Jeremy Harris
100 MW
OK, if you're ebike pedals OK with no throttle (many don't pedal so well like this) and you don't want any motor input unless your pedal torque exceeds some pre-defined level, then what you propose will have the following effect:
On the flat, pedalling with a low crank torque, the motor will try and run at a much lower speed than you're travelling at, as the throttle input speed command will be much lower than your actual speed (if it has regen then it'll be acting as a big brake).
On a hill, as the pedal crank torque increases the motor will try and make the bike go faster, pushing the controller hard into current limiting mode, because the bike speed will most probably be well below the demanded speed.
As the hill levels out, the bike will accelerate as the controller starts to come out of current limiting but still tries to accelerate up to the demanded speed, until the point where the bike speed matches the pedal crank torque speed demand.
At this point the motor will start to slow down as pedal crank torque produces a speed command that is lower than the bikes actual road speed.
What I think you will find is that the motor will try and run much slower than you're going most of the time, then will try and run much faster than you're going as you go up a hill, or hit a headwind. You may find this works for you, but it isn't close to being torque control, or power control, it's just really having a control system that will feel maybe a bit like an on-off switch, depending on whether or not the pedal torque sensor demand is greater or less than the actual road speed.
Proper torque control would give you the 'bionic leg' feel, where motor torque boost is directly proportional to pedal torque - pedal harder and you get more torque boost, pedal less hard and you get less torque boost. This would feel pretty natural and allow the motor to try and run at a speed that matches road speed all the time, reducing drag.
The key to understanding this is that with torque (or power) control the motor rpm depends on road speed and load, rather than just the throttle setting. The throttle input (which may come from a pedal or other torque sensor) only controls the amount of motor torque/power boost that's wanted and in theory has no effect on motor rpm. This is pretty close to the way a car or motorcycle throttle works - you only need a very small throttle increase at no load to get to maximum rpm, because the throttle is effectively a torque demand control. This makes cruising simpler, because you don't need to try and do the fine tuning that we tend to do with a speed throttle to maintain just the right speed with a low power demand.
Jeremy
On the flat, pedalling with a low crank torque, the motor will try and run at a much lower speed than you're travelling at, as the throttle input speed command will be much lower than your actual speed (if it has regen then it'll be acting as a big brake).
On a hill, as the pedal crank torque increases the motor will try and make the bike go faster, pushing the controller hard into current limiting mode, because the bike speed will most probably be well below the demanded speed.
As the hill levels out, the bike will accelerate as the controller starts to come out of current limiting but still tries to accelerate up to the demanded speed, until the point where the bike speed matches the pedal crank torque speed demand.
At this point the motor will start to slow down as pedal crank torque produces a speed command that is lower than the bikes actual road speed.
What I think you will find is that the motor will try and run much slower than you're going most of the time, then will try and run much faster than you're going as you go up a hill, or hit a headwind. You may find this works for you, but it isn't close to being torque control, or power control, it's just really having a control system that will feel maybe a bit like an on-off switch, depending on whether or not the pedal torque sensor demand is greater or less than the actual road speed.
Proper torque control would give you the 'bionic leg' feel, where motor torque boost is directly proportional to pedal torque - pedal harder and you get more torque boost, pedal less hard and you get less torque boost. This would feel pretty natural and allow the motor to try and run at a speed that matches road speed all the time, reducing drag.
The key to understanding this is that with torque (or power) control the motor rpm depends on road speed and load, rather than just the throttle setting. The throttle input (which may come from a pedal or other torque sensor) only controls the amount of motor torque/power boost that's wanted and in theory has no effect on motor rpm. This is pretty close to the way a car or motorcycle throttle works - you only need a very small throttle increase at no load to get to maximum rpm, because the throttle is effectively a torque demand control. This makes cruising simpler, because you don't need to try and do the fine tuning that we tend to do with a speed throttle to maintain just the right speed with a low power demand.
Jeremy
what i'm really looking for is a system that will ensure that the pedaling force that i'm expending (i.e., my muscle contribution) does not exceed a predefined amount.
