An Active Disturbance Rejection Control Solution for Electro-Hydraulic Servo Systems

The intriguing history of disturbance cancellation control is reviewed in this thesis first, which demonstrates that this unique control concept is both reasonable and practical. One novel form of disturbance cancellation, ADRC (Active Disturbance Rejection Control), attracts much attention because of its good disturbance rejection ability and simplicity in implementation. Hydraulic systems tend to have many disturbances and model uncertainties, giving us a great motivation to find out a good control method. In this thesis, electro-hydraulic servo control problem is reformulated to focus on the core problem of disturbance rejection. An ADRC solution is developed and evaluated against the industry standard solution, with promising result

A neural network-based inversion method of a feedback linearization controller applied to a hydraulic actuator

In this work, we use a neural network as a substitute for the traditional analytic functions employed as an inversion set in feedback linearization control algorithms applied to hydraulic actuators. Although very efective and with strong stability guarantees, feedback linearization control depends on parameters that are difcult to determine, requiring large amounts of experimental efort to be identifed accurately. On the other hands, neural networks require little efort regarding parameter identifcation, but pose signifcant hindrances to the development of solid stability analyses and/or to the processing capabilities of the control hardware. Here, we combine these techniques to control the positioning of a hydraulic actuator, without requiring extensive identifcation procedures nor losing stability guarantees for the closed-loop system, at reasonable computing demands. The efectiveness of the proposed method is verifed both theoretically and by means of experimental results

A Review of Control Techniques for Wind Energy Conversion System

Wind energy is the most efficient and advanced form of renewable energy (RE) in recent decades, and an effective controller is required to regulate the power generated by wind energy. This study provides an overview of state-of-the-art control strategies for wind energy conversion systems (WECS). Studies on the pitch angle controller, the maximum power point tracking (MPPT) controller, the machine side controller (MSC), and the grid side controller (GSC) are reviewed and discussed. Related works are analyzed, including evolution, software used, input and output parameters, specifications, merits, and limitations of different control techniques. The analysis shows that better performance can be obtained by the adaptive and soft-computing based pitch angle controller and MPPT controller, the field-oriented control for MSC, and the voltage-oriented control for GSC. This study provides an appropriate benchmark for further wind energy research

Hybrid modeling and control of mechatronic systems using a piecewise affine dynamics approach

This thesis investigates the topic of modeling and control of PWA systems based on two experimental cases of an electrical and hydraulic nature with varying complexity that were also built, instrumented and evaluated. A full-order model has been created for both systems, including all dominant system dynamics and non-linearities. The unknown parameters and characteristics have been identi ed via an extensive parameter identi cation. In the following, the non-linear characteristics are linearized at several points, resulting in PWA models for each respective setup. Regarding the closed loop control of the generated models and corresponding experimental setups, a linear control structure comprised of integral error, feed-forward and state-feedback control has been used. Additionally, the hydraulic setup has been controlled in an autonomous hybrid position/force control mode, resulting in a switched system with each mode's dynamics being de ned by the previously derived PWA-based model in combination with the control structure and respective mode-dependent controller gains. The autonomous switch between control modes has been de ned by a switching event capable of consistently switching between modes in a deterministic manner despite the noise-a icted measurements. Several methods were used to obtain suitable controller gains, including optimization routines and pole placement. Validation of the system's fast and accurate response was obtained through simulations and experimental evaluation. The controlled system's local stability was proven for regions in state-space associated with operational points by using pole-zero analysis. The stability of the hybrid control approach was proven by using multiple Lyapunov functions for the investigated test scenarios.publishedVersio

Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Current and advanced act control system definition study. Volume 2: Appendices

The current status of the Active Controls Technology (ACT) for the advanced subsonic transport project is investigated through analysis of the systems technical data. Control systems technologies under examination include computerized reliability analysis, pitch axis fly by wire actuator, flaperon actuation system design trade study, control law synthesis and analysis, flutter mode control and gust load alleviation analysis, and implementation of alternative ACT systems. Extensive analysis of the computer techniques involved in each system is included

Investigation of Novel Displacement-Controlled Hydraulic Architectures for Railway Construction and Maintenance Machines

This dissertation aims at showing how to transform hydraulic systems of railway multi-actuator machinery characterized by inefficient state-of-the-art systems into the 21st Century. Designing machines that are highly efficient, productive, reliable, and cost affordable represents the target of this research. In this regard, migrating from valve-controlled architectures to displacement-controlled layouts is the proper answer. Displacement-controlled systems remove the losses generated by flow throttling typical of conventional circuits, allow an easy implementation of energy recovery (e.g. during regenerative braking), and create the possibility for the use of hybrid systems capable of maximizing the downsizing of the combustion engine. One portion of the dissertation focuses on efficient propulsion systems suitable for railway construction and maintenance machines. Two non-hybrid architectures are first proposed, i.e. a novel layout grounded on two independent hydrostatic transmissions (HSTs) and two secondary controlled hydraulic motors (SCHMs) connected in parallel. Three suitable control strategies are developed according to the specific requirements for railway machines and dedicated controllers are implemented. Detailed analyses are conducted via high-fidelity virtual simulations involving accurate modeling of the rail/wheel interface. The performance of the propulsion systems is proven by acceptable velocity tracking, accurate stopping position, achieving regenerative braking, and the expected behavior of the slip coefficients on both axles. Energy efficiency is the main emphasis during representative working cycles, which shows that the independent HSTs are more efficient. They consume 6.6% less energy than the SCHMs working with variable-pressure and 12.8% less energy than the SCHMs controlled with constant-pressure. Additionally, two alternative hybrid propulsion systems are proposed and investigated. These architectures enable a 35% reduction of the baseline machine’s rated engine power without modifying the working hydraulics. Concerning the working hydraulics, the focus is to extend displacement-controlled technology to specific functions on railway construction and maintenance machines. Two specific examples of complete hydraulic circuits for the next generation tamper-liners are proposed. In particular, an innovative approach used to drive displacement-controlled dual function squeeze actuators is presented, implemented, and experimentally validated. This approach combines two functions into a unique actuator, namely squeezing the ballast and vibrating the tamping tools of the work-heads. This results in many advantages, such as variable amplitude and variable frequency of the tamping tools’ vibration, improved reliability of the tamping process, and energy efficient actuation. A motion of the squeeze actuator characterized by a vibration up to 45 Hz, i.e. the frequency used in state-of-the-art systems, is experimentally confirmed. In conclusion, this dissertation demonstrates that displacement-controlled actuation represents the correct solution for next-generation railway construction and maintenance machines

Active vibration control of flexible bodied railway vehicles via smart structures

Future railway vehicles are going to be designed lighter in order to achieve higher speed. Suppressing the flexible modes becomes a crucial issue for improving the ride quality of the light-weight high speed railway vehicles. The concept of smart structure brings structural damping to flexible structures by integrating smart actuators and sensors onto the structure. Smart structure eliminates the need for extensive heavy mechanical actuation systems and achieves higher performance levels through their functionality for suppressing the flexible modes. Active secondary suspension is the effective conventional approach for vibration control of the railway vehicle to improve the ride quality. But its ability in suppressing the flexible modes is limited. So it is motivated to combine active structural damping for suppressing the flexible modes and the vibration control through active secondary suspension which has an effect on both rigid and flexible modes. The side-view model of the flexible-bodied railway vehicle integrated with piezoelectric actuators and sensors is derived. The procedure for selection of placement configurations of the piezoelectric actuators and sensors using structural norms is presented. Initial control studies show that the flexibility of the vehicle body will cause a considerable degradation in ride quality if it is neglected in the design model. Centralized and decentralized control strategies with various control approaches (e.g. modal control with skyhook damping, LQG/H2 control, H_infinity control and model predictive control (MPC))are applied for the combined control of active structural damping and active suspension control. The active structural damping effectively suppresses the flexible modes as a complement to the work of the active suspension control