Slide 1 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Modelling and Simulation of a Hydraulic-Mechanical Load-Sensing System in CoCoViLa environment Gunnar Grossschmidt Mait Harf Pavel Grigorenko Tallinn University of Technology Institute of Machinery and Institute of Cybernetics

Slide 2 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Introduction Fluid power systems, in which working pressure (pressure in pump output) is kept proportional to load, are called hydraulic load-sensing systems. Such systems are mainly used with the purpose to save energy. Hydraulic load-sensing systems are automatically regulating systems with a number of components and several feedbacks. Feedbacks make the system very sensitive and unstable for performance and simulation. A very precise parameter setting, especially for resistances of hydraulic valve spools and for spring characteristics, is required to make the system function. Steady state conditions and dynamic behavior of the hydraulic load- sensing system are simulated.

Slide 3 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Pump with regulator: Variable displacement axial piston pump Electric motor Control valves Control cylinder Hydraulic motor feeding chain: Tube RL-zu Pressure compen- sator Ridw Measuring valve Rwv Check valve Meter-in throttle edge Rsk-zu Hydraulic motor Rverb Hydraulic motor output chain: Meter-out throttle edge Rsk-r Tube RL-ab p 0 = const R IDVW Scheme of the hydraulic-mechanical load-sensing system

Slide 4 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Components Spool valve Spool valve inflow slot Spool valve outflow slot Constant resistor Positioning cylinder Swash plate with spring Throttle edges Measuring throttle edge Rvw Pressure compensator throttle edge Ridw Meter-in throttle edge Rsk-zu Meter-out throttle edge Rsk-r ControllerValve block

Slide 5 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Object-oriented modelling based on multi-pole models with oriented causality is used for fluid power systems. Four forms (causalities) of six-pole models for a hydraulic cylinder The hydraulic cylinder has three pairs of variables: p1, Q1; p2, Q2; x (or v), F; where p1, p2 – pressures in the cylinder chambers, Q1, Q2 – volume flow rates in cylinder chambers, x, v – position and velocity of the piston rod, F – force on the piston rod. For composing a model for the fluid power system, it is necessary to build multi-pole models of components and connect them between themselves. Multi-pole models

Slide 6 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Composing the model Component models VP - control valve RVP - meter-in throttle edge of control valve ZV - positioning cylinder REL - constant resistor RVT - meter-out throttle edge of control valve PV - variable displacement pump ME - electric motor RIDVWlin - linear measu- ring valve with pres- sure compensator RSKZ, RSKA - meter-in and meter-out throttle edge for hydraulic motor MH - hydraulic motor IEH - hydraulic interface element RtuHS - tubes Multi-pole model of the hydraulic-mechanical load- sensing system for steady-state conditions

Slide 7 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Simulation steps First, the hydraulic motor, hydraulic pump, electric motor and fluid parameters must be chosen. Second, initial approximate values of pressures, pressure differences for pump control, maximum displacements of the valves, parameters of springs, geometry of valves working slots, etc. must be set up. Third, all the models of components must be tested separately. For this purpose, for every component the simulation problem must be composed, approximate input signals must be chosen and finally, action of the component must be simulated. Fourth, the separately tested component models must be connected into more complicated subsystems and finally into whole system and tested in behavior. Fifth, components models must be revised and parameters values of the system must be adjusted as a result of solving simulation tasks.

Slide 8 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Meter-out throttle edge for hydraulic motor Fig. 9 - Simulated pressure drop in measuring valve with pressure compensator depending on the displacement of the directional valve

Slide 9 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Clutch with inertia Fig. 9 - Simulated pressure drop in measuring valve with pressure compensator depending on the displacement of the directional valve

Slide 10 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Hydraulic motor subsystem

Slide 11 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Simulation of steady state conditions

Slide 12 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Simulation of dynamics Simulation characteristics Initial displacement of the directional valve m. Initial load moment of the drive mechanism 65 Nm. Step change (during 0.01 s) is applied to: - the initial load moment - the initial displacement of the directional valve. Time step 5 µs. Simulated time 0.5 s (results are calculated for points).

Slide 13 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Initial displacement of the directional valve m Load moment of the drive mechanism 65 Nm Step change m (during 0.01 s) applied to the initial displacement Time step is 5 µs Simulated time is 0.5 s (results have been calculated for points). Simulation time 17.1 s

Slide 14 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Initial load moment of the drive mechanism 65 Nm. Displacement of the directional valve m Step change 45 Nm (during 0.01 s) applied to the initial load moment. Time step is 5 µs Simulated time is 0.5 s (results have been calculated for points). Simulation time 18.8 s

Slide 15 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Size and complexity The package for modelling and simulation of the load-sensing system contains: - 42 classes, including 27 component classes; - more than 1000 variables; - 17 variables that have to be iterated during the computations; - 73 links between system components. The automatically constructed Java code for solving the simulation task of the dynamics of the load-sensing system contains 4124 lines and involves 5 algorithms for solving subtasks.

Slide 16 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY 3D simulation 3D simulation of steady state conditions Calculated 1000 x 1000 points Calculation time 119 s

Slide 17 G. Grossschmidt, M. Harf, P. Grigorenko TALLINN UNIVERSITY OF TECHNOLOGY Thank you for attention