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On this tutorial, I’ll share how I take advantage of Blackbox logs to tune filters and PID on a Betaflight FPV Drone. I will likely be utilizing PIDToolBox as the first instrument for filter and PID tuning, with Blackbox Explorer as a secondary instrument for Feedforward and common troubleshooting.
Disclaimer: This information is supposed for informational functions solely. The writer holds no accountability for damages ensuing from actions taken by the readers.
Blackbox is just not a should for tuning as defined on this information, but it surely offers full perception into what’s taking place with the drone and means that you can unleash its full potential. Issues like noise filtering and tiny overshoots are seen solely in Blackbox. For those who’re a perfectionist or simply somebody who likes to tinker, that is the tutorial for you.
In case you are new to Blackbox, make sure that to take a look at the Blackbox for inexperienced persons tutorial..
I spent over 200 hours making this 8000-word tutorial! For those who discover my content material helpful, please take into account supporting my work.
Getting Began
Tuning targets
Utilizing Blackbox to tune our FPV drone, we goal to realize two principal targets:
- Extra Efficient Use of Filters: Use minimal filtering to attenuate delay however sufficient to maintain noise at a suitable stage.
- Optimized PID Positive aspects and Associated Settings: Make sure the drone flies exactly and responsively.
Fundamental configurations
0. {Hardware} Guidelines
- Flight Controller (FC) Stack: Select an FC stack with rubber grommets (gummies) for sturdiness and noise efficiency.
- Metallic Screws: Use steel screws for the FC stack; keep away from nylon/plastic screws/standoffs as they’re susceptible to breakage and vibrations. If spacers are wanted, use tender silicone ones. Lighter titanium screws can save a number of grams.
- Locking Stack Screws: Safe the stack screws firmly with a steel nut earlier than mounting the 4in1 ESC. In case your body has pressed insert nuts, further nuts are usually not wanted. Tighten screws by hand first, then give a remaining squeeze with a wrench/screwdriver.
Use 4 plastic nuts to safe the FC stack. Tighten the nuts by hand to keep away from excessively crushing the gummies, permitting the tender mount to work successfully.
1. Blackbox Recording Settings
Choose the next settings within the Blackbox Configuration:
- Logging Machine: Onboard Flash or SD Card
- Logging Charge: 2KHz (or 1.6KHz for BMI270 Gyro)
- Debug Mode: GYRO_SCALED (data unfiltered gyro sign)
- Information Included: To avoid wasting house for longer recordings, deselect pointless information like Altitude, GPS, and Magnetometer, or go away at default.
2. Disable the ADC filter in your OpenTX/EdgeTX radio (System -> {Hardware}) to cut back latency.
3. ESC settings:
I’ve a submit explaining the greatest BLHeli32 settings. Right here’s the abstract (for five″ drones):
For BLHeli_32 ESC:
- Rampup Energy: 30%
- Motor Timing: 24
- PWM Frequency: Set LOW and HIGH to mounted 24KHz or 48KHz. 48KHz is mostly safer for gyro noise, making your quad smoother and simpler to tune. 24KHz gives higher braking energy, which is useful for prop wash dealing with and responsiveness, however with the next threat of vibration. In case you are on the fence, simply go along with 48KHz.
For BLHeli_S ESC, flash Bluejay to allow bi-directional DShot, required for RPM filter and Dynamic Idle. I’ve a information on methods to flash it right here: https://oscarliang.com/bluejay-blheli-s/
3. Flash the newest model of Betaflight firmware to your flight controller and go away PID/filter settings at default. Allow Skilled Mode in Betaflight Configurator to entry all sliders and choices on the PID Tuning web page.
Within the Configuration tab, set your PID Loop Frequency, and within the Motor tab, set your ESC protocol:
- DShot300 for 4KHz or 3.2KHz Loop Frequency
- DShot600 for 8KHz Loop Frequency
4. Within the Motors tab, allow Bi-directional DShot.
Most fashionable ESCs help Bi-directional DShot. I’ve a tutorial on methods to allow RPM filter. For BLHeli_32 ESC it really works out of the field, however if in case you have BLHeli_S ESC, you’ll want to flash Bluejay firmware (tutorial) first.
Examine if it’s working correctly by working the motors within the Motors tab (with out propellers) and making certain the error charge (E) stays at 0%. If not, attempt a slower DShot protocol like DShot300 or DShot150. If errors persist, you would possibly simply have to surrender on Bi-directional DShot and RPM filter.
As soon as enabled, go to PID tuning tab, Filter Settings, the place you may allow the Gyro RPM filter, the most effective filters in Betaflight.
5. Load the suitable RC_Link preset.
Totally different RC hyperlinks require particular RC smoothing and feedforward configurations. Unsuitable config may cause stuttering and vibrations. My favourite RC hyperlink is ExpressLRS, take a look at what radio gear I take advantage of right here.
Loading the appropriate RC_Link preset in Betaflight will apply the mandatory configurations routinely. Bear in mind to decide on choices primarily based in your flying fashion, for most individuals it might be Freestyle.
For Crossfire, lock the packet charge to both 50Hz (longer vary, greater latency) or 150Hz (decrease latency, much less vary) utilizing the TBS Agent Lite LUA script.
6. Decrease TPA
Within the PID tuning tab, set the TPA breakpoint from 1350 to 1750 to keep away from TPA masking oscillation points at low/mid throttle throughout tuning. Tremendous-tune TPA on the finish if oscillation points happen at excessive throttle, however typically I might decrease the usage of TPA every time doable.
The best way to use PIDToolBox and Blackbox Explorer?
I will likely be utilizing each PIDToolBox (PTB) and Blackbox Explorer (BE) in my PID and filter tuning.
PIDToolBox will likely be our principal instrument, it’s by far essentially the most highly effective Blackbox instrument accessible. It means that you can examine a number of logs aspect by aspect, making it simpler to see the results of your filter adjustments. The Step Response instrument is very helpful for tuning PID. The spectral analyzer in PTB makes use of decibels on the Y-axis, offering extra correct and goal comparisons. PTB additionally estimates filter delays, which may be very useful.
Nevertheless, PTB might be slower and fewer intuitive to make use of in comparison with Blackbox Explorer. For fast checks or troubleshooting a single log, BE is quicker and simpler. However for noise and filter tuning, PTB is the way in which to go.
Filters Tuning
You’ll find all of the filters in Betaflight within the PID Tuning tab. Don’t be intimidated by all of the settings, on this tutorial, we are going to principally solely deal with the inexperienced sections (RPM filter and Dynamic Notch) and modify the orange sections (Gyro and D Time period Lowpass Filters) utilizing the sliders. No want to the touch the pink sections.
Additional studying: Study in regards to the several types of filter in Betaflight on this tutorial.
Good {hardware} can scale back the necessity for in depth filtering. Guarantee your body is well-designed with out resonance points, use well-balanced propellers, and high-quality motors with easy bearings.
Performing Flight for Noise Evaluation
- Take Off: Fly ahead with minimal throttle and stick inputs.
- Throttle Sweeps: Slowly ramp up throttle to 100% over 5-10 seconds. This check reveals vibrations throughout the throttle vary and body resonances.
- Repeat: Carry out 2-3 throttle sweeps, then land and disarm.
That is what a typical throttle sweep log would appear to be (see the underside bar for throttle adjustments).
Gyro Noise Frequency Defined
Open the throttle sweeps log in Blackbox Explorer and click on on “Gyro_Scaled” on the appropriate hand pane, that is the unfiltered gyro sign. Take away the takeoff and touchdown elements of the log by urgent “i” and “o”.
Right here’s a breakdown of the uncooked gyro sign frequency graph from a typical 5″ FPV Drone:
- Beneath 20Hz: Drone flight actions.
- 20Hz – 100Hz: Propwash and oscillations from suboptimal PID, problematic ESC config, dangerous RC hyperlink settings, and so forth.
- 100Hz – 250Hz: Body resonance or unfastened elements.
- Above 250Hz: Noise from motors and propellers, and harmonics.
Every part beneath 20Hz is “good” drone movement reacting to the sticks.
Between 20Hz and 100Hz is the place undesired vibrations, similar to oscillations and propwash, happen. As a common rule of thumb, you wish to see little exercise on this frequency vary. Having some is regular, however an excessive amount of means you’ve gotten an oscillation situation that must be addressed. Typically, we attempt to keep away from filtering beneath 100Hz as a result of these are actual motions of the drone that we both wish to work with or towards. Filtering on this low-frequency vary can truly make issues worse as a result of it introduces an incredible quantity of latency. Analyzing the spectra below 100Hz can provide you perception into vibration or mid-throttle oscillation points and the way nicely the copter handles propwash.
We don’t care about something above 1000Hz as these have little impact on our drone. What we wish to deal with filtering is the noise between 100Hz and 1000Hz.
Delay Brought on by Filtering
Maybe not intuitive, however over-filtering can truly trigger oscillation to point out up as noise within the sub-100Hz spectra. That’s as a result of filtering creates delay. When the quad tries to appropriate the error, the response may be too late as a result of delay, which might be counterproductive. It may make the error worse and create a suggestions loop, inflicting the drone to oscillate.
That’s why, if we use much less filtering, noise points below 100Hz can typically truly get higher as a result of latency is decreased and the quad can react sooner to appropriate PID errors. Utilizing much less filtering additionally means that you can push PID positive aspects greater, which makes your quad monitor setpoint higher and helps fight propwash.
You’ll find out how a lot delay is added to the Gyro sign on account of filtering by plotting Gyro and Gyro_Scaled and measuring the hole between them.
In PTB, it routinely estimates the delay attributable to gyro filtering and D-term filtering (see the highest proper nook of the primary graph within the second column).
Filter Technique
My common filter technique is to remove motor noise bands utilizing the RPM filter, then crush out body resonances with dynamic notch filters, and eventually, scale back the ambient noise flooring with Gyro and D-term lowpass filters. I will likely be tuning filters on this order:
RPM Filter > Dynamic Notch Filter > Gyro Lowpass > D-term Lowpass
We wish to use as little filtering as doable to attenuate latency, however on the similar time, we’d like sufficient filtering to keep away from burning our motors when flying house with a bent prop. You possibly can actually play it protected and apply extra filtering than wanted, however over-filtering makes the drone really feel disconnected and sluggish to react as a result of elevated delay. It may additionally worsen propwash. So, we have to attempt for a steadiness.
Aside from checking Blackbox logs, motor temperature is one other helpful indicator in filter tuning. When motors get too sizzling, it often signifies that the filtering is just too aggressive.
Professional Tip: Scorching Motors – How Scorching is Too Scorching?
As a common rule of thumb, for those who pinch the motor bell and may’t maintain your fingers on it for quite a lot of seconds, it’s too sizzling and you might be in all probability pushing your settings too aggressively.
How Clear is Your Construct?
Earlier than we start tuning, it’s essential to verify if in case you have a clear construct. Begin by performing throttle sweeps as beforehand described.
Load the log in PIDToolBox, click on on the Spectral Analyzer, choose “Gyro prefilt” (the uncooked, unfiltered gyro sign; “Gyro” is the filtered sign), and hit Run.
The default filter settings in Betaflight are pretty conservative, and most builds ought to be capable of scale back filtering from there. In case your quad is already noisy with default filter settings, as a substitute of accelerating filtering, it’s best to search for doable mechanical or electrical points. Guarantee you’ve gotten a capacitor on the ESC enter energy, all screws are tightened, and also you’re utilizing contemporary new props, and so forth.
On a clear 5″ quad, there ought to be little exercise between ~50Hz (the quad’s actions) and ~200Hz (motor vibration). If in case you have lots of noise on this area, it may very well be electrical noise (maybe the gyro enter energy is just too noisy, or it requires an additional capacitor on the ESC enter energy) or mechanical (e.g., a wire hitting the gyro). Reaching optimum filtering on this situation can be more difficult.
As prompt by the writer of PIDToolBox, it’s ultimate to have the general noise flooring beneath -30dB above 50Hz. For D-term, it’s ultimate to have the general noise flooring beneath -10dB. Analyzing the noise ranges in these areas can provide you an excellent indication of how easy your quad flies. The noise stage is influenced by the construct high quality of the drone, the standard of the {hardware}, and typically you would possibly simply have a loud gyro.
In case your quad is noisier than this (e.g., there’s a peak within the center above 0dB), then you will want extra filtering. It’s not the tip of the world; it simply means the latency will likely be greater, and also you gained’t be capable of push PID positive aspects as excessive.
Tuning RPM filter
Motor noise is the first supply of noise for FPV drones, and the RPM filter is without doubt one of the handiest filters in Betaflight for tackling motor noise. On a clear construct, the RPM filter and Dynamic Notch filters will do many of the work, permitting us to disable many different filters to attenuate latency.
Let’s take a look at some examples of motor noise:
- Load the “Throttle Sweeps” log in PTB, click on Spectral Analyzer and click on “Freq x Throttle“.
- Beneath “Presets” choose “Gyro Prefilt, Gyro, Dterm Prefilt, Dterm” and hit Run. That is what I name “warmth maps”.
Right here’s a breakdown of what we’re taking a look at:
- Near 0Hz: The very shiny horizontal line on the backside (1) represents the drone’s movement reacting to the sticks.
- Round 200Hz: This horizontal line (2) signifies body resonance. Its frequency doesn’t change with throttle place however is strongest the place it intersects with the motor band.
- Elementary Motor Noise Band: This diagonal line (3) is often the brightest. Motor noise usually will increase in frequency with throttle stage.
- Harmonics: These are multiples of the basic motor noise band. In our instance, harmonics (typically dimmer and more durable to identify) present up as traces (4) and (5). Strive adjusting the size in the event that they aren’t seen. Word that 2-blade propellers have a tendency to point out extra and stronger harmonics than 3-blade props.
We are going to use RPM filter to deal with these motor noise bands.
The aim is to optimize the variety of RPM harmonics used and set the best doable “Min Frequency” primarily based on the beginning frequency of the motor band. Fewer RPM harmonics and the next min frequency end in much less filtering and decrease latency.
Use the Information Cursor Device, click on on the place the motor band begins to seek out the precise frequency. Affirm this within the roll/pitch/yaw graphs and take the bottom frequency.
Right here’s an instance from my new Supply One V5 construct:
- On the left, is the default RPM Filter, 3 harmonics with a min frequency of 100Hz.
- On the appropriate, I modified it to 2 Harmonics with min frequency of 160Hz
By lowering one harmonics and lift the cutoff frequency, you may maybe see extra unfiltered noise from the third motor harmonics.
Though it’s fairly weak, it might nonetheless get amplified when it will get into D time period. Let’s verify the Dterm warmth map beneath on the appropriate, as you may see, a tiny little bit of gyro noise has develop into fairly dangerous Dterm noise.
On this instance, it’s in all probability higher to have 3 harmonics in RPM filter.
The opposite factor you might need seen is a few noise round 116Hz left unfiltered as a result of we raised the min freq to 160Hz. To handle that, we have now to decrease Min Freq, i.e. round 20Hz beneath the noise frequency can be ultimate.
Right here’s a comparability of gyro sign after filtering utilizing 3 completely different settings:
- left: 2 harmonics 160Hz min freq
- mid: 3 harmonics 130Hz min freq
- proper: 3 harmonics 100Hz min freq
To crush out the motor bands, it appears we will’t actually scale back RPM filter. On this instance, the default settings (3 harmonics and 100Hz min frequency) labored greatest.
RPM Crossfading
This superior characteristic fades within the RPM filter energy over a variety (form of like TPA), the default is sweet for many 5″ builds however it may be optimized particularly for bigger or smaller builds, because the motor noise would possibly begin greater or decrease in frequency, and also you would possibly want it to fade in additional rapidly or slowly will depend on the noise. This characteristic is simply accessible in CLI, for instance:
set rpm_filter_min_hz = 100 set rpm_filter_fade_range_hz = 50
This implies the RPM filter begins at 100Hz at minimal energy and reaches full energy at 150Hz.
Q Worth
Rising the Q worth of a notch filter makes it extra targeted on the focused frequency, lowering latency. Alter this within the CLI:
set rpm_filter_q = 500
Default values often work nicely, however you may fine-tune by growing the Q worth till motor noise turns into seen within the filtered gyro diagram, then again off. Don’t exceed 1000.
RPM Filtering Dimming
This permits particular person management of every RPM filter to focus on harmonics. For instance, when utilizing 3-blade propellers, the second harmonics is often not very robust, however the third harmonics is. On this case you should utilize extra filtering energy on the third harmonics and fewer on the 2nd:
set rpm_filter_weights = 100, 0, 80
And when utilizing 2-blade propellers, the place 2nd harmonics is stronger than the third harmonics, you are able to do one thing like this:
set rpm_filter_weights = 100, 80, 0
You possibly can additional lower RPM filter weights so long as motor noise isn’t seen within the filtered gyro diagram.
Tuning Dynamic Notch Filter
The dynamic notch filter suppresses sign peaks within the gyro sign, that are principally vibrations from the body or different {hardware} elements, similar to body resonance, antennas, GoPro mounts, and bent propellers.
When the RPM filter is enabled, Betaflight will routinely scale back the quantity of Dynamic Notch filtering through the use of fewer notches and the next Q worth because the RPM filter will do many of the heavy lifting. You possibly can additional tune the Dynamic Notch filter primarily based in your setup.
Determine Body Resonances: Have a look at the warmth map and determine what number of body resonances there are to find out the variety of notches wanted. As much as 5 notches can be utilized, however often, 1 or 2 are enough until your drone is poorly constructed or in a beat-up situation. With the RPM filter enabled, 1 notch is often sufficient to deal with body resonance.
Decide Q Worth: The Q worth determines the width of the filter. A better Q worth means a narrower filter, which ends up in much less filtering and decrease latency.
- Default Q: Begin with the default Q of 500.
- Alter Q: If the default is working nicely, attempt growing it to 600 and even 700. Keep away from exceeding 1000. For those who nonetheless see body resonance noise after filtering, decrease the Q worth.
- Examine D-term Heatmap: Analyze the D-term heatmap to see how adjustments within the Q worth have an effect on D-term noise.
Set Min/Max Frequency: These are the cutoff frequencies, defining the efficient vary of the Dynamic Notch filter. Add 20-30Hz to every aspect of the resonance for the vary.
Keep away from setting the Min Frequency too excessive for security causes, as bent props can create large resonance. In case of a crash, a broader frequency vary can assist catch new resonances and forestall motor overheating or injury. We don’t know precisely the place that resonance goes to be, however having a wider frequency vary has the next probability of catching it. If the Dynamic Notch fails to catch these newly pop up resonances on account of Min Frequency is about too excessive, your motors can get sizzling and even burn in these conditions.
With out RPM Filter: In case your quad can’t use RPM Filter, for instance on a tiny whoop, you may attempt to allow Dynamic Notch Filter with 5 harmonics, Q issue 350 and Min Frequency at 100Hz as a place to begin, then tune it by working your method up.
In an instance setup, there seems to be one body resonance round 210Hz.
I attempted growing Q to 700 and setting the min/max frequency to 160-230Hz, however Q was clearly too excessive. There may be extra unfiltered noise, and it will get into Dterm and get amplified.
Lastly, after I set Q to 450, the noise is satisfactorily managed. Within the beneath graphs, on the left is Q=700, the appropriate is Q=450. You possibly can verify Dterm heatmap once more to substantiate that is working nicely.
Tuning Gyro Lowpass Filter
Normally, you can begin by turning off the Gyro Lowpass 1 filter as it’s typically pointless. Check fly aggressively for 30 seconds and verify the motor temperature to make sure they don’t seem to be sizzling earlier than continuing.
Use the “Gyro Filter Multiplier” slider to cut back Gyro Lowpass 2 a few notches at a time. Transferring the slider to the appropriate will increase the frequency, which reduces filtering, leading to much less delay, higher prop wash dealing with, and the potential for greater PID positive aspects.
Right here’s a comparability of the gyro frequency spectrum at completely different Gyro Lowpass filter slider values: 1.0 (brown), 1.5 (pink), and a couple of.0 (orange).
The three traces virtually overlap, suggesting that the Gyro Lowpass filter isn’t considerably affecting the sign and might be decreased. Curiously, the noise within the sub-100Hz spectrum barely improves with much less filtering, which aligns with our earlier discussions.
Necessary Concerns:
- By no means disable the Gyro Lowpass 2 filter for 2K/4K PID loop frequencies on account of anti-aliasing causes.
- Minimal Frequency:
- For 2K loop time, go away Gyro Lowpass 2 at a minimal of 500Hz.
- For 4K, you may set Gyro Lowpass 2 as much as 1000Hz.
- For 8K, you may disable Gyro Lowpass 2 solely if noise isn’t a difficulty.
Tuning D Time period Lowpass
D time period is far noisier than Gyro on account of its delicate nature and noise will get amplified as frequency will increase. Subsequently, be further cautious and conservative when coping with D Time period filtering.
Strive transferring the “D Time period Filter Multiplier” slider to the appropriate a notch at a time and see how the drone responds in a 30-second check flight (do some acro strikes), additionally verify motor temperature after touchdown. In the event that they get sizzling it’s best to return a notch or two.
Keep away from being too aggressive with lowering D Time period filtering. Depart some headroom for doable bent props throughout flight. Too little D Time period filtering mixed with a broken propeller can result in sizzling or burned motors.
Right here’s a comparability of D-term filtering slider positions: 1.0 (brown), 1.3 (pink), and 1.6 (orange). As seen within the heatmap, much less filtering ends in extra noise for D-term, not like Gyro lowpass.
From left to proper, the heatmap reveals unfiltered D time period, D-term lowpass filter at 1.0, 1.3, and 1.6.
For those who hear the motors getting tough (thrilling oscillation) as you scale back D-term filtering, it’s as a result of rising noise beneath 100Hz. You possibly can verify this by checking the <100Hz graphs. On this instance, staying beneath 1.3, possibly 1.2 and even simply 1.1, can be safer.
After tuning PID positive aspects, revisit D Time period filtering to see if it may be additional optimized.
If the D Time period traces are very noisy, one or two clicks extra filtering on the slider might assist. If the D time period hint may be very clear, you may maybe scale back filtering a bit extra (if motors are usually not sizzling). See beneath graphs, the left has a loud D time period hint, the appropriate is far cleaner.
Necessary: NEVER disable D-Time period lowpass filters utterly, you’ll burn your motors.
Gyro/D Time period Notch Filters
There’s no have to allow Gyro Notch Filter and D Time period Notch Filter, these are static notch filters which have develop into legacy since RPM filter and dynamic notch filters are doing many of the work.
Nevertheless, if there’s a robust resonance at a particular frequency (similar to body resonance), a static notch filter might be useful. The dynamic notch filter often covers it, so a static notch filter is commonly pointless. You possibly can attempt including a static notch for identified body resonance and scale back the dynamic notch depend by one to see which technique works higher on your setup.
Yaw Lowpass Filter
The default yaw lowpass filter at 100Hz cutoff has minimal latency penalty and might be left untouched. This filter is very helpful for whoops, because it helps to cut back yaw spin in collisions.
PID Tuning
To tune PID utilizing Blackbox, I comply with the “Basement Tuning” technique utilizing PIDToolBox. This technique is beginner-friendly and might be carried out in a small house like a basement or bed room, therefore the identify. It entails performing a sequence of quick flights with barely completely different PID values, then evaluating the logs to seek out the optimum positive aspects.
Through the flights, transfer the quad round on the pitch and roll axes. You possibly can study extra in regards to the basement technique on this video by PIDToolbox.
Though the strategy is named “basement tuning,” I’m not snug doing this indoors. I’ve had a few “fly to the moon” incidents up to now, practically drilling a gap within the ceiling. Subsequently, I all the time carry out these checks in a backyard or native park for security.
Charge Profile and Angle Mode
Performing basement tuning flights requires good line-of-sight flying expertise to maintain the drone managed in a confined house. Listed here are some tricks to make it simpler. Do this charge profile:
- Middle Sensitivity 250
- Max Charge 400
- Expo 0.00
This profile has a low max charge, making it much less prone to lose management for those who transfer the sticks an excessive amount of. The excessive and linear heart stick sensitivity ensures the stick inputs are vital sufficient for correct logging.
Performing the check in Angle mode could make it even simpler than in Charge mode. In accordance with the writer of PIDToolBox, Angle mode works simply in addition to Charge mode, however you’ll want to do the next first:
- Go to the Setup tab and calibrate the accelerometer.
- Within the PID Profile Settings, set the Angle mode energy to 100.
- Click on Save to make sure the adjustments are utilized.
Discovering P/D Steadiness
Initially, decrease these positive aspects in order that they don’t intervene with our tuning:
- Set the “Stick Response” slider (Feed Ahead) to 0
- Set the “Dynamic Damping” (D Max) slider to 0
- Set the “Drift-Wobble” (I positive aspects) slider to 0.2, it’s low sufficient that it shouldn’t introduce overshoot but have just a bit I phrases to assist stabilize the quad higher, makes it simpler to regulate
Alter the “Damping” (D positive aspects) slider, begin with a minimal worth you wish to check. For a typical 5-inch FPV drone, 0.6 is an efficient place to begin.
Here’s what you wish to carry out within the flight:
- Arm and hover
- Always transferring the roll and pitch stick for 20-30 seconds, the extra actions the extra correct will probably be
- Do as huge strikes as you may with out hitting the partitions (ideally full stick deflections)
- You possibly can transfer each pitch and roll collectively so long as you may maintain it below management
- Strive to not cease/hover for too lengthy throughout flight, and be as steady as you may
Elevating the Damping slider by 0.2 every time and repeat the flight: e.g, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6. While you increase D achieve too excessive, your motors will sound tough, due to this fact you may’t all the time check the final one or two values, which is ok.
The quickest method to change slider worth is by going into Betaflight OSD menu, Profile, Simplified Tuning. However if you’re unable to do that then simply plug within the USB cable and use the Betaflight Configurator.
It’s a good suggestion to vary battery each 2-3 flights to make sure the end result isn’t affected by voltage. Energy cycle the quad by unplugging the battery earlier than each flight so it creates a brand new log. Or just select “Save and Reboot” within the OSD menu so that you don’t have to unplug.
16MB reminiscence ought to be sufficient for six 30-second flights for those who time it nicely.
After you’ve gotten accomplished all of the flights, obtain them to your laptop. To arrange the logs higher, I’ve a folder construction created for this course of, obtain right here: https://drive.google.com/file/d/1tx1AV2lOMgknAwIB3VFhqP1i6VpDLVjr/view?usp=share_link
And I rename the logs to one thing like “01 d06“, “02 d08” and so forth (01 means first check flight, d06 means damping slider worth 0.6), and put them within the “02 PD Steadiness” folder.
Load all of the logs in PTB, undergo every one and take away the take-off and touchdown elements for every log (to do that, allow “Trim” on the appropriate hand panel).
Click on the “Step Resp Device“, choose all of the recordsdata and click on Run. if in case you have offset within the curves (gyro curve transferring away from setpoint in the direction of the tip), allow Y Correction.
It’s fairly straight-forward, merely decide the most effective wanting line, that’s your optimum Damping slider worth. The perfect response ought to look one thing just like the inexperienced line within the following graph, little to no overshoot. Having a tiny little bit of overshoot is appropriate.
In case your traces don’t look easy however have numerous ups and downs, that’s referred to as oscillation, and it’s an indicator that the sign is just too noisy or your actions aren’t large enough.
The graphs on the appropriate are additionally extraordinarily useful:
- Peak is highest amplitude of the overshoot (ideally the nearer to 1 the higher)
- Latency is the time it takes to achieve setpoint (ideally the decrease the higher)
When D achieve is low, you’re going to get overshoot and even oscillation. As D achieve will increase, there will likely be much less overshoot and Peak will lower, however Latency will go up in consequence. When D is just too excessive (undershoot), the preliminary peak may not even attain the setpoint and this isn’t ultimate. Discover a response that has minimal overshoot and but has comparatively low Latency.
You possibly can zoom in and see it extra clearly (or choose fewer logs, and hit Run once more). We solely want to have a look at Roll and Pitch axis.
In our instance, it’s fairly clear the perfect worth is orange (3) for each pitch and roll, so that may be 1.0.
It’s fairly widespread to have a distinct PD steadiness on pitch and roll as a result of completely different weight distribution. If that’s the case for you, take the Damping slider to the place you need for pitch, write down the pitch D achieve, then take the Damping slider to the place you need for roll, and modify the Pitch Damping slider to match the pitch D achieve you simply wrote down.
Typically it’s higher to be a little bit extra conservative and keep away from having D achieve too excessive. In case you are on the fence, all the time go along with much less D achieve (the next P/D ratio), so you may increase your total PID positive aspects greater on the finish since D is often the limiting issue.
What I’ve discovered is that the step response instrument tends to be fairly delicate and the P/D steadiness may be decrease than what I’d personally favor. So I usually bump up P/D steadiness by 5-10% after discovering a perfect worth. That’s simply my private desire, you can provide {that a} attempt if you would like.
Drone dimension additionally impacts PD ratio, bigger drones are inclined to have greater P:D ratio. For instance a 5″ would possibly use 0.8-1.1 Damping slider whereas a tiny whoop would possibly use 1.4-1.6.
Discovering Max D Achieve
Do the identical check for Grasp Multiplier slider, transfer the slider in 0.2 steps. For a 5″ drone, begin with values similar to 0.8, 1.0, 1.2, 1.4, 1.6, and 1.8.
Be cautious and don’t stand too near the quad throughout this check. When D achieve is just too excessive, the quad might shoot up unexpectedly. Pay shut consideration to motor noise, and cease instantly for those who hear thrilling oscillation.
You would possibly discover that the shapes of the step response don’t change a lot between completely different values and that the Peak values stay roughly the identical. It’s because the response curve form is principally decided by the P/D ratio. Rising the positive aspects gained’t considerably have an effect on the response form, however bumping up P/D positive aspects can scale back latency.
You have got reached the perfect Grasp Multiplier achieve when one of many following happens:
- Thrilling Oscillation: For those who hear thrilling oscillation, you may’t enhance D achieve any additional.
- Latency Plateau: If latency doesn’t lower anymore (or little or no), it means you’ve gotten reached the higher certain tuning window. The motors are working at their hardest, and you aren’t gaining any extra efficiency from them.
The utmost achieve achievable is influenced by the noise stage of your construct and the quantity of filtering used. Much less filtering permits for greater PID positive aspects. Typically, it’s safer to cut back the Grasp Multiplier slider by a notch or two as soon as you discover the utmost worth. Keep away from pushing D achieve to the restrict to account for potential points like bent props.
Drones utilizing greater cell depend batteries (greater voltage) are inclined to require decrease D positive aspects. For instance, on a 6S quad, D positive aspects may be within the 30s, whereas on a 4S they’re often within the 40s.
In my instance, 1.6 appears to be the worth that offers the least quantity of latency, with little enchancment when growing to 1.8.
For those who can’t hear thrilling oscillations, use the Spectral Analyzer to plot D-term. As positive aspects enhance, motors might produce an exhilarating sound peaking round 40-80Hz, particularly when throttling up. If noise on this frequency vary will increase with greater positive aspects, it signifies the onset of PID-related oscillations.
On this instance, you may clearly see peaks round 60Hz for 1.4 (olive), 1.6 (inexperienced), and 1.8 (cyan). Though 1.6 reveals latency enchancment, I might not threat it and would possible select 1.4 and even 1.3 to be protected.
There may be ongoing debate on whether or not it’s higher to have extra D-term filtering and better D achieve, or much less D-term filtering and decrease D achieve. Nevertheless, by no means run with much less D-term filtering and excessive D achieve as this may result in disastrous outcomes for those who hit an impediment or bend a prop. It’s no joke, talking from expertise right here:
After discovering the optimum D achieve, verify setpoint monitoring by plotting Gyro and Setpoint. The traces ought to be roughly parallel, indicating the quad is accelerating and decelerating on the similar charge because the setpoint. Nevertheless, there would possibly nonetheless be a big hole between them, indicating latency. Within the subsequent step, we are going to scale back this hole utilizing Feedforward.
Tuning Feed Ahead
Feed Ahead (FF) accelerates your quad while you transfer the sticks, making your quad extra responsive and nearer to the setpoint. In contrast to P time period, which reacts solely when there’s a PID error, Feed Ahead measures the speed of stick deflection. It will get the motors transferring as quickly because the stick strikes, making it a lot sooner than P time period.
Feed Ahead helps the quad reply promptly to stay inputs, offering a extra rapid and managed flying expertise. It’s helpful for all flying kinds, together with cinematic flying, because it reduces latency between stick enter and quad response.
When tuning Feed Ahead I favor to do some snap rolls and flips and verify Gyro/Setpoint traces. Use your typical charge profile, or a default charge profile in Betaflight (simply swap to an unused charge profile) to get a good max charge at full stick. You possibly can verify my charges right here: https://oscarliang.com/charges/#My-Charges
As an alternative of utilizing the step response instrument in PTB, use BE to verify the setpoint/gyro traces. The gyro ought to monitor the setpoint extra carefully with much less delay. Ideally, the gyro ought to be proper on prime of the setpoint.
If Feed Ahead overshoots (gyro strikes earlier than the setpoint), the FF is just too excessive. Within the following demonstration, 0.5 is method too low, 1.0 continues to be not excessive sufficient, however 1.5 is a tiny bit an excessive amount of and overshoots. I feel Feedforward at 1.3-1.4 ought to do it on this instance.
If the FF achieve is just too excessive, it might trigger the P time period to react in the other way, attempting to counteract it.
Doesn’t matter what your flying fashion is, feedforward might be helpful and doesn’t apply solely to sure forms of flying. Even cinematic flying can profit from an excellent quantity of feedforward, if you’re transferring your stick easily and slowly, then feedforward gained’t kick in anyway. While you want snappy response FF will scale back the latency between stick enter and quad response. In order for you easy flying, simply use expo, extra RC smoothing or decrease your charge.
There’s an non-obligatory setting, Feedforward increase (FF Enhance). You wish to enhance it if gyro lagging behind setpoint initially of a transfer, however catching up in a while. However it’s best to scale back it if gyro will get forward of the setpoint initially of a transfer, however falls behind later.
Tuning I Achieve
The perfect I achieve is basically primarily based on really feel. You don’t want lots of I achieve when you’ve gotten optimum P and D positive aspects; you simply want sufficient to maintain the drone from drifting and wandering. In case you are cruising ahead with minimal stick inputs, the drone ought to maintain its place for some time. If there’s any drifting, then you definately want the next I achieve.
The I time period in Betaflight has a REALLY WIDE tuning window, particularly for highly effective 5″ quads. Usually, a variety of 0.5 to 1.5 on the I time period slider works wonderful for five″ quads. This broad window permits us to tune every thing else first and modify the I time period final. With a excessive I achieve, your quad will really feel extra exact, but when the I achieve is just too excessive, chances are you’ll expertise sluggish oscillations, which you wish to keep away from.
I discovered the step response instrument in PTB is just not efficient for locating the I time period, because the step response for pitch and roll stays equivalent whatever the I achieve slider worth (e.g., 0.4 to 2.0). Nevertheless, you should utilize it for tuning Yaw I achieve, which I discover often lands round 1 on the slider for 5-inch quads.
You possibly can tune the I achieve by wanting by way of the goggles and listening to the motors. For those who goal to push the I achieve as excessive as doable, attempt transferring the I achieve slider up till you discover sluggish bouncebacks and oscillations throughout quick strikes, then scale back it a notch or two. Nevertheless, it’s actually onerous to get our quads to point out bouncebacks, due to options like “I-term loosen up” in Betaflight. These days, you should utilize extraordinarily excessive I achieve with out a lot damaging affect (similar to bouncebacks).
For five″ quads, I often go away the I achieve slider at 1.
With I-term loosen up, you may modify the cutoff primarily based on the drone’s responsiveness. For freestyle drones, you may often go away it on the default setting. For racing drones, enhance it to 30. For heavier drones like cinelifters and seven″ long-range drones carrying a GoPro, set the cutoff to 10.
Dynamic Damping
Dynamic Damping is a characteristic that reinforces D achieve to the utmost throughout sharp strikes however doesn’t enhance it throughout regular flight. This helps in lowering motor warmth.
That is how I usually use Dynamic Damping:
- Word down your present D Max worth. This worth ought to be the identical as Spinoff as a result of the Dynamic Damping slider is about to 0 in the intervening time.
- Start by growing the Dynamic Damping slider to 1.
- Then scale back the Damping slider till the D Max worth stays the identical as earlier than, this can decrease the baseline D achieve used throughout regular flights to maintain your motors cool.
Or you may simply go away Dynamic Damping slider at 0 and don’t change your Damping slider unchanged, it’s as much as you.
Different Settings
Anti Gravity Positive aspects
Anti-Gravity (AG) positive aspects assist scale back wobbling and nostril dips while you punch out after which let go of the throttle. AG briefly boosts I achieve throughout throttle pumps to mitigate these undesirable dips. Nevertheless, if the AG achieve is about too excessive, your quad might expertise speedy oscillation (stutter) while you launch the throttle, as a result of AG boosts each P and I.
Default is 8, scale back it for those who see wobbles throughout quick throttle adjustments. For five″ freestyle drones, I discovered 8 to 12 an excellent vary.
You possibly can tune AG by wanting within the goggles, or verify for nostril dip in Blackbox logs, and see the impact of anti-gravity.
Dynamic Idle
Dynamic Idle improves stability, enhances propwash dealing with, and reduces the prospect of ESC desync. It will increase motor velocity when the throttle is at zero, enhancing management authority and responsiveness at low throttle inputs. Different advantages embrace sharper flip and roll stops, extra responsive in low throttle and simpler braking.
When Dynamic Idle is about, Static Motor Idle (in %) within the Motors tab is disengaged.
To setup Dynamic Idle, you’ll want to
- Allow bi-directional DShot within the Motor Tab (if you have already got RPM filter enabled, you might be all set)
- Enter an acceptable Idle RPM worth within the PID Tuning web page (e.g., 20 to 40 for five″ drones).
The beneficial Idle RPM worth will depend on propeller dimension and pitch. Smaller and decrease pitch propellers typically require greater values. Alter the worth greater in windy circumstances to counteract instability.
| Prop Sizes | Excessive Pitch Props | Low Pitch Props |
| 31mm/1.2″ | 84 | 167 |
| 40mm/1.6″ | 62 | 124 |
| 2″ | 50 | 100 |
| 2.5″ | 40 | 80 |
| 3″ | 33 | 66 |
| 3.5″ | 28 | 57 |
| 4″ | 25 | 50 |
| 5″ | 20 | 40 |
| 6″ | 16 | 33 |
| 7″ | 14 | 28 |
| 8″ | 12 | 25 |
| 10″ | 10 | 20 |
Concerns for Dynamic Idle:
- Excessive Worth: Reduces cling time when the drone is the wrong way up (motors push more durable in the direction of the bottom). It may additionally make the quad hover barely at zero throttle, making throttle administration more durable.
- Low Worth: Dangers low throttle instability.
Setting the Preferrred Worth:
- Decide ESC Idle Worth: Default is often 5.5%. Check your motor within the motor tab utilizing a smoke stopper or bench energy provide to restrict present.
- Examine RPM: Spin the motor on the ESC idle worth (e.g., 5.5%, slider at round 1055) and word the reported RPM (requires bi-directional DShot).
- Set Dynamic Idle: Use the RPM worth divided by 100 as the perfect Dynamic Idle worth.
Throttle Enhance
Throttle Enhance will increase your throttle worth while you quickly transfer the throttle stick up, providing you with further energy. This may make throttle responses extra dynamic however can even make them unpredictable.
- Default Worth: 5
- Adjustment Suggestions:
- For those who discover the throttle onerous to handle, scale back the worth.
- Some racers disable Throttle Enhance solely by setting it to 0.
- Experiment with smaller values to see what works greatest on your flying fashion.
Voltage Sag Compensation
This characteristic reduces the utmost motor drive worth when the battery is full and will increase it because the battery voltage drops. It offers extra constant flight efficiency all through the flight. However watch out it’d make you neglect when to land as a result of the quad would really feel comparable by way of the entire pack.
Thrust Linearization
- Really useful Setting: Allow Thrust Linearization at 20%.
- Advantages:
- Boosts PID to enhance responsiveness and management at low throttle.
- Lowers PID at excessive throttle to cut back oscillations (much like TPA).
- Helps with nostril dips and is very helpful for whoops and drones utilizing 48KHz PWM frequency on ESCs.
Word: Because it boosts PID at low throttle, you would possibly have to decrease the grasp multiplier slider if motors get sizzling.
TPA
TPA stands for Throttle PID Attenuation.
To wonderful tune TPA, carry out a throttle sweep and verify the frequency vs. throttle heatmap. For those who get oscillations above a sure throttle stage, wherein case TPA can assist.
Within the newest Betaflight it solely attenuates D achieve above sure throttle stage (which is often the reason for the oscillations). Within the older Betaflight it attenuates each P and D, if you would like you may deliver this again by typing in CLI: set tpa_mode = PD.
Usually I favor to set throttle worth in TPA as excessive as doable, so D achieve is extra fixed throughout a wider throttle vary. Ensure that to set the throttle worth a little bit decrease than the place the place the D time period associated oscillations begin to present up. For instance, if oscillation begins round 1800 throttle, I might do one thing like this: TPA = 0.75, 1750.
Revisiting D Time period Filtering
After making the above adjustments, revisit D time period filtering to see if changes are wanted. Enhance or scale back filtering as required.
I Time period Rotation and Absolute Management
These options are typically not wanted for FPV freestyle drones and are extra helpful for line-of-sight pilots.
Tuning Yaw
Yaw typically doesn’t require a lot tuning because the default achieve works nicely. The tuning window for Yaw is kind of broad. In contrast to pitch and roll that are primarily based on thrust generated by propellers, yaw is predicated on the inertia generated by propeller rotation. Subsequently, yaw will inherently be too sluggish to overshoot setpoint, and there’s little have to tune yaw PID.
Yaw can also be too sluggish for D phrases to have any significant impact and it’s typically not required. Nevertheless you may allow it if you would like, but it surely would possibly introduce extra drawback than it solves, like vibrations and so forth. So we’re left with P and I phrases for Yaw.
You possibly can tune Yaw utilizing the step-response evaluation like we did with Pitch and Roll. Moreover, if sluggish oscillations happen within the again a part of the graph, then I-Time period is just too excessive. If quick oscillations happen, then P-Time period is just too excessive.
If in case you have yaw shakes when doing throttle pump, you may isolate yaw from the slider tuning, and set Yaw PID individually. To do that, go to the PID tuning tab, within the ‘Slider Mode’ dropdown record, choose RP (Roll Pitch), as a substitute of RPY (Roll Pitch Yaw). This can exclude yaw values from the sliders, and means that you can enter PID numbers for yaw. For five″ freestyle and cinematic builds, attempt 100 for each P and I might be an excellent place to begin. You can too attempt greater values as yaw tends to be fairly sluggish reacting.
There isn’t any excellent tune
How good is sweet sufficient? You possibly can all the time spend extra time taking part in with filters and PID numbers, and you may even see enhancements however it may be situational and the time you spend money on it may not be proportional to the end result. I usually simply cease when it appears “adequate” and go away it there until I’ve a particular drawback I wish to clear up.
Troubleshooting Suggestions
Unhealthy Gyro
A 5-inch FPV drone ought to fly easily on default Betaflight settings. In case your quad experiences vibrations, it may very well be on account of mechanical or electrical points, or typically a nasty gyro on the flight controller (FC). Right here’s methods to diagnose a nasty gyro:
- Symptom: One axis is considerably noisier than the others, particularly within the decrease frequency spectrum beneath 200Hz.
- Analysis: Rotate the FC by 90 levels. If the noisy axis follows the rotation, the gyro may very well be defective.
Within the instance beneath, the pitch axis is far noisier than roll and yaw, with bursts of D time period noise attributable to the noisy gyro.
- Potential Causes:
- Excessive energy wires close to the gyro.
- Noisy energy provide to the FC.
- Poor board design.
Options:
- Eradicating any excessive energy wires close to the gyro .
- You possibly can attempt utilizing a 1000uF low ESR capacitor on the ESC energy.
- If already utilizing a capacitor, attempt soldering an extra smaller 220uF-470uF capacitor to the ability of the FC (VBAT/VCC pad).
- Defective Gyro, changing FC.
RC Smoothing
RC smoothing is important in Betaflight to keep away from points with feedforward. Correct RC smoothing settings rely in your RC hyperlink. It’s greatest to load the suitable RC_Link preset to keep away from errors.
The Auto Issue is probably one of the vital essential values, decrease is extra twitchy and responsive whereas the next worth is softer and smoother however extra sluggish. Right here’s a common rule I personally comply with:
- 20-25: Racing
- 30: Default worth, nice for Freestyle
- 50: Cinematic
- 90: Extraordinarily easy cruising (noticeable delay)
- 120: Highest smoothness with out hassle (vital delay)
Unhealthy gear/pilot require greater RC smoothing too, e.g. Low high quality radio management gear, worn out gimbals, pilots with shaky fingers, and so forth. Principally something that may contribute to jerkiness in RC instructions.
If doable, verify black field logs to substantiate you’ve gotten easy setpoints, if the setpoint isn’t easy (has steppings from RC instructions), merely enhance the smoothing barely.
If in case you have noise in setpoint that peaks round 50Hz, 150Hz, 250Hz or 500Hz, then there may be in all probability an issue with RC smoothing. These frequencies are widespread packet charges in RC hyperlink. On this instance, it’s Crossfire 150Hz.
In case you are not utilizing sufficient filtering for the RC instructions, you may not have smoothed out the RC sign sufficient and it might create noise on the frequency of your radio hyperlink packet charge.
RC smoothing removes stepping and bumpiness in your set-point, it makes P time period hint much less jerky. Nevertheless it additionally provides delay to feedforward in addition to setpoint, so your quad would possibly really feel a little bit bit much less responsive. RC Smoothing is helpful, however an excessive amount of smoothing defeats the aim of getting quick RC packet charges like ExpressLRS gives.
The aim is to easy out the steppings however not including an excessive amount of delay. In order for you smoother RC enter, attempt including some extra expo, it has comparable impact but it surely gained’t provide the latency penalty.
One of the best ways is to only load the suitable RC Hyperlink preset as I talked about right here. For those who did not load the right RC_Link preset on your specific RC hyperlink and packet charge, it may additionally trigger issues to Feedforward. On this instance, feedforward jitters as a result of lack of stepping smoothing in RC instructions.
PID Sum too low?
If the PID_Sum hits the default 500 restrict (50%) as a result of PID settings are very excessive, you may increase the restrict to 1000. To do that, enter the next command within the CLI: set pid_sum_limit=1000. Nevertheless it doesn’t all the time make a distinction in flight behaviour as motors would possibly saturate at this charge anyway.
ADC Filter Jitters Inflicting Oscillations
For those who expertise random vibrations and wobbles on account of feedforward jitters, even after making use of the right RC Hyperlink preset or growing RC smoothing, the problem may very well be as a result of ADC filter.
Make sure the ADC filter is turned off in your radio’s system menu below the {hardware} web page.
Feedforward spikes seem within the Blackbox logs when the ADC filter is turned on, inflicting undesirable oscillations and vibrations.
Edit Historical past
- Nov 2022 – Information created
- Jun 2024 – Up to date to Betaflight 4.5
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