Pump/valves coordinate control of the independent metering system for mobile machinery

Analytical energy dissipation in large and medium-sized hydraulic press

Because of its significant impact on the cooperative regenerative braking performance of electrified vehicles, the modulation effect of a hydraulic brake is of great importance. To improve the hydraulic brake control performance further, a novel pressure-difference-limiting control method for hydraulic pressure modulation based on on–off solenoid valves is proposed. The linear relationship between the coil current and the pressure difference across the valve is obtained. The characteristics of pressure-difference-limiting modulation are simulated and analysed. Then, a cooperative regenerative braking control algorithm based on the pressure-difference-limiting modulation of the hydraulic brake is designed. Hardware-in-the-loop tests of the algorithm under typical braking procedures are carried out. The test results demonstrate the validity and feasibility of the developed regenerative braking control algorithm and indicate that the proposed pressure-difference-limiting modulation method, which has an advantage over the conventional control based on a pulse-width-modulated signal with respect to the control accuracy of the hydraulic brake pressure, has great potential to improve the braking performance of a vehicle.

Hardware-in-the-loop simulation of pressure-difference-limiting modulation of the hydraulic brake for regenerative braking control of electric vehicles

This paper proposes a decoupling compensation method for damping improvement of the electrohydraulic control system with multiple actuators. The low damping property of hydraulic systems has been a remarkably troublesome issue for a few decades. Previously, this issue with one actuator has been addressed effectively by state feedback and signal compensation, e.g., dynamic pressure feedback. However, the poor damping with multiple actuators is still intractable and pendent due to the complex coupling effect of different loads. A decoupling compensator based on pump/valve combined control is proposed for a typical electrohydraulic system with multiple actuators for mobile machinery. Using decoupling control of different load branches, the coupling hydraulic circuit with multiple cylinders is transformed into multiple separate single-cylinder circuits with dynamic compensation. The dynamic characteristics of different actuators are then improved synchronously without mutual interference, while the steady performance remains the same without loss of controllability. Compound motion tests on a 2-ton hydraulic excavator were carried out. The results showed that the proposed compensator reduced velocity and pressure oscillations under different working conditions, so the dynamic performance is improved for the multiactuator system.

Decoupling Compensation for Damping Improvement of the Electrohydraulic Control System With Multiple Actuators

Optimal design of an electro-hydraulic valve for heavy-duty vehicle clutch actuator with certain constraints

A Novel Pressure-Feedback Based Adaptive Control Method to Damp Instabilities in Hydraulic Machines

The Modeling of Electrohydraulic Proportional Valves

Active Vibration Damping in Hydraulic Construction Machinery

The goal of this article is to formulate and validate a model for the prediction of the mechanical dynamics of hydraulic actuators controlled by means of proportional directional valves (PDVs) The model inputs are the pressure at the PDVs ports and the current to the solenoids: no further input is required even when additional elements are installed in the line between PDV and actuator The model finds application in closed-loop control of mobile electrohydraulic machines for load handling, construction and agriculture These machines are typically based on open-loop control of the actuator speed Nevertheless, these machines are often characterized by non-cyclical operation, large disturbances (eg drive on uneven ground) and time-varying parameters (eg load mass) Due to these features, closed-loop control has potential to improve the machine dynamics with consequent benefits in terms of productivity and operation safety However, because of the harsh working conditions, the installation of feedback

Davide Cristofori

Papers

A Novel Pressure-Feedback Based Adaptive Control Method to Damp Instabilities in Hydraulic Machines

The Modeling of Electrohydraulic Proportional Valves

Active Vibration Damping in Hydraulic Construction Machinery

Modeling hydraulic actuator mechanical dynamics from pressure measured at control valve ports

PhD theses completed in 2014: Modeling and Experimental Evaluation of the Effective Bulk Modulus for a Mixture of Hydraulic Oil and Air