Deceleration function

[Vanisp]

Dear Sir,

We have to design a small mobile antenna control system using NI-7352 motion card in LabVIEW 8.5.

1. We would like to use the deceleration function for smooth stop. But we would like to decelerate at a faster rate. Inspite of loading high deceleration values, we could not see much of difference in the deceleration. The time taken to decelerate from the max. velocity to zero by plotting a velocity vs time graph. 

Kindly let me know if further details are required.

Regards.

[Jochen]

Hello,

could you please describe your system a bit more in detail? Here are some specific questions:

• What type of motor and drive are you using?
• When decelerating the drive has to provide a way to get rid of the energy generated by the motor (if it's a DC motor). Does your drive provide full 4Q (4 quadrant) capabilities?
• Does your motor provide enough power to decelerate the mechanical system fast enough or is it possible that the inertia is too high?
• Could you please provide a piece of code to demonstrate the issue?
• What deceleration values have you used?

Thanks,

Jochen Klier

National Instruments

[Vanisp]

Dear Mr.Jochen,

I am very sorry for the delayed response.

We are using AC drive and AC Linear motor for our application. It is a three axes based linear motion application (length 1metre each). The feedback is a Linear encoder (4000 count per 100 mm). 

The Velocity of the motion is 2 metre/s.

We have set the control loop gains to Kp = 16, Kd = 44, Ki = 2, Il = 5 and Td = 2. The rise time is 66 ms and settling time is 0.2 s with step length = 2000 and sample = 500. The motion seems to be smooth with these parameters but we do not know how far this is a critically damped system.

We have enabled and set the software limits, But unfortunately the the axis stops after say a 1000 counts after the set counts.

Kindly help us out

[Jochen]

With the information that you have provided, it's still hard to analyze what's going on. The behavior you see with software limit is expected, as the axes don't stop immediately if a software limit is hit, but they decelerate with the configured deceleration value. Typically this is intended behavior, as an immediate halt stop means high forces, that could be hazardeous to the mechanical system.

Does the initial problem still exist? Please answer the other questions from my initial post. Does the problem also occurr with a standard example? Please post some code.

Thanks,

Jochen

Message Edited by Jochen on 10-30-2009 04:44 PM