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Re: [Question #707635]: Strange servo using ServoPIDController


Question #707635 on Yade changed:

Yade Guide posted a new comment:
Hey kyle2000, check out some related threads. This is an automated

Title: "A problem with using the ServoPIDController() function"
Question by wangkaichao on 08 Apr 2023:
 The user is encountering difficulties with using the ServoPIDController() function in Yade on Ubuntu 22.04. They are seeking assistance in setting the target value to a sine function of time within their code. The user has provided information about the function's usage and suggested solutions, including using labels and PyRunner for more advanced options.    

Title: "Servo control of flexible membrane using ServoPIDController"
Question by kyle2000 on 13 Jul 2023:
 The user is seeking help with using a ServoPIDController for servo control of a flexible membrane with confining pressure. They have been advised to assign corresponding center-oriented forces to the grid nodes and start with a simpler approach by prescribing force directly to the nodes using O.forces.setPermF. If insisting on servo control, the user can use ServoPIDController for each grid node, calculating the confining stress area and targeting a specific force value. The user asked if the 'axis' in PIDController should be defined individually for each node, to which the response was yes, with a few considerations. They are also looking into the correctness of the function for calculating the stress on the loading plate and confining stress. The difficulty lies in determining proper proportional parameters for kP, kI, and kD. A user suggested reading the wikipedia article and testing the parameters on a simple example. Another user confirmed that the function for calculating the stress on the loading plate and confining stress looks correct.    

Title: "About servo process of triaxialStressController engine"
Question by littlefish on 14 Mar 2019:
 The user is having difficulty controlling servo processes in a triaxialStressController engine for a triaxial test with wall boundaries. They experience large fluctuations in confining pressure when axial strain exceeds 20-30%. The user wonders if there's a way to control the confining pressure within a smaller range during the test.        <br>    In response to this issue, Bruno suggests that large fluctuations can have various causes and recommends providing more information for a more accurate answer. He mentions that when the tolerance is zero, servo-control will do its best unless the difference is exactly zero.

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