2 DOF Full 360 Flight sim cockpit using arduino mega , quadrature Encoder & AC 3 phase Motors

Thread Starter

hossamzayed

Joined Sep 6, 2015
17
I'm building a 2 DOF Full 360 Flight sim cockpit using arduino mega as my controller.
Kindly check this link if you want to know more about my project
http://forums.x-plane.org/index.php?showtopic=88536&hl=

My questions is:
In order to control (AC 1.5 kw 1400 rpm Induction Motor) direction and on/off state (no speed control required) in a rapidly changing manner (in terms of may be 4 times switching per second .... or may be more I can't tell) what is my best option:
1- Variable Frequency Driver
2- Mechanical Relay
3- Solid State Relay
4- Another option I don't know

Note: I'm still learning AC power basics so I would need a detailed explanation or references to read on the matter
Thanks and waiting for your kind feedback
 

Alec_t

Joined Sep 17, 2013
11,858
to control (AC 1.5 kw 1400 rpm Induction Motor) direction and on/off state (no speed control required) in a rapidly changing manner (in terms of may be 4 times switching per second
Trying to reverse a motor of that rating 4 times per sec is asking rather a lot of it! :eek:
 

MaxHeadRoom

Joined Jul 18, 2013
22,308
Sounds like a job for a servo with a planetary gearbox, ratio dependant on rate of travel.
Torque increases at the rate of reduction, and motor to load inertia ratio reduces by the square of the reduction.
Max.
 

kubeek

Joined Sep 20, 2005
5,742
Trying to reverse a motor of that rating 4 times per sec is asking rather a lot of it! :eek:
Well, the motor might survive, but I doubt the VFD would cooperate. The motor will be running at near stall current basically the whole time, so the cooling of the motor and current rating of the VFD needs to be sized accordingly. Also, how many revolutions, or fractions of one do you expect it to make in those 250ms?

Don´t these setups usually use hydraulics?
 

Thread Starter

hossamzayed

Joined Sep 6, 2015
17
Sounds like a job for a servo with a planetary gearbox, ratio dependant on rate of travel.
Torque increases at the rate of reduction, and motor to load inertia ratio reduces by the square of the reduction.
Max.
if there is a servo that can move around a 0.5 ton weight and turn it in sudden reverse direction I would appreciate to know where to purchase it
 

Thread Starter

hossamzayed

Joined Sep 6, 2015
17
washing machines always stop before reversing, there wouldn't be time to do that if the reversing happens 4 times/sec.
you're right I guess, and as I said I'm new to AC motors still studying it. I just guessed that washing machines as an application is the closest thing to what I'm trying to achieve.
 

Thread Starter

hossamzayed

Joined Sep 6, 2015
17
Don´t these setups usually use hydraulics?
concerning hydraulics , I have no experience with them. but i saw a lot of simulation rigs using hydrolics , but I have not seen any of them offer the full 360 rotation. which is my intention basically
 

kubeek

Joined Sep 20, 2005
5,742
You can get hydraulic rotating actuators, they are quite expensive, but should be able to do what you want.

As for the reality of what you actually want, imagine you being in the seat and being subjected to such change of direction four times a second, even just for an eight of a turn back and forth. Not only I don´t think any airplane is capable of that unless it had disintegrated and is falling from the sky, but I think your body wouldn´t be happy either. Maybe a more realistic set of requirements will get you better results that can actually be realised in this world without hundreds of thousands of dollars budget. And without killing someone in the process.

edit: ah, typing too slow
 

MaxHeadRoom

Joined Jul 18, 2013
22,308
if there is a servo that can move around a 0.5 ton weight and turn it in sudden reverse direction I would appreciate to know where to purchase it
The Galil link uses servo motors, to move that weight it is almost imperative that a smaller motor be used with very high gearing, see my ref to torque and motor to load inertia ratio, also large CNC machines have used servo's to move that kind of load with no problem, either ballscrews or a reduction of some kind is used.
There are very large servo's available, besides I do not see a direct drive induction motor reversing a 0.5 ton weight in a rapid motion.
There are electronic controlled hydraulic servo valves but very expensive.
Back in the 80's Bosch made a hydraulically controlled CNC machine using these.
Max.
 

Thread Starter

hossamzayed

Joined Sep 6, 2015
17

This is a link to a project on youtube , and probably he is trying to make the same project hence he was using the flight simulator program to drive the motors direction. I tried contacting him but he is not replying . Anyway I'm in a learning process and I will be buying that VFD and AC motor anyway as they are within my budget. The problem is I have very little knowledge of AC motors and how they would react to such control signals. and as Kubeek said " The motor will be running at near stall current basically the whole time, so the cooling of the motor and current rating of the VFD needs to be sized accordingly " that's what exactly the DC motors were doing, and I had to do a lot of code tweeking to allow for longer periods between check and correct angle signals so as not to burn out the motors(which happened to 1 of the DC motors).

If any one can check my project link at X-plane forum and guide me regarding the required frequency of switching of and on demonstrated in the video link I provided , as I don't know how to calculate it , I would really appreciate it.
 

kubeek

Joined Sep 20, 2005
5,742
That motor is geared, which completely changes the game. Also it is not moving any load, and is reversing less than once a second with gentle stops. See the difference to what you originally proposed?

So let me reiterate, you need to define the basics before you get further into this. What is the moment of inertia of the seat arrangement, at least roughly? What is the peak angular velocity, and how much time is there from start to peak to stop, or in other words the maximum acceleration?
With such details you can calculate what power you need to have to accelerate the setup and then stop it. The gearing doesn't change the power required, it just makes it easier for the motor to achieve it.

My physics is a bit rusty, but calculating these things shouldn't be really hard once you have the nmbers that go into this.
 

Thread Starter

hossamzayed

Joined Sep 6, 2015
17
There are rotary pneumatic actuators available but I know nothing of their capabilities.
Many thanks for the info, these were really new to me . I'm checking those out now. I hope they could provide a good solution but I have no idea yet if they are available in my country or how much they would cost
 

Thread Starter

hossamzayed

Joined Sep 6, 2015
17
That motor is geared, which completely changes the game. Also it is not moving any load, and is reversing less than once a second with gentle stops. See the difference to what you originally proposed?

So let me reiterate, you need to define the basics before you get further into this. What is the moment of inertia of the seat arrangement, at least roughly? What is the peak angular velocity, and how much time is there from start to peak to stop, or in other words the maximum acceleration?
With such details you can calculate what power you need to have to accelerate the setup and then stop it. The gearing doesn't change the power required, it just makes it easier for the motor to achieve it.

My physics is a bit rusty, but calculating these things shouldn't be really hard once you have the numbers that go into this.
well concerning those calculations , I had a friend help me out with it a few weeks ago and he cam up with these values
AC 1.5 kw 1400 rpm Induction Motor is required for such application.
A reduction gear ratio 1:20 is required for a 1400 rpm motor to give a 70 rpm shaft
(I'm basically an architectural engineer so I turn to friends in other fields in such aspects as for electronics I've been studying it as a hobby for 1 year now)
I'll try check with him again and get the other values you mentioned
 
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