Luyu Li

Development of Wireless MEMS Inclination Sensor System for Swing Monitoring of Large-Scale Hook Structures

A modular wireless microelectromechanical system (MEMS) inclination sensor system (WMISS) is developed and tested for providing structural health monitoring of large-scale hook structures. The operating principle of a 3-D-MEMS-based dual-axis inclinometer is analyzed. A wireless MEMS sensor is integrated using sensing disposal, wireless communication, and power units. The WMISS is calibrated by using a laser displacement sensor in a pendular structure. The maximal error of the wireless MEMS inclination sensor is about 1%. The resolution is plusmn0.0025deg. With the new-type tuned mass damper control module, an experiment on a WMISS for the swing monitoring of a Lanjiang hook model is developed. Experimental results indicate that the developed WMISS is highly precise, convenient, stable, and low cost and has long range, and thus, a WMISS can accurately and conveniently monitor the swing of a Lanjiang hook model.

Wireless Sensing and Vibration Control With Increased Redundancy and Robustness Design

Control systems with long distance sensor and actuator wiring have the problem of high system cost and increased sensor noise. Wireless sensor network (WSN)-based control systems are an alternative solution involving lower setup and maintenance costs and reduced sensor noise. However, WSN-based control systems also encounter problems such as possible data loss, irregular sampling periods (due to the uncertainty of the wireless channel), and the possibility of sensor breakdown (due to the increased complexity of the overall control system). In this paper, a wireless microcontroller-based control system is designed and implemented to wirelessly perform vibration control. The wireless microcontroller-based system is quite different from regular control systems due to its limited speed and computational power. Hardware, software, and control algorithm design are described in detail to demonstrate this prototype. Model and system state compensation is used in the wireless control system to solve the problems of data loss and sensor breakdown. A positive position feedback controller is used as the control law for the task of active vibration suppression. Both wired and wireless controllers are implemented. The results show that the WSN-based control system can be successfully used to suppress the vibration and produces resilient results in the presence of sensor failure.

Experimental study of wireless structural vibration control considering different time delays

With the development of wireless communication technology, active structural vibration control based on a wireless sensor network has tended to replace the traditional wired control method. However, the problem of time delay in a wireless control system is inevitable and requires serious attention. In this study, a wireless active vibration control scheme consisting of a cantilever beam with a piezoelectric actuator is proposed and implemented. Experimental results indicate that wireless control gives good control performance; however, because of the influence of time delay, the performance of wireless control is slightly worse than that of wired control. Therefore, a novel method for time delay compensation is presented in this study to resolve this problem. This approach takes advantage of the finite difference method to extend the state space of the cantilever beam. Additional time delay states are used to form the extended state space model for time delay compensation. Simulation and experimental results demonstrate that this method can effectively compensate for time delay and enables the wireless control system to exhibit excellent control performance that can be favorably compared with that of wired control.

Wireless inclinometer acquisition system for reducing swing movement control module experiment of hook model

Large Scale Heavy Derrick Lay Barge is very important for sea work. Under intense wind and wave load, the hook on the Barge will vibrate so large that in some cases it can not work. Through installing the Tuned Mass Damper(TMD) on the hook, the vibration will be reduced to a certain range to meet the demand on sea work, which is also important for increasing the efficiency of sea work. To design the suitable TMD for the hook, the dynamical parameters should be specified beforehand. Generally, the related dynamical parameters such as inclinometer and acceleration are measured by wire sensors. But due to the restriction of the actual condition, the wire sensors are very hard to implement. Recently, the wireless sensors have been presented to overcome the shortcomings of wire ones. It is more suitable and also convenient to utilize wireless sensors to acquire the useful data of large scale heavy derrick lay barge. In this paper, the hook reducing swing movement control module is designed for large scale heavy derrick lay barge. Secondly, wireless inclinometer sensor system is integrated using the technique of MEMS, sensing and wireless communication. Finally, the hook reducing swing movement control module is validated by the developed wireless inclinometer data acquisition system. The wireless inclinometer sensor can be used not only in swing monitoring for large scale heavy derrick lay barges Hook, but also in vibration monitoring for TV tower, large crane. In general, it has great application foreground.

Design and analysis of a dual-stator permanent magnet machine for the refrigerator linear compressor

In the application of household refrigerator, the linear compressor is popularly adopted due to its no crank mechanism and directly oscillated by the inside drive machine and the helical coil springs.

The research on electromagnetic and thermal issue of the high power density permanent magnet synchronous motor based on thermal conductivity optimization of the armature end

This paper investigates the relationship between the electromagnetic parameters and the extreme input current in a permanent magnet synchronous motor (PMSM). It is found that the direct-axis inductance, DC resistance, and back-EMF for no load conditions have a large influence on the limit of the extreme input current. Hence, the lower back-EMF and smaller direct-axis inductance can help to improve the max output power of PMSM. Finite element analysis is performed for thermal modelling using the ANSYS Workbench and verified by test experiments.

Design and initial validation of a wireless control system based on WSN

At present, cantilever structure used widely in civil structures will generate continuous vibration by external force due to their low damping characteristic, which leads to a serious impact on the working performance and service time. Therefore, it is very important to control the vibration of these structures. The active vibration control is the primary means of controlling the vibration with high precision and strong adaptive ability. Nowadays, there are many researches using piezoelectric materials in the structural vibration control. Piezoelectric materials are cheap, reliable and they can provide braking and sensing method harmless to the structure, therefore they have broad usage. They are used for structural vibration control in a lot of civil engineering research currently. In traditional sensor applications, information exchanges with the monitoring center or a computer system through wires. If wireless sensor networks(WSN) technology is used, cabling links is not needed, thus the cost of the whole system is greatly reduced. Based on the above advantages, a wireless control system is designed and validated through preliminary tests. The system consists of a cantilever, PVDF as sensor, signal conditioning circuit(SCM), A/D acquisition board, control arithmetic unit, D/A output board, power amplifier, piezoelectric bimorph as actuator. DSP chip is used as the control arithmetic unit and PD control algorithm is embedded in it. PVDF collects the parameters of vibration, sends them to the SCM after A/D conversion. SCM passes the data to the DSP through wireless technology, and DSP calculates and outputs the control values according to the control algorithm. The output signal is amplified by the power amplifier to drive the piezoelectric bimorph for vibration control. The structural vibration duration reduces to 1/4 of the uncontrolled case, which verifies the feasibility of the system.