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Hydraulic Control Systems

This paper presents a new modified Perturbation and Observation (PO however, P&O prone to failure especially when high changes in irradiance, oscillation around the MPP and the convergence speed. To face this challenge and in order to overcome the drawbacks of the classical P&O MPPT, a new method based on variable-step size of modified P&O MPPT method using PID controller tuned by genetic algorithm is presented. The efficiency of the proposed method has been studied successfully using a boost converter connected to a Solarex MSX-60 model. Analysis and comparison with the classical fixed step size P&O and that developed genetic variable step size are presented. The efficiency and improvements of the proposed algorithm in transient, steady-state and dynamic responses, especially under rapidly changing atmospheric conditions, related to ripple, overshoot and response time have been demonstrated. Algorithm robustness was verified using different schemes for temperature and insolation proving its ability to track the maximum power point in case of random and fast changing atmospheric conditions.

Variable step size modified P&O MPPT algorithm using GA-based hybrid offline/online PID controller

High precision and fast response are of great significance for hydraulic pressure control in automotive braking systems. In this paper, a novel sliding mode control based high-precision hydraulic pressure feedback modulation is proposed. Dynamical models of the hydraulic brake system including valve dynamics are established. An open loop load pressure control based on the linear relationship between the pressure-drop and coil current in valve critical open equilibrium state is proposed, and also experimentally validated on a hardware-in-the-loop test rig. The control characteristics under different input pressures and varied coil currents are investigated. Moreover, the sensitivity of the proposed modulation on valve's key structure parameters and environmental temperatures are explored with some unexpected drawbacks. In order to achieve better robustness and precision, a sliding mode control based closed loop scheme is developed for the linear pressure-drop modulation. Comparative tests between this method and the existing methods are carried out. The results validate the effectiveness and superior performance of the proposed closed loop modulation method.

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High-Precision Hydraulic Pressure Control Based on Linear Pressure-Drop Modulation in Valve Critical Equilibrium State

Permanent magnet synchronous motors (PMSMs) are known as highly efficient motors and are slowly replacing induction motors in diverse industries. PMSM systems are nonlinear and consist of time-varying parameters with high-order complex dynamics. High performance applications of PMSMs require their speed controllers to provide a fast response, precise tracking, small overshoot and strong disturbance rejection ability. Sliding mode control (SMC) is well known as a robust control method for systems with parameter variations and external disturbances. This paper investigates the current status of implementation of sliding mode control speed control of PMSMs. Our aim is to highlight various designs of sliding surface and composite controller designs with SMC implementation, which purpose is to improve controller’s robustness and/or to reduce SMC chattering. SMC enhancement using fractional order sliding surface design is elaborated and verified by simulation results presented. Remarkable features as well as disadvantages of previous works are summarized. Ideas on possible future works are also discussed, which emphasize on current gaps in this area of research.

https://www.mdpi.com/1996-1073/12/9/1669/pdf

Robust Speed Control of PMSM Using Sliding Mode Control (SMC)—A Review

Theoretical investigation of the contributions of the excitation forces to the vibration of an axial piston pump

The steady state and dynamic characteristics of a two-stage pressure relief valve with proportional solenoid control of the pilot stage is studied theoretically as well as experimentally. The mathematical model is studied within the MATLAB-SIMULINK environment and the non-linearities have been considered via the use of appropriate SIMULINK blocks. The detailed modelling has resulted in a good comparison between simulation and measurement, albeit assumptions had to be made regarding the solenoid dynamic characteristic based upon practical experience. The use of this characteristic combined with additional dynamic terms not previously considered allows new estimations of internal characteristics to be made such as the damping flowrate. The overall dynamic behaviour has been shown to be dominated by the solenoid characteristic relating force to applied voltage.

The static and dynamic characteristics of a pressure relief valve with a proportional solenoid-controlled pilot stage

An industry-grade proportional valve is much cheaper and rugged than a servovalve. A feedforward controller for a proportional valved system has been developed here to achieve tracking controls beyond 1 Hz that are usually attained by servovalves. For compensating the higher nonlinearities, feedforward controllers have been designed offline by proposing appropriate static models for friction and valve flow and executing the supporting experiments. These controllers have been implemented with real-time PID feedback of only the piston displacement. Excellent tracking performance has been obtained up to 2 Hz that has deteriorated with an increase in cylinder friction.

Approaching Servoclass Tracking Performance by a Proportional Valve-Controlled System

The present work aims at developing a methodology for designing a swash-plate axial-piston pump whose barrel kidneys are wider than the bridges separating the kidney ports on the plate. Besides red...

Effects of flow inertia modelling and valve-plate geometry on swash-plate axial-piston pump performance

For many hydraulic systems, fixed-displacement axial-piston pumps often employ swash plate. The design challenge for such a pump is to minimize the pressure and flow ripples and the consequent nois...

Theoretical simulation of ripples for different leading-side groove volumes on manifolds in fixed-displacement axial-piston pump:

Rugged electrohydraulic systems are preferred for remote and harsh applications. Despite the low bandwidth, large deadband and flow nonlinearities in proportional valves valve and highly nonlinear friction in industry-grade cylinders that comprise rugged systems, their maintenance are much easier than very sophisticated and delicate servocontrol and servocylinder systems. With the target of making the easily maintainable system to perform comparably to a servosystem, a feedforward control has been designed here for compensating the nonlinearities. A PID feedback of the piston displacement has been employed in tandem for absorbing the unmodeled effects. All the controller parameters have been optimized by a real-coded genetic algorithm. The agreement between the achieved real-time responses for step and sinusoidal demands with those achieved by modern servosystems clearly establishes the acceptability of the controller design.

Rana Saha

Papers

The static and dynamic characteristics of a pressure relief valve with a proportional solenoid-controlled pilot stage

Approaching Servoclass Tracking Performance by a Proportional Valve-Controlled System

Effects of flow inertia modelling and valve-plate geometry on swash-plate axial-piston pump performance

Theoretical simulation of ripples for different leading-side groove volumes on manifolds in fixed-displacement axial-piston pump:

GA-optimized feedforward-PID tracking control for a rugged electrohydraulic system design