I don't quite agree. Torque is by definition analog, but a torque sensor is not by definition analog. I can imagine a mechanical sensor giving a discrete output, for example by pressing down over a series of ever stiffer flaps. (Of course an analog sensor can give a digital signal via D/A converter, but that isn't what I mean.)
Maybe controllers are (almost) always designed to use an analog voltage as torque input; Saneagle will know much better than I do if that is so.
But I absolutely agree with his main point: what matters is how the controller uses the torque input.
Microprocessors generally have two types of input:
1. Digital - 0v or 5v, can be used for logic.
2. Analogue - continuous 0v to 5v, has to be converted within the processor to a digital value using an A to D converter.
I've played with some microprocessors that had a derived digital input called pulsing. There must be some sort of pre-logic in the processor that converts the 5v pulse into a digital on/off signal. There are probably a load more derived signals to make programming easier.
The logic in the programming can do anything it wants with those inputs. The problem with responding to analogue inputs is instability, where you get overshoot and resonance problems, which require quite a lot of code to bring under control. That's one reason why I believe that power is stepped according to the torque sensor input rather than proportional. The question is how many steps. I'm pretty sure that my TSDZ2 has two steps.
It's difficult to evaluate because of the effect of your own pedalling. Rather than talk in torque figures, I'm going to approximate with power because it'seasier to understand the numbers. Let's say for each level there are two steps with a stepping up threshold of 100w pedal power and you're on level 1. Below 100w pedalling, you get the low motor power and above 100w, you get higher motor power. And the two steps in motor power are 50w and 100w on level 1.
When you pedal at 50w, you get 50w from the motor, making 100w total. If you increase you pedalling to 70w, you get 70 +50 = 120w, so it feels like you're getting more power, which is true, but the motor isn't giving more. When you pedal at 99w, you get 149w. Therefore, when you pedal harder, you get more power, and it feels proportional to your pedal power, but the motor isn't increasing its power.
When you cross the threshold at 100w pedal power, the motor steps up its power to 100w, so you get 200w total. The difference between 149w and 200w is still not really enough to feel the step when you're on level 1; however, on level 4, that jump in motor power is something like 250w to 500w, which means that the change in total power is from 349w to 600w, so can be easily felt, and it's a bit like an on/off switch.
Everything I feel with my TSDZ2 matches this theory. You can feel the step in level 3 too, but it's on level 4, where it's very noticeable and wakes you up to being able to detect it on the other levels, once you know it's there. I think the above explains why people think their TSDZ2 power is proportional to pedal force when it isn't. If you have one, try it again after reading this and let us know what you think.
www.pedelecs.co.uk
