Speed control ROV motors


#1

Hi,
Whi in backward the engine power of the motors is reduced by half? so it is very difficult to
travel back.
Whi in curve a motor pushes forward at 100% power and the other
back at only 50%? So it makes a curve but can not turn the rov on its own axis.
The rotation axis is fundamental to take the pictures and turn around in a small
space.
In which way can change the engine power (not the fine calibration
on the web page), making it equal? The same for up and down power … (but less important).
And …
The right joystick of the gamepad is now used only for lifting and lowering. The command left-right of this joystick can be used just for the rotation axis (a motor 100% forward and the other backward the motor 100%). Whi not?
Steve


#2

No answer?
I am the only one interested in this engine management?


#3

Props are pitched to be efficient in one direction and rotation. So depending on the pitch and rotation of your props you will get varying degrees of speed in forward or reverse. It is an engineering trade off. Since you tend to go in forward more than reverse the props are pitched that direction,


#4

One of the things we’re currently working on implementing and starting to test this week and next is an improved/expanded set of PID controllers and control interfaces, which will allow the user to do things like command in-place rotations and lateral movements to achieve a specific pose. This has been something of a challenge, due to problems with our previous IMU, but the new IMU will allow us to continue working on these features. I’m going to try and knock out these controls with a PID controller first, so let’s see where that goes over the next few days.


#5

Hi Charles

Frist off Hooray Go for it :thumbsup:

My 2cents although a full PID implementation would be great, in the ocean no real perturbations happen fast enough to really require a derivative response and that a PI implementation would be fine (and most likely far more stable)


#6

Oh yea, I’m just in the habit of saying/writing the D in there. Water is definitely a good D term!


#7

Yep force of habit. Pid controller is a generic descriptive for the paradigm on vehicle control methodology. Just did a half decent altitude hold with just a P term on ultrasonic measures lol


#8

surely it is so but I’m not talking about the performance due to the design of the props, but the choice to keep the lower the rotation speed of the motors in reverse


#9

I think it would be correct to replace free of charge or for a very low price in the old IMU who has just recently purchased!


#10

The control of the rotation on the axis is very useful and important!
I suggest you maintain command of the curve right and left as they are, but to add the rotation using the right joystick of the gamepad.
the rotation would use a motor 100% forward and one back 100%


#12

Hi,
i can probe to modify the code???
Axis rotation for my application is important
Thanks


#13

Steve,

As captainrwooten mentioned above, the props are less efficient in reverse than they are in the forward direction. To compensate for this the software includes motor_modifiers which by default drive the motors twice as fast in reverse, this is applied to all three motors independantly (i.e. the opposite of the behaviour you described in your original post).

If you want to try and adjust this the motor modifiers are contained in:
/opt/openrov/cockpit/src/lib/config.js

for example:
‘thrust_modifier_port’ : 1
and
’thrust_modifier_nport’ : 2

sets the port thruster to get scaled up by a factor of one in the forward direction and a factor of two in the reverse direction.