Do-It-Yourself Drone: Lesson 6. Performance Check.

Content

Introduction

In Lesson 5, you should have finished assembling the drone (without installing the propellers). Take your time, as even small mistakes can lead to a crash. You still have a few steps before your first flight, so be patient and follow the guidelines below. As in the previous lesson, we will continue to assume that you are using radio control equipment to interact with the UAV (as the most widely used control method currently).

flight controller

• Not all flight controllers are the same, so the setup procedure really depends on the model you choose. If you haven’t already, take the time to read the user manual of your chosen flight controller in detail from start to finish. Missing the smallest detail can make the difference between the first successful flight and a complete write-off. A well-written user manual should include everything you find on this page plus more, so it’s recommended to use this tutorial as a checklist and not as a replacement/alternative to the developer’s main instructions.
• Most flight controllers provide a step-by-step procedure for selecting settings for a specific UAV configuration, including full control over PID values. The values ​​for each (P, I and D) can be adjusted for your specific frame and flying style; from something more stable for using the platform in aerial photography, to something more like sports flying (flipping, drone racing, etc.). It usually starts with the default values ​​for each field, and if you are not experienced enough to change them, it is recommended to leave everything as it is until the first flight.
• The flight controller manual should also tell you how to set the minimum powerplant RPM, that is, set the speed at which the motors rotate when they are armed. Initially, you can set this value relatively low – enough to see that the motors are spinning, but not so much that the UAV will move under the influence of the thrust generated by them. The maximum thrust, if you can set this value, should be the maximum thrust that your control gear can provide.

• One aspect that can be discussed in the flight controller’s user manual without making any suggestions is the flight mode. Going back to Lesson 4, “Flight Mode” determines which sensors are used to stabilize the drone, as well as its function/purpose. The most common sensors found on a flight controller are: gyroscope, accelerometer, barometer, compass, and possibly GPS.
• If this is your first drone, the most stable flight mode available for your flight controller, which uses the most sensors available to stabilize the drone, is highly recommended. This is generally due to the fact that the PID settings may be too far from your frame/settings, which is why it is better to choose the default PID values. If you have flown before, ACRO mode (which uses only the gyroscope) may be the best.
• Most flight controllers will also allow you to change “flight mode” mid-flight via a backup channel. For example, if your remote control has six channels, you might consider assigning channels 5 or 6 (which are often associated with switches) to be able to change the flight mode while flying the drone. Before flying, make sure you know which switch position corresponds to which flight mode.
• It is highly recommended not to use GPS waypoints or any more advanced features/sensors (such as an ultrasonic distance sensor to determine the distance to the ground) until you are sure that the UAV is well configured. Some manuals suggest using only the ACRO (acrobatic) mode, however, if you do not have significant piloting experience, it will not be physically possible for you to fly in this mode, the mode is the most difficult to control, since stabilization is excluded.

Control equipment configuration

• Some remotes have different operation modes, such as Airplane, Helicopter, Car, etc. In Lesson 4 (Section: Controls) we discussed the four main control channels: Throttle (Gas), Yaw (Yaw), Pitch (Pitch) and Roll (Roll), which are usually values ​​associated with airplanes or helicopters. If the flight controller manual does not specify a specific mode for the transmitter, it is recommended to use Airplane mode.
• There are two types of remote control: Mode 1 (Mode 1) and Mode 2 (Mode 2). Mode 2 (most common) with this type of control Throttle (Gas) and Yaw (Yaw) associated with the left channel / stick / joystick, Pitch (Pitch) and Roll (Roll) with the right. You can also double check their assignment by directly moving the sticks to make sure the values ​​are not inverted.

• Transmitter modes often add a channel/signal “offset” level to make the motion more appropriate for a particular system, however most flight controllers take care of any offset and as such prefer “raw” values. If your transmitter does not have any modes, just check which channel/stick/joystick is responsible for what.
• A general purpose RC transmitter can only provide a limited range of signals on each channel, and so in this lesson we advise you to find out what range of values ​​a RC transmitter can provide, and whether the minimum and maximum values ​​can be configured (either as values ​​or in percent of the default range). For example, MultiWii-based flight controllers require transmitters that can provide a full pulse range of 500ms to 2500ms, while the default setting can only be 1000ms to 2000ms, as this is a common configuration for R/C aircraft. Read your transmitter’s manual to learn how to set signal endpoints/range (if possible).
• If your controller has an LCD display, you can often do so through the interface under “Settings”.
• “Control equipment test for max. remote distance” is easiest to implement with the help of a friend/assistant, or connect a buzzer or other visual/audio feedback to the RC drone. Some higher end models have a range test function. The purpose of the test is to see how far a signal is transmitted before the receiver can no longer detect it. It is recommended to resort to a range test only after the so-called “Combat flight” (Fight flight – the performance of the drone is checked at a short distance, within the direct line of sight of the pilot-drone). Procedure for range testing:

1. Turn on the control equipment, then the drone.
2. Move back 15 meters and activate the switch associated with the buzzer; You must hear it.
3. If you don’t have a buzzer, turn on the drone and make sure the motors are running.
4. Disable the buzzer/rearm the drone
5. Repeat these steps as you move further and further away (line of sight) until the aircraft responds to your input.
6. This will be the absolute maximum distance you can fly your drone.
7. You might think that you don’t plan to fly it that far, but remember that the drone moves on three axes and things can go wrong.

ESC calibration

ESCs will work out of the box, but the signals (PWM/PWM) associated with minimum and maximum throttle may not match what your transmitter provides. Therefore, you need to “teach” each ESC, the necessary values. Make sure the propellers are not mounted on the motors. Refer to the user manual for your flight controller. Once reprogrammed, the ESC retains its configured configuration even when it is not powered. Therefore, each ESC is only programmed once, during initial testing/setup.

There is usually a section in the flight controller manual that talks about calibrating the ESC and explains how to do it. If not, you can try one of the methods below. Once again, if your propellers haven’t been removed yet, now is the time to do so.

Transmitter

1. Connect one ESC to the “Throttle” pin on your receiver. If your ESC does not have a BEC connected, you can connect one BEC enabled ESC to another pin on the receiver (such as the battery input) just to power the receiver.
2. Connect the ESC to the appropriate motor (if not already connected).
3. Set the stick/joystick associated with “Throttle” to maximum (usually the left stick/joystick and full forward/up) and then turn on the transmitter.
4. Connect the LiPo battery to the power distribution board or directly to this ESC (if the connectors are compatible).
5. The motor should beep three times (11.1V LiPo) followed by a short pause and then two short beeps (corresponding to the maximum beep).
6. Immediately after short beeps, move the Throttle stick / joystick to the lowest position (which corresponds to the minimum signal).
7. The motor should beep three times (11.1V LiPo) followed by a long beep.
8. Throttle range for this ESC is now set, move on to the next one until all ESCs are calibrated.

Other Methods

Follow the instructions in the product’s user manual to match the ESC’s minimum/maximum input range to what it will receive from the transmitter.

1. USB: Some ESC models are programmed via USB, either on their own or with an adapter.
2. Programming board: External ESC programming board, can be used with almost any ESC and is a standalone device.
3. Microcontroller: This way is not widely used, but it is certainly possible to reprogram the ESC with a microcontroller if you have the correct code and can connect properly.
4. Flight controller: Some flight controllers allow you to calibrate or program the ESC through their software interface. Read the instructions for your flight controller to see if this is possible.

Motor and main rotor (propeller). Direction.

You are now ready to install the propellers. Let’s go back to lesson 3, which discusses the direction of the main rotor so that it creates thrust. All propellers have a top and bottom, as well as the direction of rotation “CW” (clockwise) and “CCW” (counterclockwise). At the top of the prop, there is usually text indicating its height and diameter. When the propeller is mounted on the motor shaft, this upper part points to the sky, regardless of whether the motor is mounted on the top of the drone beam or at the bottom of it.

Pilot pre-flight checklist

Although a drone is not as complex or dangerous as a real passenger aircraft, you are still a pilot and must have a pre-flight checklist to make sure that the upcoming flight will not endanger people or property. The list below covers only the essentials and is mandatory before every flight (not just before the first).

1. Make sure you have any of the available visual ways of knowing which side of your drone is in front. At a minimum, add colored tape to the two front beams.
2. Make sure the control equipment battery is charged.
3. Shake the UAV lightly – nothing should loosen, rattle, or fall to the ground. You never know what may have shifted or broken as a result of a hard landing on a previous flight.
4. Make sure the propellers are still securely fastened.
5. Turn on the control gear first, then power on the aircraft (keep your hands off the rotors).
6. Make sure you can arm and disarm the motors without fail (they should spin at low RPM on “Arm” and stop spinning on “Disarm”)
7. Make sure you calibrate or the sensors are well calibrated (you should do this regularly)
8. Perform a transmitter range test.
9. Make sure the flying area is completely clear, and if anyone is within it, let them know, especially curious kids; that you are flying a UAV, and that you should not approach until the drone has landed with a complete stop of the motors.

Testing

Until you have gained sufficient confidence in your abilities as a pilot and drone designer, the following procedure is suggested for all drones prior to their first flight.

1. Turn on the motors and make sure they rotate in the correct directions as described in the flight controller manual.
2. Raise the Throttle stick/joystick very slowly and make sure the propellers are pushing air down towards the ground. Using tissue paper is a safe option for visual inspection.
3. Move the Pitch stick/joystick forward/backward very carefully to make sure the aircraft tilts forward/backward correctly.
4. Very carefully move the roll stick/joystick to each side to make sure the drone responds correctly.

If a drone is not behaving properly, there are many possible causes, the most common being:

• One or more motors are rotating in the wrong direction.
• The flight controller has not been set up correctly and what it thinks is “forward” is different from your actual UAV.
• One or more pins between the receiver and the flight controller are connected incorrectly or even in the wrong place.
• Perhaps everything is set up correctly, just responding too quickly or abruptly to user input.

Contingency plan

Most accidents result in the drone crashing, and most accidents happen when you are just starting out in the field and/or with a new drone. The list below is intended to give you things to think about and some ideas on how, and why, to respond to novice pilots. The decision is made on a case-by-case basis, and in some situations may be contrary to what is suggested here. So, get to know yourself, get to know the environment, and be careful! In almost all cases, it will be better to lose the drone than to risk collision with people or property.

The drone is very far away and you don’t know which direction it is heading.

• Slow down the throttle and see if the drone responds (checks if there is a connection).
• If the drone reacts to gas, try landing right there (if you can).
• If this place is not suitable for landing, carefully try to point the drone forward (nothing drastic), and if the drone reacts by leaning on your position, moving left or right in the sky, will allow you to determine its orientation. If it doesn’t seem to be moving left or right, it may be moving towards or away from you, so undo what you just did and try “snav” to the left.

The aircraft suddenly veered sharply off course (with or without reason).

• If you don’t have piloting skills (to try and recover it), drop the throttle completely and let it fall: in such a case, contemplating drastic action could result in you losing sight of the drone or, worse, the drone starting to climb for falling from a greater distance.

The drone moves quickly towards people.

• Gas to the maximum so that he gains height and flies over them; your drone will probably still be in the correct general orientation, so it’s better to lose the drone than to fly into people.
• After reaching the optimal height, try to regain control, then position it so that it is above the free landing area.

The drone is moving towards you quickly.

• Gas to zero; let him ram the ground, than fly to your head.

The drone does not respond to input from the control equipment.

• In such a case, there is nothing you can do. If your drone is still in the air, your remote control batteries may have run out.

The drone is losing its propeller.

• The loss of a propeller affects both thrust and yaw (Yaw); try correcting the yaw first (you probably need to hold the stick/joystick linked to the Yaw at the end position) and then at the same time carefully move the throttle/joystick up to prevent collision, then throttle down.

The first flight

Regardless of your previous experience in piloting, your first flight, especially with a custom multi-engine UAV, should be as discreet as possible. The purpose of the first flight is to make sure everything is set up correctly; as well as identifying any major problems.

• Location: open area, away from buildings, people and property. For example: an empty football field, a baseball field and so on would be ideal. There shouldn’t be any wind at all.
• Go through the pilot’s pre-flight checklist.
• Stand about 2 meters away from the drone with the front of the drone facing away from you.
• Arm the motors.
• Gently move the Throttle stick/joystick up. Reach the point where the drone is ready to take off. There may be some ground effect that causes the drone to bounce slightly, but don’t worry.
• Add throttle to get the drone off the ground and get used to the controls – try to keep it within a certain radius and see how it reacts to your stick/joystick movements.
• Make small, gradual and smooth movements – nothing too sudden. Lower the throttle stick to prevent a crash.
• If your drone is not behaving as expected (for example, moving the Pitch axis causes it to pitch as well as roll to the left or right), something is wrong and you will need to investigate the causes of the identified problems.
• If the drone behaves as expected, your task is to keep its position stable at a height of 1.2-2 meters from the ground. Don’t get too mad, so fast.

Additional flights

Now that you’ve worked out the glitches and are comfortable flying in a controlled environment, you can begin your second flight.

• Since the drone is still not fully tested, we suggest that you go through a full pre-flight procedure for the first flight, which should not take much time.
• Using fluid motions, get used to how the drone reacts to your stick/joystick movements while keeping it at a safe distance.
• Adaptation to piloting a drone should be carried out without the help of FPV and various sensors.