Moosetracks
Member
OP
Why the spikes? Again, I suspect the friction is variable and you are suffering from what is commonly called slip/stick or Stribeck friction.Through what? I have a lot of experience, many decades, with hydraulic systems. I am a member of the International Hydraulic Fluid Power Hall of Fame.
Through a saw
What environment? Over 35+ years I think I have just about everything.
Sawmill primary breakdown
What hydraulic motion controller? I design, make and sell hydraulic motion controllers. I am familiar with many of my competitors too.
RMC
What is it pushing against? Again, is there variable friction?
Wood
So you have position feed back or are these position just chosen manually?
The motion controller positions the cylinder in position control mode. I then use the motion controllers event step tables to do the rest. The event steps look something like this.
Step 1 Extend Full stroke out normal speed out until load cell is over setpoint 1
Step 2 Retract cylinder at slower speed until load cell is under setpoint 2
Step 3Hold current position, but if load cell goes over setpoint 1 then go to step 2
I was originally planning on using the motion controllers force control mode, but in the end on the advice from the RMC people I ended up using event steps and have been much happier with the performance.
What values?
Right now I am looking for a range of 500 which is about 10% of the load cells range or greater to determine if the load cell actually picked up the force during the manual move. I didn't want to enter new setpoints into the controller if the load wasn't registering.
]quote]
I could possibly just use a min and max value. However when you move the arm manually it has a tendency to create some spikes as you push and pull it.
I tried to explain below
My thought was with the 600 samples taken every 100ms I would do something like this... Take 600 samples, sort them all from high to low. Knock off the highest 20 and the lowest 20. 20 samples would be about 2 seconds of maneuvering the guide into position Then I would take what was left and average the 20 highest and 20 lowest and see how that works.
[/quote[
Your still aren't clear about what you will do with your high and low numbers.
When I am done with the above I end up with one high value and one low value. The two values are put in the motion controllers event steps table.
I think you need to tell us what the source is of your "noise"?
Is it really "noise" or is it variable friction?
The load cell is very accurate. That is not the noise issue. I would call the noise human error. I am creating a teaching routine to load values into the event steps table. The person doing the teaching will grab the end of the guide while the cylinder and everything is off. They will push it in to the desired deflection. The guide is made of fiberglass and metal. Imagine something like a snow ski. It has an inch or so of deflection from slight pressure on the load cell to full pressure on the load cell. When you move this by hand they could push too hard initially and then back off a little. That is why I have them hold it in the desired deflection for 10 seconds. And then when they let go the fiberglass will bounce a little on the way out creating a value that is under the at rest or "no pressure" value. I am afraid that if I used min and max The min could be too low and the max could be too high. The work instruction will be to hold it at the desired pressure for 10 seconds. My code chops off the lower values for 2 seconds worth of data and chops off the higher values for 2 seconds. As long as the hold it at the right spot for 5-10 seconds I should have a good range of values. I could possibly just remove the 2 seconds of data on each end and then use the max and min... I just felt better getting a more than one data point.
I have a sample of data collected from a a train that I just did. I will post it below and see what you guys think. I look forward to seeing how you would get the setpoints based on this data.