Torque sensing pedal assist
 

I've starting doing basic research and I'm under the impression that most ebikes supply assist power in response to pedaling. Power is cut if the cyclist stops pedaling and power is restarted, sometimes abruptly, by resuming crank rotation. The amount of power provided is determined by switching modes or levels on a manual controller.

Alternatively, the more advanced systems adjust the power amount by measuring the cyclist power at the crank. These systems may also have a manual adjustment of power levels, but the system uses torque sensors to micromanage the amount of assist.

What are a few examples of systems that actually micro adjust assist based on the effort produced by the cyclist?

The Copenhagen Wheel is one such system. It is unique in being contained entirely in the hub of the rear wheel. Everything: battery, motor and controller. All e-assist systems will one day be made this way but for now most have separate modules for the battery, motor and controller functions.

The Yamaha mid drive is also torque sensing;

More expensive bikes have torque sensors instead of cadence sensors. Stromer, for example.

AFAIK, all the major manufacturers (Specialized, Trek, Giant ...) have torque sensors on their mid-drives. Many (all) have a cadence system too and use the torque, cadence and bike speed to determine the amount of assist also factoring in the level the assist is set at. Lots of individuals opine that torque sensors are superior to cadence, but I've ridden many bikes with torque sensors and own a Yamaha-equipped Haibike, and IMO the cadence-only system on my BBS02 hardtail is as good as the others.

I have a GenZe 102 that is torque sensing. Indeed, you stop pedaling, it stops helping. I find the torque sensing will help up to the PAS level. On flat ground, little help is needed. Going up a hill, more help, higher PAS, is needed. Higher PAS on level ground does not affect anything or give too much help. It can cause abrupt starts, though.

The GenZe Nearly New bikes are quite affordable.

The help on the hills is exactly what I'd like to have. Ideally, any assistance on the flat would be just enough to overcome the extra weight and mechanical friction imposed by the drivetrain.

I was wasting time on the interwebs recently and found out there are a couple of torque sensing bottom brackets available. They aren't all that cheap, but they aren't power meter expensive either.

OMB Barrett - finally coming over to the dark side?
You're looking for a "torque sensing" rather than cadence sensing system. Are you looking to build a bike, or are you looking for something off the shelf.

Personally I just use a throttle because I like the precision of them (and I run low power). Since you are an acomplished biker, you might be happy with a low power assist for hills where it is basically an on/off system. The trick with ebikes is that they get heavy quickly - which has to be ballanced out with the hill climbing advantages...

I'm ready to use an electric assist road bike on those days when I want to ride for an hour or two but when I'd like to avoid suffering on the hills. I expect that these rides will supplement my usual rides on my regular road bikes. I've avoided "active recovery" rides in the past since every hill is usually a peak effort.

I'm looking at two models: The Orbea Gain D30 which is an aluminum frame model with a Ebikemotion low power cadence sensing motor, this bike is about 30 lbs. I'm also looking at the Yamaha Urban Rush which is a mid-drive torque sensing drive system with more power, this bike weighs about 40 lbs. I'm investigating a test ride of each.

OP, you might be interested in a Revel Propulsion mid-drive system which adds about 10 pounds to a bike and employs a torque sensor. I tested one and it was pretty impressive. Possibly the weight could be reduced by a couple of pounds with a smaller battery. The second iteration is being introduced next month AFAIK. Also, look at C58's lightweight e-builds.

Thanks for the recommendation! I saw your thread: https://www.bikeforums.net/electric-...ropulsion.html

The system is something I'll seriously consider. It looks like it's adaptable to a steel road bike I have. If I understand correctly, It's power output is completely torque dependent, or does the display include settings that can be adjusted while riding?

Don’t forget the Tong-Shen tsdz2, a torque sensing mid-drive. I have one and I love it, even more than the bbs-02 it replaced.
much cheaper than the revel unit , but battery is not included.

The TSDZ2 package I installed on my wife's bike is working very well. I recommend it highly for performance and value.

Gentlemen, thank you for the recommendation. The Tong-Shen looks like a true torque sensing system for the active cyclist. I'm reading that the power assist tapers off as the cadence increases above 90 rpm, it this accurate? It's not a deal breaker, but I'm interested to know the specifics. Also, at what speed does the power assist begin to taper.

Thanks'

Nominally, 90 rpm is the assist limit. The TSDZ2 can be programmed for higher cadences though. The speed at which it tapers is dependent on what gear you are in. The programmed limit is 28 mph.

There is a group of enthusiasts who have developed open source firmware for the TSDZ2. Installing this firmware is said to allow expanded control of the operating parameters for better performance. I have not availed myself of this resource but it sounds intriguing. I purchased the kit from EcoCycles in Nashville, TN. This vendor does offer the open source firmware pre-installed as well as a lot of support for doing it yourself.

Hi "Moe"

I contacted Dave at Eco Cycles and we discussed the options and services they provide for the TSDZ2. I'm planning on ordering the system with the 52v updates and battery this month. I hope to be using the bike in March.

Thanks for the tip!

David Hall of Eco Cycles was great to deal with. He answered all of my pre-purchase questions in impressive detail, and went above and beyond to resolve some issues with my order. Working with Eco Cycles was one of the best vendor experiences that I've had in a long time.

I have both kinds of ebikes (torque and cadance). The torque sensing motor is a Bosch Performance CX mid drive and you can hardly feel the motor in EMTB mode. IN EMTB mode the PAS multiplier scales with your input. That results in it being difficult to feel the motor input. In Turbo mode, the PAS multiplier is fixed at 300% and it is noticeable as to the the motor input. My other bike has a cadance sensing rear hub motor (it's a DAS-KIT). The hub motor is very noticable WRT motor input. Just touch the pedals and start them spinning and the motor just goes, and feels like a kick in the pants.

The hub motor gives you more speed and acceleration for the money. The Bosch mid drive is more expensive, but also more suitable for technical terrain that you find when riding a mountain bike. You do not want a motor to just kick in full power when you move the pedals while navigating tricky terrain. The mid drive motor also lends itself to more rider exercise because you have to pedal harder to get more power from the motor. The hub drive just puts in max power up to the PAS speed limit. IOW PAS sets the point where the motor stops contributing. It doesn't actually set the motor assist power.

The caveat here is that this info is specific to the Bosch mid drive and DAS-KIT hub drive.

The controller that Eco Cycles is providing with the TSDZ2 has 9 power levels, all of which are responding to the torque sensor in the bottom bracket. The power levels are adjustable. If the system works as described, I'll set the power levels to gently overcome mechanical resistance at the low end and to provide a large multiplier at the higher end. A throttle is optional, but I'm not interested in an electric powered ride that doesn't really require any effort.

Hopefully, I'll be able to ride with many different levels of assist. At times I'll just use a small fraction of the power available, and will enjoy an experience nearly identical to having no assist on a good road bike. At the other end of the spectrum, I'd like enough assistance to climb a 20% hill while keeping my heart rate below 125 bpm.

I'm excited to see what the system can do.

I think this thread would be much more helpful if all the acronyms being used were written out in full at least the first time they are used. I've dabbled in this e-assist stuff since the early and mid-90's and I'm seeing acronyms in this thread I've never seen before. Never got further than paper napkin flow charting though. Back then Ni-CAD batteries were still a thing. Throttle was still king but some crude torque sensors had appeared. That's all changed and it doesn't look like Li-ion battery technology is going to be improved upon in my riding lifetime. About my only question is: how is it possible to have a torque sensing crank drive system? It seems like the motor assist turning the crank would make it impossible for the torque sensor to know just how much human input into the system is going on. Back when I was designing systems on napkins I ruled out both torque sensing and crank drive together for that reason. Clearly I was wrong. But why was that?

I agree that acronyms should be explained, as you outlined.

Torque sensing is achieved by using strain gauges, see: https://www.omega.com/en-us/resources/strain-gages . It's not difficult to measure the torque developed by the cyclist and isolate it from the torque developed by the electric motor. The torque developed by the motor is transferred directly to the chainring. The torque developed by the cyclist is measured in the axle between the crank arms.

Think about a tandem bicycle: The power developed by each rider is measurable and is independent. Now imagine that the captain is human and the stoker is electric and the stoker produces power in a proportional response to the power produced by the captain.

For anyone interested in this subject, Ron (aka spinning magnets) has written an execlent in depth article on the TSDZ2
I would highly recommend it if you want to do in depth.

TSDZ2, mini 750W mid-drive with torque sensing:
https://www.electricbike.com/tsdz2-7...orque-sensing/


The Bafang units have been around the longest, but this unit is close on its heals. Anything newer I would be a little wary of. Bafang gets a lot of the attention because it is big and potentially powerful (i.e. there isn't much point in pedaling at some of those power levels). But this unit looks great for people who actually want to pedal, and want the bike to feel like a bicycle rather than a moped.

I love a lightweight build that rides like a bicycle. Been riding my 25lb 25mph ebike for the better part of a decade now.

We recently purchased a pair of 2019 Giant Lafree city bikes with mid drive Yamaha motors. They are a combo of up to six sensors in full auto mode. The five programmable levels are based in percent of your effort and can add up to 300%. It measures speed toque cadence slope and other factors to give a very realistic feel. I'm enjoying the bike a lot! On longer trips, I ride 50 to150 assist and can get about 100km (62miles) on a charge. Mid drive works great because we get to use the 8speed derailleur to its full extent. Based on riding mine another friend just bought a Giant Explore at $2700 CAD. The 250 W motor has all the power you would want and uses power sparingly. For health reasons my wife had mostly stopped riding with the group. She's back and enjoying it. Could not be happier with the riding experience. We tried some no-name specials and were disappointed. The Giant does not have a throttle.

Just installed a TSDZ2 from Eco-ebike on Thursday. Love it so far, got the kit from them. Dave answered all my questions beforehand and was very helpful. After the purchase, due to a delay in shipping, they threw in an additional controller. I would purchase from them again and recommend them.

Added the kit to my commuter, I gain/lose about 300 feet on the 10 mile commute and the gain is on the way home, which sucks at the end of the day and the usual headwind on the way home. Looking forward to actually riding it back into the office, when I'm not working from home anymore.

Thanks,

LB