OPTIMIZATION OF PARAMETERS OF THE MOBILE MACHINE ADAPTIVE HYDRAULIC CIRCUIT

Mobile machine hydraulic circuits tend to adopt electrohydraulics. Such hydraulic circuits are based on controlled pumps, modulated hydraulics, sensors and controllers. This allows adapting the hydraulic circuit operating modes to the changes of external conditions of the machine operation. Application of hydraulic circuits with electrohydraulics in mobile machines allows to use mobile machines efficiently with a high number of removable endangers, increases their performance and improves the quality of performed works. The authors propose an adaptive hydraulic circuit for a mobile machine. The operation process in the adaptive hydraulic circuit in static and dynamic modes is determined by the interaction of the pump controller and pressure differential control valves. The hydraulic system operation stability, its fast response and readjustment are determined by the controller parameters. It has been revealed that the main parameters affecting the dynamic characteristics of the hydraulic system are: throttle area and coefficient of amplifying the pump controller orifice, dampener area and coefficient of amplifying the pressure differential control valve orifice. These parameters affect the stability, controlling and readjustment time in the hydraulic circuit differently. A functional including the values of controlling time , σ controlling and losses in the pump controller was used as an optimization criterion. The optimization has been made according to the developed mathematical model applying the method developed by I. Sobol and R. Statnikov. During the optimization each controller parameter changed on 3 levels. 81 tests were made and the best combination of controller parameters for the optimization criterion was determined. The following hydraulic circuit operation values were reached under the optimal values of parameters = 1.0·10-6 m2, = 1.0·10-3 m, = 1.2·10-6 m2, = 10·10-3 m: = 1.1 с, σ = 32 %, = 0.82 kW that comply with the requirements towards hydraulic circuits of mobile machines.

Evaluation of Pressure Resonance Phenomena in DCT Actuation Circuits

The paper investigates hydraulic wave propagation phenomena through hydraulic circuits of power transmission systems by means of numerical approaches. The actuation circuit of a Dual-Clutch Transmission (DCT) power transmission system supplied by a Gerotor pump is analyzed. A steady state approach is adopted to detect resonance phenomena due to Gerotor design parameters and circuit lengths, while one-dimensional numerical models are implemented to predict the pressure oscillations through the hydraulic ducts for the whole pump operating domain. CFD-1D pipelines are adopted to address the pressure oscillation behavior through the hydraulic pipeline, while spectral maps and order tracking techniques are used to evaluate their fluctuation intensity in function of the pump speed rate. The numerical models are validated with experimental tests performed on an ad hoc test rig for power transmission systems and a good match is found between the numerical and the experimental results. Pump design parameters as well as hydraulic accumulators and resonators are numerically investigated to quantitatively evaluate their improvement on the circuits’ hydro-dynamic behavior. Furthermore, simplified numerical models are implemented to investigate the frequency response behavior of the hydraulic circuits by means of linear analysis. This approach resulted to be particularly effective for the prediction of the resonance frequencies location, and it can be adopted as an optimization tool since significant simulation time can be saved. Finally, the performance of the circuits operating with an eco-friendly fluid is evaluated numerically and the results are compared with the ones obtained with a traditional petroleum-based oil.

ON THE CHOICE OF THE PARAMETERS OF VIBRATION DAMPERS FOR HYDRAULIC CIRCUITS OF CONTROL SYSTEMS

The article deals with the problem of choosing OF the parameters of vibration dampers for hydraulic circuits of control systems, taking into account the provision of dynamic accuracy of the system after their installation. The concept of a correction factor, which is the ratio of Laplace images of the corresponding parameters of the working medium in the hydraulic circuit before and after the damper installation is introduced. A dependence that associate the relative deviation of the system-controlled parameter with the correction factor is obtained. A condition for checking the effectiveness of the damper, taking into account the preservation of the required quality of regulation in the system is formulated.

A Study of a New Bidirectional Pressure-Regulating Valve for Hydraulically Interconnected Suspension Systems

Due to inevitable inner leakage in hydraulic circuits and structural limits of a hydraulically interconnected suspension (HIS) system, pressure difference between HIS's two independent hydraulic circuits leads to vehicular unbalance under noncornering driving conditions and deteriorates HIS's performance under steering driving conditions. In order to address this problem, a new bidirectional pressure-regulating valve was designed to balance hydraulic pressures in the two HIS's hydraulic circuits under noncornering driving conditions. Moreover, it separates the two hydraulic circuits and enables HIS's antirollover function under cornering driving conditions. Detailed structure and functions of this valve were introduced first. Systematic and computational fluid dynamics (CFD) simulation results show that the gap between the spool and cylinder is of importance to valve's performance. Experimental results validate that the developed valve satisfies all requirements of the HIS. Furthermore, the valve can distinguish steering and nonsteering conditions and enables HIS's function accurately without any pressure shock.