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Uncontrolable oscillation at lower speeds (< 10KMPH) in Front Wheels in Lateral Direction, Where as the oscillations disappear above 15KMPH

ilapakurti Venkata Naga
My ADAMS Car Model sets up an uncontrollable oscillation at lower speeds (< 10KMPH)
The vehicle is Front Engine Front wheel driven type
Simulation: 10KMPH Mainitain on Plain road
The oscillation is observed in Front Wheels
The Oscillation is missing above 15KMPH
I have checked all the bushes for Self excitation warning. Nothing
Power train is connected properly to the drive shafts and drive shafts are properly attached to the spindle.
Solver Setting Used: GSTIFF/I3
 
SI2 setting is giving an acceptable result, but I am wondering if I am missing something in modelling. If anybody else has encountered any such problem, please guide.
Attached Files (1)
  • 0
    It sounds very much like the driver model.
    Open the event builder and load the driver_file.xml that was created when you did your canned run.
    At the top you find the PID values for the driver controller in one tab. Try to decrease the P and I values and set D=0.
    Particular if you are modeling a heavy vehicle you have to change these values. If you find a set of values that works for you (I often have to run an DOE or optimization to find the best set of values), copy the event file to your home directory and rename it ".smartdriver.xml". Then that will be used for all your simulations.
     
    There is a slight chance that it is the tire data that causes the vibrations. Unlikely, but possible. Check the USER_MODE in the tire property file and if it is above 10, remove the first digit so that is below 10 (for example 14 -> 4. 23 ->3).
     
  • 0
    You have a >5 deg side slip angle when going straight ?
     
    Next to the driver model, it can also happen when the wheel is wobbling during rotation (for example due to unbalanced masses, too soft stiffness in the tie-rod or misalignment of rotational axes)
    Have you checked the animation & results ?
     
    If the steering demand shows this effect, then it's the driver.
    If it's just the wheel, then animate with icons on to see if there's misalignment.
     
  • 0
    I am also facing same problem while running my heavy truck model over twist track. I am using LatPth, P and D gain equal to zero and I gain 0.1
    The issue disappeared on flat road but it occurs when running on durability tracks such as twist track, corrugated tracks etc. Please help
  • 0
    Why do you set P = 0.0? Running only a I-controller gives you a 90° phase lag between input and control action making the system hard to control.
     
  • 0
    I received following response from MSC support team. They mentioned to use zero P and D gains. I have attached PDF of their response.
    Attached Files (1)
  • 0
    Still the issue is not resolved, even if I used their recommended values of PID
     
  • 0
    I have had models that behaves well with P=D=0, but only for certain events. And it is very dependent on vehicle and event.
    Here is my generic truck values:
          vxP="1000"
          vxI="500"
          vxD="0"
          LatPthP="0.1"
          LatPthI="0.1"
          LatPthD="0"
          LatAyP="0.1"
          LatAyI="10"
          LatAyD="0"
          LatAyCP="0.003"
          LatAyCI="0.001"
          LatAyCD="0"
          SteFrcP="10"
          SteFrcI="20"
          SteFrcD="3"
          SteTrqP="10"
          SteTrqI="20"
          SteTrqD="3"
    (I think this is too aggressive on throttle control though)
     
    And here is what I used for a specific off-road military truck (6x6) driving over a *very* uneven terrain:
          vxP="100"
          vxI="50"
          vxD="0"
          LatPthP="0.100000"
          LatPthI="0.120000"
          LatPthD="0.000000"
          LatAyP="1"
          LatAyI="10"
          LatAyD="0"
          LatAyCP="0.003"
          LatAyCI="0.001"
          LatAyCD="0"
          SteFrcP="10"
          SteFrcI="20"
          SteFrcD="3"
          SteTrqP="8.35000"
          SteTrqI="43.1400"
          SteTrqD="9.10000"
     
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