Characterization and Attenuation of Sandwiched Deadband Problem Using Describing Function Analysis and Its Application to Electro-Hydraulic Systems Controlled by Closed-Center Valves

2004 ◽  
Author(s):  
Song Liu ◽  
Bin Yao
Keyword(s):  
Closed Loop ◽  
Controller Design ◽  
Function Analysis ◽  
Nonlinear Behavior ◽  
Hydraulic Systems ◽  
Describing Function ◽  
Widespread Application ◽  
Actuator Dynamics ◽  
Loop Bandwidth ◽  
Highly Nonlinear

Sandwiched deadbands can be seen in a wide variety of systems, such as electro-hydraulic systems controlled by closed-center valves. In such a system, the deadband is between the plant and actuator dynamics and therefore can not be compensated directly like an input deadband. Though this sandwiched deadband problem may be attenuated to certain degree through sophisticated advanced control techniques, the increased cost and the necessity of actuator state feedback prohibit their widespread application in the industry. An economical and popular method is to add an inverse deadband function in the controller to cancel or compensate the highly nonlinear behavior of the deadband. However, such a solution requires that the dynamics before the deadband (eg. the valve dynamics) is fast enough to be neglected — a requirement that can not be met in reality unless the closed loop bandwidth of the overall system is limited very low. To raise the achievable closed loop bandwidth for a much improved control performance, it is essential to be able to precisely characterize the effect of this sandwiched deadband on the stability and performance of the overall closed-loop system, which is the main focus of the paper. Specifically, a describing function based nonlinear analysis will be conducted to predict when the instability will occur and how the resulting limit cycle depends on the actuator dynamics and the targeted closed-loop bandwidth. Based on the analysis, the optimal closed-loop bandwidth can be determined to maximize the achievable overall system performance. The technique is applied to an electro-hydraulic system controlled by closed-center valves to optimize the controller design.

Characterization and Attenuation of Sandwiched Deadband Problem Using Describing Function Analysis and Application to Electrohydraulic Systems Controlled by Closed-Center Valves

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Song Liu ◽  
Bin Yao
Keyword(s):  
Closed Loop ◽  
Function Analysis ◽  
Closed Loop Control ◽  
Control Performance ◽  
Nonlinear Feedback ◽  
Describing Function ◽  
Loop Control ◽  
Actuator Dynamics ◽  
And Performance ◽  
The Stability

Unlike input deadband, the sandwiched deadband between actuator and plant dynamics is very difficult to be explicitly compensated for due to the proceeding actuator dynamics whose effect may not be negligible. The paper presents a practical way to overcome the design conservativeness of existing methods in dealing with sandwiched deadband. Specifically, a describing function based nonlinear analysis method is proposed to characterize the effect of the sandwiched deadband on the stability and performance of the overall closed-loop system. The analysis results can be used to determine the highest closed-loop bandwidth that can be achieved without inducing residual limit cycles and instability. Optimal controller parameters can then be found to maximize the achievable closed-loop control performance. The technique is applied to an electrohydraulic system controlled by closed-center valves and a nonlinear feedback controller. Simulation results showed severe oscillations as the feedback control gains are increased to the predicted threshold values. Comparative experimental results also showed the effectiveness of the proposed method in reducing the conservativeness of traditional design and the improved closed-loop control performance in implementation.

Adaptive Neural Network in Compensation the Dynamics and Position Control of a Servo-Hydraulic System With a Flexible Load

2005 ◽  
Author(s):  
Hassan Yousefi ◽  
Heikki Handroos
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Hydraulic System ◽  
Position Control ◽  
Reference Model ◽  
Differential Evolution Algorithm ◽  
Nonlinear Behavior ◽  
System Stability ◽  
Hydraulic Systems ◽  
Highly Nonlinear

Asymmetrical servo-hydraulic systems are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Because of changing system parameters, using the same gain will cause overshoot or even loss of system stability. The highly nonlinear behavior of these devises makes them idea subjects for applying different types of sophisticated controllers. This paper is concerned with using two artificial neural networks in compensation the dynamics and position tracking of a second order model reference in a flexible servo-hydraulic system. In present study, a neural network as an acceleration feedforward and another one as a gain scheduling of a proportional controller are proposed. Differential evolution algorithm is used to find the weights and biases to avoid the local minima. The proposed controller was verified with a commonly used p-controller. The results suggest that if the neural networks choose and train well, they improve all performance evaluation criteria such as stability, fast response, and accurate reference model tracking in servo-hydraulic systems.

Mathematical Modeling of Passive Hydraulic Engine Mounts

2008 ◽  
Author(s):  
Shanzhong Shawn Duan ◽  
Andrew Ries
Keyword(s):  
Vibration Isolation ◽  
Traditional Approach ◽  
Nonlinear Behavior ◽  
Form Solution ◽  
Chamber Pressure ◽  
Hydraulic Systems ◽  
Force Transmission ◽  
Engine Mounts ◽  
Electrical Systems ◽  
Highly Nonlinear

Hydraulic engine mounts are widely used in automotive powertrain for vibration isolation. A lumped mechanical parameter model is a traditional approach for modeling and simulation of such mounts. This paper presents a mathematical model of passive hydraulic engine mounts with a double-chamber, an inertia track, a decoupler, and a plunger. The model is developed based on analogy between electrical systems and mechanical-hydraulic systems. The model is created to capture both the low and high frequency dynamic behavior of hydraulic mounts. The model will be further used to find the approximate pulse responses of the mounts in terms of the force transmission and top chamber pressure. The close form solution from the simplified linear model may provide some insight into the highly nonlinear behavior of the mounts. Various operational scenarios are also discussed.

Controller Design For Nonlinear Systems Based on Simultaneous Stabilization Theory and Describing Function Models

1988 ◽  
Vol 110 (2) ◽  
pp. 134-142 ◽  
Author(s):  
A. Nassirharand ◽  
J. H. Taylor ◽  
K. N. Reid
Keyword(s):  
Position Control ◽  
Controller Design ◽  
Design Procedure ◽  
Describing Function ◽  
Simultaneous Stabilization ◽  
Single Input Single Output ◽  
Single Output ◽  
Highly Nonlinear ◽  
Sinusoidal Input ◽  
Function Models

A new systematic and algebraic linear control system design procedure for use with highly nonlinear plants is developed. This procedure is based on simultaneous stabilization theory and sinusoidal-input describing function models of the nonlinear plant, and is presently applicable to single-input single-output, time-invariant, deterministic, stable, and continuous-time systems which are representable in standard state-variable differential equation form. Three software utilities to implement the controller design procedure are also outlined. This method and the associated software is applied to a position control problem of the sort encountered in robotics, and the results are compared with those previously obtained using both linear and nonlinear PID control.

scholarly journals Limit Cycle Behavior of Smart Fluid Dampers Under Closed Loop Control

2005 ◽  
Vol 128 (4) ◽  
pp. 413-428 ◽  
Author(s):  
Neil D Sims
Keyword(s):  
Limit Cycle ◽  
Closed Loop ◽  
Controller Design ◽  
Nonlinear Models ◽  
Control Strategies ◽  
Nonlinear Behavior ◽  
Closed Loop Control ◽  
Loop Control ◽  
Fluid Dampers ◽  
Limit Cycle Behavior

Semiactive vibration dampers offer an attractive compromise between the simplicity and fail safety of passive devices, and the weight, cost, and complexity of fully active systems. In addition, the dissipative nature of semiactive dampers ensures they always remain stable under closed loop control, unlike their fully active counterparts. However, undesirable limit cycle behavior remains a possibility, which is not always properly considered during the controller design. Smart fluids provide an elegant means to produce semiactive damping, since their resistance to flow can be directly controlled by the application of an electric or magnetic field. However, the nonlinear behavior of smart fluid dampers makes it difficult to design effective controllers, and so a wide variety of control strategies has been proposed in the literature. In general, this work has overlooked the possibility of undesirable limit cycle behavior under closed loop conditions. The aim of the present study is to demonstrate how the experimentally observed limit cycle behavior of smart dampers can be predicted and explained by appropriate nonlinear models. The study is based upon a previously developed feedback control strategy, but the techniques described are relevant to other forms of smart damper control.

Adaptive and Nonlinear Control of Discharge Pressure for Variable Displacement Axial Piston Pumps

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Janne Koivumäki ◽  
Jouni Mattila
Keyword(s):  
Controller Design ◽  
Design Method ◽  
Pressure Control ◽  
Feedback Signal ◽  
Hydraulic Systems ◽  
Axial Piston Pumps ◽  
Highly Nonlinear ◽  
Variable Displacement ◽  
Discharge Pressure ◽  
Axial Piston

This paper proposes, for the first time without using any linearization or order reduction, an adaptive and model-based discharge pressure control design for the variable displacement axial piston pumps (VDAPPs), whose dynamical behaviors are highly nonlinear and can be described by a fourth-order differential equation. The rigorous stability proof, with an asymptotic convergence, is given for the entire system. In the proposed novel controller design method, the specifically designed stabilizing terms constitute an essential core to cancel out all the stability-preventing terms. The experimental results reveal that rapid parameter adaptation significantly improves the feedback signal tracking precision compared to a known-parameter controller design. In the comparative experiments, the adaptive controller design demonstrates the state-of-the-art discharge pressure control performance, enabling a possibility for energy consumption reductions in hydraulic systems driven with VDAPP.

scholarly journals Modelling and robust control of an unmanned coaxial rotor helicopter with unstructured uncertainties

2017 ◽  
Vol 9 (1) ◽  
pp. 168781401668796 ◽  
Author(s):  
Zhi-Yan Dong ◽  
Shun-An Liu ◽  
Chao Liu ◽  
Jin-Lin Liu ◽  
Lei Feng
Keyword(s):  
Robust Control ◽  
Closed Loop ◽  
Controller Design ◽  
General Rule ◽  
Step Response ◽  
Integrative Approach ◽  
Actuator Dynamics ◽  
Coaxial Rotor ◽  
Uncertainty Model ◽  
Empirical Coefficients

A complete methodology for an unmanned coaxial rotor helicopter with unstructured uncertainties was proposed to achieve high-accuracy tracking performance from modelling to robust control. An integrative approach was introduced to systematically construct a whole dynamic model. The key parameters were selected carefully after iteratively being checked by empirical coefficients to decrease the budget and risk of programme. Moreover, a new control scheme is proposed to simultaneously incorporate six inputs to control six states based on the investment of singularity value responses and the general rule of relative gain array. Coprime factor uncertainty model is considered to represent a class of unstructured uncertainties, such as unmolded actuator dynamics and unpredicted interferences between two rotors. Furthermore, the [Formula: see text] loop-shaping control was proposed to apply the control design of the coaxial rotor helicopter to manage complicated uncertainties and multivariable coupling. Finally, simulation results show the effectiveness of the proposed controller design in the step response of the closed loop. The stable closed-loop plant is achieved and the tolerant size of unstructured uncertainty is up to 36.09%. Good step responses and satisfied decoupling were also investigated in detail.

Mode-Based Controller Design for Hammerstein Models Using Closed-Loop Tranjent Response Data

2016 ◽  
Vol 136 (5) ◽  
pp. 625-632
Author(s):  
Yoshihiro Matsui ◽  
Hideki Ayano ◽  
Shiro Masuda ◽  
Kazushi Nakano
Keyword(s):  
Closed Loop ◽  
Controller Design ◽  
Response Data ◽  
Hammerstein Models

scholarly journals Robust H∞ Loop Shaping Controller Synthesis for SISO Systems by Complex Modular Functions

2021 ◽  
Vol 26 (1) ◽  
pp. 21
Author(s):  
Ahmad Taher Azar ◽  
Fernando E. Serrano ◽  
Nashwa Ahmad Kamal
Keyword(s):  
Design Methodology ◽  
Closed Loop ◽  
Complex Analysis ◽  
Controller Design ◽  
Filter Design ◽  
Design Procedure ◽  
Elliptic Functions ◽  
Loop System ◽  
Closed Loop System ◽  
Loop Shaping

In this paper, a loop shaping controller design methodology for single input and a single output (SISO) system is proposed. The theoretical background for this approach is based on complex elliptic functions which allow a flexible design of a SISO controller considering that elliptic functions have a double periodicity. The gain and phase margins of the closed-loop system can be selected appropriately with this new loop shaping design procedure. The loop shaping design methodology consists of implementing suitable filters to obtain a desired frequency response of the closed-loop system by selecting appropriate poles and zeros by the Abel theorem that are fundamental in the theory of the elliptic functions. The elliptic function properties are implemented to facilitate the loop shaping controller design along with their fundamental background and contributions from the complex analysis that are very useful in the automatic control field. Finally, apart from the filter design, a PID controller loop shaping synthesis is proposed implementing a similar design procedure as the first part of this study.

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