Experimental investigation and performance analysis of a dual-cylinder opposed linear compressor

Huiming Zou,Liqin Zhang,Guohong Peng,Changqing Tian 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.8

The dual-cylinder opposed linear compressor (DOLC) contains a couple of symmetrical gas loads on the two sides of the movement components. Because the gas loads are symmetrical, the balanced position of movement components will not be offset by gas force during the operating process, and piston displacement can be detected and controlled more easily. Based on the kinetics and thermodynamics theory, the non-linear gas load of the DOLC was linearized by the Fourier method. The relationship between the supply voltage and displacement is presented. Through air compression experiments, the operation features of the DOLC with different syntonic spring groups were analyzed. The performance of the DOLC was considerably affected by work conditions and the stiffness of syntonic spring groups;the closer the work condition was to the sympathetic vibration, the higher the observed efficiency of the DOLC. A jump, hysteresis, and an unstable phenomenon in the process of voltage regulation occurred around sympathetic vibration conditions. In the process of increasing voltage on a certain discharge pressure condition, the displacement jump phenomenon occurred when the intrinsic frequency approacheds power frequency, causing the discharge pressure to drop synchronously. In the process of decreasing voltage on the lower discharge pressure condition, the displacement shrink phenomenon occurred when the intrinsic frequency approached power frequency. Because sympathetic vibration conditions changed with discharge pressures, a hysteresis district existed between the displacement jump point and shrink point. The DOLC worked unstably on the hysteresis district because the discharge pressure fluctuated between the two values. To make the DOLC work stably on higher efficiency, the intrinsic frequency should be configured to a slightly larger value than the power frequency by setting the syntonic spring groups and the mass of movement components to the ratings on the work conditions. Controlling the power frequency after is needed to adhere to the intrinsic frequency of the variable work conditions.

Full Diversity Space-Frequency Codes for Frequency Asynchronous Cooperative Relay Networks with Linear Receivers

Huiming Wang,Qinye Yin,Xiang-Gen Xia IEEE 2011 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.59 No.1

<P>In this paper, we propose a family of distributed space-frequency codes (SFCs) for frequency asynchronous cooperative relay networks with multiple carrier frequency offsets (CFOs) and flat fading channels. The codes have the special structures that the columns of each code matrix can be divided into several orthogonal groups and each group is stacked by several sub-blocks with Toeplitz structure. These codes possess two interesting properties: a) Even under the frequency-asynchronous scenario, the codes can , namely, if R relay nodes participate the cooperation adopting the proposed SFCs, then at the destination node, the achievable diversity order is R; b) Only , such as zero-forcing (ZF) and minimum mean square error (MMSE) receivers, are required to collect the full cooperative diversity, instead of the maximum likelihood (ML) detector as utilized in most existing STC (SFC) schemes. The codes in this family have different symbol rates, orthogonality and performances for different numbers of relay nodes, which can be adjusted by choosing different design parameters. It is shown that frequency-reversal SFC (FR-SFC), and frequency-shift SFC (FS-SFC) proposed in previous papers are only two special members of the code family, and new SFCs outperforming both of them are proposed.</P>

Performance characteristics around the TDC of linear compressor based on whole-process simulation

Huiming Zou,Mingsheng Tang,HONGBO XU,SHUANGQUAN SHAO,Changqing Tian 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.10

A whole-process simulation platform is established for linear compressor to analyze the performance characteristics on different pistondisplacement conditions from small oscillation without pumping till to rushing out of the top dead center (TDC). The measuring methodsof the related parameters in the model are presented and the values of these parameters are obtained from an actual test. The simulatedresults agreed well with the experimental results under the same working conditions. The errors of the effective voltage, the effectivecurrent, the compression efficiency and the phase angle between the current and the displacement were within ±6.9%,±8.5%,±6.2%and±13.4%, respectively. Based on this simulation platform, the performance characteristic around the TDC of the linear compressor ondifferent working conditions is analyzed. The performance comparison on 60 Hz shows that the compression efficiency near to the TDCon 0.7 MPa is higher than that on 0.5 MPa because the phase angle α under that condition is around 90°, but the operation reliability on0.7 MPa is worse than that on 0.5 MPa because the jump phenomenon happens when the piston displacement goes near to the TDC. Thejump phenomenon results in unstable operation as the piston displacement jumps from the position before the TDC to the position afterthe TDC. According to the simulation on different power frequency, two important performance characteristics are inferred. One is thatthere is an inflection point in the curve of the phase angle α versus the displacement at the TDC. This characteristic is a good choice forthe TDC detection. The other is that the jump phenomenon is prone to happening when there exist different displacement responses onthe same voltage value, becoming inconspicuous when the power frequency is decreased and disappearing when the power frequency isincreased. Based on this characteristic, the jump phenomenon can be avoided through suitable system configuration and frequency adjustment.

On the Disturbance Rejection Control of Flexible-joint Robot: A GPIO-based Approach

Huiming Wang,Yang Zhang,Xiaolei Chen,Xianlun Tang,I-Ming Chen 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.8

A robust disturbance rejection control scheme is addressed for the trajectory tracking problem of a flexible-joint robot (FJR). The system is always severely affected by various types of unknown disturbances including model errors, couplings, changing working environments as well as unmodeled dynamics. These disturbances on the link and actuator side will deteriorate the control performance of FJR. By considering all the disturbances as an unknown lumped time-varying disturbance, a flatness description of FJR is developed. Then, a new output feedback controller is constructed through the estimates of unmeasurable states and unknown lumped disturbance provided by a generalized proportional integral observer (GPIO). The stability of the closed-loop system with the driven of the proposed control scheme is guaranteed under some mild assumptions. Compared with the conventional linear active disturbance rejection control (LADRC) scheme, test results are presented to demonstrate the feasibility and efficacy of the proposed control approach.

Robust variable selection in partially varying coefficient single-index model

Huiming Zhu,Zhike Lv,Keming Yu,Chao Deng 한국통계학회 2015 Journal of the Korean Statistical Society Vol.44 No.1

By combining basis function approximations and smoothly clipped absolute deviation(SCAD) penalty, this paper proposes a robust variable selection procedure for a partiallyvarying coefficient single-index model based on modal regression. The proposed proceduresimultaneously selects significant variables in the parametric components and thenonparametric components. With appropriate selection of the tuning parameters, we establishthe theoretical properties of our procedure, including consistency in variable selectionand the oracle property in estimation. Furthermore, we also discuss the bandwidthselection and propose a modified expectation–maximization (EM)-type algorithm for theproposed estimation procedure. The finite sample properties of the proposed estimatorsare illustrated by some simulation examples.

Development of large bore superconducting magnet for wastewater treatment application

Huiming Liu,Dong Xu,Fuzhi Shen,Hengcheng Zhang,Laifeng Li 한국초전도저온학회 (구 한국초전도저온공학회) 2017 한국초전도저온공학회논문지 Vol.19 No.1

Three new eyeless Draconarius spiders (Araneae, Amaurobiidae) from limestone caves in Guizhou, southwestern China

Huiming Chen,Mingsheng Zhu,Joo-Pil Kim 한국거미연구소 2008 한국거미 Vol.24 No.2

Three new eyeless species of Draconarius from limestone caves in Guizhou, China, are diagnosed, described and illustrated: Draconarius tortus sp. nov., D. proximus sp. nov. and D. digituliscaput sp. nov.. Both of them are troglobite, with reduced eyes.

Deep Learning for Image Denoising

HuiMing Li 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.3

Continuous Sliding Mode Control for Permanent Magnet Synchronous Motor Speed Regulation Systems Under Time-Varying Disturbances

Huiming Wang,Shihua Li,Jun Yang,XingPeng Zhou 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4

This article explores the speed regulation problem of permanent magnet synchronous motor (PMSM) systems subjected to unknown time-varying disturbances. A continuous sliding mode control (CSMC) technique is introduced for the speed loop to enhance the robustness of PMSM systems and eliminate the chattering phenomenon caused by high-frequency switch function in the conventional control law. However, the high control gain of the CSMC law in the presence of strong disturbances leads to large steady-state speed fluctuations for PMSM systems. In many application fields, PMSM systems are affected by time-varying disturbances instead of constant disturbances. For example, electric bicycles are usually affected by changing environmental disturbances, including wind speeds, road conditions, etc. These disturbances may be in the form of constant, ramp, and parabolic disturbances. Hence, a generalized proportional integral (GPI) observer is employed to estimate these types of disturbances. Then, the disturbance estimation method and the aforementioned CSMC method are combined to establish a composite sliding mode control method called the CSMC+GPI method for the speed loop of PMSM systems. Contrary to the conventional sliding mode control technique, the proposed method completely eliminates the chattering phenomenon caused by the switching function in the conventional control law. Moreover, a small control gain for the CSMC+GPI method is chosen by feed-forwarding estimated values to the speed controller. Hence, the steady-state speed fluctuations are small. The effectiveness of the proposed control scheme is verified by simulation and experimental result.

Development of large bore superconducting magnet for wastewater treatment application

Liu, Huiming,Xu, Dong,Shen, Fuzhi,Zhang, Hengcheng,Li, Laifeng The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.1

Water issue, especially water pollution, is a serious issue of 21st century. Being an significant technique for securing water resources, superconducting magnetic separation wastewater system was indispensable. A large bore conduction-cooled magnet was custom-tailored for wastewater treatment. The superconducting magnet has been designed, fabricated and tested. The superconducting magnet was composed of NbTi solenoid coils with an effective horizontal warm bore of 400 mm and a maximum central field of 2.56T. The superconducting magnet system was cooled by a two-stage 1.5W 4K GM cryocooler. The NbTi solenoid coils were wound around an aluminum former that is thermally connected to the second stage cold head of the cryocooler through a conductive copper link. The temperature distribution along the conductive link was measured during the cool-down process as well as at steady state. The magnet was cooled down to 4.8K in approximately 65 hours. The test of the magnetic field and quench analysis has been performed to verify the safe operation for the magnet system. Experimental results show that the superconducting magnet reached the designed magnetic performance.