On this tutorial, I’ll share how I take advantage of Blackbox logs to tune filters and PID on a Betaflight FPV Drone. I might be utilizing PIDToolBox as the first instrument for filter and PID tuning, with Blackbox Explorer as a secondary instrument for Feedforward and common troubleshooting.
Disclaimer: This information is supposed for informational functions solely. The writer holds no accountability for damages ensuing from actions taken by the readers.
Blackbox is just not a should for tuning as defined on this information, however 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. 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, make sure that to take a look at the Blackbox for novices tutorial..
I spent over 200 hours making this 8000-word tutorial! If you happen to discover my content material helpful, please think about supporting my work.
Getting Began
Tuning objectives
Utilizing Blackbox to tune our FPV drone, we goal to attain two essential objectives:
- Extra Efficient Use of Filters: Use minimal filtering to attenuate delay however sufficient to maintain noise at an appropriate degree.
- Optimized PID Positive factors and Associated Settings: Make sure the drone flies exactly and responsively.
Fundamental configurations
0. {Hardware} Guidelines
- Flight Controller (FC) Stack: Select an FC stack with rubber grommets (gummies) for sturdiness and noise efficiency.
- Metallic Screws: Use steel screws for the FC stack; keep away from nylon/plastic screws/standoffs as they’re liable to breakage and vibrations. If spacers are wanted, use mushy silicone ones. Lighter titanium screws can save a couple of grams.
- Locking Stack Screws: Safe the stack screws firmly with a steel nut earlier than mounting the 4in1 ESC. In case your body has pressed insert nuts, extra nuts are usually not wanted. Tighten screws by hand first, then give a remaining squeeze with a wrench/screwdriver.
Use 4 plastic nuts to safe the FC stack. Tighten the nuts by hand to keep away from excessively crushing the gummies, permitting the mushy mount to work successfully.
1. Blackbox Recording Settings
Choose the next settings within the Blackbox Configuration:
- Logging Gadget: Onboard Flash or SD Card
- Logging Charge: 2KHz (or 1.6KHz for BMI270 Gyro)
- Debug Mode: GYRO_SCALED (information unfiltered gyro sign)
- Knowledge Included: To avoid wasting house for longer recordings, deselect pointless knowledge like Altitude, GPS, and Magnetometer, or go away at default.
2. Disable the ADC filter in your OpenTX/EdgeTX radio (System -> {Hardware}) to scale 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 gives higher braking energy, which is useful for prop wash dealing with and responsiveness, however with a better threat 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 flash it right here: https://oscarliang.com/bluejay-blheli-s/
3. Flash the most recent model of Betaflight firmware to your flight controller and go away PID/filter settings at default. Allow Skilled Mode in Betaflight Configurator to entry all sliders and choices on the PID Tuning web page.
Within the Configuration tab, set your PID Loop Frequency, and within the Motor tab, set your ESC protocol:
- DShot300 for 4KHz or 3.2KHz Loop Frequency
- DShot600 for 8KHz Loop Frequency
4. Within the Motors tab, allow Bi-directional DShot.
Most trendy ESCs help Bi-directional DShot. I’ve a tutorial on allow RPM filter. For BLHeli_32 ESC it really works out of the field, however if in case you have BLHeli_S ESC, it’s worthwhile to flash Bluejay firmware (tutorial) first.
Verify 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 may allow the Gyro RPM filter, top-of-the-line filters in Betaflight.
5. Load the suitable RC_Link preset.
Totally different RC hyperlinks require particular RC smoothing and feedforward configurations. Incorrect config could cause stuttering and vibrations. My favourite RC hyperlink is ExpressLRS, try what radio gear I take advantage of right here.
Loading the appropriate RC_Link preset in Betaflight will apply the required configurations mechanically. Bear in mind to decide on choices based mostly in your flying model, for most individuals it might be Freestyle.
For Crossfire, lock the packet fee to both 50Hz (longer vary, larger 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 decrease using TPA each time potential.
The best way to use PIDToolBox and Blackbox Explorer?
I might be utilizing each PIDToolBox (PTB) and Blackbox Explorer (BE) in my PID and filter tuning.
PIDToolBox might be our essential instrument, it’s by far probably the most highly effective Blackbox instrument accessible. It means that you can evaluate a number of logs aspect by aspect, making it simpler to see the results of your filter adjustments. The Step Response instrument is very helpful for tuning PID. The spectral analyzer in PTB makes use of decibels on the Y-axis, offering extra correct and goal comparisons. PTB additionally estimates filter delays, which may be very useful.
Nevertheless, PTB could 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 concentrate on the inexperienced sections (RPM filter and Dynamic Notch) and modify the orange sections (Gyro and D Time period Lowpass Filters) utilizing the sliders. No want to the touch the pink sections.
Additional studying: Study 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 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 take a look at exhibits 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 adjustments).
Gyro Noise Frequency Defined
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:
- Underneath 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.
All the pieces under 20Hz is “good” drone movement reacting to the sticks.
Between 20Hz and 100Hz is the place undesired vibrations, comparable to oscillations and propwash, happen. As a common rule of thumb, you need to see little exercise on this frequency vary. Having some is regular, however an excessive amount of means you could have an oscillation problem that must be addressed. Typically, we attempt to keep away from filtering under 100Hz as a result of these are actual motions of the drone that we both need to work with or in opposition to. Filtering on this low-frequency vary can truly make issues worse as a result of it introduces an incredible quantity of latency. Analyzing the spectra underneath 100Hz can provide 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 need to concentrate on filtering is the noise between 100Hz and 1000Hz.
Delay Brought on by Filtering
Maybe not intuitive, however over-filtering can truly trigger oscillation to indicate up as noise within the sub-100Hz spectra. That’s as a result of filtering creates delay. When the quad tries to appropriate the error, the response is likely to be too late because of the delay, which could be counterproductive. It will probably 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 underneath 100Hz can typically truly 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 larger, which makes your quad monitor setpoint higher and helps fight propwash.
You’ll find out how a lot delay is added to the Gyro sign because of filtering by plotting Gyro and Gyro_Scaled and measuring the hole between them.
In PTB, it mechanically 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 common 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 flooring with Gyro and D-term lowpass filters. I might be tuning filters on this order:
RPM Filter > Dynamic Notch Filter > Gyro Lowpass > D-term Lowpass
We need 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 dwelling with a bent prop. You possibly can definitely 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 probably 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 often signifies that the filtering is simply too aggressive.
Professional Tip: Scorching Motors – How Scorching is Too Scorching?
As a common rule of thumb, in case you pinch the motor bell and may’t hold your fingers on it for various seconds, it’s too scorching and you might be most likely pushing your settings too aggressively.
How Clear is Your Construct?
Earlier than we start tuning, it’s vital to examine if in case you have a clear construct. Begin by performing throttle sweeps as beforehand described.
Load the log in PIDToolBox, click on on the Spectral Analyzer, choose “Gyro prefilt” (the uncooked, unfiltered gyro sign; “Gyro” is the filtered sign), and hit Run.
The default filter settings in Betaflight are pretty conservative, and most builds ought to have the ability to cut back filtering from there. In case your quad is already noisy with default filter settings, as a substitute of accelerating filtering, it is best to search for potential mechanical or electrical points. Guarantee you could have 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 ought to be little exercise between ~50Hz (the quad’s actions) and ~200Hz (motor vibration). When you have quite a lot of 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 can be more difficult.
As recommended by the writer of PIDToolBox, it’s ideally suited to have the general noise flooring under -30dB above 50Hz. For D-term, it’s ideally suited to have the general noise flooring under -10dB. Analyzing the noise ranges in these areas can provide 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 will want extra filtering. It’s not the top of the world; it simply means the latency might be larger, 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 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 taking a look at:
- Near 0Hz: The very vibrant horizontal line on the backside (1) represents the drone’s movement reacting to the sticks.
- Round 200Hz: This horizontal line (2) signifies body resonance. Its frequency doesn’t change with throttle place however is strongest the place it intersects with the motor band.
- Elementary Motor Noise Band: This diagonal line (3) is often the brightest. Motor noise usually will increase in frequency with throttle degree.
- Harmonics: These are multiples of the elemental motor noise band. In our instance, harmonics (usually dimmer and more durable to identify) present up as traces (4) and (5). Strive adjusting the dimensions in the event that they aren’t seen. Notice that 2-blade propellers have a tendency to indicate extra and stronger harmonics than 3-blade props.
We’ll use RPM filter to care for these motor noise bands.
The purpose 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 Device, 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 proper, I modified it to 2 Harmonics with min frequency of 160Hz
By lowering one harmonics and lift the cutoff frequency, you may maybe see extra unfiltered noise from the third motor harmonics.
Though it’s fairly weak, it may well nonetheless get amplified when it will get into D time period. Let’s examine the Dterm warmth map under on the proper, as you may see, a tiny little bit of gyro noise has change 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 observed is a few noise round 116Hz left unfiltered as a result of we raised the min freq to 160Hz. To handle that, we’ve got to decrease Min Freq, i.e. round 20Hz under the noise frequency can 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 will’t actually cut 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 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 larger or decrease in frequency, and also you would possibly want it to fade in additional rapidly or slowly relies on the noise. This characteristic is simply accessible in CLI, for instance:
set rpm_filter_min_hz = 100 set rpm_filter_fade_range_hz = 50
This implies the RPM filter begins at 100Hz at minimal power and reaches full power at 150Hz.
Q Worth
Rising the Q worth of a notch filter makes it extra targeted on the focused frequency, lowering latency. Alter this within the CLI:
set rpm_filter_q = 500
Default values often work effectively, however you may 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 often not very robust, 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 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, comparable to body resonance, antennas, GoPro mounts, and bent propellers.
When the RPM filter is enabled, Betaflight will mechanically cut back the quantity of Dynamic Notch filtering through the use of fewer notches and a better Q worth because the RPM filter will do a lot of the heavy lifting. You possibly can 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 often, 1 or 2 are enough except 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 ends up in much less filtering and decrease latency.
- Default Q: Begin with the default Q of 500.
- Alter Q: If the default is working 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.
- Verify D-term Heatmap: Analyze the D-term heatmap to see how adjustments within the Q worth have an effect on D-term noise.
Set Min/Max Frequency: These are the cutoff frequencies, defining the efficient vary of the Dynamic Notch filter. Add 20-30Hz to every aspect of the resonance for the vary.
Keep away from setting the Min Frequency too excessive for security causes, as bent props can create large resonance. In case of a crash, a broader frequency vary can assist catch new resonances and forestall motor overheating or harm. We don’t know precisely the place that resonance goes to be, however having a wider frequency vary has a better likelihood of catching it. If the Dynamic Notch fails to catch these newly pop up resonances because of Min Frequency is ready 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 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 approach 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, once I set Q to 450, the noise is sufficiently managed. Within the under graphs, on the left is Q=700, the proper is Q=450. You possibly can examine Dterm heatmap once more to verify 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 examine the motor temperature to make sure they don’t seem to be scorching earlier than continuing.
Use the “Gyro Filter Multiplier” slider to scale back Gyro Lowpass 2 a few notches at a time. Shifting 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 larger 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 (pink), and a pair of.0 (orange).
The three traces virtually overlap, suggesting that the Gyro Lowpass filter isn’t considerably affecting the sign and could be decreased. Curiously, the noise within the sub-100Hz spectrum barely improves with much less filtering, which aligns with our earlier discussions.
Necessary Concerns:
- By no means disable the Gyro Lowpass 2 filter for 2K/4K PID loop frequencies because of anti-aliasing causes.
- Minimal Frequency:
- For 2K loop time, go away Gyro Lowpass 2 at a minimal of 500Hz.
- For 4K, you may set Gyro Lowpass 2 as much as 1000Hz.
- For 8K, you may disable Gyro Lowpass 2 completely if noise isn’t a difficulty.
Tuning D Time period Lowpass
D time period is far noisier than Gyro because of its delicate nature and noise will get amplified as frequency will increase. Subsequently, be additional cautious and conservative when coping with D Time period filtering.
Strive shifting 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 take a look at flight (do some acro strikes), additionally examine motor temperature after touchdown. In the event that they get scorching it is best to return a notch or two.
Keep away from being too aggressive with lowering D Time period filtering. Go away 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 (pink), 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 exhibits 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 cut back D-term filtering, it’s because of the rising noise under 100Hz. You possibly can affirm this by checking the <100Hz graphs. On this instance, staying under 1.3, perhaps 1.2 and even simply 1.1, can 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 could assist. If the D time period hint may be very clear, you may maybe cut back filtering a bit extra (if motors are usually not scorching). See under graphs, the left has a loud D time period hint, the proper is far cleaner.
Necessary: 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 change into legacy since RPM filter and dynamic notch filters are doing a lot of the work.
Nevertheless, if there’s a robust resonance at a particular frequency (comparable to body resonance), a static notch filter could be useful. The dynamic notch filter often covers it, so a static notch filter is usually pointless. You possibly can strive 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 could be left untouched. This filter is very 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” technique utilizing PIDToolBox. This technique is beginner-friendly and could be carried out in a small house like a basement or bed room, therefore the title. It includes performing a sequence of quick flights with barely completely different PID values, then evaluating the logs to search out the optimum good points.
Throughout the flights, transfer the quad round on the pitch and roll axes. You possibly can study extra concerning the basement technique on this video by PIDToolbox.
Though the strategy known as “basement tuning,” I’m not snug doing this indoors. I’ve had a few “fly to the moon” incidents previously, almost drilling a gap within the ceiling. Subsequently, I all the time carry out these exams in a backyard or native park for security.
Charge 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 this fee profile:
- Heart Sensitivity 250
- Max Charge 400
- Expo 0.00
This profile has a low max fee, making it much less more likely to lose management in case you 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 take a look at in Angle mode could make it even simpler than in Charge mode. In keeping with the writer of PIDToolBox, Angle mode works simply in addition to Charge mode, however it’s worthwhile 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 adjustments are utilized.
Discovering P/D Stability
Initially, decrease these good points so 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 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 manage
Alter the “Damping” (D good points) slider, begin with a minimal worth you need to take a look at. For a typical 5-inch FPV drone, 0.6 is an efficient place to begin.
Here’s what you need 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 it will likely be
- Do as huge strikes as you may with out hitting the partitions (ideally full stick deflections)
- You possibly can transfer each pitch and roll collectively so long as you may hold it underneath 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. Whenever you elevate D achieve too excessive, your motors will sound tough, subsequently you may’t all the time take a look at the final one or two values, which is okay.
The quickest strategy 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 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 ought to be sufficient for six 30-second flights in case you time it effectively.
After you could have accomplished all of the flights, obtain them to your laptop. To arrange the logs higher, I’ve a folder construction created for this course of, obtain right here: https://drive.google.com/file/d/1tx1AV2lOMgknAwIB3VFhqP1i6VpDLVjr/view?usp=share_link
And I rename the logs to one thing like “01 d06“, “02 d08” and many others (01 means first take a look at 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 proper hand panel).
Click on the “Step Resp Device“, choose all of the recordsdata and click on Run. if in case you have offset within the curves (gyro curve shifting away from setpoint in direction of the top), allow Y Correction.
It’s fairly straight-forward, merely choose the most effective wanting 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 appropriate.
In case your traces don’t look clean however have plenty of 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 achieve setpoint (ideally the decrease the higher)
When D achieve is low, you’re going to get overshoot and even oscillation. As D achieve will increase, there might 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 have a look at Roll and Pitch axis.
In our instance, it’s fairly clear the best worth is orange (3) for each pitch and roll, so that will be 1.0.
It’s fairly widespread to have a unique PD steadiness on pitch and roll because of the completely different weight distribution. If that’s the case for you, take the Damping slider to the place you need for pitch, write down the pitch D achieve, then take the Damping slider to the place you need for roll, and modify the Pitch Damping slider to match the pitch D achieve you simply wrote down.
Generally it’s higher to be somewhat extra conservative and keep away from having D achieve too excessive. If you’re on the fence, all the time go together with much less D achieve (a better P/D ratio), so you may elevate your total PID good points larger on the finish since D is often the limiting issue.
What I’ve discovered is that the step response instrument tends to be fairly delicate and the P/D steadiness is likely to be decrease than what I’d personally want. So I usually bump up P/D steadiness by 5-10% after discovering an excellent worth. That’s simply my private choice, you can provide {that a} strive in order for you.
Drone measurement additionally impacts PD ratio, bigger drones are inclined to have larger 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 take a look at for Grasp Multiplier slider, transfer the slider in 0.2 steps. For a 5″ drone, begin with values comparable 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 take a look at. When D achieve is simply too excessive, the quad could shoot up unexpectedly. Pay shut consideration to motor noise, and cease instantly in case you 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 principally 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 could have reached the best Grasp Multiplier achieve when one of many following happens:
- Thrilling Oscillation: If you happen to hear thrilling oscillation, you may’t improve D achieve any additional.
- Latency Plateau: If latency doesn’t lower anymore (or little or no), it means you could have reached the higher sure tuning window. The motors are working at their hardest, and you aren’t gaining any extra efficiency from them.
The utmost achieve achievable is influenced by the noise degree of your construct and the quantity of filtering used. Much less filtering permits for larger 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 achieve to the restrict to account for potential points like bent props.
Drones utilizing larger cell depend batteries (larger voltage) are inclined to require decrease D good points. For instance, on a 6S quad, D good points is likely to be within the 30s, whereas on a 4S they’re often within the 40s.
In my instance, 1.6 appears to be the worth that offers the least quantity of latency, with little enchancment when rising to 1.8.
If you happen to can’t hear thrilling oscillations, use the Spectral Analyzer to plot D-term. As good points improve, motors could produce an exhilarating sound peaking round 40-80Hz, particularly when throttling up. If noise on this frequency vary will increase with larger 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 exhibits latency enchancment, I might not threat it and would possible 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 achieve, or much less D-term filtering and decrease D achieve. Nevertheless, by no means run with much less D-term filtering and excessive D achieve as this will result in disastrous outcomes in case you hit an impediment or bend a prop. It’s no joke, talking from expertise right here:
After discovering the optimum D achieve, examine setpoint monitoring by plotting Gyro and Setpoint. The traces ought to be roughly parallel, indicating the quad is accelerating and decelerating on the similar fee because the setpoint. Nevertheless, there would possibly nonetheless be a big 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 once 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 shifting 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 quick 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 want to do some snap rolls and flips and examine Gyro/Setpoint traces. Use your regular 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 examine my charges right here: https://oscarliang.com/charges/#My-Charges
As an alternative of utilizing the step response instrument in PTB, use BE to examine the setpoint/gyro traces. The gyro ought to monitor the setpoint extra intently with much less delay. Ideally, the gyro ought to be proper on prime of the setpoint.
If Feed Ahead overshoots (gyro strikes earlier than the setpoint), the FF is simply too excessive. Within the following demonstration, 0.5 is approach too low, 1.0 remains to be not excessive sufficient, however 1.5 is a tiny bit an excessive amount of and overshoots. I believe Feedforward at 1.3-1.4 ought to do it on this instance.
If the FF achieve is simply too excessive, it may well trigger the P time period to react in the other way, attempting to counteract it.
Doesn’t matter what your flying model is, feedforward could be helpful and doesn’t apply solely to sure varieties of flying. Even cinematic flying can profit from a superb quantity of feedforward, if you’re shifting your stick easily and slowly, then feedforward received’t kick in anyway. Whenever you want snappy response FF will cut back the latency between stick enter and quad response. In order for you clean flying, simply use expo, extra RC smoothing or decrease your fee.
There’s an non-obligatory setting, Feedforward increase (FF Enhance). You need to improve it if gyro lagging behind setpoint firstly of a transfer, however catching up in a while. However it is best to cut back it if gyro will get forward of the setpoint firstly of a transfer, however falls behind later.
Tuning I Acquire
The best I achieve is essentially based mostly on really feel. You don’t want quite a lot of I achieve when you could have optimum P and D good points; 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, you then want a better I achieve.
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 high-quality for five″ quads. This large window permits us to tune every little thing else first and modify the I time period final. With a excessive I achieve, your quad will really feel extra exact, but when the I achieve is simply too excessive, you might expertise gradual oscillations, which you need to keep away from.
I discovered the step response instrument in PTB is just not efficient for locating the I time period, because the step response for pitch and roll stays equivalent whatever the I achieve slider worth (e.g., 0.4 to 2.0). Nevertheless, you need to use it for tuning Yaw I achieve, which I discover often lands round 1 on the slider for 5-inch quads.
You possibly can tune the I achieve by wanting by way of the goggles and listening to the motors. If you happen to goal to push the I achieve as excessive as potential, strive shifting the I achieve slider up till you discover gradual bouncebacks and oscillations throughout quick strikes, then cut back it a notch or two. Nevertheless, it’s actually onerous to get our quads to indicate bouncebacks, because of options like “I-term chill out” in Betaflight. These days, you need to use extraordinarily excessive I achieve with out a lot adverse impression (comparable to bouncebacks).
For five″ quads, I often go away the I achieve slider at 1.
With I-term chill out, you may modify the cutoff based mostly on the drone’s responsiveness. For freestyle drones, you may often go away 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 achieve to the utmost throughout sharp strikes however doesn’t improve it throughout regular flight. This helps in lowering motor warmth.
That is how I usually use Dynamic Damping:
- Notice down your present D Max worth. This worth ought to be the identical as Spinoff as a result of the Dynamic Damping slider is ready to 0 in the intervening time.
- Start by rising 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 achieve used throughout regular flights to maintain your motors cool.
Or you may simply go away Dynamic Damping slider at 0 and don’t change your Damping slider unchanged, it’s as much as you.
Different Settings
Anti Gravity Positive factors
Anti-Gravity (AG) good points assist cut back wobbling and nostril dips once you punch out after which let go of the throttle. AG quickly boosts I achieve throughout throttle pumps to mitigate these undesirable dips. Nevertheless, if the AG achieve is ready too excessive, your quad could expertise fast oscillation (stutter) once you launch the throttle, as a result of AG boosts each P and I.
Default is 8, cut back it in case you see wobbles throughout quick throttle adjustments. For five″ freestyle drones, I discovered 8 to 12 a superb vary.
You possibly can tune AG by wanting within the goggles, or examine for nostril dip in Blackbox logs, and see the impact of anti-gravity.
Dynamic Idle
Dynamic Idle improves stability, enhances propwash dealing with, and reduces the prospect of ESC desync. It will increase motor velocity when the throttle is at zero, 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 ready, Static Motor Idle (in %) within the Motors tab is disengaged.
To setup Dynamic Idle, it’s worthwhile 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 helpful Idle RPM worth relies on propeller measurement and pitch. Smaller and decrease pitch propellers typically require larger values. Alter the worth larger 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 grasp time when the drone is the wrong way up (motors push more durable in direction of the bottom). It will probably additionally make the quad hover barely at zero throttle, making throttle administration more durable.
- Low Worth: Dangers low throttle instability.
Setting the Ideally suited Worth:
- Decide ESC Idle Worth: Default is often 5.5%. Take a look at your motor within the motor tab utilizing a smoke stopper or bench energy provide to restrict present.
- Verify 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 best Dynamic Idle worth.
Throttle Enhance
Throttle Enhance will increase your throttle worth once you quickly transfer the throttle stick up, supplying you with additional energy. This will make throttle responses extra dynamic however may also make them unpredictable.
- Default Worth: 5
- Adjustment Ideas:
- If you happen to discover the throttle onerous to handle, cut back the worth.
- Some racers disable Throttle Enhance completely by setting it to 0.
- Experiment with smaller values to see what works greatest in your flying model.
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 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 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 scale back oscillations (just like TPA).
- Helps with nostril dips and is very 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 high-quality tune TPA, carry out a throttle sweep and examine the frequency vs. throttle heatmap. If you happen to get oscillations above a sure throttle degree, by which case TPA can assist.
Within the newest Betaflight it solely attenuates D achieve above sure throttle degree (which is often the reason for the oscillations). Within the older Betaflight it attenuates each P and D, in order for you you may deliver this again by typing in CLI: set tpa_mode = PD.
Usually I want to set throttle worth in TPA as excessive as potential, so D achieve is extra fixed throughout a wider throttle vary. Be certain that to set the throttle worth somewhat decrease than the place the place the D time period associated oscillations begin to present up. For instance, if oscillation begins round 1800 throttle, I might do one thing like this: TPA = 0.75, 1750.
Revisiting D Time period Filtering
After making the above adjustments, revisit D time period filtering to see if changes are wanted. Improve 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 achieve works effectively. The tuning window for Yaw is kind of large. Not like pitch and roll that are based mostly on thrust generated by propellers, yaw relies on the inertia generated by propeller rotation. Subsequently, 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. Nevertheless you may allow it in order for you, however 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 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 listing, choose RP (Roll Pitch), as a substitute 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, strive 100 for each P and I might be a superb place to begin. You may also strive larger values as yaw tends to be fairly gradual reacting.
There isn’t a good tune
How good is sweet sufficient? You possibly can all the time 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 end result. I usually simply cease when it seems “ok” and go away it there except I’ve a particular drawback I need to remedy.
Troubleshooting Ideas
Unhealthy 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 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 far 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 strive utilizing a 1000uF low ESR capacitor on the ESC energy.
- If already utilizing a capacitor, strive soldering an extra smaller 220uF-470uF capacitor to the ability of the FC (VBAT/VCC pad).
- Defective Gyro, changing FC.
RC Smoothing
RC smoothing is crucial in Betaflight to keep away from points with feedforward. Correct RC smoothing settings rely in your RC hyperlink. It’s greatest to load the suitable RC_Link preset to keep away from errors.
The Auto Issue is probably one of the crucial vital values, decrease is extra twitchy and responsive whereas a better worth is softer and smoother however extra sluggish. Right here’s a common rule I personally comply with:
- 20-25: Racing
- 30: Default worth, nice for Freestyle
- 50: Cinematic
- 90: Extraordinarily clean cruising (noticeable delay)
- 120: Highest smoothness with out hassle (vital delay)
Unhealthy gear/pilot require larger RC smoothing too, e.g. Low high quality radio management tools, worn out gimbals, pilots with shaky fingers, and many others. Principally something which may contribute to jerkiness in RC instructions.
If potential, examine black field logs to verify you could have clean setpoints, if the setpoint isn’t clean (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 may be most likely an issue with RC smoothing. These frequencies are widespread packet charges in RC hyperlink. On this instance, it’s Crossfire 150Hz.
If you’re not utilizing sufficient filtering for the RC instructions, you may not have smoothed out the RC sign sufficient and it may 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. Nevertheless it additionally provides delay to feedforward in addition to setpoint, so your quad would possibly really feel somewhat bit much less responsive. RC Smoothing is helpful, however an excessive amount of smoothing defeats the aim of getting quick RC packet charges like ExpressLRS gives.
The purpose is to clean out the steppings however not including an excessive amount of delay. In order for you smoother RC enter, strive including some extra expo, it has related impact however 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. If you happen to did not load the right RC_Link preset in your specific 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 may elevate the restrict to 1000. To do that, enter the next command within the CLI: set pid_sum_limit=1000. However 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 right 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 underneath 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
