Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  1. PNachtwey

    Hydraulic Damper

    3DDave is right about the spring effect. A damper needs something that turns kinetic energy into heat like an orifice. I have seen shocks made for tanks and other heavy vehicles. They have an orifice that restricts flow. The energy needs to go somewhere. In this case it will be heat unless...
  2. PNachtwey

    Sawmill parallel cylinder lift issues

    I understand. I am very familiar with big sawmills where horizontal band saws the moved up and down user servo qualify valves and have MDT feedback. How does Wood Mizer do this? I am surprised a geared flow divider isn't more accurate going up. Ditto the look for leaks. I find the obvious...
  3. PNachtwey

    Things you love/hate with mathcad

    I first started using Mathcad back in the early 90s. I think it was Mathcad 3 or 4. What I liked about it was the symbolic processing. I stopped updating Mathcad 13 because the symbolic processor was changed and not as good in Mathcad 14. I tried Mathematica. It was OK. I could solve a...
  4. PNachtwey

    Hydraulic Pressure Data Logging

    Anything that would change the velocity. That requires acceleration and that requires force which requires pressure. Obstructions will cause this. Do you have an encoder on the motor, even a tachometer a would be good as long as it as be recorded. Instrumenting things can get expensive real...
  5. PNachtwey

    Hydraulic Pressure Data Logging

    I have seen this when the over hauling load is traveling fast and the valve is shut quickly. Good data will help find what is wrong but one should record much more than just the pressure. Other things that might be important should be recorded too so it is easy to see a correlation...
  6. PNachtwey

    Hydraulic Pressure Data Logging

    Since no one has come up with a solution. Our cheapest analog motion controller can to that easily but it will blow your budget. It can capture data at rates as short as 250 micro seconds and can be configured to trigger on events so when the pressure spike occurs, you won't miss it an the data...
  7. PNachtwey

    Hydraulic Pressure Data Logging

    You can get a HMI for that price. I doubt you will get a sensor and HMI for that price. The HMI will not have any data logging. The Raspberry PI, analog "hat", display and sensor wil probably cost more than $500 and then there is "some assembly required" I doubt you can do what you want to...
  8. PNachtwey

    Measure the volume of a cavity with compressed air?

    What is the vessel filled with before starting? What is the volume? At sea level air weighs 1.225 kg/m^3 One could measure by the weight change using the density and pressure. This assumes there is only one type of gas inside. https://en.wikipedia.org/wiki/Density_of_air Peter Nachtwey...
  9. PNachtwey

    How do I change the boom lift speed at the end of the operation using hydraulic cylinders and motor?

    @FluidPowerUser. I have a YouTube channel called Peter Ponters PID. It is advanced and covers many topics not just hydraulics. You better be up on your Laplace transforms and differential equations. I cover motor, temperature, level control too. I could teach control theory. I just happened...
  10. PNachtwey

    Stiffness of hydraulic oil

    It looks good but what are you going to do with the stiffness value? I usually compute the natural frequency. Peter Nachtwey Delta Motion http://www.deltamotion.com http://forum.deltamotion.com/ IFPS Hall of Fame Member
  11. PNachtwey

    How do I change the boom lift speed at the end of the operation using hydraulic cylinders and motor?

    Few in the hydraulic world have even figured out the control theory for controlling hydraulics. You won't find it in a book. Buy a hydraulic motion controller unless the system is very basic. A simple PI or PID control is not enough. Me neither. I/we have solutions but without info we can do...
  12. PNachtwey

    How do I change the boom lift speed at the end of the operation using hydraulic cylinders and motor?

    I agree. A boom is not a rigid structure. The natural frequency will change with load changes and boom extensions. Bang-bang valves may induce oscillations. So will rapid acceleration or deceleration attempts with a proportional valve. The required motion appears to be very slow. Is there...
  13. PNachtwey

    Feedforward: why does feedBACK reduce itself?

    I am responding to the poor tracking. Kp*(0-act_vel) subtracts from the control signal all gthe time. Kp*(tar_vel-act_vel) does not. If the actual trajectory is following the target trajectory the change in control output is zero whereas the P and D gains subtract from the control output on...
  14. PNachtwey

    Feedforward: why does feedBACK reduce itself?

    Feedback is negative! A simple incremental PID is u(n)=u(n-1)=Ki*(tar_pos-act_pos)+Kp*(tar_vel-act_vel)+Kd*(tar_acc-act_act) An I-PD is the same but the tar_vel and tar_acc are set to 0 because the Kp and Kd act only on the feed back state, not the target...
  15. PNachtwey

    Feedforward: why does feedBACK reduce itself?

    Now I see what you are getting at. The closed loop gains can interfere with the feed forwards if the closed loop gain is only used in the feed back path ( act only on changes in the actual position instead of the error ). Simply put, there are different forms of PID. The 22 Dec picture shows a...
  16. PNachtwey

    Feedforward: why does feedBACK reduce itself?

    I am here now. I am going to use motion control as an example. The output due to feed forwards are generated by mulitpying the target speed by the velocity feed foward and adding the target acceleration by the acceleration feed forward gain. Our motion controllers also add the target jerk x the...
  17. PNachtwey

    Mathcad Prime - subscript . and unit font

    @samirhyatkhan. I will try the trial versions. I have over 800 Mathcad worksheets. I have been using Mathcad since version 3. It is the devil I know. I am retired now. The problem is that no one where I used to work wants to get into the math so I don't know how useful it will be. At this...
  18. PNachtwey

    Mathcad Prime - subscript . and unit font

    I find Maple Flow interesting, but I stopped upgrading Mathcad at version 13. I would be interested if Maple Flow can import Mathcad 13 files. I still use Mathcad but try to do more in python. Peter Nachtwey Delta Motion http://www.deltamotion.com http://forum.deltamotion.com/ IFPS Hall of...
  19. PNachtwey

    Accumulator maximum pressure & minimum pressure

    There are now simple formulas. I use a simulator. If necessary I can simulate the motion of two actuators running asynchronously but usually two are running in tandem so it is simple...
  20. PNachtwey

    My pneumatic cylinder needs to push down 25% of its capacity at the start and then push with 100%.

    How precise does this need to be? What to you mean by capacity? When you use the word push I think of force. Are you really trying to control force? In this case force = pressure1*area1-pressure0*area0. Even if you vent the exhausting side there will still be atmospheric pressure opposing the...

Part and Inventory Search

Back
Top