Hello! I've been working on a project where I need to attach 2 hub motors to a tricycle, and come up with a control scheme involving torque control. Researching about BLDC motors and drivers I kept ending up in these forums, so I suppose this would be the best place to ask questions!
I'm using a Kelly controller in torque mode, KBS48051X, to control a brushless DC hub motor rated @ 250W, 15Nm. These Kelly controllers seem to have some popularity as far as Chinese components go, but I find the lack of information a bit troublesome.
My question is, how precise of a torque control can I expect from these controllers? Is it reasonable to expect both motors would give out similar torque for the same input?
I built a straightforward device to measure the output torque x input, using a moment arm pressing against a force sensor at stalled condition. What I found is the output torque is highly dependent on the stator-rotor angle, and stall torque is fairly unpredictable. I believe the reason might be due to the nonlinearity aspect of BLDC motors (such as the "cogging" behaviour), due to the structure and alignment of permanent magnets and stator, and perhaps the 6 step trapezoidal control scheme. Maybe when the motor is actually spinning I could get some consistent torque?
In addition, something else I've noticed is sometimes the motor won't start in torque mode, no matter the input. If I move it a little by hand, then it will start spinning. Basically, the motor won't start in torque mode for some specific angles. Could this be due to cogging? From what I read so far, cogging should be somewhat mild, and shouldn't prevent the motor from starting altogether.
I'm using a Kelly controller in torque mode, KBS48051X, to control a brushless DC hub motor rated @ 250W, 15Nm. These Kelly controllers seem to have some popularity as far as Chinese components go, but I find the lack of information a bit troublesome.
My question is, how precise of a torque control can I expect from these controllers? Is it reasonable to expect both motors would give out similar torque for the same input?
I built a straightforward device to measure the output torque x input, using a moment arm pressing against a force sensor at stalled condition. What I found is the output torque is highly dependent on the stator-rotor angle, and stall torque is fairly unpredictable. I believe the reason might be due to the nonlinearity aspect of BLDC motors (such as the "cogging" behaviour), due to the structure and alignment of permanent magnets and stator, and perhaps the 6 step trapezoidal control scheme. Maybe when the motor is actually spinning I could get some consistent torque?
In addition, something else I've noticed is sometimes the motor won't start in torque mode, no matter the input. If I move it a little by hand, then it will start spinning. Basically, the motor won't start in torque mode for some specific angles. Could this be due to cogging? From what I read so far, cogging should be somewhat mild, and shouldn't prevent the motor from starting altogether.
