking along the same lines, but now it looks like my "torque sensor" is also a cadence sensor. In which case I really have a power-sensing bike.

The Rook comes as a Class 2 with assist cutting out at 20 mph. And that gives us the trail and bikeway access we're after.

 

[fooferdoggie]

If I sold off all the LEGO that's not gonna fit in our new house -- which is most of it -- I could commission NASA to build me a custom ebike made of unobtainium from the ground up. With inertial guidance, a 100 kW mid-drive motor from the X-57 Maxwell, full rover-grade suspension, and a miniature 14-year MMRTG (multimission radionuclide thermoelectric generator) instead of a battery. It'd weigh 3 lbs.

X-57 Maxwell

Then I'd be a player in the "my bike's better than your bike" game.

my problem was I really only liked the largest sets. the last one I did was the coliseum. but now it just sits while the granddaughter plays with it and loses pieces. loved the roller coaster and carousel. Did MOC's but getting the pieces was a pain and expensive. had a way cool USS enterprise but it was so delicate Could not work on it with my fumble hands. this guy I had to resort to gluing together and even then it was a challenge.
but I ride so much that just bike maintenance alone is
maybe 700 or more a year between just tires, chains, and brake pads.

 

[Jeremy McCreary]

My wife's been encouraging the whole ebike thing to draw me away from LEGO spending. It may work.

I tend to build MOCs that move in some way. (For those who don't know, MOC is short for "my own creation" -- i e., a build from loose parts, not from a set.) Recently got hooked on building spinning tops -- which like ebike motor control systems turn out to be way more complicated than they look.

 

[linklemming]

Some of the torque sensor that are on the rear dropout do have a cadence sensor incorporated

Pedal Sensor / Torque + Cadence Sensor

Dual cadence + torque sensor hardware for Current-Series E-bikes. Frame-mounted rear dropout torque sensor. Made from a CNC milled block of 7000-Series Aluminum. Built-in high sensitivity digitally processed cadence sensor for near zero-lag startup and improved noise filtered torque-sensing over...

www.juicedbikes.com

A bad side effect of these is measuring the cadence off the rear cog. In doing so, you get variable cadence depending on what gear you use.

If one then uses cadence as a basis for determining human power and then uses this to determine assist, you effectively have assist which can vary according to which gear is selected (depending on algorithm).

An example is a friends Juiced CCX using this torque sensor with a Grin GMAC motor, phaserunner and Cycle Analyst 3 (CA3) from hilleater.com. You can see the calculated human power vary depending on what gear you are in. A net effect is the bike feels faster as you accelerate thru the gears as you are getting more assist in the higher gears. Its kindof a cool feeling. The downside is when you shift down to climb a hill, the assist goes down which is the last thing you want.

Unfortunately we really dont know how manufacturers are doing it so all we are doing is speculating.

On the TSDZ2 code I posted, its a pretty simple calculation but it feels less responsive than my Brose based bikes. The TSDZ2 has a hardware low pass filter which really limits the responsiveness of the torque sensor. The feeling of the bike seemed to match what the equation I posted was doing. I played with making it better effectively adding a boost function (adding assist base on rate of change of human power) but the low pass filter seemed to be the limiting factor(response time).

My Brose based bikes on the other hand are much more responsive (especially my specialized). Whether this is do to higher sampling, better torque sensor circuits or the software adding additional assist based on the how fast the human power changes or some other unknown algorithm (highly likely).

I recently bought a specialized turbo levo and the mission control app parameters give insight to how some of the algorithm(s) likely work (which is more complex than on the TSDZ2). Specialized has some prettty detailed videos on youtube explaining the parameters.

No I am not a one brand wonder or specialized fanboy as i have several DIY ebikes (GMAC and BBSHD), That being said, my turbo levo has the best feeling PAS by far which is tunable via the mission control app.

 

[gromike]

I would like to know what a good torque sensor bike would feel like. My experience is with cadence sensing and throttle. That just leads me to an ebike that is a motorcycle. I have the superpower, but it just subtracts from the beauty of a bicycle.

 

[Jeremy McCreary]

A bad side effect of these is measuring the cadence off the rear cog. In doing so, you get variable cadence depending on what gear you use.

If one then uses cadence as a basis for determining human power and then uses this to determine assist, you effectively have assist which can vary according to which gear is selected (depending on algorithm).

An example is a friends Juiced CCX using this torque sensor with a Grin GMAC motor, phaserunner and Cycle Analyst 3 (CA3) from hilleater.com. You can see the calculated human power vary depending on what gear you are in. A net effect is the bike feels faster as you accelerate thru the gears as you are getting more assist in the higher gears. Its kindof a cool feeling. The downside is when you shift down to climb a hill, the assist goes down which is the last thing you want.

Very helpful. Need to pay more attention in upcoming rides now that I know what to look for, but pretty sure I've seen some of those effects.

 

[Jeremy McCreary]

I would like to know what a good torque sensor bike would feel like. My experience is with cadence sensing and throttle. That just leads me to an ebike that is a motorcycle. I have the superpower, but it just subtracts from the beauty of a bicycle.

You might try a rental with torque-sensing if you can find one.

Wife and I tested 6 ebikes before buying. The first 5 had cadence sensors only. Some felt more natural than others, but all felt a little off to us. We knew from our research that many prefer torque-sensing but had no idea what that really meant in the saddle. And few bikes offered it in our under-$3,000 price range.

The torque-sensing Surface 604 Rook was test ride no. 6, and the feel was like night and day. After 15 min of riding, we went back to the bike shop and bought 2 on the spot. We haven't regretted it.

That said, I've read that torque-sensing isn't always the best choice. Others here can explain it better than I, but definitely worth investigating.

 

[gromike]

Trek is the only brand of torque-sensing bike that I can trial in my town. Guess I should just ask for a test ride. I want to experience what a torque sensor feels like. I can build a rocketship with a bafang mid drive, but would much prefer the experience of being twenty year-old honking on a bike.

 

[fooferdoggie]

I would like to know what a good torque sensor bike would feel like. My experience is with cadence sensing and throttle. That just leads me to an ebike that is a motorcycle. I have the superpower, but it just subtracts from the beauty of a bicycle.

the goal is the bike will feel just like a standard road bike or mountain bike. but that takes less effort. so you don't have that kick or boost.

 

[AHicks]

Regarding "cadence sensing". For what it's worth, any system I've messed with have had cadence sensors that only tell the controller the crank is moving, that's it. They DO NOT tell it anything else. Nothing I've messed with anyway. Anything that has to do with speed is measured by a speed sensor. I've never seen, or heard of anything that would do both (sense crank movement AND measure how fast it's turning). -Al

 

[Funpilot]

I have ordered a new Electric Bike Company Mode E with the first torque sensor offered by them. They will be shipping these in mid to late February, so I am expecting them to implement it properly as they set such high standards.

 

[Rexlion]

Now that we're up in years, I think my wife's sensors have quit working...

 

[fooferdoggie]

Now that we're up in years, I think my wife's sensors have quit working...

that could get you in the doghouse

 

[Jeremy McCreary]

that could get you in the doghouse

I'm not afraid of the doghouse anymore. With 9 consecutive life sentences, what's one more?

 

[Gionnirocket]

How the hell do you kill a message that's been started but not yet posted?

I ask because I just started a different question, then realized I already had the answer before posting. But it won't go away! I clear out all the text, go to another thread, come back to this page, and everything I deleted from the composition textbox is there again!

All I could think of was to change the original question to this one.

Click on the floppy disk icon and delete draft

 

[Jeremy McCreary]

Click on the floppy disk icon and delete draft

View attachment 143917

Thanks! For some reason, my tool bar is often unresponsive. But when it's working, I know now what to do.