On this tutorial, I’ll share how I exploit Blackbox logs to tune filters and PID on a Betaflight FPV Drone. I shall be utilizing PIDToolBox as the first software for filter and PID tuning, with Blackbox Explorer as a secondary software for Feedforward and normal troubleshooting.
Disclaimer: This information is supposed for informational functions solely. The creator 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 offers 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. If you happen to’re a perfectionist or simply somebody who likes to tinker, that is the tutorial for you.
If you’re new to Blackbox, ensure to take a look at the Blackbox for inexperienced persons tutorial..
I spent over 200 hours making this 8000-word tutorial! If you happen to discover my content material helpful, please contemplate supporting my work.
Getting Began
Tuning objectives
Utilizing Blackbox to tune our FPV drone, we purpose to realize two important objectives:
- Extra Efficient Use of Filters: Use minimal filtering to attenuate delay however sufficient to maintain noise at a suitable degree.
- Optimized PID Features 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.
- 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 delicate silicone ones. Lighter titanium screws can save just a few 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 should 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 delicate 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)
- Knowledge Included: To avoid wasting house for longer recordings, deselect pointless information like Altitude, GPS, and Magnetometer, or depart 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 fastened 24KHz or 48KHz. 48KHz is mostly 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. If you’re 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 the best way to flash it right here: https://oscarliang.com/bluejay-blheli-s/
3. Flash the most recent model of Betaflight firmware to your flight controller and depart PID/filter settings at default. Allow Professional 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 trendy ESCs help Bi-directional DShot. I’ve a tutorial on the best way to allow RPM filter. For BLHeli_32 ESC it really works out of the field, however in case you have BLHeli_S ESC, that you must 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, strive 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’ll be able to allow the Gyro RPM filter, among the best 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 acceptable RC_Link preset in Betaflight will apply the mandatory configurations robotically. Bear in mind to decide on choices based mostly in your flying type, for most individuals it could 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. Positive-tune TPA on the finish if oscillation points happen at excessive throttle, however typically I’d decrease the usage of TPA at any time when potential.
Tips on how to use PIDToolBox and Blackbox Explorer?
I shall be utilizing each PIDToolBox (PTB) and Blackbox Explorer (BE) in my PID and filter tuning.
PIDToolBox shall be our important software, it’s by far essentially the most highly effective Blackbox software out there. It means that you can evaluate a number of logs aspect by aspect, making it simpler to see the consequences of your filter modifications. The Step Response software 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 may 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 best way to go.
Filters Tuning
You will discover 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: Study in regards to the various kinds of filter in Betaflight on this tutorial.
Good {hardware} can scale back the necessity for intensive filtering. Guarantee your body is well-designed with out resonance points, use well-balanced propellers, and high-quality motors with clean 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).
Gyro Noise Frequency Defined
Open the throttle sweeps log in Blackbox Explorer and click on on “Gyro_Scaled” on the precise 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:
- Underneath 20Hz: Drone flight actions.
- 20Hz – 100Hz: Propwash and oscillations from suboptimal PID, problematic ESC config, dangerous RC hyperlink settings, and many others.
- 100Hz – 250Hz: Body resonance or unfastened components.
- Above 250Hz: Noise from motors and propellers, and harmonics.
The whole lot under 20Hz is “good” drone movement reacting to the sticks.
Between 20Hz and 100Hz is the place undesired vibrations, resembling oscillations and propwash, happen. As a normal 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 got an oscillation situation that must be addressed. Usually, we attempt to keep away from filtering under 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 really make issues worse as a result of it introduces an incredible quantity of latency. Analyzing the spectra beneath 100Hz may give you perception into vibration or mid-throttle oscillation points and the way effectively 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 really 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 right the error, the response is likely to be too late because of the delay, which will be counterproductive. It will possibly 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 beneath 100Hz can typically really get higher as a result of latency is decreased and the quad can react sooner to right PID errors. Utilizing much less filtering additionally means that you can push PID beneficial properties increased, which makes your quad observe setpoint higher and helps fight propwash.
You will discover out how a lot delay is added to the Gyro sign because of filtering by plotting Gyro and Gyro_Scaled and measuring the hole between them.
In PTB, it robotically 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 normal filter technique is to eradicate motor noise bands utilizing the RPM filter, then crush out body resonances with dynamic notch filters, and eventually, scale back the ambient noise ground with Gyro and D-term lowpass filters. I shall be tuning filters on this order:
RPM Filter > Dynamic Notch Filter > Gyro Lowpass > D-term Lowpass
We wish to use as little filtering as potential to attenuate 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’ll be able to actually play it secure and apply extra filtering than wanted, however over-filtering makes the drone really feel disconnected and gradual to react because of the elevated delay. It will possibly 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 scorching, it normally signifies that the filtering is simply too aggressive.
Professional Tip: Scorching Motors – How Scorching is Too Scorching?
As a normal rule of thumb, should you pinch the motor bell and may’t hold your fingers on it for various seconds, it’s too scorching and you’re in all probability pushing your settings too aggressively.
How Clear is Your Construct?
Earlier than we start tuning, it’s essential to test 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, you must search for potential mechanical or electrical points. Guarantee you’ve got a capacitor on the ESC enter energy, all screws are tightened, and also you’re utilizing recent 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). If in case you have numerous noise on this area, it could possibly 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 tougher.
As instructed by the creator of PIDToolBox, it’s supreme to have the general noise ground under -30dB above 50Hz. For D-term, it’s supreme to have the general noise ground under -10dB. Analyzing the noise ranges in these areas may give you a superb indication of how clean 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 have to extra filtering. It’s not the top of the world; it simply means the latency shall be increased, and also you gained’t be capable of push PID beneficial properties as excessive.
Tuning RPM filter
Motor noise is the first supply of noise for FPV drones, and the RPM filter is among the handiest filters in Betaflight for tackling motor noise. On a clear construct, the RPM filter and Dynamic Notch filters will do a lot of the work, permitting us to disable many different filters to attenuate 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“.
- Underneath “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 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.
- 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 strains (4) and (5). Attempt adjusting the size in the event that they aren’t seen. Notice that 2-blade propellers have a tendency to point out extra and stronger harmonics than 3-blade props.
We’ll use RPM filter to maintain these motor noise bands.
The objective is to optimize the variety of RPM harmonics used and set the very best potential “Min Frequency” based mostly on the beginning frequency of the motor band. Fewer RPM harmonics and a better min frequency lead to much less filtering and decrease latency.
Use the Knowledge Cursor Instrument, click on on the place the motor band begins to search 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 precise, I modified it to 2 Harmonics with min frequency of 160Hz
By decreasing one harmonics and lift the cutoff frequency, you’ll be able to maybe see extra unfiltered noise from the third motor harmonics.
Though it’s fairly weak, it might probably nonetheless get amplified when it will get into D time period. Let’s test the Dterm warmth map under on the precise, as you’ll be able to see, a tiny little bit of gyro noise has turn out to be fairly dangerous Dterm noise.
On this instance, it’s in all probability higher to have 3 harmonics in RPM filter.
The opposite factor you may need observed is a few noise round 116Hz left unfiltered as a result of we raised the min freq to 160Hz. To handle that, we now have to decrease Min Freq, i.e. round 20Hz under the noise frequency could be supreme.
Right here’s a comparability of gyro sign after filtering utilizing 3 totally 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 power over a variety (kind of like TPA), the default is nice 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 characteristic is barely 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
Growing the Q worth of a notch filter makes it extra centered on the focused frequency, decreasing latency. Modify this within the CLI:
set rpm_filter_q = 500
Default values normally work effectively, however you’ll be able to fine-tune by rising 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 need to 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’ll be able to 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, resembling body resonance, antennas, GoPro mounts, and bent propellers.
When the RPM filter is enabled, Betaflight will robotically scale back the quantity of Dynamic Notch filtering by utilizing fewer notches and a better Q worth because the RPM filter will do a lot of the heavy lifting. You’ll be able to additional tune the Dynamic Notch filter based mostly in your setup.
Establish Body Resonances: Take a look at the warmth map and establish 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 adequate 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. The next Q worth means a narrower filter, which leads to much less filtering and decrease latency.
- Default Q: Begin with the default Q of 500.
- Modify Q: If the default is working effectively, strive rising it to 600 and even 700. Keep away from exceeding 1000. If you happen to 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 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 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 because of Min Frequency is about too excessive, your motors can get scorching 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’ll be able to 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 means up.
In an instance setup, there seems to be one body resonance round 210Hz.
I attempted rising Q to 700 and setting the min/max frequency to 160-230Hz, however Q was clearly too excessive. There’s 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 under graphs, on the left is Q=700, the precise is Q=450. You’ll be able to test Dterm heatmap once more to substantiate that is working effectively.
Tuning Gyro Lowpass Filter
Usually, 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 test the motor temperature to make sure they aren’t scorching 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 precise will increase the frequency, which reduces filtering, leading to much less delay, higher prop wash dealing with, and the potential for increased PID beneficial properties.
Right here’s a comparability of the gyro frequency spectrum at totally different Gyro Lowpass filter slider values: 1.0 (brown), 1.5 (crimson), and a couple of.0 (orange).
The three strains virtually 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 because of anti-aliasing causes.
- Minimal Frequency:
- For 2K loop time, depart Gyro Lowpass 2 at a minimal of 500Hz.
- For 4K, you’ll be able to set Gyro Lowpass 2 as much as 1000Hz.
- For 8K, you’ll be able to disable Gyro Lowpass 2 completely if noise isn’t a difficulty.
Tuning D Time period Lowpass
D time period is way noisier than Gyro because of 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.
Attempt shifting the “D Time period Filter Multiplier” slider to the precise a notch at a time and see how the drone responds in a 30-second check flight (do some acro strikes), additionally test motor temperature after touchdown. In the event that they get scorching you must return a notch or two.
Keep away from being too aggressive with decreasing D Time period filtering. Depart some headroom for potential bent props throughout flight. Too little D Time period filtering mixed with a broken propeller can result in scorching 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, in contrast to 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.
If you happen to hear the motors getting tough (thrilling oscillation) as you scale back D-term filtering, it’s because of the rising noise under 100Hz. You’ll be able to affirm this by checking the <100Hz graphs. On this instance, staying under 1.3, possibly 1.2 and even simply 1.1, could be safer.
After tuning PID beneficial properties, 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 could assist. If the D time period hint may be very clear, you’ll be able to maybe scale back filtering a bit extra (if motors should not scorching). See under graphs, the left has a loud D time period hint, the precise is way cleaner.
Essential: NEVER disable D-Time period lowpass filters fully, 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 out to be legacy since RPM filter and dynamic notch filters are doing a lot of the work.
Nonetheless, if there’s a sturdy resonance at a particular frequency (resembling body resonance), a static notch filter will be useful. The dynamic notch filter normally covers it, so a static notch filter is usually pointless. You’ll be able to strive including a static notch for recognized body resonance and scale 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 helpful for whoops, because it helps to cut back yaw spin in collisions.
PID Tuning
To tune PID utilizing Blackbox, I observe the “Basement Tuning” methodology utilizing PIDToolBox. This methodology is beginner-friendly and will be accomplished in a small house like a basement or bed room, therefore the identify. It includes performing a sequence of brief flights with barely totally different PID values, then evaluating the logs to search out the optimum beneficial properties.
Throughout the flights, transfer the quad round on the pitch and roll axes. You’ll be able to study extra in regards to the basement methodology on this video by PIDToolbox.
Though the tactic known as “basement tuning,” I’m not comfy doing this indoors. I’ve had a few “fly to the moon” incidents up to now, practically drilling a gap within the ceiling. Due to this fact, I all the time carry out these assessments in a backyard or native park for security.
Fee Profile and Angle Mode
Performing basement tuning flights requires good line-of-sight flying abilities to maintain the drone managed in a confined house. Listed below are some tricks to make it simpler. Do that 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 should you transfer the sticks an excessive amount of. The excessive and linear heart stick sensitivity ensures the stick inputs are important sufficient for correct logging.
Performing the check in Angle mode could make it even simpler than in Fee mode. Based on the creator of PIDToolBox, Angle mode works simply in addition to Fee mode, however that you must 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 begin with, decrease these beneficial properties in order that they don’t intrude 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 beneficial properties) 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 manage
Modify the “Damping” (D beneficial properties) slider, begin with a minimal worth you wish to check. For a typical 5-inch FPV drone, 0.6 is an effective start line.
Here’s what you wish to carry out within the flight:
- Arm and hover
- Continually shifting the roll and pitch stick for 20-30 seconds, the extra actions the extra correct will probably be
- Do as massive strikes as you’ll be able to with out hitting the partitions (ideally full stick deflections)
- You’ll be able to transfer each pitch and roll collectively so long as you’ll be able to hold it beneath management
- Attempt to not cease/hover for too lengthy throughout flight, and be as steady as you’ll be able to
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 acquire too excessive, your motors will sound tough, subsequently you’ll be able to’t all the time check the final one or two values, which is okay.
The quickest technique 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 must unplug.
16MB reminiscence needs to be sufficient for six 30-second flights should you time it effectively.
After you’ve got accomplished all of the flights, obtain them to your pc. 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 every one and take away the take-off and touchdown components for every log (to do that, allow “Trim” on the precise 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 shifting away from setpoint in the direction of the top), allow Y Correction.
It’s fairly straight-forward, merely choose the very best trying line, that’s your optimum Damping slider worth. The best 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 suitable.
In case your traces don’t look clean 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 precise 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’re going to get overshoot and even oscillation. As D acquire will increase, there shall be much less overshoot and Peak will lower, however Latency will go up consequently. When D is simply too excessive (undershoot), the preliminary peak won’t even attain the setpoint and this isn’t supreme. Discover a response that has minimal overshoot and but has comparatively low Latency.
You’ll be able to 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 will be 1.0.
It’s fairly frequent to have a unique PD steadiness on pitch and roll because of the totally 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 a little bit extra conservative and keep away from having D acquire too excessive. If you’re on the fence, all the time go together with much less D acquire (a better P/D ratio), so you’ll be able to increase your total PID beneficial properties increased on the finish since D is normally the limiting issue.
What I’ve discovered is that the step response software tends to be fairly delicate and the P/D steadiness is likely to be decrease than what I’d personally favor. So I usually bump up P/D steadiness by 5-10% after discovering an excellent worth. That’s simply my private desire, you may give {that a} strive if you’d like.
Drone dimension 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 resembling 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 could shoot up unexpectedly. Pay shut consideration to motor noise, and cease instantly should you hear thrilling oscillation.
You would possibly discover that the shapes of the step response don’t change a lot between totally 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. Growing the beneficial properties gained’t considerably have an effect on the response form, however bumping up P/D beneficial properties can scale back latency.
You’ve reached the perfect Grasp Multiplier acquire when one of many following happens:
- Thrilling Oscillation: If you happen to hear thrilling oscillation, you’ll be able to’t improve D acquire any additional.
- Latency Plateau: If latency doesn’t lower anymore (or little or no), it means you’ve got 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 beneficial properties. Generally, 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 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 beneficial properties. For instance, on a 6S quad, D beneficial properties is likely to 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 offers the least quantity of latency, with little enchancment when rising to 1.8.
If you happen to can’t hear thrilling oscillations, use the Spectral Analyzer to plot D-term. As beneficial properties improve, motors could produce an exciting sound peaking round 40-80Hz, particularly when throttling up. If noise on this frequency vary will increase with increased beneficial properties, it signifies the onset of PID-related oscillations.
On this instance, you’ll be able to clearly see peaks round 60Hz for 1.4 (olive), 1.6 (inexperienced), and 1.8 (cyan). Though 1.6 reveals latency enchancment, I’d not danger it and would probably select 1.4 and even 1.3 to be secure.
There’s 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 may result in disastrous outcomes should you hit an impediment or bend a prop. It’s no joke, talking from expertise right here:
After discovering the optimum D acquire, test setpoint monitoring by plotting Gyro and Setpoint. The strains 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 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 whenever 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 shifting 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 instant and managed flying expertise. It’s helpful 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 test 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’ll be able to test my charges right here: https://oscarliang.com/charges/#My-Charges
As an alternative of utilizing the step response software in PTB, use BE to test 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 high 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 means 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 might probably trigger the P time period to react in the other way, making an attempt to counteract it.
Doesn’t matter what your flying type is, feedforward will be helpful and doesn’t apply solely to sure sorts of flying. Even cinematic flying can profit from a superb quantity of feedforward, if you’re shifting 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. If you would like clean flying, simply use expo, extra RC smoothing or decrease your fee.
There’s an non-obligatory setting, Feedforward increase (FF Increase). You wish to improve it if gyro lagging behind setpoint at the beginning of a transfer, however catching up in a while. However you must scale back it if gyro will get forward of the setpoint at the beginning of a transfer, however falls behind later.
Tuning I Acquire
The best I acquire is basically based mostly on really feel. You don’t want numerous I acquire when you’ve got optimum P and D beneficial properties; you simply want sufficient to maintain the drone from drifting and wandering. If you’re 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 variety of 0.5 to 1.5 on the I time period slider works positive for five″ quads. This extensive window permits us to tune all the pieces 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 software 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 need to use it for tuning Yaw I acquire, which I discover normally lands round 1 on the slider for 5-inch quads.
You’ll be able to tune the I acquire by trying by way of the goggles and listening to the motors. If you happen to purpose to push the I acquire as excessive as potential, strive shifting the I acquire slider up till you discover gradual bouncebacks and oscillations throughout quick strikes, then scale back it a notch or two. Nonetheless, it’s actually exhausting to get our quads to point out bouncebacks, because of options like “I-term loosen up” in Betaflight. These days, you need to use extraordinarily excessive I acquire with out a lot unfavorable influence (resembling bouncebacks).
For five″ quads, I normally depart the I acquire slider at 1.
With I-term loosen up, you’ll be able to regulate the cutoff based mostly on the drone’s responsiveness. For freestyle drones, you’ll be able to 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 characteristic 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:
- Notice 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 intervening time.
- Start by rising the Dynamic Damping slider to 1.
- Then scale 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’ll be able to 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 Features
Anti-Gravity (AG) beneficial properties assist scale back wobbling and nostril dips whenever you punch out after which let go of the throttle. AG briefly boosts I acquire throughout throttle pumps to mitigate these undesirable dips. Nonetheless, if the AG acquire is about too excessive, your quad could expertise speedy oscillation (stutter) whenever you launch the throttle, as a result of AG boosts each P and I.
Default is 8, scale back it should you see wobbles throughout quick throttle modifications. For five″ freestyle drones, I discovered 8 to 12 a superb vary.
You’ll be able to tune AG by trying within the goggles, or test 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 possibility of ESC desync. It will increase motor velocity when the throttle is at zero, bettering management authority and responsiveness at low throttle inputs. Different advantages embrace 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, that you must
- Allow bi-directional DShot within the Motor Tab (if you have already got RPM filter enabled, you’re all set)
- Enter an appropriate Idle RPM worth within the PID Tuning web page (e.g., 20 to 40 for five″ drones).
The advisable Idle RPM worth depends upon propeller dimension and pitch. Smaller and decrease pitch propellers typically require increased values. Modify the worth increased in windy situations 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 hold time when the drone is the other way up (motors push tougher in the direction of the bottom). It will possibly additionally make the quad hover barely at zero throttle, making throttle administration tougher.
- Low Worth: Dangers low throttle instability.
Setting the Superb 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 notice 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 also can make them unpredictable.
- Default Worth: 5
- Adjustment Suggestions:
- If you happen to discover the throttle exhausting to handle, scale back the worth.
- Some racers disable Throttle Increase completely by setting it to 0.
- Experiment with smaller values to see what works greatest in your flying type.
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 would make you overlook when to land as a result of the quad would really feel related by way 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 cut back oscillations (much like TPA).
- Helps with nostril dips and is particularly helpful for whoops and drones utilizing 48KHz PWM frequency on ESCs.
Notice: Because it boosts PID at low throttle, you would possibly must decrease the grasp multiplier slider if motors get scorching.
TPA
TPA stands for Throttle PID Attenuation.
To positive tune TPA, carry out a throttle sweep and test the frequency vs. throttle heatmap. If you happen to get oscillations above a sure throttle degree, by 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, if you’d like you’ll be able to deliver this again by typing in CLI: set tpa_mode = PD.
Usually I favor to set throttle worth in TPA as excessive as potential, so D acquire is extra fixed throughout a wider throttle vary. Be sure 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’d 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 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 acquire works effectively. The tuning window for Yaw is kind of extensive. In contrast to pitch and roll that are based mostly 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’ll be able to allow it if you’d like, nevertheless it would possibly introduce extra drawback than it solves, like vibrations and many others. So we’re left with P and I phrases for Yaw.
You’ll be able to 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.
If in case you have yaw shakes when doing throttle pump, you’ll be able to 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 listing, 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, strive 100 for each P and I’d be a superb start line. You may as well strive increased values as yaw tends to be fairly gradual reacting.
There isn’t a good tune
How good is nice sufficient? You’ll be able to 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 put money into it won’t be proportional to the end result. I usually simply cease when it seems “adequate” and depart it there until I’ve a particular drawback I wish to remedy.
Troubleshooting Suggestions
Dangerous Gyro
A 5-inch FPV drone ought to fly easily on default Betaflight settings. In case your quad experiences vibrations, it could possibly be because of mechanical or electrical points, or typically a nasty gyro on the flight controller (FC). Right here’s the best way to diagnose a nasty gyro:
- Symptom: One axis is considerably noisier than the others, particularly within the decrease frequency spectrum under 200Hz.
- Analysis: Rotate the FC by 90 levels. If the noisy axis follows the rotation, the gyro could possibly be defective.
Within the instance under, the pitch axis is way 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’ll be able to strive utilizing a 1000uF low ESR capacitor on the ESC energy.
- If already utilizing a capacitor, strive soldering a further 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 maybe probably the most essential values, decrease is extra twitchy and responsive whereas a better worth is softer and smoother however extra sluggish. Right here’s a normal rule I personally observe:
- 20-25: Racing
- 30: Default worth, nice for Freestyle
- 50: Cinematic
- 90: Extraordinarily clean cruising (noticeable delay)
- 120: Highest smoothness with out hassle (important delay)
Dangerous gear/pilot require increased RC smoothing too, e.g. Low high quality radio management tools, worn out gimbals, pilots with shaky fingers, and many others. Principally something that may contribute to jerkiness in RC instructions.
If potential, test black field logs to substantiate you’ve got clean setpoints, if the setpoint isn’t clean (has steppings from RC instructions), merely improve the smoothing barely.
If in case you have noise in setpoint that peaks round 50Hz, 150Hz, 250Hz or 500Hz, then there’s in all probability an issue with RC smoothing. These frequencies are frequent packet charges in RC hyperlink. On this instance, it’s Crossfire 150Hz.
If you’re not utilizing sufficient filtering for the RC instructions, you won’t 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 a little bit 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 clean out the steppings however not including an excessive amount of delay. If you would like smoother RC enter, strive including some extra expo, it has related impact nevertheless it gained’t provide the latency penalty.
One of the simplest ways is to simply load the suitable RC Hyperlink preset as I talked about right here. If you happen to did not load the proper RC_Link preset in your explicit RC hyperlink and packet fee, it may also trigger issues to Feedforward. On this instance, feedforward jitters because of the 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’ll be able to 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 fee anyway.
ADC Filter Jitters Inflicting Oscillations
If you happen to expertise random vibrations and wobbles because of feedforward jitters, even after making use of the proper RC Hyperlink preset or rising RC smoothing, the problem could possibly be because of the ADC filter.
Make sure the ADC filter is turned off in your radio’s system menu beneath 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
