Having a well tuned FPV drone is something you won’t fully appreciate until you’ve tried it. Only then will you realise what you’ve been missing out on as your quad glides along seemingly on rails, responding precisely to your every input. The purpose of this guide is to help you get to grips with the basics of PID tuning and rate tuning as quickly as possible. Very soon your FPV drone will be tuned to perfection and flying seamlessly![vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1912″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
What are PID’s and why must we tune them?
“PID” is an acronym for Proportional, Integral and Derivative gains. The purpose of a PID loop is to calculate an error value by comparing a desired input value to a measured process value. Once the error value is calculated, the proportional, integral and derivative gains are used to calculate and implement a correction to the unwanted error. By changing the values associated with the PID gains, the performance of the craft can be improved by reducing the frequency of error that occurs during flight. To understand how the PID loop implements these changes, consider an analogy.
Imagine that you must kick a ball so that it comes to rest exactly on a certain point. If you can only kick the ball once at the start point than an exact force must be exerted on the ball so that it will come to rest at the desired point. This is difficult and would require plenty of trial and error to correctly complete the task. Imagine that if after you initially kick the ball you can control its acceleration and deceleration as it rolls, this will allow you to reduce or increase the speed of the ball as it approaches the end point. This technique is much more efficient than simply kicking the ball because it is less prone to error. This is similar to what happens when the PID loop attempts to accurately react to a stick input[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”153″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
What Affects PID Tuning?
The flight ‘feel’ of a multicopter is largely determined by the hardware selected for the build; motors, propellers, ESC’s and the frame play a key role in determining how an FPV drone will perform once in the air. Even environmental factors such as atmospheric can affect how a quad is tuned. PID tunes are extremely subjective, it is important that you tune your FPV drone befitting of your own unique flying style and environment.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”135″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Rates and Expo are not PID’s
A common mistake for FPV beginners to make is the confusion of PID’s and rates. Rates are independent of PID’s, their purpose is to determine how the quadcopter reacts to stick input. Rates and expo are key to us human operators because they assist in masking our numerous input errors.
To see what I mean, hold your hand in front of your face as still as you can. Notice the minute twitches in your fingers? This is the ‘input error’. If the rates/expo curve were linear, each of these tiny hand movements would destabilise the quad and prevent us from flying smoothly. By adjusting rates and expo, we change how rapidly an FPV drone rotates around each axis (rates), as well as the amount of stick movement from the neutral position required to cause the quad to move (expo).[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1896″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Where to Begin?
The advancement of flight controller technology has led to a stark increase in flight performance prior to tuning. Previous flight controller firmwares demanded substantial PID tuning to occur before reaching the baseline level of modern flight controller firmware. Due to this, the best place to start is with the rates and expo located in the PID tuning section. This way we can perfect stick feel before moving on to flight performance, preventing any confusion between rates/expo and PID’s.
In this example, we’ll be doing our PID’s and rates/expo tuning in the ButterFlight configurator. If you are using a different flight controller firmware, the basic level PID tuning explained in this guide should also be applicable to your choice of firmware. Go ahead and manoeuvre over to the PID tuning window.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1892″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Once in the PID tuning tab, you’ll notice that there is a lot going on! In the PID tuning tab, you can not only edit PID values but also preview rates/expo curves and edit other PID controller parameters. For now we’ll ignore everything except the rates/expo columns and preview window.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1893″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Notice the three columns; RC Rate, Super Rate and RC Expo. These are the numbers you will be changing to manipulate how your quad quad responds to stick commands. Let’s go over these one by one.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1895″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
RC Rate
RC Rate determines how rapidly the FPV drone will rotate about an axis, if you’re familiar enough with computers you can liken this to mouse sensitivity. The greater the number is the faster the quadcopter will react and spin. Contrary to what you might believe, most racers prefer slower rates around 600 degrees per second to improve the accuracy of their flying. Freestylers usually bump their rates up to achieve clean and quick tricks, such as snap rolls. Notice how RC Rate on pitch and roll are tied to the same value while yaw RC Rate is separated.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Expo
Expo determines the steepness of your rates curve, this can be visualised in the rates window. By increasing Expo, stick sensitivity reduces around centre stick and the outer stick ranges increase in sensitivity. This is ideal if you wish to improve the smoothness of stick transition.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Super Rate
Super Rate is a relatively new parameter that was introduced by BetaFlight. Super Rate is essentially a combination of RC Rate and Expo, increasing Super Rate values vastly quickens rotation speed in the far reaches of the stick range. At the same time, sensitivity reduces around centre stick. Although Super Rate has replaced the primary function of Expo, Expo can still be used in conjunction with RC Rate and Super Rate if an extremely dull centre stick region is desired.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Rate Tuning
Tuning RC Rate, Expo and Super Rate is a feel based exercise, the most efficient method is to simply change up the values and flight test it. If you don’t like how it feels, you can always revert back and try again. Personally I prefer to ballpark RC Rate and Super Rate before flying the craft, than I figure out what must be changed next. Rates and expo are interchangeable between different multicopters, usually you can adhere to a set of rates across your entire fleet.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
PID Tuning
Over to the left of the PID’s/Rates table are the PID’s, the proportional, integral and derivative gains. We’ll discuss how each of these values affects the flight of your multirotor. Notice that a unique set of variables is designated to each axis. If you want to tune movement along the pitch axis, be sure not to accidentally change values in the roll or yaw rows.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1894″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
PID Tuning Technique
There are a vast variety of different PID tuning techniques invented and adopted by a broad range of FPV pilots. Of all of these different PID tuning methods, none are inherently superior. The PID tuning guide detailed in this article is a basic set of guidelines purposed to get you familiar with the underlying processes of PID tuning. Experiment with different PID tuning techniques to discover what is right for you. It should be noted that the process outlined in this article should be done using FPV for best results.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Step One – Finding the Right P Values
Tuning the P gain is essentially changing how quickly your quadcopter reacts to your inputs, raise the P values to increase sensitivity and decrease the P values to reduce sensitivity. It may take several attempts before you find a set of values that fit. To test the influence of the P values during flight, rapidly move the roll, pitch and yaw sticks side to side alternatively causing the quad to wobble back and forth along a particular axis. Observe how rapidly your quadcopter changes direction, this will assist in determining the appropriateness of the P values.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Step Two – Tuning the I Gain
Wobbling during throttle change is a common symptom of low I gain, increasing the I gain will force the quadcopter to hold position more diligently. The best method to check for I gain wobble is simply revving the throttle up and down while hovering. Overly high I gain is a little trickier to detect, try executing several rolls and flips to check how resistive the quadcopter is to rapid movement. If the drone feels too rigid, decrease the I gain to increase the fluidity of the flight behaviour.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Step Three – Determining the Derivative
The derivative is a final touch to the tune, used to soften or sharpen the flight characteristics of the drone. To find the ‘baseline’ for the D gain firstly increase or decrease D until you find the lowest value at which propwash is minimised. You can search for propwash by throttling straight ahead before rapidly turning 180 degrees and flying in the opposite direction to which you started. If your quad wobbles rapidly for a short time, you’ve got propwash. If D gain is too high you’ll notice a strange warbling noise, quickly reduce the D gain before your motors are damaged.
Once you’ve ascertained the D gain baseline, you need to decide how you want your quad to feel in the air. If you’re a racer that desires a snappy reactive quad, keep the D gain as low as possible. If freestyle is your preference, boost the D values to increase the smoothness of your quad. After achieving the ideal D values, you may need to slightly retune the P gain if you made large changes to the initial D values. Usually a higher P gain requires a higher D gain and vice versa. [/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1917″ img_size=”large” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Many FPV pilots jokingly speak of PID and rate tuning as ‘the dark arts’ of the hobby. Being heavily feel based, it truly is an unusual concept to grasp especially for newer pilots that lack flight experience. Remember that PID and rate tuning are entirely subjective, don’t be anxious to experiment a little and find out exactly what works best for you.[/vc_column_text][/vc_column][/vc_row]
This is great info! Thanks!
Good to hear you enjoyed it Yoshi.
I’ve been looking for a beginner’s guide to PID tuning, and this helped a lot. Thanks!
wow .what a great read on pid tuning .its is a big help .getfpv ,.com is a very good site.
wow .what a great read on pid tuning .its is a big help .getfpv ,.com is a very good site.
Great guide!
Gold, best explanation I’ve found