Equivalent Simulink Model for Hydraulic System
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From: Jithendra Dharmavaram on 4 Mar 2010 05:40 Hi, I would like to have an equivalent Simulink model for a Hydraulic circuit. I tried using the equations from SimHydraulics Toolbox reference guide but, the results are not the same. A simple application i am using is to control the hydraulic cylinder's motion. The inference from comparing my Simhyraulics model and Simulink model show that for extend the position tends to about 30% (of stroke) plus the cylinder stroke length and then smoothens the curve to reach about 10% (of stroke) plus the cylinder stroke length with some peaks and stays for a while if there is still a input pressure. But in Simulink when i change the configuration parameters the result were different for same values, if i have a stiff solver there are more peaks until actual stroke than with the non-stiff solver. It seemed strange to me. Can somebody help me in this regard. I wanted to have Simulink model for hydraulic circuit because i need to integrate this circuit in other simulink model. Thanks in advance, Regards, Jithendra Dharmavaram
From: Jithendra Dharmavaram on 4 Mar 2010 13:51 Hi, I am using input as pressure for the hydraulic cylinder, is it the flow rate to be used as input to hydraulic cylinder where the pressure is calculated from the differential equation? I should use the simulink model for hydraulic circuit rather than using simhydraulics toolbox for my project. Can anybody help me in this regard. Thanks in Advance, Regards, Jithendra Dharmavaram "Jithendra Dharmavaram" <d.jithendra(a)gmail.com> wrote in message <hmo2mp$l3m$1(a)fred.mathworks.com>... > Hi, > I would like to have an equivalent Simulink model for a Hydraulic circuit. I tried using the equations from SimHydraulics Toolbox reference guide but, the results are not the same. A simple application i am using is to control the hydraulic cylinder's motion. The inference from comparing my Simhyraulics model and Simulink model show that for extend the position tends to about 30% (of stroke) plus the cylinder stroke length and then smoothens the curve to reach about 10% (of stroke) plus the cylinder stroke length with some peaks and stays for a while if there is still a input pressure. But in Simulink when i change the configuration parameters the result were different for same values, if i have a stiff solver there are more peaks until actual stroke than with the non-stiff solver. It seemed strange to me. Can somebody help me in this regard. I wanted to have Simulink model for hydraulic > circuit because i need to integrate this circuit in other simulink model. > > Thanks in advance, > > Regards, > Jithendra Dharmavaram
From: Arnaud Miege on 8 Mar 2010 08:39 "Jithendra Dharmavaram" <d.jithendra(a)gmail.com> wrote in message <hmovep$42n$1(a)fred.mathworks.com>... > Hi, > I am using input as pressure for the hydraulic cylinder, is it the flow rate to be used as input to hydraulic cylinder where the pressure is calculated from the differential equation? I should use the simulink model for hydraulic circuit rather than using simhydraulics toolbox for my project. Can anybody help me in this regard. > > Thanks in Advance, > > Regards, > Jithendra Dharmavaram I would recommend using SimHydraulics rather than Simulink for the following reasons: - you don't get any algebraic loops with SimHydraulics as it uses the Simscape network engine and doesn't rely on inputs/outputs. It is numerically more robust. - Models are a lot more readbale and understandable as you don't have feedback loops and wires crossing everywhere. - you can very easily swap from input flow rate & output pressure to the other way round, without having to re-formulate the equations as you would in Simulink - all the equations for the blocks are fully documented, or equivalent Simscape blocks when the SimHydraulics components are constructed from basic Simscape blocks rather than equations. - You can integrate your SimHydraulics model with normal Simulink (for example for control design) using sensors/sources combined with Simulink to PS and PS to Simulink blocks. You say that you haven't been able to get the same results. It's probably because you have made assumptions in the Simulink implementation that are not present in the SimHydraulics one. Either that or you're not using it correctly. HTH, Arnaud
From: Jithendra Dharmavaram on 9 Mar 2010 05:54 Thanks for your advice. I have also gone through the Simhydraulics thoroughly but, its hard to convince somebody. So, i have to rely on simulink rather than simhydraulics. I am impressed with simhydraulics and i have worked on it, got results. Thanks once again. Regards, Jithendra Dharmavaram "Arnaud Miege" <arnaud.miege(a)nospam.mathworks.co.uk> wrote in message <hn2ulm$1mu$1(a)fred.mathworks.com>... > "Jithendra Dharmavaram" <d.jithendra(a)gmail.com> wrote in message <hmovep$42n$1(a)fred.mathworks.com>... > > Hi, > > I am using input as pressure for the hydraulic cylinder, is it the flow rate to be used as input to hydraulic cylinder where the pressure is calculated from the differential equation? I should use the simulink model for hydraulic circuit rather than using simhydraulics toolbox for my project. Can anybody help me in this regard. > > > > Thanks in Advance, > > > > Regards, > > Jithendra Dharmavaram > > I would recommend using SimHydraulics rather than Simulink for the following reasons: > - you don't get any algebraic loops with SimHydraulics as it uses the Simscape network engine and doesn't rely on inputs/outputs. It is numerically more robust. > - Models are a lot more readbale and understandable as you don't have feedback loops and wires crossing everywhere. > - you can very easily swap from input flow rate & output pressure to the other way round, without having to re-formulate the equations as you would in Simulink > - all the equations for the blocks are fully documented, or equivalent Simscape blocks when the SimHydraulics components are constructed from basic Simscape blocks rather than equations. > - You can integrate your SimHydraulics model with normal Simulink (for example for control design) using sensors/sources combined with Simulink to PS and PS to Simulink blocks. > > You say that you haven't been able to get the same results. It's probably because you have made assumptions in the Simulink implementation that are not present in the SimHydraulics one. Either that or you're not using it correctly. > > HTH, > > Arnaud
From: Arnaud Miege on 9 Mar 2010 10:57
"Jithendra Dharmavaram" <d.jithendra(a)gmail.com> wrote in message <hn59cb$1mt$1(a)fred.mathworks.com>... > Thanks for your advice. I have also gone through the Simhydraulics thoroughly but, its hard to convince somebody. So, i have to rely on simulink rather than simhydraulics. I am impressed with simhydraulics and i have worked on it, got results. Thanks once again. > > Regards, > Jithendra Dharmavaram You can always inspire yourself from the Simulink demos sldemo_hydcyl.mdl, sldemo_hydcyl4.mdl and sldemo_hydrod.mdl. HTH, Arnaud |