Acceleration / deceleration

13 years 3 months ago #18027638 by bgreat
Acceleration / deceleration was created by bgreat
Hello,

I am using an AX3500 in position mode via RS-232 and using an optical encoder for feedback. Controller software rev 1.7b and Encoder 1.7.

Reading the manual, it seems that I should be able to set the motor acceleration by setting the Acceleration register. I have tried from maximum to minimum and I see no change in acceleration or deceleration when running in position mode. I have been able to limit acceleration by setting the proportional gain, but this a kludge and does not help with deceleration.

Does the acceleration value not work in position mode? If not, is there a firmware update that will allow me to control acceleration/deceleration in position mode?

Also, is there a firmware update that allows control of maximum speed when in position mode? When doing multiaxis control, it is very difficult (impossible?) to do accurate trajectories with out having support for acceleration/speed/deceleration profiles. Is this available in a firmware update?

Thank you,
Bill


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13 years 3 months ago #18039274 by jweber
Replied by jweber on topic Re:Acceleration / deceleration

It is very hard to do multiaxis control with a PID. PID's are more useful for simple pick and place robots where the trajectory variables never change. In my post about true position/speed control, I kind of described how a position profile along with accel and decel points would be calculated for each axis. I believe roborun is more of a simple debugging tool and exercise the motors program. However, I would like to see it evolve into a more complex program featuring real time multiaxis control of a complete robotic manipulator, because I would be greatly interested in that for control of my bot too. I do realize that this probably will be border line on commercial manipulator software costing thousands of dollars so I'm not expecting anything soon. But maybe cosma has something in the works that we don't know about. yes?

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13 years 3 months ago #18039720 by jweber
Replied by jweber on topic Re:Acceleration / deceleration
I did find something of interest at <A href=" www.trossenrobotics.com/store/c/2738-Rob...opment-Software.aspx " target=_blank> www.trossenrobotics.com/store/c/2738-Rob...opment-Software.aspx called the Trossen Robotics system. The overview of the system sounds promising for control of a complete robot but there hasn't been any update in months... This could work for the software but then you need to connect the controllers to the main computer. I would need one roboteq for my drive system and three for the manipulator working together all at once and right now that doesn't seem possible.

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13 years 3 months ago #18043335 by cosma
Replied by cosma on topic Re:Acceleration / deceleration
The acceleration parametter controls the rate at which the command value goes from its existing position to the desired one. It does not control the acceleration and decceleration when going from point a to point b.

Adding "S-curve" or trapezoidal acceleration is something that we have contemplated but doing it right requires more processing power than is currently available on the MCU we use.

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13 years 3 months ago #18055146 by jweber
Replied by jweber on topic Re:Acceleration / deceleration

Why can't a main board like a mini-itx do the calculations and processes then tell the ESC's what to do?

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