Understanding Radio control (Remote control by location)

Thread Starter

camerart

Joined Feb 25, 2013
2,107
Hi,
I would like to know how a radio control Transmitter changes the model controls of the receiver.
e,g, Move a joystick one way and motor speeds up on the model.

EDIT: I've edited the title, as this may be a unique way to control models?
Cheers, Camerart
 
Last edited:

MrChips

Joined Oct 2, 2009
21,868
There are different schemes with different levels of sophistication:

1) Single channel ON/OFF control
2) Multi-channel proportional control
3) Digital

1) My first R/C plane I built as a teenager used single channel 27MHz ON/OFF carrier. The only thing you could do is steer left or right using a mechanism called an escapement. This method of control is common in inexpensive R/C cars and boats that can go forward/reverse, left/straight/right.

2) The most common yet simple R/C control is PWM carrier to control an analog servo motor. A typical servo motor receives pulses every 20ms. The pulse width is controlled by the joystick and can range from 1ms to 2ms with 1.5ms being the center or neutral position. The servo motor position is monitored by a potentiometer and uses a feedback loop to match the incoming PWM command.

3) Digital commands are used at the highest level of sophistication. With a digital command you can use the digital information for any purpose. My 6-axis robot arm uses digital commands. Joystick positions are transmitted digitally to the receiver. The receiver uses that information for whatever purpose is required.
 

trebla

Joined Jun 29, 2019
209
Different manufacturers use different standards for encoding RF signals and the proportional control information as well. But receiver channels outputs give usually a standard (50Hz) or high-speed (100-200 Hz) servo control signal, depending from TX-RX equipments channel settings.
 

Thread Starter

camerart

Joined Feb 25, 2013
2,107
Hi Mr C and T,
My question is a bit ambiguous, as it's difficult to explain exactly I want.

In another thread, I (along with much help from other members) have designed and built a Transmitter/Receiver pair

The pair are designed to SEND and RECEIVE the location that the model (REMOTE) should move to, at the moment each PCB is READing DATA from GPS, Joysticks, Compass, Altimeter etc and now I need to know how to convert raw transmitter DATA so that the RECEIVER can convert it to PWM for the motors/servo control, so mixing etc.

Here is the thread of the TX RX pair: https://forum.allaboutcircuits.com/threads/remote-control-by-location-pic-in-oshonsoft.148795/

C.
 

jpanhalt

Joined Jan 18, 2008
10,233
Hi Mr C and T,
... now I need to know how to convert raw transmitter DATA so that the RECEIVER can convert it to PWM for the motors/servo control, so mixing etc.
Since your projects began, drone technology has been developed that does that and more. Some are almost autonomous. Several years ago, Intel did a nighttime, choreographed demonstration of a bunch of drones moving to music.

Here's a link to a more recent show:

They are currently at about 500 drones simultaneously.

You need to program the flight characteristics of your drones. A drone simulator program does that. Are there any open-source flight simulators for drones?
 

Thread Starter

camerart

Joined Feb 25, 2013
2,107
Since your projects began, drone technology has been developed that does that and more. Some are almost autonomous. Several years ago, Intel did a nighttime, choreographed demonstration of a bunch of drones moving to music.

Here's a link to a more recent show:

They are currently at about 500 drones simultaneously.

You need to program the flight characteristics of your drones. A drone simulator program does that. Are there any open-source flight simulators for drones?
Hi J2,
I have seen the deveolopments of drone technology, since I started this project, and had a go on some of them, which are pretty amazing.

When I thought of this system, I added an incremental encoder, in order to dial the direction of the REMOTE (Tricopter Drone). I did this because my eyes are at the stage where sometimes I can't tell which direction the REMOTE is aiming, so quite often I had to crash it down, so it wouldn't stray into no go areas. I haven't seen a direction dial on any of the modern drones.

I'm here now, so onwards and upwards,
thanks.
C.
 

Thread Starter

camerart

Joined Feb 25, 2013
2,107
So, what is the question?
Hi Mr C, (Apologies for the capitals, I need them to help me read)

Bear in mind that this is new to me, so I'm making it up as I go along, and will correct it as I go forward!

The transmitter is at BASE and the REMOTE starts at BASE, so the locations/altitude are the same. The location is LAT LONG from each GPS. The Altitude is READ from each barometer chip. The direction is aimed using the TX DIAL (In degrees), so away from BASE.

1/ALTITUDE: Both ALTs are the same, so when the THROTTLE is pushed forward the CALCULATION should add height in MTRs to the RECEIVER ALT READing, all motors will lift the REMOTE to that height. 'Say' 1MTR, then the REMOTE will stay at 1MTR.

2/DIRECTION: No RUDDER joystick! Set the TX DIAL to the required REMOTE direction. The REMOTE is at 1MTR and the (RUDDER) SERVO will move in order to rotate the REMOTE to the degree of the DIAL.

3/ The LOCATION! I'll leave the location for now, as it is a bit difficult for me to figure out yet.

I hope this gives some idea of what's supposed to happen.
C.
 

MrChips

Joined Oct 2, 2009
21,868
We still do not understand the question.
The TX sends a position value.
The RX moves the motor to the requested position.

Edit: cross posted.
 

andrewmm

Joined Feb 25, 2011
574
As technology moves on, its difficult.
what I did 5 years ago, i woudl now not modify , but re start , smaller, faster, cheaper , better.

For instance, an IMU is you rfirend here. many arduino drone systems,

e.g.

https://www.mydronelab.com/blog/arduino-quadcopter.html
https://www.instructables.com/id/Arduino-Drone-With-GPS/
https://www.hobbyrc.co.uk/flight-controllers-2?orderby=11
https://www.sparkfun.com/pages/accel_gyro_guide

Some, you put in the coordinates you want to go to, and it goes,
some with "return to base" option,
some set up for racing through hoops,
 

Thread Starter

camerart

Joined Feb 25, 2013
2,107
As technology moves on, its difficult.
what I did 5 years ago, i woudl now not modify , but re start , smaller, faster, cheaper , better.

For instance, an IMU is you rfirend here. many arduino drone systems,

e.g.

https://www.mydronelab.com/blog/arduino-quadcopter.html
https://www.instructables.com/id/Arduino-Drone-With-GPS/
https://www.hobbyrc.co.uk/flight-controllers-2?orderby=11
https://www.sparkfun.com/pages/accel_gyro_guide

Some, you put in the coordinates you want to go to, and it goes,
some with "return to base" option,
some set up for racing through hoops,
Hi A,
I am not modifying, but moving forward (slowly)

If I had the skill to do what you say, perhaps I would agree and start again. Unforunately partly because I can only talk BASIC, and not Arduino, also a lot of other peoples time and a lot of effort has gone into the present sytem, and I would be letting them down to even think about it.

I have Ardupilot which does much of what you say, like enter co-ordinates, but not what I want, so I've never used it. With the Arduino system, lumps of CODE are added into systems, like Lego, but I don't suppose the users know what's going on, and maybe they don't need to know, but more or less, I know every bit of my system, and it is interesting.

This system will have 'Return to BASE' and could be set to race through hoops, if that's what's wanted.
Thanks, for your interest.
C.
 

Thread Starter

camerart

Joined Feb 25, 2013
2,107
FWIW, "Mastering Electronics" by John Watson has a "final project" of a radio control system. Even includes PCB layout.
Hi U,
A appreciate your suggestion, but it isn't really answering my question. If you look at my post #4 and follow the link, you will see that the PCBs are made and programmed apart from the control, which is what I would like advice about.
C
 
Last edited:

trebla

Joined Jun 29, 2019
209
As i understood your question right, you want to know how to make your vehicle move to desired destination? If your transmitter is sending position data, then your receiver must calculate difference values from current position to destination position. If it needs to move left then receiver must send servo pulses less than 1.5ms (case of reversed channels more than 1.5ms) to roll channel input of control unit. If your vehicle is on the spot to receiver must send 1.5ms pulses (servo neutral) to control unit inputs. Maybe you want add some PID algorithm to avoid control overshoots which can force helicopters to "chickendance" behavior.
 

Thread Starter

camerart

Joined Feb 25, 2013
2,107
As i understood your question right, you want to know how to make your vehicle move to desired destination? If your transmitter is sending position data, then your receiver must calculate difference values from current position to destination position. If it needs to move left then receiver must send servo pulses less than 1.5ms (case of reversed channels more than 1.5ms) to roll channel input of control unit. If your vehicle is on the spot to receiver must send 1.5ms pulses (servo neutral) to control unit inputs. Maybe you want add some PID algorithm to avoid control overshoots which can force helicopters to "chickendance" behavior.
Hi T,
I think you are correct, apart from the only PWM is on the REMOTE, when controlling the motors/servo, so no transmitting pulses, only DATA.
If you look at the outlines in #10.
Here is an example: The TRANSMITTER and RECEIVER ALT meters output pascals, which can be converted to mtrs, which are set to zero at BASE. When the THROTTLE joystick is moved forward, then some height is added to the TRANSMITTER ALT, 'say' 1 (MTR), which is transmitted to the REMOTE, then the REMOTE compares its BASE ALT=zero +1 to REMOTE ALT=0 and speeds up the motors and lifts the REMOTE, till the REMOTE ALT = the new BASE ALT.

The outputs of all of the calculations will be in PWM, and be fed into a control board which will compensate for PID 'chickendancing' It's possible, at a later date that this could be programmed on the PCB, but for now, I think this is easier.
C.
 
Last edited:

trebla

Joined Jun 29, 2019
209
For altitude control, there is no "servo neutral" for holding the altitude. The higher is the altitude to hold, the longer control pulse must be sent (more power to the motors). These values must be determined experimentally depending on the weight and the motors/props.
Also, GPS is not very precise for holding your vehicle in one spot, you may want to use some inertial sensors to compensate light drifting.
 

Thread Starter

camerart

Joined Feb 25, 2013
2,107
For altitude control, there is no "servo neutral" for holding the altitude. The higher is the altitude to hold, the longer control pulse must be sent (more power to the motors). These values must be determined experimentally depending on the weight and the motors/props.
Also, GPS is not very precise for holding your vehicle in one spot, you may want to use some inertial sensors to compensate light drifting.
Hi T,
The DATA that goes between TRANSMITTER and REMOTE is all in numbers. If we stick to the ALT example for instance:

Both TRANSMITTER and REMOTE have ALT peripherals, READing pressure and converting it to MTRS, on the ground both are set to zero.

The TRANSMITTER sends e,g, a 1 (MTR), the REMOTE receives the 1 and compares it to it's ALT READing zero, and sends PWM to the motors, which lift the REMOTE. The REMOTE zero starts incrementing from it's ALT peripheral READing, until it also READs 1, then it sets the motor PWMs to 'neutral' as long as the received DATA matches it's ALT READing.
C.
 

trebla

Joined Jun 29, 2019
209
If your multicopter control works that way but usually setting servo signal to neutral in throttle channel does not cause altitude hold, copter will ascend or descend depending of current altitude.

On yaw, nick and roll channels servo neutral means steady behavior, increasing difference between servo neutral pulse converts to movement speed through nick and roll angles and may result flip upside down if difference from neutral is applied too fast and on extreme amount. On yaw channel the last is not an issue.
 
Top