Apart from tuning PID, you must also tune BLHeli settings in your ESC to attain higher flight efficiency together with your FPV drone. In this text I’ll share my BLHeli_32 configurations that I take advantage of which give me the very best outcomes, and clarify what they do.
If you don’t wish to learn the lengthy article, right here is the abstract. However inventory settings or a set set of settings won’t work on each construct, it is best to actually “tune” it.
- PWM Frequency: 48KHz for freestyle; Default (or larger) for racing
- Motor Timing: 22 or Auto for freestyle; 25 (or larger) for racing
- ESC Protocol: DShot600 for 8K/8K, or DShot300 for 4K/4K (Looptime in Betaflight)
- If you might have ESC desync, attempt to set Demag to High, excessive Motor Timing, decrease Rampup Power
If you might be utilizing the most recent firmware (32.8 or newer), you may attempt Variable PWM frequency by setting PWM Frequency Low to minimal (as little as it will probably go), whereas setting PWM Frequency High to most (as excessive as it will probably go).
I’ll go right into a bit extra element what every setting means.
The “PWM Frequency” setting in BLHeli_32 adjustments how typically the microcontroller (MCU) within the ESC sends updates to the MOSFET. This principally means how typically the ESC drives the motor. This PWM setting is fully unrelated to ESC protocol, FC looptime or the PWM frequency setting in Betaflight.
The default worth for PWM Frequency in BLHeli_32 is 24KHz. By elevating it to 48KHz it is best to discover an enchancment within the smoothness of your flight efficiency instantly.
When you enhance the PWM frequency, the motors ought to run smoother and have a tendency to generate much less noise. It solves “mid throttle oscillations” in lots of circumstances, some even declare their motors come down cooler in addition to getting longer flight time due to the improved effectivity.
96KHz can also be attainable in sure ESC’s.
Why does larger PWM Frequency assist scale back vibrations?
At decrease PWM frequencies, there may be some aliasing/conflicts between the commutation charge and the PWM replace charge.
Commutation charge is the time it takes to detect a zero crossing and change by way of one suggestions cycle, there are 6 commutations per one eRPM, so it’s tied on to RPM
This may end up in some odd vibrations or roughness at sure throttle positions. Raising the PWM frequency to the FETs can transfer the harmonics the place this occurs outdoors the vary of the commutation charge.
Downsides of Higher PWM Frequency
So why is the default not 48KHz then? Well, as a result of there isn’t a free lunch!
Higher PWM frequency offers you smoother flying expertise on the expense of a bit of energy loss (only a few %). Because of this, larger PWM can scale back peak present draw barely too, which isn’t essentially a nasty factor for the longevity of the ESC.
At larger PWM Frequency, the torque at low RPM will also be decreased barely and so your low finish throttle would possibly really feel softer and fewer responsive. It may additionally barely lower prop wash dealing with too.
For racers who wish to have all the facility and responsiveness accessible, would possibly truly want decrease PWM frequency resembling 24KHz. Lower than 24KHz is just not beneficial.
If you’re a perfectionist, you may give 48KHz a attempt, then slowly again it down to search out the right center floor between energy and smoothness. Every setup is totally different.
Variable PWM Frequency
Since model 32.8, Variable PWM Frequency is now attainable, it adjustments with the throttle place, i.e. it makes use of decrease PWM Frequency when throttle is low, and makes use of the next PWM Frequency when throttle is excessive.
This offers you the very best of each worlds. When your throttle is low, it offers you larger torque and higher stability. As you enhance throttle it offers you higher smoothness. The minimal and most PWM frequency is determined by your specific ESC. For instance with the Tekko32 F3, the vary is between 48KHz and 96KHz.
You might wish to retune PID after setting this.
By setting each high and low to the identical worth principally disables it, and you’ve got a set PWM frequency.
The default Motor Timing in BLHeli_32 is “16 Deg”, which appears to work simply tremendous for almost all of builds. However I all the time enhance it when I’m configuring my ESC.
Generally talking, the next motor timing is much less prone to have “desync” points. Increasing motor timing additionally will increase the facility of your motor on the expense of effectivity.
If you set Demag to excessive, setting motor timing larger is nice because it helps to realize among the efficiency again.
If you’re after uncooked energy, you may attempt setting motor timing to round 25, or perhaps even barely larger. I don’t suggest utilizing max settings simply in case of surprising issues. When the timing is about too excessive for a motor, it can are inclined to run hotter, this will increase the chance of burning out a motor in a crash, or when one thing stops your motors from spinning freely.
For a superb stability between energy and effectivity, 22 appears to be a superb worth to get began. For a mini quad, it’s pointless to set motor timing decrease than the default, until you might be driving an enormous motor and propeller (e.g. 10″).
The optimum motor timing worth can truly change with motor RPM, so if you’re not sure you may simply use the “Auto” possibility, which lets the ESC resolve what motor timing to make use of on the fly. Generally, the auto possibility offers a superb center floor between effectivity and energy by way of the entire throttle vary.
Personally I haven’t seen an enormous distinction when swapping motor timing settings between Auto and 22, however give it a try to let me know within the remark which setting works finest in your setup.
Regardless of the variations in efficiency, DShot is certainly extra CPU intensive. This has been the rationale for some to go for Multishot, to permit extra processing energy to run the “final” 32K/32K Gyro sampling and looptime.
Anyway, give each protocols a attempt if you wish to experiment. Personally I really feel very minimal distinction in efficiency between the two protocols, however when utilizing DShot:
- I don’t have to fret about ESC calibration (calibration doesn’t do something when working DShot)
- I take advantage of ESC beacon which depends on DShot command
- You want DShot so as to use ESC Telemetry
- Betaflight 4.1 recommends DShot300 for RPM Filter when working 4K looptime, or DShot600 for 8K/8K
This setting can assist scale back “desync”. Just go away the setting at default until you might have desync points, in any other case change it to excessive. (what is ESC desync)
High energy builds (e.g. 6S or hexacopters) that undergo from electrical noise might profit from setting demag to High, however normally Medium is okay.
You would possibly expertise efficiency losses by setting it to excessive, because it’s principally backing down acceleration so as to scale back present spikes and noise.
Rampup Power is a setting designed to cut back present spikes as a result of sudden will increase in throttle by limiting the change of energy.
It’s beforehand referred to as Startup Power in older BLHeli model.
If the motors are pushing near the restrict of your ESC’s, present spikes from punch-outs may inflict injury, lowering Rampup Power can reduce this danger.
Leave it at default if you’re not sure, however you may tune it and make your quad fly extra effectively, however word that setting it too low can result in slower motor response.
I don’t usually contact this until I’ve ESC desync points, or extreme electrical noise.
If you actually wish to play with it, right here is how. Try to decrease the worth just a bit every time, till you discover a distinction in efficiency, then again off. For most builds it’s not even noticeable whenever you decrease it to 25% (50% is the default).
Current safety limits the amperage passing by way of the ESC. The goal is just like Rampup Power, however the Current Protection setting is extra particular on present restrict.
I like to recommend leaving this setting to off (default), until you realize what you might be doing.
Potentially this can be utilized to guard your ESC from “burning” because of present spikes, crashing and desyncs. But so long as the present score of your ESC meets the requirement, you shouldn’t want to fret about it.
For mini quad? Just go away them to default 🙂 A variety of these settings are for mounted wings and planes.
- Jun 2018 – Article created
- Nov 2018 – Added Demag Compensation
- Feb 2019 – Updated Rampup Power and Current Protection
- Jan 2020 – Revised
- May 2021 – Added information concerning new characteristic, variable PWM Frequency