Feedback Control to Prevent Damage by Rotor Rubbing After an Impact Load

2009 ◽  
Author(s):  
Lucas Ginzinger ◽  
Benjamin Heckmann ◽  
Heinz Ulbrich
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Control Strategy ◽  
Impact Load ◽  
Operation Mode ◽  
Rotor System ◽  
Contact Forces ◽  
Normal Operation ◽  
Control Force ◽  
Auxiliary Bearing

A new approach to control a rubbing rotor by applying an active auxiliary bearing has been developed. The control force is applied indirectly using the auxiliary bearing, only in case of rotor rubbing. The auxiliary bearing is actuated using two unidirectional actuators. A three-phase control strategy has been developed which stabilizes the rotor system in case of an impact load and effectively avoids “backward whirling” which is very destructive. As soon as the load ceased the auxiliary bearing is separated from the rotor again and normal operation mode is continued. During the normal operation state, the feedback control does not interfere with the rotor system at all. A test rig has been developed to experimentally verify the control system. Various experiments show the success of the control strategy. In case of rubbing, the contact forces are reduced up to 95 percent. At the same time, the rotor deflection is decreased too. The activation and deactivation of the control system is operated fully automatically. A simulation framework for an elastic rotor including the non-smooth nonlinear dynamics of contacts is presented, which has been used to develop the feedback controller.

Efficient and Robust Rub Control With an Active Auxiliary Bearing

2007 ◽  
Author(s):  
Lucas Ginzinger ◽  
Heinz Ulbrich
Keyword(s):  
Control System ◽  
Control Strategy ◽  
High Efficiency ◽  
Industrial Applications ◽  
Rotor System ◽  
Contact Forces ◽  
Smooth Transition ◽  
Normal Operation ◽  
Control Force ◽  
Auxiliary Bearing

In this contribution, a new approach to control a rubbing rotor by applying an active auxiliary bearing is presented. The auxiliary bearing is attached to the foundation via two unidirectional actuators. The control force is applied indirectly using the auxiliary bearing, only in case of rotor rubbing. During a normal operation state, the feedback control does not interfere with the rotor system at all. A robust control system has been developed which significantly reduces the intensity of rubbing by stabilizing the rotor system and assuring an optimal rubbing state in case of a too large rotor amplitude. The two-phase control strategy guarantees a smooth transition from free rotor motion to the state of synchronous full annular rub. A test rig has been developed to experimentally verify the control system. Various experiments show the success of the control strategy. In case of rubbing, the contact forces are reduced up to 80 per cent, which results in significantly lower loads. At the same time, the rotor deflection is decreased too. For industrial applications, the activation of the control system can be operated fully automatically. The high efficiency of the control algorithm allows an implementation on microcontrollers. The developed control of the auxiliary bearing reduces the load and the noise of the system during rotor rubbing significantly.

Application of Combined Feedforward and Feedback Controller With Shaped Input to Benchmark Problem

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Young Joo Shin ◽  
Peter H. Meckl
Keyword(s):  
Feedback Control ◽  
Control Strategy ◽  
Control Strategies ◽  
Control Design ◽  
Single Frequency ◽  
Benchmark Problems ◽  
Control Force ◽  
Benchmark Problem ◽  
Advantages And Disadvantages ◽  
Robust Control Design

Benchmark problems have been used to evaluate the performance of a variety of robust control design methodologies by many control engineers over the past 2 decades. A benchmark is a simple but meaningful problem to highlight the advantages and disadvantages of different control strategies. This paper verifies the performance of a new control strategy, which is called combined feedforward and feedback control with shaped input (CFFS), through a benchmark problem applied to a two-mass-spring system. CFFS, which consists of feedback and feedforward controllers and shaped input, can achieve high performance with a simple controller design. This control strategy has several unique characteristics. First, the shaped input is designed to extract energy from the flexible modes, which means that a simpler feedback control design based on a rigid-body model can be used. In addition, only a single frequency must be attenuated to reduce residual vibration of both masses. Second, only the dynamics between control force and the first mass need to be considered in designing both feedback and feedforward controllers. The proposed control strategy is applied to a benchmark problem and its performance is compared with that obtained using two alternative control strategies.

On Selection of Control Parameters for H∞ Output Feedback

2005 ◽  
Author(s):  
Chang-Ching Chang ◽  
Chi-Chang Lin
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Output Feedback ◽  
Delay Time ◽  
Output Feedback Control ◽  
Feedback Gain ◽  
Control Force ◽  
Control Parameters ◽  
Structural Responses ◽  
Control Forces

In this paper, an H∞ direct output feedback control algorithm through minimizing the entropy, a performance index measuring the tradeoff between H∞ optimality and H2 optimality, is employed to design the control system in reducing structural responses due to dynamic loads such as earthquakes. The control forces are obtained from the multiplication of direct output measurements by a pre-calculated time-invariant feedback gain matrix. To achieve optimal control performance, the strategy to select both control parameters γ and α is extensively investigated. The decrease of γ or increase of α results in better control effectiveness, but larger control force requirement. For a single degree-of-freedom (SDOF) damped structure, exact solutions of output feedback gains and control parameters are derived. It can be proved analytically that the LQR control is a special case of the proposed H∞ control. Direct velocity feedback control is effective in reducing structural responses with very small number of sensors and controllers compared with the DOFs of the structure. In active control of a real structure, control force execution time delay cannot be avoided. Relatively small delay time not only can render the control ineffective, but also may cause system instability. In this study, explicit formulas to calculate maximum allowable delay time and critical control parameters are derived for the design of a stable control system. Some solutions are also proposed to increase the maximum allowable delay time.

scholarly journals PD Plus Dynamic Pressure Feedback Control for a Direct Drive Stewart Manipulator

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1125 ◽  
Author(s):  
Chenyang Zhang
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Dynamic Characteristics ◽  
Control Strategy ◽  
Dynamic Pressure ◽  
Control Input ◽  
Servo Motor ◽  
Direct Drive ◽  
Pressure Feedback ◽  
Current Coupling

In order to ensure good dynamic characteristics, servo valve is usually adopted as the drive part of Stewart manipulator which causes huge power consumption, while direct drive electro-hydraulic servo system has the advantages of energy saving, simple structure, convenient installation, and low failure rate. But its dynamic characteristics are so poor that it can only be applied to occasions where quick response is not needed. On the consideration above, following works are done in this paper. Since current coupling exists in the control system based on the speed of the servo motor as the control input, the control system of the direct drive Stewart manipulator is established based on the current of the servo motor as the control input in which the current coupling can be solved. In order to improve the dynamic characteristics of the direct drive Stewart manipulator, a Proportion Differentiation (PD) plus dynamic pressure feedback control strategy is also put forward in this paper, which is verified by using a simulated hydraulically driven Stewart manipulator. Simulation results show that both dynamic coupling and current coupling are solved and the control strategy proposed in this paper can significantly increase the bandwidths of all degrees of freedom.

On the Control of Synchronous Vibration in Rotor/Magnetic Bearing Systems Involving Auxiliary Bearing Contact

2002 ◽  
Author(s):  
Patrick Keogh ◽  
Matthew Cole ◽  
Necip Sahinkaya ◽  
Clifford Burrows
Keyword(s):  
Controller Design ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Normal Operation ◽  
Design Parameters ◽  
Full Control ◽  
Bearing Contact ◽  
Vibratory Motion ◽  
Auxiliary Bearing ◽  
Bearing Design

During the normal operation of rotor/magnetic bearing systems, contacts with auxiliary bearings or bushes are avoided. However, auxiliary bearings are required under abnormal conditions and in malfunctions situations to prevent contact between the rotor and stator laminations. Studies in the open literature deal largely with rotor drop and the requirements of auxiliary bearing design parameters for safe run-down. Rotor drop occurs when the rotor is de-levitated and no further means of magnetic bearing control is available. This paper considers the case when full control is still available and rotor/auxiliary bearing contact has been induced by an abnormal operating condition or temporary fault. It is demonstrated that events leading to contact from a linearly stable rotor orbit can drive the rotor into a non-linear vibratory motion involving persistent contacts. Furthermore, the phase of the measured vibration response may be changed to such an extent that synchronous controllers designed to minimize rotor vibration amplitudes will worsen the rotor response, resulting in higher contact forces. A modified controller design is proposed and demonstrated to be capable of returning a rotor from a contacting to a non-contacting state.

Active Power Control Strategy with Auxiliary Frequency Regulation Function of Wind Farms

2014 ◽  
Vol 536-537 ◽  
pp. 1257-1260
Author(s):  
Guan Qi Liu ◽  
Li Na Wu
Keyword(s):  
Power Control ◽  
Control Strategy ◽  
Power Plants ◽  
Operation Mode ◽  
Wind Farms ◽  
Active Power ◽  
Normal Operation ◽  
Frequency Regulation ◽  
Active Power Control ◽  
System Frequency

The fluctuations and uncertainties of wind power increase the frequency regulation pressure of conventional power plants. This paper introduces an active power control strategy with auxiliary frequency regulation function of wind farms. With this active power control strategy, wind farms can work in normal operation mode or in auxiliary regulation mode. Wind farms in normal operation mode can trace the power command to the utmost extent. When the system frequency drops large, to respond this change, the wind farms can switch to auxiliary regulation mode automatically. Simulation results show that the wind farms can assist the conventional power plants to regulate the system frequency effectively.

The Optimization to Control System of Desulfurization in Furnace of 300MW CFB Boiler

2012 ◽  
Vol 614-615 ◽  
pp. 1509-1513
Author(s):  
Xiang Jie Kong ◽  
Jian Yun Bai ◽  
Li Hong Liu
Keyword(s):  
Control System ◽  
Power Plant ◽  
Feedback Control ◽  
Knowledge Base ◽  
Control Strategy ◽  
Transmission System ◽  
Cfb Boiler ◽  
Feedback Control Strategy

This paper contraposes 300MW CFB boiler of Shanxi certain coal-fired power plant, then optimize the control system of desulfurization and remake limestone transmission system. Collect the signal to establish knowledge base for judging starting or stalling control of feeding machine through lots of experiments. Adopt feedback control strategy to adjust the speed of feeding machine. Achieve the purpose of automatically controling the starting or stalling of feeding machine and the speed of feeding machine finally.

Thermal Assessment of Dynamic Rotor/Auxiliary Bearing Contact Events

2006 ◽  
Vol 129 (1) ◽  
pp. 143-152 ◽  
Author(s):  
Patrick S. Keogh ◽  
Woon Yik Yong
Keyword(s):  
Contact Area ◽  
Initial Conditions ◽  
Frictional Heating ◽  
Thermal Response ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Normal Operation ◽  
Permanent Loss ◽  
Auxiliary Bearing ◽  
Transient Thermal

Under normal operation, a rotor levitated by magnetic bearings will rotate without making contact with any stator component. However, there are a number of circumstances that may lead to temporary or permanent loss of levitation. These include full rotor drop events arising from power loss, momentary fault conditions, sudden changes in unbalance, high levels of base acceleration, and other aerodynamically induced force inputs. The spinning rotor will come into dynamic contact with an auxiliary bearing. Highly localized and transient temperatures will arise from frictional heating over the dynamically varying contact area. Rotor dynamic contact forces are predicted for a range of initial conditions leading to combinations of bounce and rub motion on the auxiliary bearing. The transient heat flux from the contact area is then ascertained. A transient thermal Green’s function is developed in a form that is effective over short or long time scales and local to the source. This enables the transient thermal response of an auxiliary bearing to be assessed for a range of dynamic contact conditions. Auxiliary bearings consisting of fixed bushings and free to rotate inner races are analyzed. The results show that significant localized contact temperatures may arise from each contact event, which would accumulate for multiple contact cases. The methodology will be of relevance for the life prediction of auxiliary bearing designs.

Controller Design for a Rubbing Rotor

2009 ◽  
Vol 147-149 ◽  
pp. 203-214
Author(s):  
Lucas Ginzinger ◽  
Roland Zander ◽  
Heinz Ulbrich
Keyword(s):  
Controller Design ◽  
Experimental Studies ◽  
Feedback Controller ◽  
Contact Forces ◽  
Smooth Transition ◽  
Control Force ◽  
Simulation Environment ◽  
Two Phase ◽  
New Approach ◽  
Auxiliary Bearing

A new approach to control a rubbing rotor by applying an active auxiliary bearing is developed. The auxiliary bearing is attached to the foundation via two unidirectional actuators. The control force is applied indirectly using the active auxiliary bearing only in case of rubbing. A framework for the development of a feedback controller for an active auxiliary bearing is presented. The theory of a robust two-phase control strategy which guarantees a smooth transition from free rotor motion to the state of full annular rub is presented. A simulation environment for the elastic rotor and the auxiliary bearing including the non-smooth nonlinear dynamics of the rubbing contact is used to develop the feedback controller. Experimental studies have been carried out at a rotor test rig. Various experiments show the outstanding success of the strategy. In case of rubbing, the contact forces are reduced up to 90%.

The Optimization Research on Vehicle ESP Control Strategy

2013 ◽  
Vol 321-324 ◽  
pp. 1548-1553
Author(s):  
Liang Hong Zhao ◽  
Ai Min Fan ◽  
Ling Qin
Keyword(s):  
Control System ◽  
Control Strategy ◽  
Control Algorithm ◽  
Stability Control ◽  
Control Force ◽  
Electronic Stability Program ◽  
Longitudinal Control ◽  
Entire Vehicle ◽  
Car Security ◽  
Controlled Object

Electronic Stability Program (ESP) is an advanced initiative system for car security. As an integration of subsystems such as ABS, TCS, ESC, etc., this new control system is designed to accurately manipulate the dynamics behaviors of vehicles under critical adhesive conditions, allowing maximum cooperation of vehicles responses to the driver's operation within physical limits. This research has firstly established a dynamical model of an entire vehicle as the controlled object in this study of ESP. Then, the paper moved on to the design of ESP control algorithm strategy, discussing the selection problem of which wheels should the longitudinal control force apply to, and finally proposing an effective improvement on operational stability control of ESP system.

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