Torque sensor vs Cadence...

BigNerd

Well-Known Member
Not all cadence sensor software is created equally, so there can be quite a difference from a practical stand point from one bike to the next. This is one of the reasons you'll hear that riding a bike before buying it is a good plan.



P-38 has done a nice job describing "speed" based cadence software. You can see that the different PAS (pedal assist) levels must be changed to change your speed.

The "other" major type of cadence sensed PAS is WAY different, and offers a much more normal experience to my way of thinking. It does this by allowing a certain amount of power to the motor, depending on PAS level chosen. This amount of power doesn't change at ANY speed. If you want more "assist" you dial up the PAS level and it supplies more power to make it easier to pedal. You want to "ghost" pedal with no effort? Set the PAS as required.

For instance - in PAS 1 my bike will have less than 100 watts available for the motor to assist you. It actually varies if you look at the watt meter, bouncing around from about 65 watts up to 100 (keep in mind the controller uses about 50 watts for internal housekeeping), but you feel none of this. It's super smooth, with no jerky on/off as your speeds change. Lets say you make a corner, and the wind direction changes to something hitting you in the face, making it more difficult to pedal. Bumping up to PAS 2 doubles the available power (to 180-200 watts or so), cutting the effort to maintain the SAME speed you were going by 1/2. Hills the same way, or maybe the pavement turned to grass. Set the PAS level for the effort you want to put into pedaling - up to level 5, and it just adds the power you want - no more - and speed has nothing to do with it. Going faster takes more effort, so you dial up the PAS level to reduce the effort to what you are looking for.

I'm going to get into this conversation because I tested this myself on my Espin Sport and a cadence sensor.

At any PAS level, there is a maximum amount of power available. While in each PAS level, how much of this power goes to the motor is inversely controlled by the cadence of your pedaling. Pedal slow, more power, pedal fast, less power.

Additionally, there is a speed limit at PAS. What this does is if you are going faster than the limit at that level, the motor only gets nominal power because there is no need to give you 100% of the available power.

To illustrate this, let's say PAS 1 gives you 100 watts (on a 500watt motor) and has a limit of 10mph.

You start pedaling, 100 watts goes to your motor because you are pedaling slow (this is why on many cadence sensor bikes there is that "jump" when you first start). Then as you pedal faster, that 100watts become 50 watts or 25 watts because you don't need that much assist. Now, say you go down a hill and exceed 10mph. The motor will only get 10watts because you are over the speed limit. This makes sense because why supply power to the motor if you are going faster than that PAS level. Even if you slow down your cadence, the motor will not receive more power until you are below the 10mph limit.

Does this sound right?
 

GenXrider

Well-Known Member
You start pedaling, 100 watts goes to your motor because you are pedaling slow (this is why on many cadence sensor bikes there is that "jump" when you first start). Then as you pedal faster, that 100watts become 50 watts or 25 watts because you don't need that much assist. Now, say you go down a hill and exceed 10mph. The motor will only get 10watts because you are over the speed limit. This makes sense because why supply power to the motor if you are going faster than that PAS level. Even if you slow down your cadence, the motor will not receive more power until you are below the 10mph limit.

Does this sound right?
It sounds like the Espin has the dreaded speed based cadence PAS system. That's unfortunate. Some other companies have moved away from a speed based PAS to a power based cadence PAS that doesn't drop power way down when hitting a particular speed in a given assist level. Start reading at this post and beyond where I have gone into a lot of detail on the matter:
 

BigNerd

Well-Known Member
It sounds like the Espin has the dreaded speed based cadence PAS system. That's unfortunate. Some other companies have moved away from a speed based PAS to a power based cadence PAS that doesn't drop power way down when hitting a particular speed in a given assist level. Start reading at this post and beyond where I have gone into a lot of detail on the matter:
How is this "dreaded"? I'm still not sure you understand how the PAS system works on the Espin Sport.

Dropping power when you hit a certain speed is a benefit, not a con, it saves battery life. Why would you need power if your bike is already going faster than that PAS level speed limit (by either doing downhill or under your own power)?
 

GenXrider

Well-Known Member
How is this "dreaded"? I'm still not sure you understand how the PAS system works on the Espin Sport.
Previous comments have implied it's speed limit cadence PAS. A new owner today stated that he thinks it is speed based also. So, this lines up with what I had suspected all along. It appears to have a high initial power surge for acceleration, but drops power way down if you try to exceed the speed programmed for a given assist level. The Ride1Up bikes and old Radbikes used to work the same way until they got wise and improved their systems. Kevin from Ride1Up discussed this change in an interview last spring/summer.
Dropping power when you hit a certain speed is a benefit, not a con, it saves battery life. Why would you need power if your bike is already going faster than that PAS level speed limit (by either doing downhill or under your own power)?
I would prefer a PAS maintain power so that I can add muscle power to further increase my speed without losing assist, just as Kevin from Ride1Up had mentioned in his video detailing the change to power based PAS. And as I mentioned in the other thread to your comment:
BigNerd said:


So there is a speed limit in the sense that it stop sending out more than a small amount of power when you exceed that speed, which makes sense because why output power if you're moving faster than that power level could move you.

In the case of Radpower, I don't get why it would still put out max power regardless of speed because isn't that just a waste? Unless there is something different in their cadence sensor control.
OK, this is a key point, which explains why you made some of your earlier comments. If you are using X watts of power in a lower assist level that provides enough power to take the bike up to 15 mph while lightly pedaling, then you start pedaling with force to get up 20 mph, the X watts of power does NOT go to waste when you go from 15 mph or 20 mph under your added muscular energy. It still provides X watts of power assistance on top of what ever muscular power you supply, which was Kevin's point when he said he may want to pedal faster up to 25 mph without losing assistance. If the X watts were to drop off significantly at 15 mph, you would have to pedal much harder to get to 20 mph. So, the assist power doesn't go to waste on the power based assist bikes. Note, class 3 will drop power at 28 mph, but that's a global limit, not specific to either PAS."

The power based assist is more rewarding when you want to get more exercise and pedal harder because it will continue to provide the same power assistance so that your speed increases more. If you want to save battery, you simply use a lower assist level while pedaling harder. Easy peasy.
 

BigNerd

Well-Known Member
Previous comments have implied it's speed limit cadence PAS. A new owner today stated that he thinks it is speed based also. So, this lines up with what I had suspected all along. It appears to have a high initial power surge for acceleration, but drops power way down if you try to exceed the speed programmed for a given assist level. The Ride1Up bikes and old Radbikes used to work the same way until they got wise and improved their systems. Kevin from Ride1Up discussed this change in an interview last spring/summer.

I would prefer a PAS maintain power so that I can add muscle power to further increase my speed without losing assist, just as Kevin from Ride1Up had mentioned in his video detailing the change to power based PAS. And as I mentioned in the other thread to your comment:

OK, this is a key point, which explains why you made some of your earlier comments. If you are using X watts of power in a lower assist level that provides enough power to take the bike up to 15 mph while lightly pedaling, then you start pedaling with force to get up 20 mph, the X watts of power does NOT go to waste when you go from 15 mph or 20 mph under your added muscular energy. It still provides X watts of power assistance on top of what ever muscular power you supply, which was Kevin's point when he said he may want to pedal faster up to 25 mph without losing assistance. If the X watts were to drop off significantly at 15 mph, you would have to pedal much harder to get to 20 mph. So, the assist power doesn't go to waste on the power based assist bikes. Note, class 3 will drop power at 28 mph, but that's a global limit, not specific to either PAS."

The power based assist is more rewarding when you want to get more exercise and pedal harder because it will continue to provide the same power assistance so that your speed increases more. If you want to save battery, you simply use a lower assist level while pedaling harder. Easy peasy.

I said this in the other thread, that's not how cadence sensors work... your argument could make sense for a torque sensor.

You keep saying pedaling with "force"... but the cadence sensor measures "cadence" of pedaling. So if you pedal with a cadence that gets you up to 20mph, the power output has already dropped because the faster you pedal, the less power you get from the motor. You have to change PAS just like you have to change gears if you want to maintain or increase speed.

If the new systems you are mentioned do not reduce power output as you pedal faster, then that would use up battery power more and the power/cadence curve would be different than what you expect. There is probably something more to that then what has been mentioned here.
 

GenXrider

Well-Known Member
I said this in the other thread, that's not how cadence sensors work... your argument could make sense for a torque sensor.

You keep saying pedaling with "force"... but the cadence sensor measures "cadence" of pedaling. So if you pedal with a cadence that gets you up to 20mph, the power output has already dropped because the faster you pedal, the less power you get from the motor. You have to change PAS just like you have to change gears if you want to maintain or increase speed.
Funny, I posted this in the other thread just before I read your comment here. And I was right, you confused "pedaling with force" with "force sensing". Here's the rest:
It's no wonder you haven't followed the cadence "speed" vs. "power" discussion if you are confusing it with a torque sensor PAS system. The torque sensor system measures how much pedaling force is applied to the pedals in calculating how much power to supply to the motor. The cadence sensor system is more like a switch checking whether the pedals are moving or stationary, with no measurement of pedaling force. You may be confused because I mentioned "pedaling with force" in the test steps, but that is to push the bike beyond a specific PAS speed of the Espin, and it is in no way related to the bike measuring your pedaling force as it is done in a torque PAS system. It's apples and oranges, and it shows you still aren't following the discussion despite all the details I have provided. I'm thinking it's hopeless.
 
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TACO MAC

New Member
Region
USA
I have just begun the daunting task of researching the different brands, models & technical features available on eBikes. (No small task, lol) My aim is to buy a bike (maybe two,) that has the features, performance, comfort, reliability & customer support that meets my needs. EBR YouTube videos are very helpful.

One aspect I do not see addressed much is torque sensor verses cadence (how hard you are pedaling.) Many of the mid range bikes have only the cadence type sensing which from my understanding, only senses that you are pedaling but not how hard. (So the motor applies the full PAS power whenever you pedal? ...Like a on/off switch?)

On the other hand I understand that bikes fitted with a strain gauge type torque sensor, senses how hard you are actually pedaling & responds with a proportional amount of electrical assist.

I have a friend who owns several eBikes & he says it's all about torque sensing & that a cadence type system is vastly inferior to the torque sensor. Is there actually a big difference in the way the two systems work & more so, is there really a big difference in the way each bike performs?

Anyone with experience riding both types of sensing?... do you feel that one system works better than the other and if so why? Can you explain any advantages or disadvantages to either?

Oh... and for the record, I anticipate doing mostly street riding, paved & gravel roads, along with some lite trail excursions.

Happy riding to All & thanks for your input!

Ride On... :cool:
ERD
Hey EasyRideDud,

I am in the same boat as you and I am doing lots and lots of research but just coming at it from a different angle. I wanna look under the hood and build one. Yes torque is extremely important but nothing to do with cadence per say. I am looking at at least 60 Nm+ and would like to be in the 75 Nm+ range. But just like a car the me RHP the more the cost. and if you build one then expect to have a real strong frame and torque bars to push the that engine to the frame. Cadence(revolutions of foot pedal) just helps the motor and HUD indicators to adjust how much "energy" is needed from the battery to help you maintain the speed you have selected, either by button or throttle. Like you trying to put the pieces together. But torque is key.
 

GenXrider

Well-Known Member
If the new systems you are mentioned do not reduce power output as you pedal faster, then that would use up battery power more and the power/cadence curve would be different than what you expect. There is probably something more to that then what has been mentioned here.
Gee, you didn't even read the post you responded to. lol Here is what it said:

The power based assist is more rewarding when you want to get more exercise and pedal harder because it will continue to provide the same power assistance so that your speed increases more. If you want to save battery, you simply use a lower assist level while pedaling harder. Easy peasy.

The power curve is actually smoother or more natural than with a speed based cadence that runs up against a wall at a specific speed and cuts your power output when you try to pedal to a higher speed.
 

McCorby

Well-Known Member
This is my understanding....so take it with a grain of salt!

Speed Based: The PAS level sets the maximum assisted vehicle speed. For example, in PAS 1, the max assist speed may be 8mph, PAS 2, 15mph.....and so on. So, in PAS 1 the motor will provide full power until 8mph has been reached. In PAS 2, it will provide full power until 15mph is reached. When max assist speed for a given PAS level has been reached the motor stops/reduces assisting. For me, this feels very unnatural.

Power based: A power based cadence system provides a set percentage of power for a given PAS level, no matter what the vehicle speed. For example, PAS 1 might provide 20% of rated power. PAS 2, 40%......and so on. Other than the vehicle’s max restricted speed (i.e. 20mph for class 1 & 2), speed is not a factor. This would seem to be a more natural feeling method of power delivery in my opinion.
 
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BigNerd

Well-Known Member
Actually, there is a 3rd, power based with a speed limiter like on my Espin Sport.

That makes more sense to me.

I’m not sure which ebike has just a speed based system because that would be inefficient.
 

GenXrider

Well-Known Member
Actually, there is a 3rd, power based with a speed limiter like on my Espin Sport.

That makes more sense to me.

I’m not sure which ebike has just a speed based system because that would be inefficient.
The Espin is speed based if it cuts power down from 400 to 20 watts when you hit a certain speed as your test showed. Power based cadence PAS maintains power up to the class speed, and the Espin does NOT do that in any meaningful way, since it drops it way down to 4% power at a speed threshold, therefore it cannot be called power based. Speed based cadence PAS applies power up to a specific speed, which is what the Espin does before power drops way down to 4%. So, putting 2 and 2 together, the Espin is not power based cadence PAS. It's speed based. The fact that there may be an early acceleration surge, or the fact that there may be some risidual power leaking through beyond the speed threshold, doesn't make it some sort of special hybrid PAS system when it's still being limited by speed in a given PAS level, that the power based PAS bikes are not limited by.
 
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McCorby

Well-Known Member
Actually, there is a 3rd, power based with a speed limiter like on my Espin Sport.

That makes more sense to me.

I’m not sure which ebike has just a speed based system because that would be inefficient.
Why would you want a speed limiter based on PAS level? I would prefer to be in control of speed, via pedal cadence and gear selection, no matter what PAS level I’m using. I just want the PAS level to set the amount of assist the motor provides no matter my speed.
 
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BigNerd

Well-Known Member
Why would you want a speed limiter based on PAS level? I would prefer to be in control of speed, via pedal cadence and gear selection, no matter what PAS level I’m using. I just want the PAS level to set the amount of assist the motor provides no matter my speed.

It's not that I want it, I'm just relaying how it is.

It's similar to the front gears and rear gears.

And to be clear, the Espin Sport does govern the power based on cadence and PAS level. It does not output 100% at each PAS level, which is why I say it's power based with a speed limit.

But just like you can control battery consumption by shifting PAS levels as GenXRider said, you can also control speed by shifting PAS levels.
 

BigNerd

Well-Known Member
The Espin is speed based if it cuts power down from 400 to 20 watts when you hit a certain speed as your test showed. Power based cadence PAS maintains power up to the class speed, and the Espin does NOT do that in any meaningful way, since it drops it way down to 4% power at a speed threshold, therefore it cannot be called power based. Speed based cadence PAS applies power up to a specific speed, which is what the Espin does before power drops way down to 4%. So, putting 2 and 2 together, the Espin is not power based cadence PAS. It's speed based. The fact that there may be an early acceleration surge, or the fact that there may be some risidual power leaking through beyond the speed threshold, doesn't make it some sort of special hybrid PAS system when it's still being limited by speed in a given PAS level, that the power based PAS bikes are not limited by.
Your assumptions are are not reflected by my tests. Please read the other thread about my explanation.
 

BigNerd

Well-Known Member
This is my understanding....so take it with a grain of salt!

Speed Based: The PAS level sets the maximum assisted vehicle speed. For example, in PAS 1, the max assist speed may be 8mph, PAS 2, 15mph.....and so on. So, in PAS 1 the motor will provide full power until 8mph has been reached. In PAS 2, it will provide full power until 15mph is reached. When max assist speed for a given PAS level has been reached the motor stops/reduces assisting. For me, this feels very unnatural.
This can't be the case. Otherwise the "jump" at PAS 1 would be equal to the "jump" at PAS 5 when you start pedaling. I know for a fact that when you first start off, you are not getting 100% power in PAS 1 so there has to be a power governance based on cadence and threshold.
 

GenXrider

Well-Known Member
And to be clear, the Espin Sport does govern the power based on cadence and PAS level. It does not output 100% at each PAS level, which is why I say it's power based with a speed limit.
It's not power based because it drops power significantly when it hits a certain speed. That makes it speed based. Power based system do NOT drop the power at a specific speed based assist level, only a global limit such as 28 mph for class 3. That's for the 100th time now. lol
 

GenXrider

Well-Known Member
Your assumptions are are not reflected by my tests. Please read the other thread about my explanation.
You've been posting a lot of misinformation, I will say that. It appears you are not really wanting to learn anything, and it's coming across as trolling. You're just trying to get people frustrated in repeatedly explaining things to you as you go in circles, keep talking past me, and use the same old tired false arguments.
 

GenXrider

Well-Known Member
But just like you can control battery consumption by shifting PAS levels as GenXRider said, you can also control speed by shifting PAS levels.
On a power based PAS bike, you control power with changing PAS levels, not speed except indirectly since power correlates with speed among other factors. You said speed because the Espin uses the speed based assist, where speed is directly changed with the assist level. You pretty much admit it, but then you deny it at the same time. lol
 

GenXrider

Well-Known Member
This can't be the case. Otherwise the "jump" at PAS 1 would be equal to the "jump" at PAS 5 when you start pedaling. I know for a fact that when you first start off, you are not getting 100% power in PAS 1 so there has to be a power governance based on cadence and threshold.
An early surge of power provided by the controller to increase acceleration, even if it's different at PAS1 vs PAS2 (yet not proven) does not mean that it's not a speed based assist. It's still speed based because it drops way down at a specific speed while power based PAS will maintain the same power as you increase speed. Ride1Up and others have moved away from the speed based assist (that Espin uses) to power based assist. Maybe you can get a different display and controller to change the way your Espin works since you said that's not what you want in your earlier post.
 

BigNerd

Well-Known Member
It's not power based because it drops power significantly when it hits a certain speed. That makes it speed based. Power based system do NOT drop the power at a specific speed based assist level, only a global limit such as 28 mph for class 3. That's for the 100th time now. lol
Again, it's power-based because each PAS level has a power limit just like power-based systems. Not sure why you aren't getting that.

Additionally, there is a speed limit for each PAS level but according to McCorby's definition, speed-based systems have 100% power available at all PAS levels. That is not the case with the Sport. The power fluctuates in correlation to pedal cadence. The max output power at each PAS level is higher for each level.

I am not arguing what is speed-based and what is power-based... just that based on the definitions from McCorby, the Sport has both.