Arduino Forum

Topics => Robotics => Topic started by: AKenny200 on Oct 21, 2019, 01:48 am

Title: Equip Quadcopter With Servos
Post by: AKenny200 on Oct 21, 2019, 01:48 am
Hello all,

I am a mech eng student, so all of this kind of shenanigans baffles and excites me. I love finding more and more comex problems that can be solved with this equipment.

Which brings me to my current issue. I love drones, and most of all I like to try and make new types of drones. For this one I am only trying to prove a proof of concept before I can take it any further.

So, I need to control 4 servos that turn 90 degrees. That is all. However, I need this to be done via RC.

I have researched and researched as many hobby approaches as I can before I have to greul through research papers on the matter and this has brought me here. I have discovered people utilising micro arduino boards to control at least two servos using the same receiver as a flight controller. But I have only seen as many as two.

As I say, I need four servos to turn 90 degrees. Hopefully controlled by the same RC controller used to fly the drone on one of the unused channels (preferably the adjustable switches).

I have a turnigy tgy IA6B receiver on hand, I'm not sure if that is any use.

I apologise for my lack of knowledge, I'm sorry if I'm asking too much and I understand. But I thought I would ask here before I have to go harass some technicians!

Thank you very much,
Kenny
Title: Re: Equip Quadcopter With Servos
Post by: slipstick on Oct 21, 2019, 10:10 am
You talk about 4 servos and one unused channel. Does that mean that you want all 4 servos to move at once i.e. no individual control of the servos? If that's all you need just make up a lead and plug all four into your receiver channel. No need for an Arduino or anything complicated.

If it is more complex than that then perhaps you can explain in a bit more detail exactly what control you need. An Arduino can easily control a lot more than 4 servos so it's mainly a matter of being clear about what the input(s) to it are and what exactly is supposed to happen for the various inputs.

Steve
Title: Re: Equip Quadcopter With Servos
Post by: MartinL on Oct 21, 2019, 04:09 pm
Hi AKenny200,

Servos are normally used for pitch/yaw control on bicopters and yaw control on tricopters:

(https://static.rcgroups.net/forums/attachments/6/0/1/5/8/7/a9029235-160-Tricotper2Servo.JPG)
Title: Re: Equip Quadcopter With Servos
Post by: AKenny200 on Oct 22, 2019, 12:33 am
You talk about 4 servos and one unused channel. Does that mean that you want all 4 servos to move at once i.e. no individual control of the servos? If that's all you need just make up a lead and plug all four into your receiver channel. No need for an Arduino or anything complicated.

If it is more complex than that then perhaps you can explain in a bit more detail exactly what control you need. An Arduino can easily control a lot more than 4 servos so it's mainly a matter of being clear about what the input(s) to it are and what exactly is supposed to happen for the various inputs.

Steve
Hello!

So, the plan is for the servos to work in pairs. Two turning 90degrees while the other two work mirrored. I'm not sure if it's as simple as swapping the positive and negative leads to achieve this.

I have a far far more complicated future plan for the servos, but I am far far too beginner to mess with anything beyond 'turn these servos 90 degrees gradually while I retain control of the four motors so I can increase and decrease thrust while the onboard gyro freaks out.

As I say, it's literally to prove a concept. I'm worried about adding too many servo motors that I can no longer control with one receiver.

Thank you to the person mentioning tri rotors, but I find many flight controllers now come pre prepared to build those craft, but it seems like you can add UP TO three servos, I really need four haha

I'm sorry if this isn't becoming any clearer, I'm trying not to give too much away right now haha

I might just have to speak to someone in real life, I feel like I'm not explaining myself well here!
Title: Re: Equip Quadcopter With Servos
Post by: MartinL on Oct 22, 2019, 09:15 am
It's possible to get an Arduino to drive any number of motor or servos, provided the microcontroller in question has enough PWM channels and enough power is provided to the servos to drive them.

You'll require 8 PWM output channels in total. 4 channels at 490Hz PWM for the motor ESCs and another 4 channels at 50Hz for the servos, (or perhaps a higher frequency in the case of digital servos). Arduino boards capable of driving this number of channels include the AVR based Arduino Mega or any of the ARM based microcontrollers.

How the servos are controlled during flight really depends entirely on your code and the number of transmitter channels you require to control them.

For example, in the case of the tricopter the servo controls the aircraft's yaw motion through the flight controller's motor mixer. The servo itself is driven by a PID control loop that causes it to not only respond to the pilot yaw stick input, but also to react to oppose any unwanted yaw rotation detected by the gyroscope.
Title: Re: Equip Quadcopter With Servos
Post by: slipstick on Oct 22, 2019, 10:41 am
Even though t's not at all clear what exactly you're trying to do, if it involves reading one RC channel and doing something with 4 servos as a result of what you read then any Arduino will be able to manage it with no real problems.

BTW swapping positive and negative is a quick way of killing a servo so forget about that!

Steve
Title: Re: Equip Quadcopter With Servos
Post by: AKenny200 on Oct 23, 2019, 12:03 am
Even though t's not at all clear what exactly you're trying to do, if it involves reading one RC channel and doing something with 4 servos as a result of what you read then any Arduino will be able to manage it with no real problems.

BTW swapping positive and negative is a quick way of killing a servo so forget about that!

Steve
Thank you from saving me from a massive error!

https://imgur.com/a/jU8gQTw

That is a quick sketch of what I'm trying to do, I hope that makes it a bit clearer! (I promise I am not 12 hahaha)

The 4 motors will act alone from the servos in this version because I just don't know enough alone to do anything beyond my mechanical analysis and some basic control! (And obviously the standard quadrotor shenanigans).


MartinL, thank you that is amazing! Im not needing to do anything as complicated as tying the control to the gyro (Yet) but you have gave me a strong idea!