Electric Parking brake/Handbrake on kelly controller

[CharlySierraGolf]

Hi,

Does anyone tried or did this with a kelly controller?

I need to put a propeller on a certain position after use in midflight.
So i need to make it a full stop. Regen braking will make it run slower but not a complete stop.

Any idea how to do that ?

Regards

 

[amberwolf]

While there could be something I haven't seen, I know of nothing in any of the kelly controllers to do that. (or any others; there was once a version of Lebowski's DIY controller brain firmware that did. Sevcon might have this feature, but they are very complicated to setup for a system).

You can ask Kelly (probably Fany there) specifically about it, if you can get across what you actually need it to do (this can be difficult).

They would need to have a version of braking that is not regen, but instead actively uses power to lock the rotor in position during braking even at zero RPM. What that might be called could be whatever that company decided to use. Electric Parking Brake function would make the most sense, but that doesn't mean they'd use it.

Some cheap controllers have an antitheft function that can attempt to fight any rotation that's started, but it takes some rotation before it activates.

To stow a prop in a specific position, you might need to use a separate MCU (arduino, etc) to drive either a separate set of phase FETs used only for this purpose, or drive the main controller's FETs with the main controller's MCU turned off or held in reset. This MCU could read a separate set of position sensors that detect the prop position (via rotor position sensors if they're enough for it, but they probably aren't). It doesn't have to "spin" the prop, it just has to move it one "click" at a time to the stow position, and either keep enough current in the motor phases to hold it there against aerodynamic forces (if this isn't too much current for the motor to handle continuosly in a locked-rotor state), or activate a locking solenoid that engages something on the rotor or prop to prevent rotation.

Note that anything that runs continuously (like the "EPB" function would have to) will constantly use power, and when power is not available it will not lock the prop. A solenoid or solenoid-like device could be used that requires power to move it, but not to hold it.

 

[harrisonpatm]

I've thought about this too, and I had an idea awhile but it might be too dumb for reasons I can't come up with.

For my motorcycle, I was thinking of piggybacking cable on top of the lugs where the 3 phase wires connect to the motor controller. And figuring out some sort of manual switch that would short all 3 wires. With all 3 shorted, on a motor this big, it would take a lot to get the motor to move. Not a full brake, enough force would still be able to move the wheel, but it would probably at least keep it in position (which is what you said you were looking for), and it shouldn't use any power.

I also thought of it because I was thinking of a parking brake, but I never wired it because I wasn't sure if it would damage the controller in ways that I don't forsee. Plus, if I accidentally left it on, then tried to throttle up, I would almost certainly damage the motor and/or controller.,

 

[amberwolf]

For my motorcycle, I was thinking of piggybacking cable on top of the lugs where the 3 phase wires connect to the motor controller. And figuring out some sort of manual switch that would short all 3 wires. With all 3 shorted, on a motor this big, it would take a lot to get the motor to move. Not a full brake, enough force would still be able to move the wheel, but it would probably at least keep it in position (which is what you said you were looking for), and it shouldn't use any power.

It won't use any power, but it doesn't actually lock the rotor completely--it just makes it harder to spin--the slower you try to turn it, the easier it is to actually do so, and it *will* still move if the forces are great enough (determined by motor characteristics, see below). .

If the prop has to be locked in a specific stowed position for a reason (like retracting it into a fairing) this method also won't work because it doesn't have a specific preference for where the shaft stops.



But as you've noted, since you're shorting all the controller's FETs this way, then if you turn the controller on while it's shorted, it could just blow up. (it probably will blow up if you actually try to use it while shorted). So you'd need to have an interlock to turn the controller off *before* the short is created, and turn it on only *after* the short is removed.

It won't hurt the motor itself to do this (as long as you aren't actually spinning it enough to generate high currents).


The other issue is that it depends on the physical motor design for how well it can resist the turning. The longer the radius of the moment arm of the motor itself (generally larger diameter rotor) and/or the greater the width of the magnet/stator interface (generally wider motor), the higher the torque forces required to spin it against the shorted fields at zero RPM.

I'm not certain, but I think that a motor with a higher kV will create a voltage at a lower RPM to begin resisting it's movement, so a "high-speed" wind of the same-otherwise motor might resist sooner than a "high torque" wind...but the HT wind might resist turning better once it does start to do so. Haven't tested this.