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Aug 26, 2015, 03:25 PM
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Mini-HowTo

Tuning your Vector equipped multicopter


Welcome!  This is a tutorial that will explain how to tune your Vector powered multicopter. This is especially important for racing multicopters where you need every bit of stability performance.

While this tutorial is focused on high performance racers, the steps taken here should be applicable to most modern multirotor airframes and flight controllers.

The PC GUI is referenced in this tutorial, but all tuning steps can be completed using the OSD stick menus - no laptop required at field:





Note that this is an advanced tutorial. It assumes that you are familiar with multirotor piloting in 3D (non-auto-leveling, sometimes called “Acro”) Mode.

Also, note that Vector software version 11.82 or higher is required for advanced tuning. As of this writing, this software is in beta, so proceed with caution!

Let’s get started!

Section 1: Preparation

Step 1: Gather your parts and build your multirotor

You'll need a high performance multirotor with at least the following:
  • A Vector Flight Controller (These instructions are applicable to other advanced flight controllers as well. Some settings may not be available, and settings values will likely be different.)
  • A stiff airframe. Preferably high thickness carbon fiber or fiberglass. The arms should be stiff enough that applying moderate force on them does not create any noticeable deflection.
  • Well balanced propellers / motors
  • Up-to-date ESCs. Support for the “OneShot125” communications protocol is highly recommended, as it provides a significant performance improvement. If you do not have OneShot125 capable ESCs, then do not enable the OneShot125 feature as specified in this tutorial.
Step 2: Getting in the air

Follow the instructions in the Vector Manual to get the model flying stably in a hover. This step will serve as the baseline for tuning, so it doesn’t need to be super dialed in. At this stage, it is probably best to avoid tweaking too many settings except for the following:
  • Enable Fast Arming: Shortens the arming sequence from about three seconds to one.
  • Max ESC/Motor Output: Set this to or below the max throttle that your ESCs will accept. This will ensure that the Vector will not request a throttle output that is beyond the ESC’s physical capability to provide. Most systems seem to work well with a setting 1900uS here.
  • Enable OneShot125 Mode: If your ESCs are OneShot125 compatible, this will provide a significant increase of performance, allowing much higher gains to be achieved. DO NOT ENABLE THIS FEATURE IF YOUR ESCs DO NOT SUPPORT OneShot125!!!
  • Set Vibration Rejection to Low: When combined with enabling OneShot125, this will make the Vector’s stabilization response even quicker. If you experience stability issues after setting this option to Low, it may indicate that your airframe has too many vibrations. Setting this back to Medium will reduce the effect of vibrations, but will not allow the highest possible level of flight precision.
  • Set Maximum Pitch / Roll during Normal Flight to 45 degrees: For those that enjoy the security of 2D Mode, increasing this limit will give you far more authority while maneuvering. This setting does not affect 3D Mode.


Section 2: Tuning

The steps below describe how to tune.

Important: The Vector uses a “PID” inner/outer control loop, similar to other advanced flight controllers. However, it’s important to remember that numeric PID tuning values are NOT interchangeable between flight controllers!

Step 1: Proportional Gain (3D Mode)

In either the OSD stick menus or the Vector’s PC UI, zero out the Integral and Derivative components of the Inner Pitch and Roll fields. 

Once you have only Proportional Gain set for the Inner Pitch and Roll axes, perform a series of test hovers in 3D Mode, increasing your Inner Proportional gain for these axes until you start to see oscillations manifest following a sharp tap on the control stick. These oscillations should be small and rapid, petering out in less than one or two seconds. If the oscillations last longer than this, reduce the Proportional gain until they no longer do.

Step 2: Integral Gain (3D Mode)

After getting the Proportional Gain dialed up to a comfortable level, begin to increase the Inner Integral Gain for Pitch and Roll. In this step, it is important to increase the Inner Integral Gain until the model precisely holds orientation whenever the stick is centered in 3D Mode. 

A good test is to pitch the model forward in 3D Mode and center the stick. The model should fly forward aggressively. If, during its acceleration, the model does not hold the initial Pitch angle, then the Integrator Gain for Pitch is too low. 
If the model begins to oscillate, then reduce the Integral Gain for the oscillating axis until the oscillations disappear.

Step 3: Derivative Gain (3D Mode)

Finally, we need to eliminate the high frequency oscillations that were found in Step 1. To do this, increase the Inner Derivative Gains for Pitch and Roll. Increase this value by small increments until a sharp tap on the Pitch/Roll control stick does not result in any bounce or wobble behavior.

In some cases, increasing the Inner Derivative Gain will reach a point where oscillations get worse instead of getting smaller. In this case, double check that you have OneShot125 enabled and that you have Vibration Reject to “Low”. If this does not solve your issue, re-try Step 1, but focus on reducing the oscillations at that stage. Once you've reduced the oscillations at Step 1, you can re-try Step 3, starting from 0 Inner Derivative Gain and working up until the oscillations are eliminated.

Step 4: Outer Proportional Gain (2D Mode)

In most cases, the Outer Proportional Gain does not need to be adjusted at all. However, since we’re going for a high performance setup here, we can tune this setting as well. First off: This setting only affects 2D Mode! 3D Mode is not affected at all by the Outer Proportional Gain. This setting dictates how hard the Vector will work to level the model in any of the 2D Modes.

Start with this setting at its default value of 30. Do not ever set this value to 0. Doing so will prevent 2D Mode from leveling the model correctly. From the default value, begin increasing this setting until you see oscillations. If you see any oscillations at all, this setting is too high. (There should have been absolutely zero oscillations upon completing Step 3, so any seen now must have been introduced by the Outer Proportional Gain's value.).

In cases where OneShot125 is enabled and the Inner PID Gains are tuned correctly, this setting can be set far higher than the default. This will allow for more precise 2D maneuvering. 



Step 5: Make It Sporty (All Modes)

Now that you've got your multirotor tuned for maximum precision, a couple of additional changes can be made to let you really take advantage of that increased capability.

Stabilizer Responsiveness: Increasing this value from the default to "4” or more makes any maneuvering in 2D Mode far more precise. Pushing this to higher values causes the Vector to follow your stick commands much more rapidly. Taking full advantage of this setting requires a well tuned high performance frame, but that’s the whole idea of this tutorial, right?

Increase your 3D Direct Rates: 2Hz for Pitch and Roll provides a comfortable level of performance for aerobatics without being too intimidating. 1Hz for Yaw allows for a snappy turning response. Combine an even higher 3D Direct Rates setting with Expo programmed into the Pitch/Roll/Yaw channels on your Tx for even more aggressive maneuvering.

Maximum Pitch and Roll Limits: If you like to fly in 2D Mode, increasing these settings will give you far more authority than the default 25 degrees. 45 degrees is a good starting point for racing. Be careful of using Alt Hold enabled modes at these Pitch/Roll angles.

Throttle Gain Reduction: If you find yourself with oscillations at very high throttle levels while experiencing stable flight at hover power, you may want to try this feature. It works by scaling all Inner PID gains by a reduction factor that is linearly mapped from 0% reduction starting at the “Throttle Gain Reduction Start Point” to whatever percentage reduction is set in the “Throttle Gain Reduction” field when the average throttle output reaches the “Max ESC/Motor Output”.

Throttle Expo: This feature remaps your Throttle input with an “expo” curve in order to give you finer resolution in whatever range you normally find yourself hovering. Depending on how you configure it, this feature should give you lots of room to finesse your throttle while in a hover, but provides easy access to the full power of the multirotor with a flick of your thumb.





Other Pro Tips

Motor Idle Throttle: In the history of Multirotor Racing, there have been many instances where very capable pilots are not able to perform a fast standing start without crashing due to not having their props spinning at idle. 

This is why the Vector requires that you configure your “Idle Throttle (microseconds)” setting to a value that ensures your props are spinning when the quad is armed. This ensures that when you punch out off the starting pad, the motors will respond immediately.

Do not configure this setting to spin your motors down at zero throttle! Doing so will compromise takeoff reliability, safety, and in-flight performance!



Vibration is Key: If you follow the prescribed steps above and still cannot get good performance, one possible culprit could be excess vibrations. 

Always be sure that your motors and props are balanced.  A good way to check if you have too much vibrations is to mount a HD video recorder on your frame with minimal vibration isolation and check if your recordings contain “jello". 

The presence of “jello", or wobbling lines in your recording, usually indicates that your frame has an imbalanced motor or insufficient vibration rejection. This can be caused by poor build quality in either your frame, motors, or propellers. In addition, even a small crash can deform a motor shaft enough to introduce significant vibrations.

It is critically important to be sure your motors and props are in as good condition as possible during your initial tuning session. For example, if you have a small nick in an otherwise flyable prop, put it aside and replace it with a new one during your tuning session. The same goes with a questionable motor. You need all your components as close to perfect as possible during tuning.
Last edited by JohnET; Oct 26, 2015 at 11:45 AM.
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Aug 26, 2015, 08:04 PM
SonicStrikeFPV
rcflyer729's Avatar
This is one of the best pid tuning tutorials I have ever read. Really good job!
Sep 01, 2015, 01:50 AM
Registered User
stormin13's Avatar
What exactly is the issue with Oneshot mode with beta version 11.82? I flew several batteries with this FW last Friday and did not notice anything unusual.
Sep 01, 2015, 08:22 AM
JohnET's Avatar
Hello,

It seemed to be a very rare occurrence where ESCs would stop responding. New firmware will be out very soon!

Regards, John
Sep 01, 2015, 11:19 PM
Registered User
stormin13's Avatar
Quote:
Originally Posted by JohnET
Hello,

It seemed to be a very rare occurrence where ESCs would stop responding. New firmware will be out very soon!

Regards, John
Okay - thanks for the update
Sep 09, 2015, 03:06 PM
billpa's Avatar
All, new firmware is posted! See info here:
Sep 10, 2015, 11:13 AM
Smasher of foam
AeroMaestro's Avatar
Quote:
Originally Posted by JohnET
Hello,

It seemed to be a very rare occurrence where ESCs would stop responding. New firmware will be out very soon!

Regards, John
Thanks, John. I just popped into this thread to ask the same thing. I'll put my quad back together with this new firmware tonight and I'm looking forward to testing it again tomorrow.

Also, this PID tuning guide really is terrific. Very clear, and very effective. And WOW, what a delight it is to tune a quad and go through three different gains and then an outer gain all through the OSD without ever plugging/unplugging any cables or dragging around a tablet or laptop. (And I did it all on one battery, too!)

Really, once this PID tuning process is understood, it's even quicker than using the APM or TauLabs autotune features -- which don't work all that well, anyway.
Sep 10, 2015, 03:01 PM
Mastering the basics
Deserteagle83's Avatar
Thanks for this tutorial. The Vector will DEFINITELY be at the heart of my next 280 build. I'm slowly falling in love with you guys and this FC system.
Sep 10, 2015, 03:06 PM
Mastering the basics
Deserteagle83's Avatar
When using the vector on a 250'ish racing frame how important is it to use the provided GPS mast? I crash often when FPV racing and I don't see it lasting long.
Sep 11, 2015, 08:48 AM
Registered User
I too did not want to put the tall GPS mast mount on my quad as its pretty vulnerable in a crash and gets in the way of the 6" props I run.

On my 250 Quad, I ended up putting my GPS/Compass unit on a horizontal 3-4" long plastic tail boom out the back of the quad. Only reason I needed to do this was to get the Compass part far enough away from the magnetic fields of the DC wiring - otherwise heading changed with motor load/speed. The GPS itself worked fine virtually anywhere.
Sep 11, 2015, 09:37 AM
Registered User
yosemitez's Avatar
Quote:
Originally Posted by Deserteagle83
When using the vector on a 250'ish racing frame how important is it to use the provided GPS mast? I crash often when FPV racing and I don't see it lasting long.
if you do not use loiter or altitude hold or rth or speed readout etc then their is no need for GPS.
Sep 11, 2015, 09:40 AM
Registered User
yosemitez's Avatar
Nice, the new advanced fc tab has sorely been needed! I have been flying my naze32 all summer as it has all these functions and I could never get the vector to fly as crisp.

Well done and will give this a try.
Sep 11, 2015, 11:22 AM
Mastering the basics
Deserteagle83's Avatar
Quote:
Originally Posted by yosemitez
if you do not use loiter or altitude hold or rth or speed readout etc then their is no need for GPS.
I want the GPS, and all the features that come with it (and the compass module thats in there)... Don't want the mast. I know it won't last past my first outing.
Sep 11, 2015, 04:48 PM
Registered User
yosemitez's Avatar
Quote:
Originally Posted by Deserteagle83
I want the GPS, and all the features that come with it (and the compass module thats in there)... Don't want the mast. I know it won't last past my first outing.
if you are racing a 250 quad why would you need any gps features?
Sep 12, 2015, 12:05 AM
Mastering the basics
Deserteagle83's Avatar
Quote:
Originally Posted by yosemitez
if you are racing a 250 quad why would you need any gps features?
Instead of having a strictly race machine I can have a quad for any occasion. FPV racing on the weekends, exploring, and fun flying during the week.

Now that you mention it, I guess I COULD just get the main FC unit and the voltage sensor.