Unable to reduce the step size without violating minimum step

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Raphael Gabor 2022-7-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1770720-unable-to-reduce-the-step-size-without-violating-minimum-step

评论： Yifeng Tang 2023-2-1

Currently trying to build up a model wich is representing a two-sided cylinder meant for compressing gas.

The model is atteched to the question (algebraic_loop.slx) and consists of three basic systems:

Thermal liquid system: Pump pushing fluid into the liquid piston and a 2-way-directional valve controlling the direction of liquid flow, as well as some check valves avoiding backflow
Gas system: Using a gas piston (driven by the liquid piston) to compress air into a gas tank, a gas source and some valves controlling the gas flow
Controll system: Controlling liquid pump, directional valves depending on the position of the piston rod. The components are controlled in a way to let the rod move between an upper and a lower bound specified by the relay inside the controller

When trying to simulate the model two warnings are displayed:

"algebraic loop" and "Solver is encountering difficulty in simulating [..] Caused by: Solver was unable to reduce the step size without violating minimum step size of 2.35762E-14 for 1 consecutive times at time 6.636 "

Fixing the alegrbaic loop by adding a transfer fctn (avoid_algebraic_loop.slx)as suggested in

https://www.mathworks.com/help/physmod/simscape/ug/limitations.html

does not solve the second warning and causes the solver to stall at T=6.636