On this tutorial, I’ll share how I exploit Blackbox logs to tune filters and PID on a Betaflight FPV Drone. I can be utilizing PIDToolBox as the first instrument for filter and PID tuning, with Blackbox Explorer as a secondary instrument for Feedforward and basic troubleshooting.
Disclaimer: This information is supposed for informational functions solely. The writer holds no duty for damages ensuing from actions taken by the readers.
Blackbox is just not a should for tuning as defined on this information, nevertheless it gives full perception into what’s occurring with the drone and means that you can unleash its full potential. Issues like noise filtering and tiny overshoots are seen solely in Blackbox. In the event you’re a perfectionist or simply somebody who likes to tinker, that is the tutorial for you.
In case you are new to Blackbox, ensure to take a look at the Blackbox for newbies tutorial..
I spent over 200 hours making this 8000-word tutorial! In the event you discover my content material helpful, please contemplate supporting my work.
Getting Began
Tuning targets
Utilizing Blackbox to tune our FPV drone, we intention to attain two fundamental targets:
- Extra Efficient Use of Filters: Use minimal filtering to reduce delay however sufficient to maintain noise at an appropriate degree.
- Optimized PID Positive aspects and Associated Settings: Make sure the drone flies exactly and responsively.
Primary configurations
0. {Hardware} Guidelines
- Flight Controller (FC) Stack: Select an FC stack with rubber grommets (gummies) for sturdiness and noise efficiency.
- Steel Screws: Use metallic screws for the FC stack; keep away from nylon/plastic screws/standoffs as they’re vulnerable to breakage and vibrations. If spacers are wanted, use mushy silicone ones. Lighter titanium screws can save just a few grams.
- Locking Stack Screws: Safe the stack screws firmly with a metallic nut earlier than mounting the 4in1 ESC. In case your body has pressed insert nuts, further nuts aren’t 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 mushy mount to work successfully.
1. Blackbox Recording Settings
Choose the next settings within the Blackbox Configuration:
- Logging Machine: Onboard Flash or SD Card
- Logging Fee: 2KHz (or 1.6KHz for BMI270 Gyro)
- Debug Mode: GYRO_SCALED (data unfiltered gyro sign)
- Information Included: To save lots of house for longer recordings, deselect pointless knowledge like Altitude, GPS, and Magnetometer, or depart at default.
2. Disable the ADC filter in your OpenTX/EdgeTX radio (System -> {Hardware}) to scale back latency.
3. ESC settings:
I’ve a publish 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 fastened 24KHz or 48KHz. 48KHz is usually safer for gyro noise, making your quad smoother and simpler to tune. 24KHz presents higher braking energy, which is useful for prop wash dealing with and responsiveness, however with a better danger of vibration. In case you are on the fence, simply go together 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 learn how to flash it right here: https://oscarliang.com/bluejay-blheli-s/
3. Flash the newest model of Betaflight firmware to your flight controller and depart 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 learn how to allow RPM filter. For BLHeli_32 ESC it really works out of the field, however in case you have BLHeli_S ESC, it’s essential to flash Bluejay firmware (tutorial) first.
Test if it’s working correctly by operating the motors within the Motors tab (with out propellers) and making certain the error fee (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.
Completely different RC hyperlinks require particular RC smoothing and feedforward configurations. Incorrect config may cause stuttering and vibrations. My favourite RC hyperlink is ExpressLRS, try what radio gear I exploit right here.
Loading the appropriate RC_Link preset in Betaflight will apply the mandatory configurations robotically. Bear in mind to decide on choices primarily based in your flying model, for most individuals it might be Freestyle.
For Crossfire, lock the packet fee to both 50Hz (longer vary, increased 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. Advantageous-tune TPA on the finish if oscillation points happen at excessive throttle, however typically I might reduce using TPA every time doable.
The best way to use PIDToolBox and Blackbox Explorer?
I can be utilizing each PIDToolBox (PTB) and Blackbox Explorer (BE) in my PID and filter tuning.
PIDToolBox can be our fundamental instrument, it’s by far probably the most highly effective Blackbox instrument obtainable. It means that you can examine a number of logs facet by facet, making it simpler to see the results of your modifications. The Step Response instrument is particularly 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 could be very useful.
Nonetheless, PTB will 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 regulate the orange sections (Gyro and D Time period Lowpass Filters) utilizing the sliders. No want to the touch the crimson sections.
Additional studying: Be taught concerning the various kinds of filter in Betaflight on this tutorial.
Good {hardware} can cut 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 like (see the underside bar for throttle modifications).
Understanding Gyro Frequency and Delay
Open the throttle sweeps log in Blackbox Explorer and click on on “Gyro_Scaled” on the proper hand pane, that is the unfiltered gyro sign. Take away the takeoff and touchdown components 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:
- Below 20Hz: Drone flight actions.
- 20Hz – 100Hz: Propwash and oscillations from suboptimal PID, problematic ESC config, unhealthy RC hyperlink settings, and many others.
- 100Hz – 250Hz: Body resonance or free components.
- 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, equivalent to oscillations and propwash, happen. As a basic rule of thumb, you wish to see little exercise on this frequency vary. Having some is regular, however an excessive amount of means you may have an oscillation concern that must be addressed. Usually, 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 in opposition to. Filtering on this low-frequency vary can really 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 properly 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.
Maybe not intuitive, however over-filtering can really trigger oscillation to indicate up as noise within the sub-100Hz spectra. That’s as a result of filtering creates one thing referred to as section delay. When the quad tries to appropriate the error, the response is simply too late as a result of delay, which is counterproductive. It makes the error worse and creates a suggestions loop, inflicting the drone to oscillate.
That’s why, if we use much less filtering, noise points below 100Hz can typically really get higher as a result of latency is decreased and the quad can react quicker to appropriate PID errors. Utilizing much less filtering additionally means that you can push PID good points increased, which makes your quad observe setpoint higher and helps fight propwash.
You’ll find out how a lot delay is added to the Gyro sign attributable to filtering by plotting Gyro and Gyro_Scaled and measuring the hole between them.
In PTB, it robotically estimates the delay brought on by gyro filtering and D-term filtering (see the highest proper nook of the primary graph within the second column).
Filter Technique
My basic filter technique is to remove motor noise bands utilizing the RPM filter, then crush out body resonances with dynamic notch filters, and eventually, cut back the ambient noise ground with Gyro and D-term lowpass filters. I can 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 reduce latency, however on the similar time, we’d like sufficient filtering to keep away from burning our motors when flying residence with a bent prop. You possibly can actually play it secure and apply extra filtering than wanted, however over-filtering makes the drone really feel disconnected and gradual to react as a result of elevated delay. It may additionally worsen propwash. So, we have to attempt for a steadiness.
Other than checking Blackbox logs, motor temperature is one other helpful indicator in filter tuning. When motors get too sizzling, it normally signifies that the filtering is simply too aggressive.
Professional Tip: Sizzling Motors – How Sizzling is Too Sizzling?
As a basic rule of thumb, if you happen to pinch the motor bell and might’t hold your fingers on it for quite a lot of seconds, it’s too sizzling and you might be most likely pushing your settings too aggressively.
How Clear is Your Construct?
Earlier than we start tuning, it’s necessary to verify 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 have the ability to cut back filtering from there. In case your quad is already noisy with default filter settings, as an alternative of accelerating filtering, you need to search for doable mechanical or electrical points. Guarantee you may have a capacitor on the ESC enter energy, all screws are tightened, and also you’re utilizing contemporary new props, and many others.
On a clear 5″ quad, there needs to be little exercise between ~50Hz (the quad’s actions) and ~200Hz (motor vibration). When you have a number of noise on this area, it may very well be electrical noise (maybe the gyro enter energy is simply 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 could be more difficult.
As urged by the writer of PIDToolBox, it’s ideally suited to have the general noise ground beneath -30dB above 50Hz. For D-term, it’s ideally suited to have the general noise ground beneath -10dB. Analyzing the noise ranges in these areas can provide you a very good indication of how easy your quad flies. The noise degree 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’ll need extra filtering. It’s not the top of the world; it simply means the latency can be increased, and also you received’t have the ability to push PID good points 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 simplest 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 reduce latency.
Let’s have 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“.
- Below “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 :
- Near 0Hz: The very vivid 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.
- Basic Motor Noise Band: This diagonal line (3) is normally the brightest. Motor noise usually will increase in frequency with throttle degree.
- Harmonics: These are multiples of the elemental motor noise band. In our instance, harmonics (usually dimmer and tougher 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 indicate extra and stronger harmonics than 3-blade props.
We’ll use RPM filter to handle these motor noise bands.
The objective 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 a better min frequency end in much less filtering and decrease latency.
Use the Information Cursor Instrument, 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 proper, I modified it to 2 Harmonics with min frequency of 160Hz
By decreasing 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 may possibly nonetheless get amplified when it will get into D time period. Let’s verify the Dterm warmth map beneath on the proper, as you may see, a tiny little bit of gyro noise has turn into fairly unhealthy Dterm noise.
On this instance, it’s most likely 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 deal with that, we’ve got to decrease Min Freq, i.e. round 20Hz beneath the noise frequency could be ideally suited.
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 are able to’t actually cut back RPM filter. On this instance, the default settings (3 harmonics and 100Hz min frequency) labored greatest.
RPM Crossfading
This superior function fades within the RPM filter power over a spread (kind 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 increased or decrease in frequency, and also you would possibly want it to fade in additional shortly or slowly depends upon the noise. This function is just 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 power and reaches full power at 150Hz.
Q Worth
Rising the Q worth of a notch filter makes it extra centered on the focused frequency, decreasing latency. Regulate this within the CLI:
set rpm_filter_q = 500
Default values normally work properly, 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 normally not very sturdy, however the third harmonics is. On this case you should use extra filtering power 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, equivalent to body resonance, antennas, GoPro mounts, and bent propellers.
When the RPM filter is enabled, Betaflight will robotically cut back the quantity of Dynamic Notch filtering by utilizing fewer notches and a better 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.
Establish 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 normally, 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 usually 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.
- Regulate Q: If the default is working properly, attempt growing it to 600 and even 700. Keep away from exceeding 1000. In the event you nonetheless see body resonance noise after filtering, decrease the Q worth.
- Test D-term Heatmap: Analyze the D-term heatmap to see how modifications 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 facet 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 might help 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 a better probability of catching it. If the Dynamic Notch fails to catch these newly pop up resonances attributable to 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, once I set Q to 450, the noise is satisfactorily managed. Within the beneath graphs, on the left is Q=700, the proper is Q=450. You possibly can verify Dterm heatmap once more to verify that is working properly.
Tuning Gyro Lowpass Filter
Typically, you can begin by turning off the Gyro Lowpass 1 filter as it’s usually pointless. Take a look at 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 scale back Gyro Lowpass 2 a few notches at a time. Transferring the slider to the proper will increase the frequency, which reduces filtering, leading to much less delay, higher prop wash dealing with, and the potential for increased PID good points.
Right here’s a comparability of the gyro frequency spectrum at completely different Gyro Lowpass filter slider values: 1.0 (brown), 1.5 (crimson), and a pair of.0 (orange).
The three traces nearly overlap, suggesting that the Gyro Lowpass filter isn’t considerably affecting the sign and will be decreased. Curiously, the noise within the sub-100Hz spectrum barely improves with much less filtering, which aligns with our earlier discussions.
Essential Concerns:
- By no means disable the Gyro Lowpass 2 filter for 2K/4K PID loop frequencies attributable to anti-aliasing causes.
- Minimal Frequency:
- For 2K loop time, depart 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 problem.
Tuning D Time period Lowpass
D time period is way noisier than Gyro attributable to its delicate nature and noise will get amplified as frequency will increase. Due to this fact, be additional cautious and conservative when coping with D Time period filtering.
Strive transferring the “D Time period Filter Multiplier” slider to the proper 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 you need to return a notch or two.
Keep away from being too aggressive with decreasing D Time period filtering. Go away 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 (crimson), and 1.6 (orange). As seen within the heatmap, much less filtering leads to 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.
In the event you hear the motors getting tough (thrilling oscillation) as you cut back D-term filtering, it’s as a result of rising noise beneath 100Hz. You possibly can affirm this by checking the <100Hz graphs. On this instance, staying beneath 1.3, perhaps 1.2 and even simply 1.1, could be safer.
After tuning PID good points, 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 could be very clear, you may maybe cut back filtering a bit extra (if motors aren’t sizzling). See beneath graphs, the left has a loud D time period hint, the proper is way cleaner.
Essential: NEVER disable D-Time period lowpass filters utterly, you’ll burn your motors.
Gyro/D Time period Notch Filters
There’s no must allow Gyro Notch Filter and D Time period Notch Filter, these are static notch filters which have turn into legacy since RPM filter and dynamic notch filters are doing many of the work.
Nonetheless, if there’s a sturdy resonance at a selected frequency (equivalent to body resonance), a static notch filter will be useful. The dynamic notch filter normally covers it, so a static notch filter is commonly pointless. You possibly can attempt including a static notch for identified body resonance and cut back the dynamic notch depend by one to see which technique works higher in your setup.
Yaw Lowpass Filter
The default yaw lowpass filter at 100Hz cutoff has minimal latency penalty and will be left untouched. This filter is particularly useful for whoops, because it helps to scale back yaw spin in collisions.
PID Tuning
To tune PID utilizing Blackbox, I comply with the “Basement Tuning” methodology utilizing PIDToolBox. This methodology is beginner-friendly and will be executed in a small house like a basement or bed room, therefore the identify. It includes performing a collection of quick flights with barely completely different PID values, then evaluating the logs to seek out the optimum good points.
In the course of the flights, transfer the quad round on the pitch and roll axes. You possibly can be taught extra concerning the basement methodology on this video by PIDToolbox.
Though the tactic is named “basement tuning,” I’m not comfy doing this indoors. I’ve had a few “fly to the moon” incidents previously, practically drilling a gap within the ceiling. Due to this fact, I at all times carry out these exams in a backyard or native park for security.
Fee 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 fee profile:
- Heart Sensitivity 250
- Max Fee 400
- Expo 0.00
This profile has a low max fee, making it much less prone to lose management if you happen to transfer the sticks an excessive amount of. The excessive and linear middle 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 Fee mode. Based on the writer of PIDToolBox, Angle mode works simply in addition to Fee mode, however it’s essential to do the next first:
- Go to the Setup tab and calibrate the accelerometer.
- Within the PID Profile Settings, set the Angle mode power to 100.
- Click on Save to make sure the modifications are utilized.
Discovering P/D Stability
To start with, decrease these good points so 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 good points) 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
Regulate the “Damping” (D good points) slider, begin with a minimal worth you wish to check. For a typical 5-inch FPV drone, 0.6 is an effective place to begin.
Here’s what you wish to carry out within the flight:
- Arm and hover
- Continuously transferring the roll and pitch stick for 20-30 seconds, the extra actions the extra correct it will likely be
- Do as massive 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 hold 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. If you increase D acquire too excessive, your motors will sound tough, subsequently you may’t at all times check the final one or two values, which is okay.
The quickest option 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 alter battery each 2-3 flights to make sure the outcome 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 must unplug.
16MB reminiscence needs to be sufficient for six 30-second flights if you happen to time it properly.
After you may have accomplished all of the flights, obtain them to your laptop. To prepare 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 many others (01 means first check flight, d06 means damping slider worth 0.6), and put them within the “02 PD Stability” folder.
Load all of the logs in PTB, undergo each and take away the take-off and touchdown components for every log (to do that, allow “Trim” on the proper hand panel).
Click on the “Step Resp Instrument“, choose all of the recordsdata and click on Run. in case you have offset within the curves (gyro curve transferring away from setpoint in the direction of the top), allow Y Correction.
It’s fairly straight-forward, merely decide the perfect 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 simply too noisy or your actions aren’t large enough.
The graphs on the proper 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 succeed in setpoint (ideally the decrease the higher)
When D acquire is low, you’ll get overshoot and even oscillation. As D acquire will increase, there can be much less overshoot and Peak will lower, however Latency will go up in consequence. When D is simply too excessive (undershoot), the preliminary peak may not even attain the setpoint and this isn’t ideally suited. 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 take 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 might be 1.0.
It’s fairly widespread to have a special 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 acquire, then take the Damping slider to the place you need for roll, and regulate the Pitch Damping slider to match the pitch D acquire you simply wrote down.
Generally it’s higher to be slightly extra conservative and keep away from having D acquire too excessive. In case you are on the fence, at all times go together with much less D acquire (a better P/D ratio), so you may increase your general PID good points increased on the finish since D is normally 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 super worth. That’s simply my private desire, you can provide {that a} attempt in order for you.
Drone measurement additionally impacts PD ratio, bigger drones are likely to have increased 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 Acquire
Do the identical check for Grasp Multiplier slider, transfer the slider in 0.2 steps. For a 5″ drone, begin with values equivalent 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 acquire is simply too excessive, the quad might shoot up unexpectedly. Pay shut consideration to motor noise, and cease instantly if you happen to 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 is because the response curve form is especially decided by the P/D ratio. Rising the good points received’t considerably have an effect on the response form, however bumping up P/D good points can cut back latency.
You’ve got reached the perfect Grasp Multiplier acquire when one of many following happens:
- Thrilling Oscillation: In the event you hear thrilling oscillation, you may’t improve D acquire any additional.
- Latency Plateau: If latency doesn’t lower anymore (or little or no), it means you may have 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 acquire achievable is influenced by the noise degree of your construct and the quantity of filtering used. Much less filtering permits for increased PID good points. Generally, it’s safer to scale back the Grasp Multiplier slider by a notch or two as soon as you discover the utmost worth. Keep away from pushing D acquire to the restrict to account for potential points like bent props.
Drones utilizing increased cell depend batteries (increased voltage) are likely to require decrease D good points. For instance, on a 6S quad, D good points may be within the 30s, whereas on a 4S they’re normally within the 40s.
In my instance, 1.6 appears to be the worth that provides the least quantity of latency, with little enchancment when growing to 1.8.
In the event you can’t hear thrilling oscillations, use the Spectral Analyzer to plot D-term. As good points improve, motors might produce an exhilarating sound peaking round 40-80Hz, particularly when throttling up. If noise on this frequency vary will increase with increased good points, 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 danger it and would possible select 1.4 and even 1.3 to be secure.
There may be ongoing debate on whether or not it’s higher to have extra D-term filtering and better D acquire, or much less D-term filtering and decrease D acquire. Nonetheless, by no means run with much less D-term filtering and excessive D acquire as this could result in disastrous outcomes if you happen to hit an impediment or bend a prop. It’s no joke, talking from expertise right here:
After discovering the optimum D acquire, verify setpoint monitoring by plotting Gyro and Setpoint. The traces needs to be roughly parallel, indicating the quad is accelerating and decelerating on the similar fee because the setpoint. Nonetheless, there would possibly nonetheless be a major hole between them, indicating latency. Within the subsequent step, we are going to cut back this hole utilizing Feedforward.
Tuning Feed Ahead
Feed Ahead (FF) accelerates your quad whenever you transfer the sticks, making your quad extra responsive and nearer to the setpoint. Not like 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 quicker than P time period.
Feed Ahead helps the quad reply promptly to stay inputs, offering a extra instant and managed flying expertise. It’s useful for all flying types, 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 ordinary fee profile, or a default fee profile in Betaflight (simply change to an unused fee profile) to get a good max fee at full stick. You possibly can verify my charges right here: https://oscarliang.com/charges/#My-Charges
As a substitute of utilizing the step response instrument in PTB, use BE to verify the setpoint/gyro traces. The gyro ought to observe the setpoint extra intently with much less delay. Ideally, the gyro needs to be proper on prime of the setpoint.
If Feed Ahead overshoots (gyro strikes earlier than the setpoint), the FF is simply 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 acquire is simply too excessive, it may possibly trigger the P time period to react in the wrong way, making an attempt to counteract it.
Doesn’t matter what your flying model is, feedforward will be helpful and doesn’t apply solely to sure kinds of flying. Even cinematic flying can profit from a very good quantity of feedforward, if you’re transferring your stick easily and slowly, then feedforward received’t kick in anyway. If you want snappy response FF will cut back the latency between stick enter and quad response. If you would like easy flying, simply use expo, extra RC smoothing or decrease your fee.
There’s an optionally available setting, Feedforward enhance (FF Increase). You wish to improve it if gyro lagging behind setpoint firstly of a transfer, however catching up in a while. However you need to cut back it if gyro will get forward of the setpoint firstly of a transfer, however falls behind later.
Tuning I Acquire
The perfect I acquire is essentially primarily based on really feel. You don’t want a number of I acquire when you may have optimum P and D good points; 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 a better I acquire.
The I time period in Betaflight has a REALLY WIDE tuning window, particularly for highly effective 5″ quads. Usually, a spread of 0.5 to 1.5 on the I time period slider works wonderful for five″ quads. This vast window permits us to tune every thing else first and regulate the I time period final. With a excessive I acquire, your quad will really feel extra exact, but when the I acquire is simply too excessive, it’s possible you’ll expertise gradual 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 an identical whatever the I acquire slider worth (e.g., 0.4 to 2.0). Nonetheless, you should use it for tuning Yaw I acquire, which I discover normally lands round 1 on the slider for 5-inch quads.
You possibly can tune the I acquire by wanting by means of the goggles and listening to the motors. In the event you intention to push the I acquire as excessive as doable, attempt transferring the I acquire slider up till you discover gradual bouncebacks and oscillations throughout quick strikes, then cut back it a notch or two. Nonetheless, it’s actually onerous to get our quads to indicate bouncebacks, because of options like “I-term chill out” in Betaflight. These days, you should use extraordinarily excessive I acquire with out a lot unfavourable influence (equivalent to bouncebacks).
For five″ quads, I normally depart the I acquire slider at 1.
With I-term chill out, you may regulate the cutoff primarily based on the drone’s responsiveness. For freestyle drones, you may normally depart it on the default setting. For racing drones, improve 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 function that reinforces D acquire to the utmost throughout sharp strikes however doesn’t improve it throughout regular flight. This helps in decreasing motor warmth.
That is how I usually use Dynamic Damping:
- Word down your present D Max worth. This worth needs to be the identical as Spinoff as a result of the Dynamic Damping slider is about to 0 in the mean time.
- Start by growing the Dynamic Damping slider to 1.
- Then cut back the Damping slider till the D Max worth stays the identical as earlier than, it will decrease the baseline D acquire used throughout regular flights to maintain your motors cool.
Or you may simply depart 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) good points assist cut back wobbling and nostril dips whenever you punch out after which let go of the throttle. AG quickly boosts I acquire throughout throttle pumps to mitigate these undesirable dips. Nonetheless, if the AG acquire is about too excessive, your quad might expertise speedy oscillation (stutter) whenever you launch the throttle, as a result of AG boosts each P and I.
Default is 8, cut back it if you happen to see wobbles throughout quick throttle modifications. For five″ freestyle drones, I discovered 8 to 12 a very good 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 pace when the throttle is at zero, bettering management authority and responsiveness at low throttle inputs. Different advantages embody sharper flip and roll stops, extra responsive in low throttle and more practical braking.
When Dynamic Idle is about, Static Motor Idle (in %) within the Motors tab is disengaged.
To setup Dynamic Idle, it’s essential 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 really useful Idle RPM worth depends upon propeller measurement and pitch. Smaller and decrease pitch propellers typically require increased values. Regulate the worth increased 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 dangle time when the drone is the other way up (motors push tougher in the direction of the bottom). It may additionally make the quad hover barely at zero throttle, making throttle administration tougher.
- Low Worth: Dangers low throttle instability.
Setting the Splendid Worth:
- Decide ESC Idle Worth: Default is normally 5.5%. Take a look at your motor within the motor tab utilizing a smoke stopper or bench energy provide to restrict present.
- Test RPM: Spin the motor on the ESC idle worth (e.g., 5.5%, slider at round 1055) and be aware the reported RPM (requires bi-directional DShot).
- Set Dynamic Idle: Use the RPM worth divided by 100 as the perfect Dynamic Idle worth.
Throttle Increase
Throttle Increase will increase your throttle worth whenever you quickly transfer the throttle stick up, supplying you with additional energy. This will make throttle responses extra dynamic however may make them unpredictable.
- Default Worth: 5
- Adjustment Suggestions:
- In the event you discover the throttle onerous to handle, cut back the worth.
- Some racers disable Throttle Increase solely by setting it to 0.
- Experiment with smaller values to see what works greatest in your flying model.
Voltage Sag Compensation
This function reduces the utmost motor drive worth when the battery is full and will increase it because the battery voltage drops. It gives 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 means of the entire pack.
Thrust Linearization
- Really helpful Setting: Allow Thrust Linearization at 20%.
- Advantages:
- Boosts PID to enhance responsiveness and management at low throttle.
- Lowers PID at excessive throttle to scale back oscillations (just like TPA).
- Helps with nostril dips and is particularly helpful for whoops and drones utilizing 48KHz PWM frequency on ESCs.
Word: Because it boosts PID at low throttle, you would possibly must 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. In the event you get oscillations above a sure throttle degree, during which case TPA might help.
Within the newest Betaflight it solely attenuates D acquire above sure throttle degree (which is normally the reason for the oscillations). Within the older Betaflight it attenuates each P and D, in order for you you may carry 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 acquire is extra fixed throughout a wider throttle vary. Ensure that to set the throttle worth slightly 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 modifications, revisit D time period filtering to see if changes are wanted. Enhance or cut back filtering as required.
I Time period Rotation and Absolute Management
These options are typically not wanted for FPV freestyle drones and are extra useful for line-of-sight pilots.
Tuning Yaw
Yaw typically doesn’t require a lot tuning because the default acquire works properly. The tuning window for Yaw is sort of vast. Not like pitch and roll that are primarily based on thrust generated by propellers, yaw relies on the inertia generated by propeller rotation. Due to this fact, yaw will inherently be too gradual to overshoot setpoint, and there’s little must tune yaw PID.
Yaw can also be too gradual for D phrases to have any significant impact and it’s typically not required. Nonetheless you may allow it in order for you, nevertheless it would possibly introduce extra downside than it solves, like vibrations and many others. 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 gradual oscillations happen within the again a part of the graph, then I-Time period is simply too excessive. If quick oscillations happen, then P-Time period is simply too excessive.
When 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 an alternative of RPY (Roll Pitch Yaw). It will 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 a very good place to begin. You too can attempt increased values as yaw tends to be fairly gradual reacting.
There isn’t any excellent tune
How good is sweet sufficient? You possibly can at all times spend extra time enjoying 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 outcome. I usually simply cease when it seems “adequate” and depart it there until I’ve a selected downside I wish to remedy.
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 attributable to mechanical or electrical points, or typically a foul gyro on the flight controller (FC). Right here’s learn how to diagnose a foul gyro:
- Symptom: One axis is considerably noisier than the others, particularly within the decrease frequency spectrum beneath 200Hz.
- Prognosis: 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 way noisier than roll and yaw, with bursts of D time period noise brought on by 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 a further smaller 220uF-470uF capacitor to the facility 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 maybe one of the necessary values, decrease is extra twitchy and responsive whereas a better worth is softer and smoother however extra sluggish. Right here’s a basic 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 bother (vital delay)
Unhealthy gear/pilot require increased RC smoothing too, e.g. Low high quality radio management gear, worn out gimbals, pilots with shaky fingers, and many others. Principally something which may contribute to jerkiness in RC instructions.
If doable, verify black field logs to verify you may have easy setpoints, if the setpoint isn’t easy (has steppings from RC instructions), merely improve the smoothing barely.
When you have noise in setpoint that peaks round 50Hz, 150Hz, 250Hz or 500Hz, then there’s most likely 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 fee.
RC smoothing removes stepping and bumpiness in your set-point, it makes P time period hint much less jerky. Nonetheless it additionally provides delay to feedforward in addition to setpoint, so your quad would possibly really feel slightly bit much less responsive. RC Smoothing is beneficial, however an excessive amount of smoothing defeats the aim of getting quick RC packet charges like ExpressLRS presents.
The objective is to easy out the steppings however not including an excessive amount of delay. If you would like smoother RC enter, attempt including some extra expo, it has comparable impact nevertheless it received’t provide the latency penalty.
The easiest way is to only load the suitable RC Hyperlink preset as I talked about right here. In the event you did not load the proper RC_Link preset in your explicit RC hyperlink and packet fee, 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. But it surely doesn’t at all times make a distinction in flight behaviour as motors would possibly saturate at this fee anyway.
ADC Filter Jitters Inflicting Oscillations
In the event you expertise random vibrations and wobbles attributable to feedforward jitters, even after making use of the proper 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
