electronic gearing

[bt_boy]

I am using the PCI 7344 board to control the gantry system. It's a 4-axis system with axis 1 and 2 slaved together (they are rigidly connected). There are some issues with using the board to control these axis while maintaining alignment.

1) homing, there is no way to home the axis (i am using the renishaw rgh22 encoders). Currently i am homing off a limit switch which is not very accurate.

2) minimizing error between the axis. I have a procedure implemented to reduce the following error between the 2 axis (down to about 20 encoder counts). However, whenever the board is reset the error information is lost and results is a cummulative error that is generated. Is there away to reset the board without losing the misalignment information.

I'd apperi
ciate any help with these issues.

[JR_A.]

The ablity to accurately home your system will be dependent on having a home switch/sensor and the accuracy of it. If you have a home switch there is a Find Home routine which allows you to set the initial and final search directions so that you can ensure you are always finding the same edge of the switch at low speed. The only way to perserve your error is to programatically save it and then recall it if you are doing separate moves on axis 1 & 2. I would recommend using the 'electronic gearing' option for the 7344 which can be setup in Measurement and Automation Explorer. In this mode, the control loop of the 7344 will automatically make the motion of axis 2 mirror axis 1 and then you won't have to worry about the error because the board will automatically minimize
it.

Regards,

JR A.
Application Engineer
National Instruments