USING SIM HYDRAULICS FOR SIMULATING MECHATRONIC SYSTEMS (original) (raw)
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MATHEMATICAL MODEL FOR A PROPORTIONAL CONTROL VALVE OF A HYDRAULIC SYSTEM
MATHEMATICAL MODEL FOR A PROPORTIONAL CONTROL VALVE OF A HYDRAULIC SYSTEM, 2020
A mathematical model for a proportional control valve in a hydraulic system is represented in this paper. Three proportional directional control valves are used in the hydraulic system. The mathematical model of the system is derived starting from the general basic equations of motion and flow rate taken into account, the V-notch spool shape of the proportional valve. The mathematical model proceeds with a general practical case for asymmetric hydraulic cylinder.
Conventional hydraulic systems use less accurate discrete valves for controlling the system actuators. The precise control of the position, speed, and pressure/force of an actuator in a less sophisticated hydraulic system with a conventional type solenoid valve is difficult to achieve, due to the jerkiness of motion that the valve spool produces. To improve the accuracy in a cost effective manner, an electronically controlled proportional valve with a special proportional electromagnet can be used. In this type, the valve output can be infinitely varied in a proportional manner in relation to the applied input signal. With the integration of electronic controllers, it is also possible to control the position or the speed of actuators remotely. Initially, proportional valves were designed for open-loop control systems in less sophisticated applications. But, they are also used in closed-loop control systems depending on the complexity of applications. The constructional features of these types of proportional valve systems are presented below. Open-loop Proportional Valve System The open-loop proportional valve system mainly consists of a proportional valve and an electronic control unit (controller). The proportional solenoid valve meant for an open-loop control system consists of a spool that is acted upon by the magnetizing force from the solenoid against the restraining force of the valve spring and places the spool at the desired position. The magnetizing force developed by the solenoid is proportional to the actual current flowing through it. The current is generated by the amplifier in proportion to the low-power voltage input signal from a potentiometer (or a joystick) and then modified by other electronic circuits in the controller. The circuit uses ramping, dither, and PWM techniques for achieving the desired result. The output signal of the amplifier must be sufficient to operate the proportional valve and place the spool at the desired position. Figure: Schematic of an open-loop proportional valve system The spool and the body of the valve are designed to open/close the flow path through the metering notches or orifices as the spool is moved through the valve body axially. The spool must move a
Modelling of a safety relief valve through a MATLAB-Simulink and CFD based approach
2016
The aim of the work is to understand the proper way to address the design and optimization procedures of a hydraulic safety relief valve. These valves are a part of the hydraulic circuit of many aircraft models, so their performances must be adapted to the specific system or engine. The only real constraints are the geometrical dimensions and the need to limit the weight of the device. This work requires gathering all the possible information available in the literature, and condensing them in a set of operations that will allow to promptly manufacture a product fitting the requirements needed. This should lead to the reduction of the amount of physical prototypes needed to obtain testing devices. The process studied uses a numerical fluid dynamic calculation approach to define the pressure field inside the valve and the forces acting on it, together with a Computational Fluid Dynamic (CFD) calculation used to identify the force distribution inside the valve. The first step deals wi...