The VESC’s speed estimators and sensored to sensorless switchover algorithm SUCKS.
There are so many things wrong with it, don’t even get me started.
It boils down to, the sensored speed estimator sucks, and when it transitions to sensorless, it’s a very ABRUPT and hard switchover, which causes other issues. Sensors lag behind the motor position due to magnetic hysteresis, and this only gets worse as speed increases. When the switchover happens, the rotor angle that the VESC is using to generate the sine waves changes very abrupty and by a large amount. This results in loss of tracking at very high currents, or an abs overcurrent fault if the difference is large enough.
The solution is purely in firmware, second order speed estimators in sensored mode, and when attempting a sensorless transition, run BOTH speed estimators simultaneously, and do the switch only when the estimators agree on speed plus or minus some tolerance. As for the angle difference, Make the switch gradual, by using a rotor angle that is between the two, and gets progressively closer to the sensorless value.
After all the drama about getting a mountain board or not, and in the end coming to the conclusion I will get one, I have work to do here first
The thing is, for the mountain board become a reality I will have to take apart my Hummie build, but I also need to have a board I can take everywhere and it’s not bulky, to be honest the Hummie one is bulky enough I lots of times I leave it it home instead of riding wherever I’m going
So I ordered the cheapest 6355 motors that were sensored, ideally I wanted to go to a lower Kv, but the price difference was too big, ended up paying $27 each 6355 180Kv motor, they will be taken apart and converted to a direct drive
Now I’m on the fence about what VESC to get, the Maker X dual 4.12 looks good and is really compact, but if one side dies I have to replace everything, I may get two flipsky 4.12, you can find them for less than $50 on AliExpress
Procrastinating in Ali express I just found a sale of Mini FSESC4.2, got two for $98 with shipping, there is a chance that they are old stock and have the cut out problem, but then its just a matter of swapping the resistors
Torque is awesome. There is no hill I can’t climb. Make sure to change the sensorless erpm, under settings->foc-> hall sensors, to 4000 min for good torque. Because when it’s set to a low numbers say 1000 then it uses sensorless mode just after starting which doesn’t know the magnet position accurately and hence is inefficient i.e. can’t produce enough torque and motor heats up more than it should.
Starting to work on the direct drive, all is just a place holder until I have the real motor in hand, the current measurements are from a old TB 6355 that looks just like the ones I will use
I managed to get it really compact and close to the wheel, I still want to try to flip the can so I can save even more space
The Paris truck is also just a place holder, I will mill a custom one using just the base plate
The initial plan was to have a key both inside the hanger and in the stator spacer, but I’m leaning in locking the stator spacer directly to the hanger
The bulk of the design is done, now I have to wait for the sacrificial motors to arrive to adjust the dimensions
For all fixtures I will be using retaining fluid, after reading a few guides from Loctite it should work, and by having no notches on the axle the stress concentration greatly diminishes, only place that there will be something is a pin between the stator and base, that is, if the motors I ordered have a notch already made
The hanger itself (body+axle) weights 342 g, so in the end it will probably be lighter that a dual 6355 belt setup
Looks really good Pedro! I want to try some tiny 4265 APS motors with a 1:3 gear drive coupled to 76mm wheels on my travel board (lightness is also the main goal)
That will look really cool. I gave up on small motors after my 5055’s, no matter how low you set the current they overheat, and higher gearing isn’t possible due to physical limitations, best of luck with it, maybe going to 1:3 will solve that
Just posting this here so I don’t forget, talked to @Gamer43 and about 60A is probably the most motor current I can push out of them, this may not be enough, but since I will take the motors apart anyway I can easily re terminate them and lower the Kv by 1.73, this will help a lot on the esc department