4/24/2014 6:09 PM | |
Posts: 5225 Rating: (1192) |
Forgive me but I am having a bit of trouble with understanding all you are saying. As reference I use the PDF document entitled: "STEP 7 S7-1200 Motion Control V11 SP2" Is the "slow" speed you are talking of is the speed of travel? Or is "slow" talking of how long it takes for the position indicater to go to "zero"? The speeds of the homing function can be set inside the wizzard where the movement is first set up. The downfall is that there is multiple movement to bring the system to stop onto the home sensor. That process takes time. For passive homing, your own coding decide how the movements are made. MC_HOME does not trigger any movement in this case. MC_HOME ensures the system is automatically set the position to zero when crossing the home sensor. A status bit gives you feedback Passive homing is helpfull when going forward and backward repeatedly and each cycle triggering the home sensor that sits in the middle. A end limit is however recommended. A system that uses a rotary movement (rotating a disk) also can use passive homing. Alternatively you can record the absolute position of the motion each time you trigger a sensor. From this information you can decide your relative position. I think the idea you have for using an encoder is a good idea. There is no need to physically buy an encoder. Many servo drives have an outfeed pulse that give feedback to what it is doing. You can use this signal as if it is an encoder. That is my 2c for now. Good luck. w |
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