Mototec 48V 1500W Pro Dirt bike Upgraded controller

[Chris Bebensee]

Hi everyone. This is my first post and I just want to say I'm happy to have found such a group of knowledgeable people. I recently got a Mototec 48V 1500w dirt bike. It has a brushless motor, but the control mechanism is speed based. What I mean is, with the variable throttle, as I advance it, it sends a 0-5V signal to the controller that apparently corresponds to an RPM that the speed controller tries to maintain. The problem is, the transition is instant instead of torque based. It's "All or nothing" until it reaches that RPM, then just maintains it. Trying to accelerate smoothly with partial throttle doesn't work and it's like a maniac until it reaches the set RPM. The bike has enough power to easily spin the wheel or pop a wheelie if you aren't paying attention, so the fact that I can't modulate the response with throttle is unfortunate. The controller does have a max speed setting and a "response time" setting, but that just makes it worse, because it just adds delay from when it tries to spin you out or put you on your back, making it even less predictable.

What I want is a torque based approach, so that throttle just commands either voltage or current to the phases of the motor, much in the same way that a decently high end RC car speed controller would. Current limiting could function as a sort of a traction control if too much power was added. This would make handling the bike much smoother and linear in operation and very suited to any surface including low traction like dirt.

To that end, I've been looking at VOTOL EM-50 and EM-100 controllers. They seem pretty reasonably priced and they are programmable. Would anyone recommend them or have a better option for a relatively cheap but decent upgrade for this bike?

Thank you all for your time,

Chris

 

[Quinc]

check out the mototec facebook group. Lots of good info and upgrades on there.

 

[Chris Bebensee]

Will do, Thanks Quinc

 

[amberwolf]

Any FOC-based controller will do what you want for the throttle and current control, so find the one that has all the other features you are after, *and* has a good well-made setup program that is easy for you to understand and use (you can run many of the setup programs without having the controller, so try them out first and see if they make sense to you. If they don't, and their instructions aren't useful / comprehensible, move on to the next....).

All of the FOC controllers will have to be setup in some detail to be used with any system, none of them are plug-and-play by their nature. If the "autotune" part of the setup program doesn't work well, you'll have to spend some time manually tuning the controller to work with your specific motor in the way you want it to operate; it's a steep learning curve that takes some patience and step-by-step work, while taking notes of everything you change and what happens when you do, so you can be sure you're heading down a good path or not, and where to back up to when it gets worse instead of better.


VESC based controllers' setup software seems to have a decent autotune routine, based on postings here on ES. The Grin Phaserunner does, too, but I don't know if it will be powerful enough for your needs.

 

[Chris Bebensee]

Any FOC-based controller will do what you want for the throttle and current control, so find the one that has all the other features you are after, *and* has a good well-made setup program that is easy for you to understand and use (you can run many of the setup programs without having the controller, so try them out first and see if they make sense to you. If they don't, and their instructions aren't useful / comprehensible, move on to the next....).

All of the FOC controllers will have to be setup in some detail to be used with any system, none of them are plug-and-play by their nature. If the "autotune" part of the setup program doesn't work well, you'll have to spend some time manually tuning the controller to work with your specific motor in the way you want it to operate; it's a steep learning curve that takes some patience and step-by-step work, while taking notes of everything you change and what happens when you do, so you can be sure you're heading down a good path or not, and where to back up to when it gets worse instead of better.


VESC based controllers' setup software seems to have a decent autotune routine, based on postings here on ES. The Grin Phaserunner does, too, but I don't know if it will be powerful enough for your needs.

Fantastic, Amberwolf!

Sounds like an interesting engineering problem. Also, there are several controllers that look identical and some say for "hub motors" and some don't say that. Is it safe to assume that any of the controllers can work with different motor types if set up correctly? I'll definitely download the software and play around before I buy.

Thanks for the reply!

 

[Chris Bebensee]

One more question. If the motor I have doesn't have sensor wires, will that be a problem? I'm sure it's brushless because it just has the three phase wires, but no sensor plug or sensor wire bundle. Thanks again.


Edit: I just realized it does have a sensor wire bundled with the phase wires. My bad.

 

[amberwolf]

Is it just a single wire or wire pair? Or a set of at least 5 wires (5v, ground, three signals)? If the former, it's probably just a speed sensor or thermal sensor, at best (though it could be some other form of encoder that sends it's signal back in a (probably proprietary) serial format over the 5v supply line; in that event it is probably only useful with the original controller the motor was designed for).

However, even if it didn't have hall sensors, then as long as the controller you choose supports Sensorless operation, it'd still work. FOC controllers sometimes do, sometimes don't. Non FOC controllers often have sensorless versions, but they may not offer the torque(phase current)-modulating throttle, which is what you want.

The big problem with sensorless is that depending on controller design it may not startup from a stop under any load very well, because it can be hard for the controller to know exactly where the rotor magnets are relative to the phase windings / stator teeth, so that the right signals can be generated to get the motor moving from a stop...but once the motor is spinning even pretty slowly it's fairly easy to detect the magnets moving around and know where they are to send the right signals.



One I tested some years back (that never became commercially available) was completley sensorless...but because of the way it detected rotor postion it was very noisy all the time even just sitting there, making a constant multifrequency sound with the motor windings as it turned them on and off in various ways to constantly check for rotor position (which the sensors do more passively and silently). It's not the only controller that works this way to do sensorless, but the only big one I have direct experience with.

(I have a generic sensorless controller on SB Cruiser that also always makes a whine with the motor to tell where the rotor is, but it's not nearly as noisy, and it's not FOC or even look-up-table-sinewave)

A DIY controller design, for which just the brain chip / board is available (open source so you can alter it as you wish if needed), called Lebowski here on ES, uses hall sensors to startup, but IIRC switches to sensorless once moving.

I don't recall how the VESC versions do it, but it's changed over the years and might have a full sensorless mode by now.

Grin's Phaserunner is based on ASI's BAC series; IIRC it has a full sensorless mode but I'm not sure how well it works under high load from a stop.

Pretty sure Kelly has some sensorless controllers, but not sure if they are FOC and/or if they support torque(current)-modulating throttle.

Most likely the Sabvoton, Votol, Fardriver, etc all have versions taht support sensorless...just don't know how well they work from a stop under load.

Regarding controllers for hubmotors vs others (like RC motors), there are some that won't work well with low speeds and high loads, so they may specify that they dont' work with hubmotors, or you may see that they are advertised for things that fly rather than roll on the ground, or for small scale models of things instead of full size EVs. If you see it is advertised for full size EVs, then look at the EVs it is supposed to work on, and if they use hubmotors it would probably work on yours too. If they don't, it depends on the drive system they do use--if it's really high RPM that's gearbox reduced to go to a drivechain or belt to the wheel, it might or might not work on a much lower RPM high load hubmotor. The details of the reasons for this are too long to go into at the moment, but it is unfortunately a problem in some cases.

Best I can say on that is first ask the manufacturer, and next post the one(s) your'e considering here in this thread and if we have experience with them we can tell you what we know.

 

[Chris Bebensee]

Awesome information! I kind of suspected that's how sensorless worked, because in my RC racing days, I did break a sensor wire once, and the car still ran, but the initial response was notchy. Once it was moving, it was better, but I really never fully evaluated it because I just bought a new sensor wire and moved on. I actually ordered a VOTOL EM80, so if I find out that it's not compatible with that motor, I'll find something that is and install that instead. I'll keep you posted.