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 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 creator holds no duty for damages ensuing from actions taken by the readers.
Blackbox shouldn’t be a should for tuning as defined on this information, however it offers full perception into what’s taking place with the drone and means that you can unleash its full potential. Issues like noise filtering and tiny overshoots are seen solely in Blackbox. When you’re a perfectionist or simply somebody who likes to tinker, that is the tutorial for you.
In case you are new to Blackbox, be certain that to take a look at the Blackbox for novices tutorial..
I spent over 200 hours making this 8000-word tutorial! When you discover my content material helpful, please take into account supporting my work.
Getting Began
Tuning targets
Utilizing Blackbox to tune our FPV drone, we intention to attain two foremost targets:
- Extra Efficient Use of Filters: Use minimal filtering to attenuate delay however sufficient to maintain noise at a suitable stage.
- Optimized PID Positive factors and Associated Settings: Make sure the drone flies exactly and responsively.
Primary configurations
0. {Hardware} Guidelines
- Flight Controller (FC) Stack: Select an FC stack with rubber grommets (gummies) for sturdiness and noise efficiency.
- Steel Screws: Use metallic screws for the FC stack; keep away from nylon/plastic screws/standoffs as they’re vulnerable to breakage and vibrations. If spacers are wanted, use delicate silicone ones. Lighter titanium screws can save a number of grams.
- Locking Stack Screws: Safe the stack screws firmly with a metallic nut earlier than mounting the 4in1 ESC. In case your body has pressed insert nuts, further nuts should not wanted. Tighten screws by hand first, then give a last squeeze with a wrench/screwdriver.
Use 4 plastic nuts to safe the FC stack. Tighten the nuts by hand to keep away from excessively crushing the gummies, permitting the delicate mount to work successfully.
1. Blackbox Recording Settings
Choose the next settings within the Blackbox Configuration:
- Logging System: Onboard Flash or SD Card
- Logging Price: 2KHz (or 1.6KHz for BMI270 Gyro)
- Debug Mode: GYRO_SCALED (data unfiltered gyro sign)
- Knowledge Included: To save lots of 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 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 provides higher braking energy, which is useful for prop wash dealing with and responsiveness, however with a better threat of vibration. In case you are on the fence, simply go along with 48KHz.
For BLHeli_S ESC, flash Bluejay to allow bi-directional DShot, required for RPM filter and Dynamic Idle. I’ve a information on tips on how to flash it right here: https://oscarliang.com/bluejay-blheli-s/
3. Flash the newest model of Betaflight firmware to your flight controller and 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 help 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 you probably have BLHeli_S ESC, it is advisable flash Bluejay firmware (tutorial) first.
Verify if it’s working correctly by working the motors within the Motors tab (with out propellers) and making certain the error price (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 may allow the Gyro RPM filter, the most effective filters in Betaflight.
5. Load the suitable RC_Link preset.
Totally different RC hyperlinks require particular RC smoothing and feedforward configurations. Unsuitable config may cause stuttering and vibrations. My favourite RC hyperlink is ExpressLRS, 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 fashion, for most individuals it might be Freestyle.
For Crossfire, lock the packet price to both 50Hz (longer vary, increased latency) or 150Hz (decrease latency, much less vary) utilizing the TBS Agent Lite LUA script.
6. Decrease TPA
Within the PID tuning tab, set the TPA breakpoint from 1350 to 1750 to keep away from TPA masking oscillation points at low/mid throttle throughout tuning. High quality-tune TPA on the finish if oscillation points happen at excessive throttle, however usually I might reduce the usage of TPA at any time when potential.
Find out how 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 foremost software, it’s by far essentially the most highly effective Blackbox software accessible. It means that you can evaluate a number of logs aspect by aspect, making it simpler to see the consequences of your modifications. The Step Response software is particularly helpful for tuning PID. The spectral analyzer in PTB makes use of decibels on the Y-axis, offering extra correct and goal comparisons. PTB additionally estimates filter delays, which may be very useful.
Nevertheless, PTB will be slower and fewer intuitive to make use of in comparison with Blackbox Explorer. For fast checks or troubleshooting a single log, BE is quicker and simpler. However for noise and filter tuning, PTB is the best way to go.
Filters Tuning
You could 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’ll principally solely give attention to 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 purple sections.
Additional studying: Study in regards to 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 reveals vibrations throughout the throttle vary and body resonances.
- Repeat: Carry out 2-3 throttle sweeps, then land and disarm.
That is what a typical throttle sweep log would appear to be (see the underside bar for throttle modifications).
Understanding Gyro Frequency and Delay
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 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:
- Beneath 20Hz: Drone flight actions.
- 20Hz – 100Hz: Propwash and oscillations from suboptimal PID, problematic ESC config, dangerous RC hyperlink settings, and so on.
- 100Hz – 250Hz: Body resonance or unfastened components.
- Above 250Hz: Noise from motors and propellers, and harmonics.
The whole lot under 20Hz is “good” drone movement reacting to the sticks.
Between 20Hz and 100Hz is the place undesired vibrations, similar 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 an oscillation subject 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 towards. Filtering on this low-frequency vary can really make issues worse as a result of it introduces an incredible quantity of latency. Analyzing the spectra below 100Hz may give you perception into vibration or mid-throttle oscillation points and the way effectively the copter handles propwash.
We don’t care about something above 1000Hz as these have little impact on our drone. What we need to give attention to filtering is the noise between 100Hz and 1000Hz.
Maybe not intuitive, however over-filtering can really trigger oscillation to indicate up as noise within the sub-100Hz spectra. That’s as a result of filtering creates one thing referred to as section delay. When the quad tries to appropriate the error, the response is just too late as a result of delay, which is counterproductive. It makes the error worse and creates a suggestions loop, inflicting the drone to oscillate.
That’s why, if we use much less filtering, noise points below 100Hz can typically really get higher as a result of latency is decreased and the quad can react quicker to appropriate PID errors. Utilizing much less filtering additionally means that you can push PID positive aspects increased, which makes your quad observe setpoint higher and helps fight propwash.
You could 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 remove motor noise bands utilizing the RPM filter, then crush out body resonances with dynamic notch filters, and eventually, cut back the ambient noise ground with Gyro and D-term lowpass filters. I 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 identical time, we’d like sufficient filtering to keep away from burning our motors when flying dwelling with a bent prop. You may actually play it secure and apply extra filtering than wanted, however over-filtering makes the drone really feel disconnected and gradual to react as a result of elevated delay. It may additionally worsen propwash. So, we have to try for a stability.
Aside from checking Blackbox logs, motor temperature is one other helpful indicator in filter tuning. When motors get too scorching, it normally signifies that the filtering is just too aggressive.
Professional Tip: Sizzling Motors – How Sizzling is Too Sizzling?
As a basic rule of thumb, in the event you pinch the motor bell and may’t maintain your fingers on it for various seconds, it’s too scorching and you’re most likely pushing your settings too aggressively.
How Clear is Your Construct?
Earlier than we start tuning, it’s vital to verify you probably have a clear construct. Begin by performing throttle sweeps as beforehand described.
Load the log in PIDToolBox, click on on the Spectral Analyzer, choose “Gyro prefilt” (the uncooked, unfiltered gyro sign; “Gyro” is the filtered sign), and hit Run.
The default filter settings in Betaflight are pretty conservative, and most builds ought to have the ability to cut back filtering from there. In case your quad is already noisy with default filter settings, as an alternative of accelerating filtering, it is best to search for potential mechanical or electrical points. Guarantee you’ve a capacitor on the ESC enter energy, all screws are tightened, and also you’re utilizing recent new props, and so on.
On a clear 5″ quad, there ought to be little exercise between ~50Hz (the quad’s actions) and ~200Hz (motor vibration). You probably have quite a lot of noise on this area, it could possibly 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 can be tougher.
As instructed by the creator of PIDToolBox, it’s best to have the general noise ground under -30dB above 50Hz. For D-term, it’s best to have the general noise ground under -10dB. Analyzing the noise ranges in these areas may give you a great indication of how clean your quad flies. The noise stage is influenced by the construct high quality of the drone, the standard of the {hardware}, and typically 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 tip of the world; it simply means the latency might be increased, and also you gained’t have the ability to push PID positive aspects as excessive.
Tuning RPM filter
Motor noise is the first supply of noise for FPV drones, and the RPM filter is without doubt one of the handiest filters in Betaflight for tackling motor noise. On a clear construct, the RPM filter and Dynamic Notch filters will do many of the work, permitting us to disable many different filters to attenuate latency.
Let’s 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“.
- Beneath “Presets” choose “Gyro Prefilt, Gyro, Dterm Prefilt, Dterm” and hit Run. That is what I name “warmth maps”.
Right here’s a breakdown of what we’re taking a look at:
- Near 0Hz: The very brilliant horizontal line on the backside (1) represents the drone’s movement reacting to the sticks.
- Round 200Hz: This horizontal line (2) signifies body resonance. Its frequency doesn’t change with throttle place however is strongest the place it intersects with the motor band.
- Basic Motor Noise Band: This diagonal line (3) is normally the brightest. Motor noise sometimes will increase in frequency with throttle stage.
- Harmonics: These are multiples of the elemental motor noise band. In our instance, harmonics (typically dimmer and more durable to identify) present up as traces (4) and (5). Attempt adjusting the dimensions in the event that they aren’t seen. Word that 2-blade propellers have a tendency to indicate extra and stronger harmonics than 3-blade props.
We’ll use RPM filter to handle these motor noise bands.
The aim is to optimize the variety of RPM harmonics used and set the best potential “Min Frequency” primarily based on the beginning frequency of the motor band. Fewer RPM harmonics and a better min frequency end in much less filtering and decrease latency.
Use the Knowledge Cursor Instrument, click on on the place the motor band begins to seek out the precise frequency. Affirm this within the roll/pitch/yaw graphs and take the bottom frequency.
Right here’s an instance from my new Supply One V5 construct:
- On the left, is the default RPM Filter, 3 harmonics with a min frequency of 100Hz.
- On the appropriate, I modified it to 2 Harmonics with min frequency of 160Hz
By decreasing one harmonics and lift the cutoff frequency, you may maybe see extra unfiltered noise from the third motor harmonics.
Though it’s fairly weak, it might probably nonetheless get amplified when it will get into D time period. Let’s verify the Dterm warmth map under on the appropriate, as you may see, a tiny little bit of gyro noise has turn into fairly dangerous 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 deal with that, we now have to decrease Min Freq, i.e. round 20Hz under the noise frequency can be best.
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 finest.
RPM Crossfading
This superior characteristic fades within the RPM filter power over a spread (type 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 may begin increased or decrease in frequency, and also you may want it to fade in additional rapidly or slowly will depend on the noise. This characteristic is just accessible in CLI, for instance:
set rpm_filter_min_hz = 100 set rpm_filter_fade_range_hz = 50
This implies the RPM filter begins at 100Hz at minimal power and reaches full power at 150Hz.
Q Worth
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
Default values normally work effectively, however you may fine-tune by growing the Q worth till motor noise turns into seen within the filtered gyro diagram, then again off. Don’t exceed 1000.
RPM Filtering Dimming
This enables particular person management of every RPM filter to focus on harmonics. For instance, when utilizing 3-blade propellers, the second harmonics is normally not very sturdy, however the third harmonics is. On this case you need to use extra filtering power on the third harmonics and fewer on the 2nd:
set rpm_filter_weights = 100, 0, 80
And when utilizing 2-blade propellers, the place 2nd harmonics is stronger than the third harmonics, you are able to do one thing like this:
set rpm_filter_weights = 100, 80, 0
You 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 principally vibrations from the body or different {hardware} parts, similar to body resonance, antennas, GoPro mounts, and bent propellers.
When the RPM filter is enabled, Betaflight will routinely 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 many of the heavy lifting. You may additional tune the Dynamic Notch filter primarily based in your setup.
Establish Body Resonances: Take a look at the warmth map and establish what number of body resonances there are to find out the variety of notches wanted. As much as 5 notches can be utilized, however normally, 1 or 2 are enough until your drone is poorly constructed or in a beat-up situation. With the RPM filter enabled, 1 notch is usually sufficient to deal with body resonance.
Decide Q Worth: The Q worth determines the width of the filter. The next Q worth means a narrower filter, which leads to much less filtering and decrease latency.
- Default Q: Begin with the default Q of 500.
- Modify Q: If the default is working effectively, strive growing it to 600 and even 700. Keep away from exceeding 1000. When you nonetheless see body resonance noise after filtering, decrease the Q worth.
- Verify D-term Heatmap: Analyze the D-term heatmap to see how modifications within the Q worth have an effect on D-term noise.
Set Min/Max Frequency: These are the cutoff frequencies, defining the efficient vary of the Dynamic Notch filter. Add 20-30Hz to every aspect of the resonance for the vary.
Keep away from setting the Min Frequency too excessive for security causes, as bent props can create large resonance. In case of a crash, a broader frequency vary 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 probability of catching it. If the Dynamic Notch fails to catch these newly pop up resonances on account 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 method up.
In an instance setup, there seems to be one body resonance round 210Hz.
I attempted growing Q to 700 and setting the min/max frequency to 160-230Hz, however Q was clearly too excessive. There may be extra unfiltered noise, and it will get into Dterm and get amplified.
Lastly, after I set Q to 450, the noise is satisfactorily managed. Within the under graphs, on the left is Q=700, the appropriate is Q=450. You may verify Dterm heatmap once more to substantiate that is working effectively.
Tuning Gyro Lowpass Filter
Most often, you can begin by turning off the Gyro Lowpass 1 filter as it’s typically pointless. Check fly aggressively for 30 seconds and verify the motor temperature to make sure they don’t seem to be scorching 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 increased PID positive aspects.
Right here’s a comparability of the gyro frequency spectrum at completely different Gyro Lowpass filter slider values: 1.0 (brown), 1.5 (purple), and a couple of.0 (orange).
The three traces nearly overlap, suggesting that the Gyro Lowpass filter isn’t considerably affecting the sign and will be decreased. Curiously, the noise within the sub-100Hz spectrum barely improves with much less filtering, which aligns with our earlier discussions.
Vital Concerns:
- By no means disable the Gyro Lowpass 2 filter for 2K/4K PID loop frequencies on account of anti-aliasing causes.
- Minimal Frequency:
- For 2K loop time, go away Gyro Lowpass 2 at a minimal of 500Hz.
- For 4K, you may set Gyro Lowpass 2 as much as 1000Hz.
- For 8K, you may disable Gyro Lowpass 2 fully if noise isn’t a problem.
Tuning D Time period Lowpass
D time period is far noisier than Gyro on account of its delicate nature and noise will get amplified as frequency will increase. Due to this fact, be further cautious and conservative when coping with D Time period filtering.
Attempt shifting 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 verify 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 decreasing 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 (purple), and 1.6 (orange). As seen within the heatmap, much less filtering ends in extra noise for D-term, not like Gyro lowpass.
From left to proper, the heatmap reveals unfiltered D time period, D-term lowpass filter at 1.0, 1.3, and 1.6.
When you hear the motors getting tough (thrilling oscillation) as you cut back D-term filtering, it’s as a result of rising noise under 100Hz. You may 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 positive aspects, revisit D Time period filtering to see if it may be additional optimized.
If the D Time period traces are very noisy, one or two clicks extra filtering on the slider might assist. If the D time period hint may be very clear, you may maybe cut back filtering a bit extra (if motors should not scorching). See under graphs, the left has a loud D time period hint, the appropriate is far cleaner.
Vital: NEVER disable D-Time period lowpass filters fully, you’ll burn your motors.
Gyro/D Time period Notch Filters
There’s no must allow Gyro Notch Filter and D Time period Notch Filter, these are static notch filters which have turn into legacy since RPM filter and dynamic notch filters are doing many of the work.
Nevertheless, if there’s a sturdy resonance at a particular frequency (similar to body resonance), a static notch filter will be useful. The dynamic notch filter normally covers it, so a static notch filter is commonly pointless. You may strive including a static notch for identified body resonance and cut 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 will 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 observe the “Basement Tuning” methodology utilizing PIDToolBox. This methodology is beginner-friendly and will be carried out in a small house like a basement or bed room, therefore the identify. It includes performing a collection of quick flights with barely completely different PID values, then evaluating the logs to seek out the optimum positive aspects.
Through the flights, transfer the quad round on the pitch and roll axes. You may study extra in regards to the basement methodology on this video by PIDToolbox.
Though the tactic 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 all the time carry out these checks in a backyard or native park for security.
Price Profile and Angle Mode
Performing basement tuning flights requires good line-of-sight flying expertise to maintain the drone managed in a confined house. Listed below are some tricks to make it simpler. Do this price profile:
- Heart Sensitivity 250
- Max Price 400
- Expo 0.00
This profile has a low max price, making it much less more likely 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 important sufficient for correct logging.
Performing the take a look at in Angle mode could make it even simpler than in Price mode. In response to the creator of PIDToolBox, Angle mode works simply in addition to Price mode, however it is advisable do the next first:
- Go to the Setup tab and calibrate the accelerometer.
- Within the PID Profile Settings, set the Angle mode power to 100.
- Click on Save to make sure the modifications are utilized.
Discovering P/D Stability
To start with, decrease these positive aspects in order that they don’t intervene with our tuning:
- Set the “Stick Response” slider (Feed Ahead) to 0
- Set the “Dynamic Damping” (D Max) slider to 0
- Set the “Drift-Wobble” (I positive aspects) slider to 0.2, it’s low sufficient that it shouldn’t introduce overshoot but have just a bit I phrases to assist stabilize the quad higher, makes it simpler to regulate
Modify the “Damping” (D positive aspects) 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
- Continuously shifting the roll and pitch stick for 20-30 seconds, the extra actions the extra correct it is going to be
- Do as huge strikes as you may with out hitting the partitions (ideally full stick deflections)
- You may transfer each pitch and roll collectively so long as you may maintain it below management
- Attempt 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 increase 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 solution to change slider worth is by going into Betaflight OSD menu, Profile, Simplified Tuning. However in case you are 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 ought to be sufficient for six 30-second flights in the event you time it effectively.
After you’ve accomplished all of the flights, obtain them to your pc. To arrange the logs higher, I’ve a folder construction created for this course of, obtain right here: https://drive.google.com/file/d/1tx1AV2lOMgknAwIB3VFhqP1i6VpDLVjr/view?usp=share_link
And I rename the logs to one thing like “01 d06“, “02 d08” and so on (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 appropriate hand panel).
Click on the “Step Resp Instrument“, choose all of the information and click on Run. you probably have offset within the curves (gyro curve shifting away from setpoint in direction of the tip), allow Y Correction.
It’s fairly straight-forward, merely decide one of the best trying line, that’s your optimum Damping slider worth. The best response ought to look one thing just like the inexperienced line within the following graph, little to no overshoot. Having a tiny little bit of overshoot is appropriate.
In case your traces don’t look clean however have numerous ups and downs, that’s referred to as oscillation, and it’s an indicator that the sign is just too noisy or your actions aren’t large enough.
The graphs on the appropriate are additionally extraordinarily useful:
- Peak is highest amplitude of the overshoot (ideally the nearer to 1 the higher)
- Latency is the time it takes to achieve setpoint (ideally the decrease the higher)
When D achieve is low, you’ll 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 just too excessive (undershoot), the preliminary peak may not even attain the setpoint and this isn’t best. 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 take a look at Roll and Pitch axis.
In our instance, it’s fairly clear the perfect worth is orange (3) for each pitch and roll, so that will be 1.0.
It’s fairly widespread to have a special PD stability on pitch and roll as a result of completely different weight distribution. If that’s the case for you, take the Damping slider to the place you need for pitch, write down the pitch D achieve, then take the Damping slider to the place you need for roll, and modify the Pitch Damping slider to match the pitch D achieve you simply wrote down.
Generally it’s higher to be a bit extra conservative and keep away from having D achieve too excessive. In case you are on the fence, all the time go along with much less D achieve (a better P/D ratio), so you may increase your total PID positive aspects increased on the finish since D is normally the limiting issue.
What I’ve discovered is that the step response software tends to be fairly delicate and the P/D stability may be decrease than what I’d personally choose. So I usually bump up P/D stability by 5-10% after discovering a perfect worth. That’s simply my private choice, you may give {that a} strive if you would like.
Drone dimension additionally impacts PD ratio, bigger drones are inclined to have increased 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 similar to 0.8, 1.0, 1.2, 1.4, 1.6, and 1.8.
Be cautious and don’t stand too near the quad throughout this take a look at. When D achieve 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 is because the response curve form is especially decided by the P/D ratio. Growing the positive aspects gained’t considerably have an effect on the response form, however bumping up P/D positive aspects can cut back latency.
You have got reached the perfect Grasp Multiplier achieve when one of many following happens:
- Thrilling Oscillation: When you hear thrilling oscillation, you may’t enhance D achieve any additional.
- Latency Plateau: If latency doesn’t lower anymore (or little or no), it means you’ve reached the higher certain tuning window. The motors are working at their hardest, and you aren’t gaining any extra efficiency from them.
The utmost achieve achievable is influenced by the noise stage of your construct and the quantity of filtering used. Much less filtering permits for increased PID positive aspects. Generally, it’s safer to cut back the Grasp Multiplier slider by a notch or two as soon as you discover the utmost worth. Keep away from pushing D achieve to the restrict to account for potential points like bent props.
Drones utilizing increased cell rely batteries (increased voltage) are inclined to require decrease D positive aspects. For instance, on a 6S quad, D positive aspects may be within the 30s, whereas on a 4S they’re normally within the 40s.
In my instance, 1.6 appears to be the worth that offers the least quantity of latency, with little enchancment when growing to 1.8.
When you can’t hear thrilling oscillations, use the Spectral Analyzer to plot D-term. As positive aspects enhance, motors might produce an exciting sound peaking round 40-80Hz, particularly when throttling up. If noise on this frequency vary will increase with increased positive aspects, it signifies the onset of PID-related oscillations.
On this instance, you may clearly see peaks round 60Hz for 1.4 (olive), 1.6 (inexperienced), and 1.8 (cyan). Though 1.6 reveals latency enchancment, I might not threat it and would probably select 1.4 and even 1.3 to be secure.
There may be ongoing debate on whether or not it’s higher to have extra D-term filtering and better D 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 could 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 achieve, verify setpoint monitoring by plotting Gyro and Setpoint. The traces ought to be roughly parallel, indicating the quad is accelerating and decelerating on the identical price because the setpoint. Nevertheless, there may nonetheless be a big hole between them, indicating latency. Within the subsequent step, we’ll cut back this hole utilizing Feedforward.
Tuning Feed Ahead
Feed Ahead (FF) accelerates your quad if you transfer the sticks, making your quad extra responsive and nearer to the setpoint. In contrast to P time period, which reacts solely when there’s a PID error, Feed Ahead measures the speed of stick deflection. It will get the motors shifting as quickly because the stick strikes, making it a lot quicker than P time period.
Feed Ahead helps the quad reply promptly to stay inputs, offering a extra instant and managed flying expertise. It’s useful for all flying kinds, together with cinematic flying, because it reduces latency between stick enter and quad response.
When tuning Feed Ahead I choose to do some snap rolls and flips and verify Gyro/Setpoint traces. Use your common price profile, or a default price profile in Betaflight (simply change to an unused price profile) to get an honest max price at full stick. You may verify my charges right here: https://oscarliang.com/charges/#My-Charges
As an alternative of utilizing the step response software in PTB, use BE to verify the setpoint/gyro traces. The gyro ought to observe the setpoint extra intently with much less delay. Ideally, the gyro ought 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 method 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 just too excessive, it might probably trigger the P time period to react in the wrong way, making an attempt to counteract it.
Doesn’t matter what your flying fashion is, feedforward will be helpful and doesn’t apply solely to sure kinds of flying. Even cinematic flying can profit from a great quantity of feedforward, in case you are shifting your stick easily and slowly, then feedforward gained’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 price.
There’s an non-obligatory setting, Feedforward increase (FF Enhance). You need to enhance 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 Achieve
The best I achieve is basically primarily based on really feel. You don’t want quite a lot of I achieve when you’ve optimum P and D positive aspects; you simply want sufficient to maintain the drone from drifting and wandering. In case you are cruising ahead with minimal stick inputs, the drone ought to maintain its place for some time. If there’s any drifting, then you definately want a better I achieve.
The I time period in Betaflight has a REALLY WIDE tuning window, particularly for highly effective 5″ quads. Sometimes, a spread of 0.5 to 1.5 on the I time period slider works wonderful for five″ quads. This extensive window permits us to tune the whole lot else first and modify the I time period final. With a excessive I achieve, your quad will really feel extra exact, but when the I achieve is just too excessive, it’s possible you’ll expertise gradual oscillations, which you need to keep away from.
I discovered the step response software in PTB shouldn’t be efficient for locating the I time period, because the step response for pitch and roll stays an identical 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 normally lands round 1 on the slider for 5-inch quads.
You may tune the I achieve by trying by means of the goggles and listening to the motors. When you intention 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 laborious 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 destructive affect (similar to bouncebacks).
For five″ quads, I normally go away the I achieve slider at 1.
With I-term chill out, you may modify the cutoff primarily based on the drone’s responsiveness. For freestyle drones, you may normally go away it on the default setting. For racing drones, enhance it to 30. For heavier drones like cinelifters and seven″ long-range drones carrying a GoPro, set the cutoff to 10.
Dynamic Damping
Dynamic Damping is a characteristic that reinforces D achieve to the utmost throughout sharp strikes however doesn’t enhance it throughout regular flight. This helps in decreasing motor warmth.
That is how I usually use Dynamic Damping:
- Word down your present D Max worth. This worth ought to be the identical as Spinoff as a result of the Dynamic Damping slider is ready to 0 in the meanwhile.
- Start by growing the Dynamic Damping slider to 1.
- Then cut back the Damping slider till the D Max worth stays the identical as earlier than, this can decrease the baseline D achieve used throughout regular flights to maintain your motors cool.
Or you may simply go away Dynamic Damping slider at 0 and don’t change your Damping slider unchanged, it’s as much as you.
Different Settings
Anti Gravity Positive factors
Anti-Gravity (AG) positive aspects assist cut back wobbling and nostril dips if 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 might expertise fast oscillation (stutter) if you launch the throttle, as a result of AG boosts each P and I.
Default is 8, cut back it in the event you see wobbles throughout quick throttle modifications. For five″ freestyle drones, I discovered 8 to 12 a great vary.
You may tune AG by trying within the goggles, or verify for nostril dip in Blackbox logs, and see the impact of anti-gravity.
Dynamic Idle
Dynamic Idle improves stability, enhances propwash dealing with, and reduces the prospect of ESC desync. It will increase motor pace when the throttle is at zero, enhancing 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 is advisable
- 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 useful Idle RPM worth will depend on propeller dimension and pitch. Smaller and decrease pitch propellers usually require increased values. Modify the worth increased in windy situations to counteract instability.
| Prop Sizes | Excessive Pitch Props | Low Pitch Props |
| 31mm/1.2″ | 84 | 167 |
| 40mm/1.6″ | 62 | 124 |
| 2″ | 50 | 100 |
| 2.5″ | 40 | 80 |
| 3″ | 33 | 66 |
| 3.5″ | 28 | 57 |
| 4″ | 25 | 50 |
| 5″ | 20 | 40 |
| 6″ | 16 | 33 |
| 7″ | 14 | 28 |
| 8″ | 12 | 25 |
| 10″ | 10 | 20 |
Concerns for Dynamic Idle:
- Excessive Worth: Reduces grasp time when the drone is the wrong way up (motors push more durable in direction of the bottom). It may additionally make the quad hover barely at zero throttle, making throttle administration more durable.
- Low Worth: Dangers low throttle instability.
Setting the Splendid Worth:
- Decide ESC Idle Worth: Default is normally 5.5%. Check 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 perfect Dynamic Idle worth.
Throttle Enhance
Throttle Enhance will increase your throttle worth if you quickly transfer the throttle stick up, providing you with further energy. This could make throttle responses extra dynamic however also can make them unpredictable.
- Default Worth: 5
- Adjustment Ideas:
- When you discover the throttle laborious to handle, cut back the worth.
- Some racers disable Throttle Enhance fully by setting it to 0.
- Experiment with smaller values to see what works finest in your flying fashion.
Voltage Sag Compensation
This characteristic reduces the utmost motor drive worth when the battery is full and will increase it because the battery voltage drops. It offers extra constant flight efficiency all through the flight. However watch out it would make you overlook when to land as a result of the quad would really feel comparable by means of the entire pack.
Thrust Linearization
- Advisable 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 (just like TPA).
- Helps with nostril dips and is particularly helpful for whoops and drones utilizing 48KHz PWM frequency on ESCs.
Word: Because it boosts PID at low throttle, you may must decrease the grasp multiplier slider if motors get scorching.
TPA
TPA stands for Throttle PID Attenuation.
To wonderful tune TPA, carry out a throttle sweep and verify the frequency vs. throttle heatmap. When you get oscillations above a sure throttle stage, by which case TPA can assist.
Within the newest Betaflight it solely attenuates D achieve above sure throttle stage (which is normally the reason for the oscillations). Within the older Betaflight it attenuates each P and D, if you would like you may deliver this again by typing in CLI: set tpa_mode = PD.
Usually I choose to set throttle worth in TPA as excessive as potential, so D achieve is extra fixed throughout a wider throttle vary. Ensure to set the throttle worth a bit decrease than the place the place the D time period associated oscillations begin to present up. For instance, if oscillation begins round 1800 throttle, I might do one thing like this: TPA = 0.75, 1750.
Revisiting D Time period Filtering
After making the above modifications, revisit D time period filtering to see if changes are wanted. Enhance or cut back filtering as required.
I Time period Rotation and Absolute Management
These options are usually not wanted for FPV freestyle drones and are extra useful for line-of-sight pilots.
Tuning Yaw
Yaw usually doesn’t require a lot tuning because the default achieve works effectively. The tuning window for Yaw is kind of extensive. In contrast to pitch and roll that are primarily based on thrust generated by propellers, yaw relies on the inertia generated by propeller rotation. Due to this fact, yaw will inherently be too gradual to overshoot setpoint, and there’s little must tune yaw PID.
Yaw can be too gradual for D phrases to have any significant impact and it’s usually not required. Nevertheless you may allow it if you would like, however it may introduce extra downside than it solves, like vibrations and so on. 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.
You probably have yaw shakes when doing throttle pump, you may isolate yaw from the slider tuning, and set Yaw PID individually. To do that, go to the PID tuning tab, within the ‘Slider Mode’ dropdown record, choose RP (Roll Pitch), as an alternative of RPY (Roll Pitch Yaw). This may 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 great place to begin. You may also strive increased values as yaw tends to be fairly gradual reacting.
There isn’t any excellent tune
How good is sweet sufficient? You may all the time spend extra time taking part in with filters and PID numbers, and you might 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 appears “ok” and go away it there until I’ve a particular downside I need to resolve.
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 on account of mechanical or electrical points, or typically a foul gyro on the flight controller (FC). Right here’s tips on how to diagnose a foul gyro:
- Symptom: One axis is considerably noisier than the others, particularly within the decrease frequency spectrum under 200Hz.
- Prognosis: 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 may strive utilizing a 1000uF low ESR capacitor on the ESC energy.
- If already utilizing a capacitor, strive soldering a further smaller 220uF-470uF capacitor to the ability of the FC (VBAT/VCC pad).
- Defective Gyro, changing FC.
RC Smoothing
RC smoothing is crucial 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 probably one of the vital values, decrease is extra twitchy and responsive whereas a better worth is softer and smoother however extra sluggish. Right here’s a basic rule I personally observe:
- 20-25: Racing
- 30: Default worth, nice for Freestyle
- 50: Cinematic
- 90: Extraordinarily clean cruising (noticeable delay)
- 120: Highest smoothness with out bother (important delay)
Unhealthy gear/pilot require increased RC smoothing too, e.g. Low high quality radio management gear, worn out gimbals, pilots with shaky fingers, and so on. Mainly something that may contribute to jerkiness in RC instructions.
If potential, verify black field logs to substantiate you’ve clean setpoints, if the setpoint isn’t clean (has steppings from RC instructions), merely enhance the smoothing barely.
You probably have noise in setpoint that peaks round 50Hz, 150Hz, 250Hz or 500Hz, then there’s most likely an issue with RC smoothing. These frequencies are widespread packet charges in RC hyperlink. On this instance, it’s Crossfire 150Hz.
In case you are not utilizing sufficient filtering for the RC instructions, you may not have smoothed out the RC sign sufficient and it might create noise on the frequency of your radio hyperlink packet price.
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 may really feel a bit bit much less responsive. RC Smoothing is helpful, however an excessive amount of smoothing defeats the aim of getting quick RC packet charges like ExpressLRS provides.
The aim 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 comparable impact however it gained’t provide the latency penalty.
One of the simplest ways is to simply load the suitable RC Hyperlink preset as I talked about right here. When you didn’t load the proper RC_Link preset in your specific RC hyperlink and packet price, it may additionally trigger issues to Feedforward. On this instance, feedforward jitters as a result of lack of stepping smoothing in RC instructions.
PID Sum too low?
If the PID_Sum hits the default 500 restrict (50%) as a result of PID settings are very excessive, you may increase the restrict to 1000. To do that, enter the next command within the CLI: set pid_sum_limit=1000. However it doesn’t all the time make a distinction in flight behaviour as motors may saturate at this price anyway.
ADC Filter Jitters Inflicting Oscillations
When you expertise random vibrations and wobbles on account of feedforward jitters, even after making use of the proper RC Hyperlink preset or growing RC smoothing, the problem could possibly be as a result of ADC filter.
Make sure the ADC filter is turned off in your radio’s system menu below the {hardware} web page.
Feedforward spikes seem within the Blackbox logs when the ADC filter is turned on, inflicting undesirable oscillations and vibrations.
Edit Historical past
- Nov 2022 – Information created
- Jun 2024 – Up to date to Betaflight 4.5