Estilita
Registered: 12/01/08
Posts: 4
|
|
| |
Reply with quote | #1 |
Hi,
I'm using the AX2850 controller in a robot and I've set the PID parameters to the maximum values. The robot has the desired behavior when its moving, but with null velocities its easy to push it if the movement is slow, it also moves if its in a ramp.
Is this a know problem? It seems like the controller can not maintain the velocities in zero if I push the robot slowly.
Thanks |
| Loading... | | |
cosma
Moderator
Registered: 04/10/04
Posts: 533
|
|
| |
Reply with quote | #2 |
It is practically impossible to lock the motors in position if you operate in closed loop speed mode.
If in a slope, the motor will act like a brake when stopped but not a very strong brake. As it starts moving, it will report a speed that is different than 0 and it will try to correct but this will not prevent it from moving in the first place.
THe most common around this is a mechanical brake on the motors. The controller can be cofigured to ouput a brake release signal as soon as there is power going out to any motor. Brake then applied as soon as both motors are stopped.
|
| Loading... | | |
Estilita
Registered: 12/01/08
Posts: 4
|
|
| |
Reply with quote | #3 |
Thanks for the answer.
But is it a software limitation or is to prevent the motors from serious vibrations?
The thing is that the robot if in a slope will never stop moving, it won't accelerate that's for sure but maintains the slow velocity it has.
Actually I have a mechanical brake but it only actuates with a approx. 30V, I'll see if I can use that brake release output.
Thanks |
| Loading... | | |
cosma
Moderator
Registered: 04/10/04
Posts: 533
|
|
| |
Reply with quote | #4 |
It is a limitation of operating in closed loop speed mode.
When the motor is stopped, it will rotate if outside force is applied. The close loop will try to adjust so that it stops as soon as speed is detected, but this will not prevent it from turning again.
|
| Loading... | | |
Estilita
Registered: 12/01/08
Posts: 4
|
|
| |
Reply with quote | #5 |
Hm ok.
Is it possible to send higher PID values than the maximum of the Robrun? |
| Loading... | | |
cosma
Moderator
Registered: 04/10/04
Posts: 533
|
|
| |
Reply with quote | #6 |
It is not possible and would probably not be the answer.
If you want total stop even in a slope and dont want to use a mechanical brake, then you would want to have the controller set in position mode when stopped.
However, switching from speed mode to position mode on the fly is not possible on this product. Future controllers in our roadmap will allow this.
|
| Loading... | | |
Estilita
Registered: 12/01/08
Posts: 4
|
|
| |
Reply with quote | #7 |
Ok, I guess I'll use the mechanical brake than.
Thanks for the answers
|
| Loading... | | |
