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.

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.

scholarly journals Performance Analysis of Closed loop Control of Diesel Generator Power Supply for Base Transceiver (BTS) Load

2019 ◽  
Vol 8 (9) ◽  
pp. 2483-2495
Keyword(s):  
Closed Loop ◽  
Control Method ◽  
Complete System ◽  
Closed Loop Control ◽  
Double Loop ◽  
Diesel Generator ◽  
Unity Power Factor ◽  
Loop Control ◽  
Bridge Rectifier ◽  
The Stability

This paper describes closed loop control of Diesel Generator (DG) supplying power to a Base Transceiver (BTS) load of a telecommunication tower, which is DC in nature. Detail modeling of Diesel Generator set has been presented.. The stability analysis of governor and excitation system has been carried out in frequency domain. When DG source is connected to the BTS load bus through bridge rectifier, the output waveform distorted due to high odd harmonics content. To solve this problem a unity power factor rectifier has been designed. For the control operation of this UPFC rectifier, double loop mode control method has been used and results are presented. The complete system has been simulated in MATLAB-SIMULINK environment.

scholarly journals Integrating topology optimization in precision motion system design for optimal closed-loop control performance

Mechatronics ◽  
2017 ◽  
Vol 47 ◽  
pp. 1-13 ◽  
Author(s):  
Gijs van der Veen ◽  
Matthijs Langelaar ◽  
Stan van der Meulen ◽  
Dick Laro ◽  
Wouter Aangenent ◽  
...  
Keyword(s):  
Topology Optimization ◽  
System Design ◽  
Closed Loop ◽  
Closed Loop Control ◽  
Control Performance ◽  
Loop Control ◽  
Motion System ◽  
Precision Motion

Closed-loop control of unsteadiness over a rounded backward-facing step

2012 ◽  
Vol 703 ◽  
pp. 326-362 ◽  
Author(s):  
Alexandre Barbagallo ◽  
Gregory Dergham ◽  
Denis Sipp ◽  
Peter J. Schmid ◽  
Jean-Christophe Robinet
Keyword(s):  
Closed Loop ◽  
Random Noise ◽  
Reduced Order Model ◽  
Estimation Accuracy ◽  
Closed Loop Control ◽  
Backward Facing Step ◽  
Order Model ◽  
Loop Control ◽  
Reduced Order ◽  
And Performance

AbstractThe two-dimensional, incompressible flow over a rounded backward-facing step at Reynolds number $\mathit{Re}= 600$ is characterized by a detachment of the flow close to the step followed by a recirculation zone. Even though the flow is globally stable, perturbations are amplified as they are convected along the shear layer, and the presence of upstream random noise renders the flow unsteady, leading to a broadband spectrum of excited frequencies. This paper is aimed at suppressing this unsteadiness using a controller that converts a shear-stress measurement taken from a wall-mounted sensor into a control law that is supplied to an actuator. A comprehensive study of various components of closed-loop control design – covering sensor placement, choice and influence of the cost functional, accuracy of the reduced-order model, compensator stability and performance – shows that successful control of this flow requires a judicious balance between estimation speed and estimation accuracy, and between stability limits and performance requirements. The inherent amplification behaviour of the flow can be reduced by an order of magnitude if the above-mentioned constraints are observed. In particular, to achieve superior controller performance, the estimation sensor should be placed upstream near the actuator to ensure sufficient estimation speed. Also, if high-performance compensators are sought, a very accurate reduced-order model is required, especially for the dynamics between the actuator and the estimation sensor; otherwise, very minute errors even at low energies and high frequencies may render the large-scale compensated linearized simulation unstable. Finally, coupling the linear compensator to nonlinear simulations shows a gradual deterioration in control performance as the amplitude of the noise increases.

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