Re:BLDC Cogging?

I can find no information regarding Roboteq controllers and BLDC cogging. Is this simply not an issue with your controllers, or does it depend on the type of feedback? I\'m specifically looking at a PERM PMS 150 double sided at 48V with hall feedback. I need precise rpm control driving a small boat propeller up to 1200 rpm; do you know how well the rpm would be controlled with such a load?

Cogging is not an issue with our controllers.

If you want to run at precise and controlled speed, then you will need to operate in close loop speed mode.

The controller can measure speed with good accuracy by timing the transitions on the hall sensors.

Note that speed is measured by measuring the time between hall sensor transitions. This technique will not work well at very low speed. At 1200 RPM it should be fine but we\'d need to know the number of poles of your motor to give a more definitive answer.

Our lowest speed would probably be 100rpm. The motor appears to have 4 poles. They mention \"pole pairs\', but I think it is because they have a single and double version of their motors where they just put a second rotor/coil up against the first. Can I have both hall and optical inputs to the controller so I get more pulses per rev for better speed regulation?
If I am using the hall sensors to control the motor, can I run it at a constant power setting? Some of the time we need tight rpm control and other times we would want to run at constant power and let the rpm vary with load. If the controller doesn\'t have that capability, could I write a BASIC script to do it by monitoring motor power and adjusting rpm to keep it at the same power point?

You can write a very simple script that switches between open loop and closed loop upon certain conditions.

In the decade since I posted this, we've had no problem with a variety of motors. We are now experiencing cogging with an Aerotech BM1400 using an HBL1696 controller. We have used other Aerotech motors (BM500 and BM250) with no problem. I would like to try Sine commutation, but our firmware is too old, you don't list the firmware update since you no longer make this controller (which is inexcusable from a support standpoint) and our Govt email system stripped the one that was sent to me. I've requested that it be sent to my personal account but have received nothing.

A common issue, especially with sensorless brushless DC motors ... 'Cogging' is a general term (possibly even a colloquial term) used to describe a brushless ...
'Cogging' is a general term (possibly even a colloquial term) used to describe   space bar clicker     a brushless motor appearing jumpy or jittery. It is much more prevalent at lower speeds than higher as high speeds tend to smooth out the motor considerably. Cogging torque is an undesirable component for the operation of such a motor. It is especially prominent at lower speeds, with the symptom of jerkiness. Cogging ...Cogging torque in dc brushless motors comes from variations in magnetic field density around a rotor's permanent magnets as they pass the nonuniform geometry of ...