Apologiies for the length of this post but I hope that my (numerous) questions are sufficiently interesting to attract responses...
I wish to use a VESC controller instead of one of the commercially available ESC products normally used in this field. The precise, demanding, application is F3a class competition aircraft for which this controller, for example, is commonly used. Why do I consider VESC?
As I understand it VESC has the following advantages not present in any sensible commercial model aircraft ESC:
- FOC = quieter, more pleasant sound in flight. Can influence the small style/smoothness/gracefulness element of judges' scores
- RPM mode - assists pilot to maintain constant flight speed, which is desirable for a number of reasons, by increasing power in up-lines and providing automatic braking in down-lines (normally only a pre-configured amount of braking is available and only on fully closing the throttle)
- RPM mode - eliminates effects of battery voltage reducing during flight (provided max RPM is not set higher than achievable on nearly exhausted batteries)
- Regenerative braking - makes possible the use of lower capacity (= lighter) battery which would help keep the aircraft under the prescribed 5Kg weight limit, especially as VESC controllers appear to be around 100gm heavier than typical model aircraft equivalents. I will not need BMS as in this application the energy replaced will always be much less than the energy drawn from the battery
- Are my above presumptions correct?
- I have seen advice in boarding forums not to use model aircraft ESCs as they are insufficiently robust, but used in their intended application model aircraft ESCs are very close to 100% reliable. The one I mention above, despite it's small size and light weight, boasts 48 output FETS and claims 99A continuous current capability, yet larger heavier VESCs claim around half that. Comment? Am I safe using, say, a 50A VESC in my application where max current will approach 90A for a few seconds 20 times during a 9 minute flight and average will be 25A to 30A? Battery is 10s lipo and approx 4Ah is consumed in approx 9 minutes.
- I have not yet decided which motor to use but am I correct in thinking that one of those commonly used, a 28 pole, will at just under 7000rpm exceed max eRPM of a VESC - or is it pole pairs which count in which case I should be ok?
- Sensorless or sensored? Required startup torque will be near zero - load being a 21" propeller weighing between 50 and 150gm plus motor inertia.
- Input will be 5v pwm 1mS - 2mS from model rc receiver. Best commercial ESCs have opto-isolated input to prevent interference from motor cables etc getting back to receiver. Should I add opto-isolation? Could I damage VESC by connecting pwm signal from receiver direct when VESC not powered up?
- What length battery cables can I use before I have to add extra capacitance mid-cable?
- What have I missed?
If you've got this far thank you, thank you, thank you. Appreciate your help...