Simscape - Allow accumulator to fully discharge without model crashing?

Question

Nicholas Gholdoian 2018-5-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/402713-simscape-allow-accumulator-to-fully-discharge-without-model-crashing

回答： Juan Sagarduy 2020-10-26

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Hello I am currently trying to model a hydraulic circuit where a gas charged accumulator is fully pressurized initially and discharges through a motor into a reservoir. The motor spins a wheel through a gear ratio with rolling resistance and mass attached. I am trying to create a simple model for a hydraulic powered bike using the accumulator discharge to propel the vehicle and measure its final distance.

The current problem I am facing is when the fluid volume in the accumulator reaches zero, the model crashes saying

At time 13.904426, one or more assertions are triggered. See causes for specific information.Liquid pressure fell below absolute zero The assertion comes from:

I found this error stems from my custom fluid configuration block displaying a error if the fluid absolute pressure falls below absolute zero.

Is there an easy to mitigate this problem either by blocking the flow from the accumulator entirely or by changing the solver configurations? I have switched the fluid configuration to display a warning instead of an error but then the model completely crashes and only displays data from the time when the accumulator volume hits zero and on.

I did want to place a logic controlled 2 way valve into the loop and once the pressure in the lines reached the precharge pressure in the accumulator it closes the valve, but the problem would probably still occur because there is leakage within the valve and the accumulator can still discharge through that.

Let me know if I am missing anything. Any help is greatly appreciated. I have attached an image of the circuit. I can publish the actual model if necessary.

Thanks, Nicholas

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Yougzz 2019-11-13

Did you find a solution to your problem ?

I'm facing the same pb ...

Thomas Holmes 2020-2-11

im also having this problem, any solutions?

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Answer 1

Juan Sagarduy 2020-10-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/402713-simscape-allow-accumulator-to-fully-discharge-without-model-crashing#answer_525153

Hi Nicholas

I think you should have a higher pressure in the tank. That will prevent the motor to overspin and thus avoiding the suction effect occurring in the model. Depending on the pressure, you would reach an equilibrium after a given time.

Good luck Juan