An innovative design method for nonlinear tuned mass damper

Li, Luyu,Du, Yongjia Techno-Press 2018 Structural monitoring and maintenance Vol.5 No.2

The commonly used TMD design method in the project assumes the TMD has pure linearity. However, in real engineering TMD will exhibit nonlinear behaviors. Without considering the nonlinearity of TMD, the control effect of the TMD that is designed by the linear design method, may be worse and even enlarge the structural response. In this paper, based on the previous study results of nonlinear TMD, the improved design method for engineering application is proposed. The linear design method and the improved design method are compared. Taking the best parameter obtained by the improved design method is less than or equal to 90% of that obtained by the original design method as the dividing line. The critical nonlinear coefficient, reaching which value the improved design method needs to be used, is given. Finally, numerical simulations on two engineering examples are conducted to proof the results.

Wavelet based system identification for a nonlinear experimental model

Li, Luyu,Qin, Han,Niu, Yun Techno-Press 2017 Smart Structures and Systems, An International Jou Vol.20 No.4

Traditional experimental verification for nonlinear system identification often faces the problem of experiment model repeatability. In our research, a steel frame experimental model is developed to imitate the behavior of a single story steel frame under horizontal excitation. Two adjustable rotational dampers are used to simulate the plastic hinge effect of the damaged beam-column joint. This model is suggested as a benchmark model for nonlinear dynamics study. Since the nonlinear form provided by the damper is unknown, a Morlet wavelet based method is introduced to identify the mathematical model of this structure under different damping cases. After the model identification, earthquake excitation tests are carried out to verify the generality of the identified model. The results show the extensive applicability and effectiveness of the identification method.

A nonlinear structural experiment platform with adjustable plastic hinges: analysis and vibration control

Li, Luyu,Song, Gangbing,Ou, Jinping Techno-Press 2013 Smart Structures and Systems, An International Jou Vol.11 No.3

The construction of an experimental nonlinear structural model with little cost and unlimited repeatability for vibration control study represents a challenging task, especially for material nonlinearity. This paper reports the design, analysis and vibration control of a nonlinear structural experiment platform with adjustable hinges. In our approach, magnetorheological rotary brakes are substituted for the joints of a frame structure to simulate the nonlinear material behaviors of plastic hinges. For vibration control, a separate magnetorheological damper was employed to provide semi-active damping force to the nonlinear structure. A dynamic neural network was designed as a state observer to enable the feedback based semi-active vibration control. Based on the dynamic neural network observer, an adaptive fuzzy sliding mode based output control was developed for the magnetorheological damper to suppress the vibrations of the structure. The performance of the intelligent control algorithm was studied by subjecting the structure to shake table experiments. Experimental results show that the magnetorheological rotary brake can simulate the nonlinearity of the structural model with good repeatability. Moreover, different nonlinear behaviors can be achieved by controlling the input voltage of magnetorheological rotary damper. Different levels of nonlinearity in the vibration response of the structure can be achieved with the above adaptive fuzzy sliding mode control algorithm using a dynamic neural network observer.

A nonlinear structural experiment platform with adjustable plastic hinges: analysis and vibration control

Luyu Li,Gangbing Song,Jinping Ou 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.11 No.3

The construction of an experimental nonlinear structural model with little cost and unlimited repeatability for vibration control study represents a challenging task, especially for material nonlinearity. This paper reports the design, analysis and vibration control of a nonlinear structural experiment platform with adjustable hinges. In our approach, magnetorheological rotary brakes are substituted for the joints of a frame structure to simulate the nonlinear material behaviors of plastic hinges. For vibration control, a separate magnetorheological damper was employed to provide semi-active damping force to the nonlinear structure. A dynamic neural network was designed as a state observer to enable the feedback based semi-active vibration control. Based on the dynamic neural network observer, an adaptive fuzzy sliding mode based output control was developed for the magnetorheological damper to suppress the vibrations of the structure. The performance of the intelligent control algorithm was studied by subjecting the structure to shake table experiments. Experimental results show that the magnetorheological rotary brake can simulate the nonlinearity of the structural model with good repeatability. Moreover, different nonlinear behaviors can be achieved by controlling the input voltage of magnetorheological rotary damper. Different levels of nonlinearity in the vibration response of the structure can be achieved with the above adaptive fuzzy sliding mode control algorithm using a dynamic neural network observer.

Low-Frequency Vibration Control of Metro Slab Track Based on Locally Resonant Theory

Chao Li,Sifeng Zhang,Qian Liu,Chong Zhou,Haichao Qin,Luyu Zhang,Minghu Zhai 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.6

Vibration control has always been one of the research hotspots in the field of urban metro system. Due to the unsatisfactory application effect of traditional vibration damping technology in practice, a novel method, based on the locally resonant theory, was introduced into metro vibration damping system to improve the low-frequency vibration reduction effect. Meanwhile, the new metro vibration reduction slab track was designed. Furthermore, the coupled model of the metro vehicle-slab track was established and verified, and the reduction effect of the new metro slab track on low-frequency vibration under the action of metro vehicles was analyzed. Results show that: 1) The new vibration reduction slab track is really in control of the low-frequency vibration (50 − 100 Hz), and the attenuation effect can reach 10 dB; 2) The new slab track has multiple low-frequency vibration band gaps, which can achieve multi-frequency vibration reduction; 3) The new slab track can reduce the vibration acceleration of the track, which can improve the comfort level of the vehicle. Therefore, the local resonance theory enriches the existing metro vibration reduction design theory and provides a method for the design of the metro vibration control.

A new approach to deal with sensor errors in structural controls with MR damper

Han Wang,Luyu Li,Gangbing Song,James B. Dabney,Thomas L. Harman 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.2

As commonly known, sensor errors and faulty signals may potentially lead structures in vibration to catastrophic failures. This paper presents a new approach to deal with sensor errors/faults in vibration control of structures by using the Fault detection and isolation (FDI) technique. To demonstrate the effectiveness of the approach, a space truss structure with semi-active devices such as Magneto-Rheological (MR) damper is used as an example. To address the problem, a Linear Matrix Inequality (LMI) based fixed-order H∞ FDI filter is introduced and designed. Modeling errors are treated as uncertainties in the FDI filter design to verify the robustness of the proposed FDI filter. Furthermore, an innovative Fuzzy Fault Tolerant Controller (FFTC) has been developed for this space truss structure model to preserve the pre-specified performance in the presence of sensor errors or faults. Simulation results have demonstrated that the proposed FDI filter is capable of detecting and isolating sensor errors/faults and actuator faults e.g., accelerometers and MR dampers, and the proposed FFTC can maintain the structural vibration suppression in faulty conditions.

A wireless decentralized control experimental platform for vibration control of civil structures

Yan Yu,Luyu Li,Xiaozhi Leng,Gangbing Song,Zhiqiang Liu,Jinping Ou 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.1

Considerable achievements in developing structural regulators as an important method for vibration control have been made over the last few decades. The use of large quantities of cables in traditional wired control systems to connect sensors, controllers, and actuators makes the structural regulators complicated and expensive. A wireless decentralized control experimental platform based on Wi-Fi unit is designed and implemented in this study. Centralized and decentralized control strategies as sample controllers are employed in this control system. An optimal control algorithm based on Kalman estimator is embedded in the dSPACE controller and the DSP controller. To examine the performance of this control scheme, a three-story steel structure is developed with active mass dampers installed on each floor as the wireless communication platform. Experimental results show that the wireless decentralized control exhibits good control performance and has various potential applications in industrial control systems. The proposed experimental system may become a benchmark platform for the validation of the corresponding wireless control algorithm.

Design and control of a proof-of-concept active jet engine intake using shape memory alloy actuators

Song, Gangbing,Ma, Ning,Li, Luyu,Penney, Nick,Barr, Todd,Lee, Ho-Jun,Arnold, Steve Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.7 No.1

It has been shown in the literature that active adjustment of the intake area of a jet engine has potential to improve its fuel efficiency. This paper presents the design and control of a novel proof-of-concept active jet engine intake using Nickel-Titanium (Ni-Ti or Nitinol) shape memory alloy (SMA) wire actuators. The Nitinol SMA material is used in this research due to its advantages of high power-to-weight ratio and electrical resistive actuation. The Nitinol SMA material can be fabricated into a variety of shapes, such as strips, foils, rods and wires. In this paper, SMA wires are used due to its ability to generate a large strain: up to 6% for repeated operations. The proposed proof-of-concept engine intake employs overlapping leaves in a concentric configuration. Each leaf is mounted on a supporting bar than can rotate. The supporting bars are actuated by an SMA wire actuator in a ring configuration. Electrical resistive heating is used to actuate the SMA wire actuator and rotate the supporting bars. To enable feedback control, a laser range sensor is used to detect the movement of a leaf and therefore the radius of the intake area. Due to the hysteresis, an inherent nonlinear phenomenon associated with SMAs, a nonlinear robust controller is used to control the SMA actuators. The control design uses the sliding-mode approach and can compensate the nonlinearities associated with the SMA actuator. A proof-of-concept model is fabricated and its feedback control experiments show that the intake area can be precisely controlled using the SMA wire actuator and has the ability to reduce the area up to 25%. The experiments demonstrate the feasibility of engine intake area control using an SMA wire actuator under the proposed design.

Design and control of a proof-of-concept active jet engine intake using shape memory alloy actuators

Gangbing Song,Ning Ma,Luyu Li,Nick Penney,Todd Barr,Ho-Jun Lee,Steve Arnold 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.7 No.1

It has been shown in the literature that active adjustment of the intake area of a jet engine has potential to improve its fuel efficiency. This paper presents the design and control of a novel proof-of-concept active jet engine intake using Nickel-Titanium (Ni-Ti or Nitinol) shape memory alloy (SMA) wire actuators. The Nitinol SMA material is used in this research due to its advantages of high power-to-weight ratio and electrical resistive actuation. The Nitinol SMA material can be fabricated into a variety of shapes, such as strips, foils, rods and wires. In this paper, SMA wires are used due to its ability to generate a large strain: up to 6% for repeated operations. The proposed proof-of-concept engine intake employs overlapping leaves in a concentric configuration. Each leaf is mounted on a supporting bar than can rotate. The supporting bars are actuated by an SMA wire actuator in a ring configuration. Electrical resistive heating is used to actuate the SMA wire actuator and rotate the supporting bars. To enable feedback control, a laser range sensor is used to detect the movement of a leaf and therefore the radius of the intake area. Due to the hysteresis, an inherent nonlinear phenomenon associated with SMAs, a nonlinear robust controller is used to control the SMA actuators. The control design uses the sliding-mode approach and can compensate the nonlinearities associated with the SMA actuator. A proof-of-concept model is fabricated and its feedback control experiments show that the intake area can be precisely controlled using the SMA wire actuator and has the ability to reduce the area up to 25%. The experiments demonstrate the feasibility of engine intake area control using an SMA wire actuator under the proposed design.

Numerical study of fly ash deposition process in low temperature economizer under SCR conditions

Shuangcheng Fu,Gang Cao,Guofu Ou,Faqi Zhou,Luyu Li 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.7

After the boiler of a thermal power plant in Nanjing was reformed for denitrification, the clogging of flyash particles occurred near the support beam of the economizer. The critical speed criterion under different workingconditions was constructed by Fluent custom code (UDF), and the change of fly ash deposition on the support beamof the economizer was simulated without ABS and with ABS. At the same time, the influence of the fin layout structureon the movement of smoke and fly ash particles was analyzed. The results show that the stagnation of fly ash particleson the supporting beam is the main cause of sediment clogging. Due to the production of ABS in the process ofdenitrification, the adhesion of fly ash particles is intensified. At the same time, the fin structure on the support beamhinders the lateral movement of fly ash particles, which causes the growth of clogged fly ash near the support plate. Onthis basis, an optimization plan for the fin structure is proposed, which improves the flue gas flow conditions andavoids the occurrence of clogging and growth of fly ash.