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Galil / Re: Kitamura T-12 with Galil DMC-1840 and Contec I/O Setup
« on: July 14, 2013, 04:02:24 PM »
I completely agree with Mike. If the motor is running away with SH, then you probably have an encoder problem.
The motor encoders can be logically reversed with the Galil MT command. Read up on that one. Also, the Galil can be setup to keep runaways from causing problems. See the OE (OFF on error) command.
As to the OFx needing to be adjusted every time, that is going to be an servo drive amplifier issue. The Galil will apply the same voltage offset every time. Could there possibly be some change in resistance on that circuit? The Fanuc drives you have may operate on a PWM control input. So I guess that third party device converts analog voltage signals to frequencies that the drive understands. If this is the case, then you may have an offset issue in the V to PWM device. You must check this and make sure that the frequency output is stable with regards to voltage applied. Also, devices like this may float if there is no input, which may explain your drift.
But this is a hard problems to solve on any servo system. The main way people handle it is to remove power from the servo amp when there is no command voltage. This is why the SH and MO Galil commands operate the AMPENx signal. I would strongly suggest working this into your control circuit. You can leave the Opto22 relay intact. Just wire the AMPENx into the circuit in series so that both the Opto22 relay and SH need to be active to enable the servo drive.
Torque and Velocity refer to the mode by which the servo drive operates, not by how it is controlled. The Galil cares not whether the drive is torque or velocity. Only the Galil PID values may change between the two modes. Tuning is accomplish the same way regardless. You are simply looking for a command response that fits your needs. If you have a servo drive that will do either torque or velocity, one may work better than the other for any particular application. But if you only have velocity control... then that is what you are going to use.
Steve
The motor encoders can be logically reversed with the Galil MT command. Read up on that one. Also, the Galil can be setup to keep runaways from causing problems. See the OE (OFF on error) command.
As to the OFx needing to be adjusted every time, that is going to be an servo drive amplifier issue. The Galil will apply the same voltage offset every time. Could there possibly be some change in resistance on that circuit? The Fanuc drives you have may operate on a PWM control input. So I guess that third party device converts analog voltage signals to frequencies that the drive understands. If this is the case, then you may have an offset issue in the V to PWM device. You must check this and make sure that the frequency output is stable with regards to voltage applied. Also, devices like this may float if there is no input, which may explain your drift.
But this is a hard problems to solve on any servo system. The main way people handle it is to remove power from the servo amp when there is no command voltage. This is why the SH and MO Galil commands operate the AMPENx signal. I would strongly suggest working this into your control circuit. You can leave the Opto22 relay intact. Just wire the AMPENx into the circuit in series so that both the Opto22 relay and SH need to be active to enable the servo drive.
Torque and Velocity refer to the mode by which the servo drive operates, not by how it is controlled. The Galil cares not whether the drive is torque or velocity. Only the Galil PID values may change between the two modes. Tuning is accomplish the same way regardless. You are simply looking for a command response that fits your needs. If you have a servo drive that will do either torque or velocity, one may work better than the other for any particular application. But if you only have velocity control... then that is what you are going to use.
Steve