Multirotor guide

Note

This page provides a general guide for things specific to Multicopter setup and tuning.
It assumes you have already setup your Ports, Modes, Navigation, Receiver, GPS, OSD etc. They are outside the scope of this document.

1. Getting your flight controller ready.

• Download latest configurator from here.

• Flash newest INAV with the full chip erase option selected.

• When asked, select your model preset type.
  If the type of model you have is not under the presets. Go to the Mixer Tab and select one of the Mixer presets in the drop-down menu. Many of the more common mixers are available here. (Tri, Hex, Octo etc)
  Press Load and Apply to make your choice.
  For even less common mixer types, also see Custom mixes for exotic setups. Other Mixer related information can also be found here and here.

• Go to the Calibration Tab and follow the instructions given to perform an Accelerometer Calibration. Run the advanced 6-point sensor calibration.

• If you use a magnetometer (recommended), it will also require setup in the Alignment Tool Tab and Calibration Tab. More specific information with regards to Flight Controller / Magnetometer alignment and calibration can be under GPS and Compass setup. You may need to attach a battery for magnetometer calibration if your GNSS/mag module is not powered by the FCs 4.5v USB pins.

• Once the above is complete. Make sure the Copter moves identical to the virtual image in the Status Tab. It must do this on all 3 axis's. An deviation indicates incorrect alignment or calibration.

• Now go to the Outputs Tab, and Enable Motor and Servo output.

• While in the Outputs Tab, select the ESC protocol of your choice.

• If the motor output plug on your flight controller does not align with the input plug of the 4 in 1 ESC. e.g. S1 to S1 and S2 to S2 etc. But instead, they may be something like S1 to S4 and S4 to S1. You can use the Motor Mixer Wizard in the Mixer Tab, to allocate a motor output from the flight Controller, to the corresponding position each motor is located, according to which of the 4 ESC's it is wired to.

• Select motor direction if required. Depending on whether you want to run Props IN or Props OUT.

2. Setup failsafe and a couple of important navigation settings

Adjusting these setting won't take long, but they are often over looked in setup. Leading to poor navigation performance or a crash landing in a Failsafe condition.

• nav_mc_hover_thr - Please read here for a more detailed explanation of why it is important to adjust this setting.

• failsafe_throttle and failsafe_of_delay - Please read through this short explanation here to help understand why adjusting these settings is required.

Guide for setting up failsafe

More advanced MC operation and tuning information can be found under Navigation modes and Navigation PID tuning (MC).

3. Tune your copter's Pitch/Roll/Yaw/Level PIDs and other values

INAV multicopter tuning can be made easier for new users with EZ-Tune.
When you load a platform preset after flashing your hardware. Multicopter EZ-Tune will be enabled by default in the Tuning Tab.
If you wish to run your own tune. Turn off the ENABLED button.

Tip

The default presets many not always be correct. Due to the influence your selected hardware can have upon the PID tune.

Example: A lower powered 5" cruiser running on a 3 cell battery, will generally require a different tune to a 5" race quad running on a 6 cell battery.
The reason being is because the 6s quad will provide far more thrust for the PID controller to work with. Actually making tuning easier. But often requiring the PID values to be lower, because the PID setpoint error can be dealt with much faster.

The image below shows an example of the preset tune for a 7" multicopter.

But in the case mentioned above under the TIP. Such a tune is better suited to a multicopter that is NOT running a stronger power train. Like a 6 cell install.

The tune below has the Integral and Derivative gains on the pitch and roll reduced, to better suit a multicopter that has a higher power to weight ratio.
If you have migrated from BetaFlight to INAV. These gains will provide a safer start point to begin tuning from. Whether it be a 3", 5" or 7" build.

4. Battery settings

Add your batteries specifications into the CLI, under # battery_profile. Or in the Configurator Configuration Tab. This is a very important step.
Overlooking this step can cause your battery to become over discharged during the flight, leading to a crash.

• vbat_warning_cell_voltage - Pre-warning. Set to 3.6v is good for a LiPo.
• vbat_min_cell_voltage - Time to land. Set to 3.4v is good for a LiPo.
• battery_capacity - Set to the rated mAh capacity of your battery pack.
• battery_capacity_warning - Generally set to 25%. Which is 25% of the batteries rated capacity.
• battery_capacity_critical - Set to 20%.

Note

Continually discharging many lithium chemistry batteries below 20% of their rated capacity under higher loads, can reduce its capacity, and also shorten the batteries life expectancy.

More in-depth battery setup information can be found here.

5. Selecting filters

At the time of writing this. INAV has the following software filter methods. They are used to isolate and remove vibrations from the Gyro and Accelerometer data.

Gyro -

• gyro_filter_mode - STATIC, DYNAMIC, ADAPTIVE
• dynamic_gyro_notch_enabled (default ON - aka Matrix filter)
• rpm_gyro_filter_enabled (default OFF - ESC telemetry, non bi-directional Dshot)
• gyro_anti_aliasing_lpf_hz (default ON - zero = OFF)
• gyro_lulu_enabled (default OFF)
• smith_predictor_delay (zero = default OFF)
• setpoint_kalman_enabled (default ON - aka Unicon filter)

Accelerometer -

• acc_lpf_hz (default of 15Hz is a good balance between performance and noise handling)
• acc_lpf_type (filter type) - BIQUAD, PT1
• acc_notch_hz (center frequency of the noise peak) - Should only be used if the peak is narrow and known by log data
• acc_notch_cutoff (lowest practical frequency the notch should be set). Only set if the above is used

Tip

Accelerometer vibrations more often cause issues for navigation control, then Gyro induced vibrations.

Lowering acc_lpf_hz below 7Hz in an attempt to filtering out vibrations, will begin to cause it's own problems. Making navigation control loose.

Filters add signal delay. And they can only remove so much noise before it begins to effect flight performance. For this reason it is always better to mechanically setup your hardware first, and eliminate as many vibrations as possible. By balancing the motors and the props.
Just because the hardware is new. Does not mean it is well balanced from factory.
If a motor isn't balanced correctly. You can generally hear it audibly, by REMOVING THE PROPS and running each motors individually through its rev range, using the motor sliders in the Outputs Tab.

It's better to run a few good filters, than to run every filter available. Which will only add even more gyro delay, with little to no benefit.
I've placed the gyro filters in the order of the ones I personally use from flight experience, from first to last.

Use silicon vibration dampeners for your flight controller. Do not tighten the stack bolts too tight. This will crush the dampener, reducing their ability to adsorb vibrations. Only tighten them firm enough to stop movement. You may have to use thread lock to prevent the nuts coming loose.

6. Get to know the CLI values.

INAV offers a lot of customization through CLI variables. It is strongly recommended to read through CLI Variable reference and available CLI variables