donn said:
I wouldn't like that. Why have a torque sensor, if you need to do some kind of cadence jump start?
That's how I feel.
There was a non-public version I was told about by Grin, but which I know of no way to get hold of, that did implement this, but it has never been put in a released version. So it *can* be done.
The one issue with this type of setup, is that if you happen to stand on the pedals at a stop waiting to go (like some trackstand maneuvers can be), you could with some sensors initiate unintended motor start, potentially at a high level if the sensor just detects distortion of the BB spindle from one side to the other. Easy to prevent by holding the ebrake, but the potential is there.
Same thing with some sensors if you climb on the bike by using one foot on a pedal even already at it's bottom downstroke.
Another issue is calibration--torque sensors in general don't stay at exactly the same zero reading, and some fluctuate quite a bit, so the potential for it to power on at a setting that starts the bike going already without being touched exists.*** Or for you to let off the pedals, but it to still think it's detecting torque, and fail to shut off the motor.****
So I can see where it wouldn't be a default mode, and should come with a warning. I can even see where it would be a mode that *requires* enabling it from the computer-side setup software, and is not available in the onscreen menus at all until then. But it should still be an option, for those of us that do need it.
***there is a way around that, and that's to calibrate it at powerup, just like other torque-based systems do, some of them by displaying a message to remove feet from pedals, then press a button, wait a second, and then it would be zeroed for the moment.
****there could also be a user-calibration like the throttle has, that provides a range of minimal torque sensing input that is classed as a deadzone, where no response will occur until output goes outside that range.
According to my reading of the CA 3.1 manual, there's a torque mode with a configurable start level. But that's in "HWatts", which if that means something like "Watts", if I remember my elementary physics means you would indeed have to be moving the crank ... but doesn't the torque sensor measure Force, not Power?
Yes, that is all basically how it works.
If you have a CA and torque sensor already, you can find out the minimum level of torque it requires on your system to start. There are ways to "trick" it into workign "better", but I haven't found a way that does it like I want it to. I would prefer pure torque up until some speed, and then cadence can take over. So, until that kind of mode is available, or I can make electronics to reroute and convert signals***** from the PAS/torque sensor, I live with the way I have it now.
***** basically it'd take the torque sensor signal itself and convert it into a throttle voltage, and then feed that into the Throttle In of the CAv3, and the torque sensor wouldn't even connect to the CA Torque sensor input at all. It would also implement both of the above *** and **** operations. The only practical way to do this is via an MCU, which I have very little idea how to program, which is why I haven't done any of this yet. (and I've been hoping Grin would release a CA version that does this so I won't have to

). The cadence sensor would also be routed to an input of the unit, and come unaltered from an output of the unit to the CA's cadence input, but the unit would mask that input except beyond whatever limit was set in it.
FWIW, you can actually have a pure-torque system if you like, by creating something to make a pulsetrain into the CA's cadence input that "enables" the torque sensor all the time, and then setting up the CA so it's response is essentialy only based on the torque input level. Not sure what settings you'd need to do that, but it should be possible, based on some of the things discussed in the CAv3 beta thread with Teklektik and Justin_LE, etc., a few years back when I first started trying ot setup the trike for torque control.