Author Topic: SRVO-46 OVC Alarm at low speeds  (Read 573 times)

Offline aishpd

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SRVO-46 OVC Alarm at low speeds
« on: April 11, 2013, 04:15:36 AM »
@All:

We have a Fanuc R-30iA controller that we use with a M-900iA 350 manipulator (<6 months old). The problem is that OVC is generated only when the robot is run at low speed and at only one point in its path. There is no problem when the robot runs during production i.e., 100%.

The OVC alarm is generated in the 5th axis (only) and at only 1 point in the cycle where the current in the J5 axis (-21.8 A) is almost close to the minimum current limit (-21.9 A). Physically, the manipulator is carrying downwards a payload of almost 285 Kg (145 Kg Hand + 140 Kg Underbody) and J5 is at an angle of ~-100° (I hope you can visualize the robot position). When I bring down the speed to 30-40%, the current at that point shoots up to almost 25 A and the OVC is issued. I find this very strange.

If it was any other robot, I would have done the payload estimation for the robot with Hand + Body (currently payload estimation of Hand + Underbody is present. I think it was determined from OLP itself) again. But here it is not possible because (A) the underbody is huge and (B) the robot just carries the underbody down from point a to point b and does not grip/clamp it in any way.

What could be the reason and any ideas how I can resolve the issue?

 :help:

Thank you!

Offline RoBoWi

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Re: SRVO-46 OVC Alarm at low speeds
« Reply #1 on: April 11, 2013, 04:53:41 PM »
Measure if you have the correct input voltage at the breaker and from the E-stop to the amp. If voltage is to low, possible you get OVC.
Also measure ohm of motor and cables with ground.

Offline rpg2007

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Re: SRVO-46 OVC Alarm at low speeds
« Reply #2 on: April 12, 2013, 09:11:17 PM »
You can change the amperage that trips this. Go to menu_status_ then go the axis. Find the max amperage rating for the axis and turn it up. You can do each joint individually. While it is running put it about 3amps higher than the may value it reaches. It probably happens when you slow it down because of the deceleration and path times are different. Give this a shot and it should fix your problems.

Offline RoBoWi

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Re: SRVO-46 OVC Alarm at low speeds
« Reply #3 on: April 13, 2013, 02:21:09 PM »
You can change the amperage that trips this. Go to menu_status_ then go the axis. Find the max amperage rating for the axis and turn it up. You can do each joint individually. While it is running put it about 3amps higher than the may value it reaches. It probably happens when you slow it down because of the deceleration and path times are different. Give this a shot and it should fix your problems.

Isn't this the disturbance torque that you are talking about?
If no, were do you set the max amperage?


Offline rpg2007

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Re: SRVO-46 OVC Alarm at low speeds
« Reply #4 on: April 13, 2013, 05:46:16 PM »
RoboWi,

You are correct. But it measures the disturbance torque in amperage. This also changes with the payload settings. So it is very important to get everything like you want it before you make the change to ensure that the collision guard works properly for the application.

Offline RoBoWi

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Re: SRVO-46 OVC Alarm at low speeds
« Reply #5 on: April 15, 2013, 12:31:54 AM »
I think OVC is set in the servo parameters and had nothing to do with payload or disturbance.
Disturbance (and payload) is used for collision detection, not OVC settings.