On this tutorial, I’ll share how I take advantage of Blackbox logs to tune filters and PID on a Betaflight FPV Drone. I can be utilizing PIDToolBox as the first software for filter and PID tuning, with Blackbox Explorer as a secondary software for Feedforward and basic troubleshooting.
Disclaimer: This information is supposed for informational functions solely. The writer holds no duty for damages ensuing from actions taken by the readers.
Blackbox isn’t a should for tuning as defined on this information, however it supplies 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. For those who’re a perfectionist or simply somebody who likes to tinker, that is the tutorial for you.
In case you are new to Blackbox, make certain to take a look at the Blackbox for inexperienced persons tutorial..
I spent over 200 hours making this 8000-word tutorial! For those who discover my content material helpful, please contemplate supporting my work.
Getting Began
Tuning targets
Utilizing Blackbox to tune our FPV drone, we purpose to realize two principal targets:
- Extra Efficient Use of Filters: Use minimal filtering to attenuate delay however sufficient to maintain noise at a suitable 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 susceptible to breakage and vibrations. If spacers are wanted, use mushy silicone ones. Lighter titanium screws can save a number of grams.
- Locking Stack Screws: Safe the stack screws firmly with a steel nut earlier than mounting the 4in1 ESC. In case your body has pressed insert nuts, further nuts will not be 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 solely 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 System: Onboard Flash or SD Card
- Logging Charge: 2KHz (or 1.6KHz for BMI270 Gyro)
- Debug Mode: GYRO_SCALED (information unfiltered gyro sign)
- Information Included: To save lots of area for longer recordings, deselect pointless information like Altitude, GPS, and Magnetometer, or go away at default.
2. Disable the ADC filter in your OpenTX/EdgeTX radio (System -> {Hardware}) to cut back latency.
3. ESC settings:
I’ve a submit explaining the finest BLHeli32 settings. Right here’s the abstract (for five″ drones):
For BLHeli_32 ESC:
- Rampup Energy: 30%
- Motor Timing: 24
- PWM Frequency: Set LOW and HIGH to fastened 24KHz or 48KHz. 48KHz is usually safer for gyro noise, making your quad smoother and simpler to tune. 24KHz affords higher braking energy, which is useful for prop wash dealing with and responsiveness, however with the next threat of vibration. In case you are on the fence, simply go 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 tips on how 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 go away 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 fashionable ESCs assist Bi-directional DShot. I’ve a tutorial on tips on how to allow RPM filter. For BLHeli_32 ESC it really works out of the field, however in case you have BLHeli_S ESC, it is advisable to flash Bluejay firmware (tutorial) first.
Test if it’s working correctly by working 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 may 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 possibly can allow the Gyro RPM filter, among the finest filters in Betaflight.
5. Load the suitable RC_Link preset.
Completely different RC hyperlinks require particular RC smoothing and feedforward configurations. Mistaken config may cause stuttering and vibrations. My favourite RC hyperlink is ExpressLRS, try what radio gear I take advantage of right here.
Loading the acceptable RC_Link preset in Betaflight will apply the mandatory configurations routinely. Keep in mind to decide on choices primarily based in your flying model, for most individuals it might be Freestyle.
For Crossfire, lock the packet fee to both 50Hz (longer vary, greater latency) or 150Hz (decrease latency, much less vary) utilizing the TBS Agent Lite LUA script.
6. Decrease TPA
Within the PID tuning tab, set the TPA breakpoint from 1350 to 1750 to keep away from TPA masking oscillation points at low/mid throttle throughout tuning. Tremendous-tune TPA on the finish if oscillation points happen at excessive throttle, however typically I’d decrease using TPA every time attainable.
The right way to use PIDToolBox and Blackbox Explorer?
I can be utilizing each PIDToolBox (PTB) and Blackbox Explorer (BE) in my PID and filter tuning.
PIDToolBox can be our principal software, it’s by far probably the most highly effective Blackbox software out there. It means that you can examine a number of logs aspect by aspect, making it simpler to see the consequences of your filter adjustments. 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 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 best way 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 largely 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 crimson sections.
Additional studying: Study concerning 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 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 to be (see the underside bar for throttle adjustments).
Gyro Noise Frequency Defined
Open the throttle sweeps log in Blackbox Explorer and click on on “Gyro_Scaled” on the appropriate hand pane, that is the unfiltered gyro sign. Take away the takeoff and touchdown elements of the log by urgent “i” and “o”.
Right here’s a breakdown of the uncooked gyro sign frequency graph from a typical 5″ FPV Drone:
- Below 20Hz: Drone flight actions.
- 20Hz – 100Hz: Propwash and oscillations from suboptimal PID, problematic ESC config, unhealthy RC hyperlink settings, and many others.
- 100Hz – 250Hz: Body resonance or unfastened elements.
- Above 250Hz: Noise from motors and propellers, and harmonics.
All the pieces beneath 20Hz is “good” drone movement reacting to the sticks.
Between 20Hz and 100Hz is the place undesired vibrations, akin to oscillations and propwash, happen. As a basic rule of thumb, you need to see little exercise on this frequency vary. Having some is regular, however an excessive amount of means you’ve got an oscillation concern that must be addressed. Usually, we attempt to keep away from filtering beneath 100Hz as a result of these are actual motions of the drone that we both need to work with or towards. Filtering on this low-frequency vary can truly make issues worse as a result of it introduces an amazing quantity of latency. Analyzing the spectra underneath 100Hz can provide you perception into vibration or mid-throttle oscillation points and the way nicely the copter handles propwash.
We don’t care about something above 1000Hz as these have little impact on our drone. What we need to concentrate on filtering is the noise between 100Hz and 1000Hz.
Delay Attributable to 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 may be too late because of the delay, which could be counterproductive. It could 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 generally truly get higher as a result of latency is lowered and the quad can react quicker to appropriate PID errors. Utilizing much less filtering additionally means that you can push PID good points greater, which makes your quad observe setpoint higher and helps fight propwash.
You’ll find out how a lot delay is added to the Gyro sign on account of filtering by plotting Gyro and Gyro_Scaled and measuring the hole between them.
In PTB, it routinely estimates the delay brought on by gyro filtering and D-term filtering (see the highest proper nook of the primary graph within the second column).
Filter Technique
My basic filter technique is to eradicate motor noise bands utilizing RPM filter, then crush out body resonances with dynamic notch filters, and eventually, scale back the ambient noise flooring with Gyro and D-term lowpass filters. I can be tuning filters on this order:
RPM Filter > Dynamic Notch Filter > Gyro Lowpass > D-term Lowpass
We need to use as little filtering as attainable to attenuate latency, however on the similar time, we want sufficient filtering to keep away from burning our motors when flying dwelling with a bent prop. You may definitely play it protected 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 could additionally worsen propwash. So, we have to attempt for a steadiness.
Other than checking Blackbox logs, motor temperature is one other helpful indicator in filter tuning. When motors get too sizzling, it often signifies that the filtering is just too aggressive.
Professional Tip: Scorching Motors – How Scorching is Too Scorching?
As a basic rule of thumb, in the event you pinch the motor bell and might’t hold your fingers on it for various seconds, it’s too sizzling 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 examine 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 scale back filtering from there. In case your quad is already noisy with default filter settings, as an alternative of accelerating filtering, you must search for attainable mechanical or electrical points. Guarantee you’ve got a capacitor on the ESC enter energy, all screws are tightened, and also you’re utilizing contemporary new props, and many others.
On a clear 5″ quad, there needs to be little exercise between ~50Hz (the quad’s actions) and ~200Hz (motor vibration). If in case you have a number of noise on this area, it may very well be electrical noise (maybe the gyro enter energy is just too noisy, or it requires an additional capacitor on the ESC enter energy) or mechanical (e.g., a wire hitting the gyro). Attaining optimum filtering on this situation could be more difficult.
As urged by the writer of PIDToolBox, it’s perfect to have the general noise flooring beneath -30dB above 50Hz. For D-term, it’s perfect to have the general noise flooring beneath -10dB. Inspecting the noise ranges in these areas can provide you an excellent 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 generally you may simply have a loud gyro.
In case your quad is noisier than this (e.g., there’s a peak within the center above 0dB), then you’ll need extra filtering. It’s not the top of the world; it simply means the latency can be greater, 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 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“.
- Below “Presets” choose “Gyro Prefilt, Gyro, Dterm Prefilt, Dterm” and hit Run. That is what I name “warmth maps”.
Right here’s a breakdown of what we’re :
- Near 0Hz: The very 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 sometimes will increase in frequency with throttle degree.
- Harmonics: These are multiples of the basic motor noise band. In our instance, harmonics (typically dimmer and more durable to identify) present up as traces (4) and (5). Attempt adjusting the size 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 are going to use RPM filter to care for these motor noise bands.
The objective is to optimize the variety of RPM harmonics used and set the very best attainable “Min Frequency” primarily based on the beginning frequency of the motor band. Fewer RPM harmonics and the next min frequency lead to much less filtering and decrease latency.
Use the Information Cursor Software, click on on the place the motor band begins to seek out the precise frequency. Affirm this within the roll/pitch/yaw graphs and take the bottom frequency.
Right here’s an instance from my new Supply One V5 construct:
- On the left, is the default RPM Filter, 3 harmonics with a min frequency of 100Hz.
- On the appropriate, I modified it to 2 Harmonics with min frequency of 160Hz
By decreasing one harmonics and lift the cutoff frequency, you possibly can 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 beneath on the appropriate, as you possibly can see, a tiny little bit of gyro noise has turn out to be fairly unhealthy Dterm noise.
On this instance, it’s in all probability higher to have 3 harmonics in RPM filter.
The opposite factor you may need seen is a few noise round 116Hz left unfiltered as a result of we raised the min freq to 160Hz. To handle that, we now have to decrease Min Freq, i.e. round 20Hz beneath the noise frequency could be perfect.
Right here’s a comparability of gyro sign after filtering utilizing 3 completely different settings:
- left: 2 harmonics 160Hz min freq
- mid: 3 harmonics 130Hz min freq
- proper: 3 harmonics 100Hz min freq
To crush out the motor bands, it appears we will’t actually scale back RPM filter. On this instance, the default settings (3 harmonics and 100Hz min frequency) labored finest.
RPM Crossfading
This superior function fades within the RPM filter energy over a spread (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 may begin greater or decrease in frequency, and also you may want it to fade in additional shortly or slowly is determined by the noise. This function is simply accessible in CLI, for instance:
set rpm_filter_min_hz = 100 set rpm_filter_fade_range_hz = 50
This implies the RPM filter begins at 100Hz at minimal energy and reaches full energy at 150Hz.
Q Worth
Growing the Q worth of a notch filter makes it extra targeted on the focused frequency, decreasing latency. Modify this within the CLI:
set rpm_filter_q = 500
The default values of 500 often work nicely, however you possibly can 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 enables 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 energy on the third harmonics and fewer on the 2nd:
set rpm_filter_weights = 100, 0, 80
And when utilizing 2-blade propellers, the place 2nd harmonics is stronger than the third harmonics, you are able to do one thing like this:
set rpm_filter_weights = 100, 80, 0
You may 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 largely vibrations from the body or different {hardware} parts, akin to body resonance, antennas, GoPro mounts, and bent propellers.
When the RPM filter is enabled, Betaflight will routinely scale back the quantity of Dynamic Notch filtering by utilizing fewer notches and the next Q worth because the RPM filter will do a lot of the heavy lifting. You may additional tune the Dynamic Notch filter primarily based in your setup.
Determine Body Resonances: Have a look at the warmth map and determine what number of body resonances there are to find out the variety of notches wanted. As much as 5 notches can be utilized, however often, 1 or 2 are ample until your drone is poorly constructed or in a beat-up situation. With the RPM filter enabled, 1 notch is often sufficient to deal with body resonance.
Decide Q Worth: The Q worth determines the width of the filter. A better Q worth means a narrower filter, which ends up in much less filtering and decrease latency.
- Default Q: Begin with the default Q of 500.
- Modify Q: If the default is working nicely, strive rising it to 600 and even 700. Keep away from exceeding 1000. For those who nonetheless see body resonance noise after filtering, decrease the Q worth.
- Test 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 might help 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 the next likelihood of catching it. If the Dynamic Notch fails to catch these newly pop up resonances on account of Min Frequency is about too excessive, your motors can get sizzling and even burn in these conditions.
With out RPM Filter: In case your quad can’t use RPM Filter, for instance on a tiny whoop, you possibly can 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, once I set Q to 450, the noise is satisfactorily managed. Within the beneath graphs, on the left is Q=700, the appropriate is Q=450. You may examine Dterm heatmap once more to substantiate that is working nicely.
Tuning Gyro Lowpass Filter
Most often, you can begin by turning off the Gyro Lowpass 1 filter as it’s typically pointless. Take a look at fly aggressively for 30 seconds and examine the motor temperature to make sure they aren’t sizzling earlier than continuing.
Use the “Gyro Filter Multiplier” slider to cut back Gyro Lowpass 2 a few notches at a time. Shifting the slider to the appropriate will increase the frequency, which reduces filtering, leading to much less delay, higher prop wash dealing with, and the potential for greater PID good points.
Right here’s a comparability of the gyro frequency spectrum at completely different Gyro Lowpass filter slider values: 1.0 (brown), 1.5 (crimson), and a couple of.0 (orange).
The three traces virtually overlap, suggesting that the Gyro Lowpass filter isn’t considerably affecting the sign and could be lowered. Apparently, the noise within the sub-100Hz spectrum barely improves with much less filtering, which aligns with our earlier discussions.
Vital Issues:
- By no means disable the Gyro Lowpass 2 filter for 2K/4K PID loop frequencies on account of anti-aliasing causes.
- Minimal Frequency:
- For 2K loop time, go away Gyro Lowpass 2 at a minimal of 500Hz.
- For 4K, you possibly can set Gyro Lowpass 2 as much as 1000Hz.
- For 8K, you possibly can disable Gyro Lowpass 2 completely if noise isn’t a difficulty.
Tuning D Time period Lowpass
D time period is way noisier than Gyro on account of its delicate nature and noise will get amplified as frequency will increase. Due to this fact, be further cautious and conservative when coping with D Time period filtering.
Attempt transferring the “D Time period Filter Multiplier” slider to the appropriate a notch at a time and see how the drone responds in a 30-second take a look at flight (do some acro strikes), additionally examine motor temperature after touchdown. In the event that they get sizzling you must return a notch or two.
Keep away from being too aggressive with decreasing D Time period filtering. Depart some headroom for attainable bent props throughout flight. Too little D Time period filtering mixed with a broken propeller can result in sizzling or burned motors.
Right here’s a comparability of D-term filtering slider positions: 1.0 (brown), 1.3 (crimson), and 1.6 (orange). As seen within the heatmap, much less filtering ends in extra noise for D-term, not like 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.
For those who hear the motors getting tough (thrilling oscillation) as you scale back D-term filtering, it’s because of the rising noise beneath 100Hz. You may affirm this by checking the <100Hz graphs. On this instance, staying beneath 1.3, perhaps 1.2 and even simply 1.1, could be safer.
After tuning PID good points, revisit D Time period filtering to see if it may be additional optimized.
If the D Time period traces are very noisy, one or two clicks extra filtering on the slider might assist. If the D time period hint may be very clear, you possibly can maybe scale back filtering a bit extra (if motors will not be sizzling). See beneath graphs, the left has a loud D time period hint, the appropriate is way cleaner.
Vital: NEVER disable D-Time period lowpass filters utterly, you’ll burn your motors.
Gyro/D Time period Notch Filters
There’s no must allow Gyro Notch Filter and D Time period Notch Filter, these are static notch filters which have turn out to be legacy since RPM filter and dynamic notch filters are doing a lot of the work.
Nonetheless, if there’s a robust resonance at a selected frequency (akin to body resonance), a static notch filter could be useful. The dynamic notch filter often covers it, so a static notch filter is commonly pointless. You may strive including a static notch for identified body resonance and scale back the dynamic notch rely 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 particularly useful for whoops, because it helps to cut back yaw spin in collisions.
PID Tuning
To tune PID utilizing Blackbox, I comply with the “Basement Tuning” technique utilizing PIDToolBox. This technique is beginner-friendly and could be finished in a small area like a basement or bed room, therefore the title. It includes performing a sequence of brief flights with barely completely different PID values, then evaluating the logs to seek out the optimum good points.
Throughout the flights, transfer the quad round on the pitch and roll axes. You may be taught extra concerning the basement technique on this video by PIDToolbox.
Though the strategy is known as “basement tuning,” I’m not snug doing this indoors. I’ve had a few “fly to the moon” incidents prior to now, almost drilling a gap within the ceiling. Due to this fact, I at all times carry out these exams in a backyard or native park for security.
Charge Profile and Angle Mode
Performing basement tuning flights requires good line-of-sight flying abilities to maintain the drone managed in a confined area. Listed here are some tricks to make it simpler. Do that fee profile:
- Middle Sensitivity 250
- Max Charge 400
- Expo 0.00
This profile has a low max fee, making it much less prone to lose management in the event 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. Based on the writer of PIDToolBox, Angle mode works simply in addition to Charge mode, however it is advisable to do the next first:
- Go to the Setup tab and calibrate the accelerometer.
- Within the PID Profile Settings, set the Angle mode energy to 100.
- Click on Save to make sure the adjustments are utilized.
Discovering P/D Steadiness
To begin with, 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
Modify 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 start line.
Here’s what you need to carry out within the flight:
- Arm and hover
- Consistently transferring the roll and pitch stick for 20-30 seconds, the extra actions the extra correct will probably be
- Do as massive strikes as you possibly can with out hitting the partitions (ideally full stick deflections)
- You may transfer each pitch and roll collectively so long as you possibly can hold it underneath management
- Attempt to not cease/hover for too lengthy throughout flight, and be as steady as you possibly can
Elevating the Damping slider by 0.2 every time and repeat the flight: e.g, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6. If you elevate D acquire too excessive, your motors will sound tough, subsequently you possibly can’t at all times take a look at the final one or two values, which is ok.
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 in the event you time it nicely.
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 take a look at flight, d06 means damping slider worth 0.6), and put them within the “02 PD Steadiness” folder.
Load all of the logs in PTB, undergo every one and take away the take-off and touchdown elements for every log (to do that, allow “Trim” on the appropriate hand panel).
Click on the “Step Resp Software“, choose all of the information and click on Run. in case you have offset within the curves (gyro curve transferring away from setpoint in the direction of the top), allow Y Correction.
It’s fairly straight-forward, merely decide the most effective trying line, that’s your optimum Damping slider worth. The perfect response ought to look one thing just like the inexperienced line within the following graph, little to no overshoot. Having a tiny little bit of overshoot is suitable.
In case your traces don’t look clean however have a number of ups and downs, that’s referred to as oscillation, and it’s an indicator that the sign is just too noisy or your actions aren’t sufficiently big.
The graphs on the appropriate are additionally extraordinarily useful:
- Peak is highest amplitude of the overshoot (ideally the nearer to 1 the higher)
- Latency is the time it takes to achieve setpoint (ideally the decrease the higher)
When D acquire is low, you’ll get overshoot and even oscillation. As D acquire will increase, there can be much less overshoot and Peak will lower, however Latency will go up in consequence. When D is just too excessive (undershoot), the preliminary peak may not even attain the setpoint and this isn’t perfect. Discover a response that has minimal overshoot and but has comparatively low Latency.
You may 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 might be 1.0.
It’s fairly widespread to have a special 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 acquire, then take the Damping slider to the place you need for roll, and modify the Pitch Damping slider to match the pitch D acquire you simply wrote down.
Typically it’s higher to be a little bit extra conservative and keep away from having D acquire too excessive. In case you are on the fence, at all times go together with much less D acquire (the next P/D ratio), so you possibly can elevate your general PID good points greater on the finish since D is often the limiting issue.
What I’ve discovered is that the step response software tends to be fairly delicate and the P/D steadiness may be decrease than what I’d personally favor. So I usually bump up P/D steadiness by 5-10% after discovering a really perfect worth. That’s simply my private desire, you can provide {that a} strive if you need.
Drone dimension additionally impacts PD ratio, bigger drones are inclined to have greater P:D ratio. For instance a 5″ may use 0.8-1.1 Damping slider whereas a tiny whoop may use 1.4-1.6.
Discovering Max D Achieve
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 akin 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 acquire is just too excessive, the quad might shoot up unexpectedly. Pay shut consideration to motor noise, and cease instantly in the event you hear thrilling oscillation.
You may discover that the shapes of the step response don’t change a lot between completely different values and that the Peak values stay roughly the identical. It’s because the response curve form is principally decided by the P/D ratio. Growing the good points received’t considerably have an effect on the response form, however bumping up P/D good points can scale back latency.
You’ve got reached the perfect Grasp Multiplier acquire when one of many following happens:
- Thrilling Oscillation: For those who hear thrilling oscillation, you possibly can’t enhance 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 greater PID good points. Typically, it’s safer to cut back the Grasp Multiplier slider by a notch or two as soon as you discover the utmost worth. Keep away from pushing D acquire to the restrict to account for potential points like bent props.
Drones utilizing greater cell rely batteries (greater voltage) are inclined to require decrease D good points. For instance, on a 6S quad, D good points may be within the 30s, whereas on a 4S they’re often within the 40s.
In my instance, 1.6 appears to be the worth that provides the least quantity of latency, with little enchancment when rising to 1.8.
For those who can’t hear thrilling oscillations, use the Spectral Analyzer to plot D-term. As good points enhance, motors might produce an exhilarating sound peaking round 40-80Hz, particularly when throttling up. If noise on this frequency vary will increase with greater good points, it signifies the onset of PID-related oscillations.
On this instance, you possibly can clearly see peaks round 60Hz for 1.4 (olive), 1.6 (inexperienced), and 1.8 (cyan). Though 1.6 exhibits latency enchancment, I’d not threat it and would doubtless select 1.4 and even 1.3 to be protected.
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 will result in disastrous outcomes in the event you hit an impediment or bend a prop. It’s no joke, talking from expertise right here:
After discovering the optimum D acquire, examine setpoint monitoring by plotting Gyro and Setpoint. The traces needs to be roughly parallel, indicating the quad is accelerating and decelerating on the similar fee because the setpoint. Nonetheless, there may 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 transferring as quickly because the stick strikes, making it a lot quicker than P time period.
Feed Ahead helps the quad reply promptly to stay inputs, offering a extra 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 favor to do some snap rolls and flips and examine Gyro/Setpoint traces. Use your standard fee profile, or a default fee profile in Betaflight (simply swap to an unused fee profile) to get an honest max fee at full stick. You may examine my charges right here: https://oscarliang.com/charges/#My-Charges
As a substitute of utilizing the step response software in PTB, use BE to examine 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 just too excessive. Within the following demonstration, 0.5 is means too low, 1.0 remains 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 just 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 forms of flying. Even cinematic flying can profit from an excellent quantity of feedforward, if you’re transferring your stick easily and slowly, then feedforward received’t kick in anyway. If 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 enhance (FF Increase). You need to enhance it if gyro lagging behind setpoint at the beginning of a transfer, however catching up afterward. 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 Achieve
The perfect I acquire is essentially primarily based on really feel. You don’t want a number of I acquire when you’ve got optimum P and D good points; you simply want sufficient to maintain the drone from drifting and wandering. In case you are cruising ahead with minimal stick inputs, the drone ought to maintain its place for some time. If there’s any drifting, you then want the next I acquire.
The I time period in Betaflight has a REALLY WIDE tuning window, particularly for highly effective 5″ quads. Usually, a spread of 0.5 to 1.5 on the I time period slider works fantastic for five″ quads. This vast window permits us to tune the whole lot else first and modify the I time period final. With a excessive I acquire, your quad will really feel extra exact, but when the I acquire is just too excessive, you could expertise gradual oscillations, which you need to keep away from.
I discovered the step response software in PTB isn’t 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 often lands round 1 on the slider for 5-inch quads.
You may tune the I acquire by trying via the goggles and listening to the motors. For those who purpose to push the I acquire as excessive as attainable, strive transferring 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 indicate bouncebacks, because of options like “I-term chill out” in Betaflight. These days, you need to use extraordinarily excessive I acquire with out a lot detrimental impression (akin to bouncebacks).
For five″ quads, I often simply go away the I acquire slider at 1.
With I-term chill out, you possibly can modify the cutoff primarily based on the drone’s responsiveness. For freestyle drones, you possibly can often go away it on the default setting. For racing drones, enhance it to 30. For heavier drones like cinelifters and seven″ long-range drones carrying a GoPro, set the cutoff to 10.
Dynamic Damping
Dynamic Damping is a function that reinforces D acquire to the utmost throughout sharp strikes however doesn’t enhance 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 meanwhile.
- 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, this may decrease the baseline D acquire used throughout regular flights to maintain your motors cool.
Alternatively, to maintain issues easy, you may also simply go away Dynamic Damping slider at 0 and go away the Damping slider unchanged, the quad will use the identical D acquire via the entire flight, it’s as much as you.
Different Settings
Anti Gravity Positive factors
Anti-Gravity (AG) good points assist scale back wobbling and nostril dips whenever you punch out after which let go of the throttle. AG quickly boosts I acquire throughout throttle pumps to mitigate these undesirable dips. Nonetheless, if the AG acquire is about too excessive, your quad might expertise fast oscillation (stutter) whenever you launch the throttle, as a result of AG boosts each P and I.
Default is 8, scale back it in the event you see wobbles throughout quick throttle adjustments. For five″ freestyle drones, I discovered 8 to 12 an excellent vary.
You may tune AG by trying 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 possibility of ESC desync. It will increase motor pace when the throttle is at zero, bettering management authority and responsiveness at low throttle inputs. Different advantages embody sharper flip and roll stops, extra responsive in low throttle and more practical braking.
When Dynamic Idle is about, Static Motor Idle (in %) within the Motors tab is disengaged.
To setup Dynamic Idle, it is advisable to
- 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 really helpful Idle RPM worth is determined by propeller dimension and pitch. Smaller and decrease pitch propellers typically require greater values. Modify the worth greater 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 |
Issues for Dynamic Idle:
- Excessive Worth: Reduces hold time when the drone is the other way up (motors push more durable in the direction of the bottom). It could additionally make the quad hover barely at zero throttle, making throttle administration more durable.
- Low Worth: Dangers low throttle instability.
Setting the Perfect 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.
- Test RPM: Spin the motor on the ESC idle worth (e.g., 5.5%, slider at round 1055) and be aware the reported RPM (requires bi-directional DShot).
- Set Dynamic Idle: Use the RPM worth divided by 100 as the perfect Dynamic Idle worth.
Throttle Increase
Throttle Increase will increase your throttle worth whenever you quickly transfer the throttle stick up, providing you with further energy. This will make throttle responses extra dynamic however may also make them unpredictable.
- The Default Worth of 5 typically works nicely
- Adjustment Ideas:
- For those who discover the throttle exhausting to handle exactly, scale back the worth.
- Some racers even disable Throttle Increase completely by setting it to 0 to have probably the most predictable throttle response attainable.
- Experiment with completely different values to see what works finest in your flying model.
Voltage Sag Compensation
This function reduces the utmost motor drive worth when the battery is full and will increase it because the battery voltage drops. It supplies 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 via 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 may must decrease the grasp multiplier slider if motors get sizzling.
TPA
TPA stands for Throttle PID Attenuation.
To fantastic tune TPA, carry out a throttle sweep and examine the frequency vs. throttle heatmap. For those who 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 often the reason for the oscillations). Within the older Betaflight it attenuates each P and D, if you need you possibly can convey this again by typing in CLI: set tpa_mode = PD.
Usually I favor to set throttle worth in TPA as excessive as attainable, so D acquire is extra fixed throughout a wider throttle vary. Be sure 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.
I Time period Rotation and Absolute Management
These options are typically not wanted for FPV freestyle drones and are extra useful for line-of-sight pilots.
Tuning Yaw
Yaw typically doesn’t require a lot tuning because the default acquire works nicely. The tuning window for Yaw is sort of vast. In contrast to pitch and roll that are primarily based on thrust generated by propellers, yaw is predicated on the inertia generated by propeller rotation. Due to this fact, yaw will inherently be too gradual to overshoot setpoint, and there’s little must tune yaw PID.
Yaw can be too gradual for D phrases to have any significant impact and it’s typically not required. Nonetheless you possibly can allow it if you need, however it may introduce extra drawback than it solves, like vibrations and many others. So we’re left with P and I phrases for Yaw.
You may 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 just too excessive. If quick oscillations happen, then P-Time period is just too excessive.
If in case you have yaw shakes when doing throttle pump, you possibly can 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 checklist, choose RP (Roll Pitch), as an alternative 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 an excellent start line. It’s also possible to strive greater values as yaw tends to be fairly gradual reacting.
There is no such thing as a excellent tune
How good is nice sufficient? You may at all times spend extra time enjoying with filters and PID numbers, and you may even see enhancements however it may be situational and the time you put money into it may not be proportional to the end result. I usually simply cease when it seems to be “adequate” and go away it there until there’s a selected drawback to be solved
Troubleshooting Ideas
Dangerous Gyro
A 5-inch FPV drone ought to fly easily on default Betaflight settings. In case your quad experiences vibrations, it may very well be on account of mechanical or electrical points, or generally a nasty gyro on the flight controller (FC). Right here’s tips on how to diagnose a nasty gyro:
- Symptom: One axis is considerably noisier than the others, particularly within the decrease frequency spectrum beneath 200Hz.
- Analysis: Rotate the FC by 90 levels. If the noisy axis follows the rotation, the gyro may very well be defective.
Within the instance beneath, the pitch axis is way noisier than roll and yaw, with bursts of D time period noise brought on by the noisy gyro. Potential Causes:
- Excessive energy wires close to the gyro.
- Noisy energy provide to the FC.
- Poor board design.
Options:
- Eradicating any excessive energy wires close to the gyro .
- You may 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 facility of the FC (VBAT/VCC pad).
- If not one of the above options works, you may simply have to exchange the 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 finest to load the suitable RC_Link preset to keep away from errors.
The Auto Issue is maybe one of the essential values, decrease is extra twitchy and responsive whereas the next worth is softer and smoother however extra sluggish. Right here’s a basic rule I personally comply with:
- 20-25: Racing
- 30: Default worth, nice for Freestyle
- 50: Cinematic
- 90: Extraordinarily clean cruising, delay may be noticeable to some
- 120: Highest smoothness attainable with out entering into hassle, however delay is noticeable
Dangerous gear/pilot require greater 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 attainable, examine black field logs to substantiate you’ve got clean setpoints, if the setpoint isn’t clean (has steppings from RC instructions), merely enhance the smoothing barely.
If in case you have noise in setpoint that peaks round 50Hz, 150Hz, 250Hz or 500Hz, then there’s in all probability an issue with RC smoothing. These frequencies are widespread packet charges in RC hyperlink. On this instance, it’s Crossfire 150Hz.
In case you are not utilizing sufficient filtering for the RC instructions, you may not have smoothed out the RC sign sufficient and it might create noise on the frequency of your radio hyperlink packet 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 may 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 affords.
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 however it received’t provide the latency penalty.
One of the best ways is to only load the suitable RC Hyperlink preset as I talked about right here. For those who didn’t load the right RC_Link preset in your specific RC hyperlink and packet fee, it may additionally 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 possibly can elevate the restrict to 1000. To do that, enter the next command within the CLI: set pid_sum_limit=1000. Nevertheless it doesn’t at all times make a distinction in flight behaviour as motors may saturate at this fee anyway.
ADC Filter Jitters Inflicting Oscillations
For those who expertise random vibrations and wobbles on account of feedforward jitters, even after making use of the right RC Hyperlink preset or rising RC smoothing, the problem may very well 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
