Abstract:A three-coil electromagnetic induction wear debris detection method with high sensitivity, low voltage and low power consumption is proposed. The induced voltage change caused by wear debris passing through the coil set is theoretically deduced, and the geometric parameters of the coil set are optimized based on the derivation. The dual LC resonance is realized by connecting capacitors of appropriate capacitance values to both sides of the coil set in parallel and in series to obtain higher excitation current and induced voltage. Experimental results show that under the excitation of sinusoidal signal of 108 kHz and 5 Vpp, the above two methods can greatly improve the signal-to-noise ratio, and ferrous debris as small as 150 μm can be clearly detected without using any amplifier circuit after the phase sensitive demodulation circuit, the active power of the excitation coil is only 1. 12 mW. The designed sensor can achieve high sensitivity while the low power consumption is balanced. The optimization idea can be used as a reference for the optimization of the same type of sensors.

Abstract:Magnetic liquid can replace solid elastic element with its unique second-order suspension force to provide the inertial element of the dip sensor with a flexible elastic force, which can greatly improve the impact resistance of the dip sensor. It has been successfully applied in petroleum exploration industry. To improve the sensitivity of the magnetic liquid dip sensor, a new structure and detection method is proposed based on the second-order suspension characteristics of magnetic liquid. The spatial distribution of magnetic field between two permanent magnets is calculated by the theory, and the static performance of the sensor with different parameters is analyzed by experiment comparisons. Results show that when the lateral clearance is 3 mm and the amount of magnetic fluid is 1. 4 g, the measurement range is 0° ~ 50°, the linearity error is 1. 004 7% , the response rate is 2. 3 mV/ °, the resolving power is 0. 023°, the repeatability error is 3. 18% , and the working performance of the sensor is the best. In addition, the performance-price-ratio index of the sensor is high and the material of the housing is environmental, which makes it has a good practical application value.

Abstract:The high-speed rotation, severe vibration and impact of the drilling tool could cause huge interference to the attitude measurement while drilling in the process of rotary steerable drilling. To address these issues, a drilling tool gravity acceleration extraction algorithm is proposed, which is based on the complementary filtering framework. First, the recursive equation of the gravitational acceleration based on the gyroscope is obtained through the cosine matrix differential equation. Then, the gravitational acceleration of the drilling tool is obtained by fusion under the framework of complementary filtering by using the complementary characteristics of the gyroscope and the accelerometer. Meanwhile, to improve the system′s robustness, the non-gravity acceleration and drilling tool rotation speed are utilized as the input of the fuzzy algorithm. The complementary filter parameters are dynamically adjusted through the fuzzy algorithm. Finally, vibration and rotation experiments are designed to evaluate the effectiveness of the algorithm. Experimental results show that the accuracy of attitude estimation is significantly improved after using the algorithm to extract the gravity acceleration. Compared with the gravity acceleration extraction algorithm based on the Kalman filter framework, the single operation time of the algorithm in the PC test environment is reduced by 31. 9% .

Abstract:To analyze the microscopic imaging characteristics of wear debris for full field-of-view online visual ferrograph (OLVF), a new reflected light microscopic imaging model is proposed. First, by taking the lambert-cosine law and the small-angle scattering theory as references, a reflected light irradiance model based on the wear debris microscopic imaging is formulated. The microscopic imaging sharpness of wear debris is evaluated quantitatively. Then, according to Matlab simulation calculation of contrast transmittance, the optimized value of optical magnification and the numerical ranges of oil attenuation coefficient detected by full field-of-view OLVF are determined. The changing rules of microscopic imaging sharpness of wear debris are investigated and determined successfully by analyzing the effectiveness of the numerical increasing of oil attenuation coefficient on contrast transmittance. Simulation results show that, under 2. 0× optical magnification and less than 2. 0 oil attenuation coefficient, wear debris deposites near the optical axis of object field of view. And the high-quality microscopic imaging of full field-of-view OLVF for detecting wear debris can be achieved. Finally, the experimental measurement of wear debris microscopic imaging is implemented by using the current full field-of-view OLVF. Results show that the full field-of-view reflected ferrograms of wear debris can be reliably obtained from different in-use lube oils with less than 2. 0 oil attenuation coefficient. It has potential for online wear monitoring by extracting the visual feature information of wear debris.

Abstract:In this article, a non-contact inductive angular displacement sensor is designed, which consists of a stator and a rotor. The rotor is obtained from the sector-shaped copper foil. The stator contains a set of excitation coils, a set of receiving coils and subsequent processing circuits. When an alternating current is applied to the excitation coil, the induced electromotive force generated by the two adjacent receiving coils is equal in magnitude and opposite in direction. Meanwhile, the induced voltage is 0. When the rotor rotates above the receiving coil, the eddy current generated in the rotor will cause and the induced voltages of two adjacent receiving coils have different changes. Through theoretical and simulation analysis, the amplitude of the induced voltages in the receiving coils changes in sine and cosine with the rotor rotation. The algorithm is applied to identify and calibrate the sine and cosine signals, and the prototype is tested with a high-precision time grid turntable with a positioning accuracy of 0. 000 3° as a reference. Results show that, after the calibration, the sensor error is 0. 1° within the range of 0° ~ 360°. It could meet actual production requirements, and the feasibility of the program is verified.

Abstract:The space-time image velocimetry (STIV) is a time-averaged velocity measurement method,which takes a testing line as the interrogation area (IA), and detects the main orientation of texture (MOT) of a generated space-time image ( STI) to estimate the 1D velocity. It has the characteristics of high spatial resolution and real-time. In practical applications, the detection accuracy of MOT is inevitably affected by environmental disturbances such as turbulence, shadow, flare, obstacle, and rain on river surface, which result in gross errors in the measurement. The image filtering technology in frequency domain is an effective method for restraining noise, which can significantly improve the texture clarity of STIs. However, the existing researches are insufficient in the sensitivity analysis of filter parameters, which limit the applicability of this method. In view of this, the video data of river surface under different conditions are collected by establishing an online video-based flow measurement system at a hydrological station. The spatial and frequency domain characteristics of STIs in six typical scenarios are analyzed. The sensitivity of three parameters of a fan filter in frequency domain, including direction angle, passband angle and radius is determined. Experimental results show that the proposed ellipse integral region is better than the existing single-pixel-wide line to detect direction angle. When the passband angle is set to be ±5. 3° and the radius is R/ 2, the filter can effectively filter out the noise interference in the above scenarios. The detection accuracy of MOT reaches 0. 1° in the normal scene and is controlled within 0. 5° in the complex noisy scene. The relative error of the surface flow velocity measurement is less than 6. 2% .

Abstract:To meet design requirements of the small off-axis space camera with compact structure and light weight, a highly lightweight integral carbon fiber main frame is designed. First, according to the design indicators and the optical system of the specific functions of the space camera, the material and structure of the main frame are determined. And the basic configuration of the carbon fiber monolithic main frame is designed. Then, the layup thickness is parameterized and optimized. The manufacturing constraints of carbon fiber composite materials are considered. The thickness and proportion of the main frame carbon fiber layup are determined. The results of parametric optimization are discretized, the stacking sequence of carbon fiber is optimized, the optimal stacking sequence is determined, the optimization design of carbon fiber is achieved, the lightweight design of the main frame is realized, and the optimization problem of complex carbon fiber parts is solved. Next, the designed carbon fiber main frame structure is substituted into the finite element model of the whole machine, and the finite element simulation analysis is implemented to verify the performance index of the main frame. Finally, the whole machine is assembled for dynamic test, and compared with the finite element analysis results. After optimization, the mass of the carbon fiber main frame is 4. 5 kg, the first-order frequency of the camera is 81 Hz, the first-order frequency of the camera obtained through the dynamic test is 78 Hz, and the simulation error is 3. 7% , which is in line with simulation results. Results further explain the rationality and correctness of the design. The design method of carbon fiber integral main frame of space camera proposed in this article has a certain reference significance for the structural design of micro off-axis three trans space camera and the lightweight optimization design of carbon fiber parts.

Abstract:To improve pseudolite positioning accuracy in the indoor multipath-contaminated environment, a multipath error correction model based on the user space position is formulated, which utilizes the spatio-temporal variation characteristics of indoor pseudolite carrier multipath. To be specific, the double-differenced carrier multipath errors of the static sampling points are extracted, and the three-dimensional coordinates of these points are taken as the input and the multipath error as the output. The error model is trained by the support vector regression based on the radial basis kernel function, and the optimal hyperparameters of the model are achieved by the leave-one-out cross-validation method. On the basis of this model, the double-differenced carrier observation equations are modified continuously through iteration. The position solutions can approximate the real coordinates to the greatest extent. Thus, the multipath is mitigated. The static relative positioning experiments in the strong-multipath-contaminated indoor environment show that the overall horizontal positioning accuracy after multipath correction is improved to the centimeter-decimeter level. The vertical accuracy within 1 m. This method can be implemented without system transformation, which is suitable for pseudolite high-precision positioning in the structured indoor environments.

Abstract:The ranging systematic error is the main factor that affects the orbit determination accuracy of geostationary earth orbit (GEO) satellites. The geostationary characteristics of GEO satellites make the ranging data systematic error. Especially for the station systematic error, it has a strong correlation with the satellite orbit. Therefore, the independent means must be used to solve. The simulation data are firstly used to analyze the impact characteristics of ground systematic error and on-board systematic error on the orbit. The FY-4B satellite ranging system is taken as an example to analyze the measured range data. The analysis results show that there is an abnormal systematic error in the FY-4B ranging system. To determine the source of this system error, a series of schemes are designed. Through experiments, the systematic error is not from the ground or the satellite. And it is determined that the systematic error of the FY-4B comes from the satellite. The orbit determination estimation is utilized to calculate the on-board systematic error to calibrate it. The calibrated observation data are used to achieve orbit determination, and the residual error of each station is reduced from 15 m to 2 m. The orbit determination accuracy is improved from 800 m to 20 m. The analysis results show that the method of calibrating the systematic error on the satellite through the orbit determination estimation is practical and effective.

Abstract:To solve the common problems of the thermoelectric effect error and the dielectric loss of the nonmetallic support frame for the bifilar, quadrifilar, octofilar and double helix calculable resistors, one kind of 1 kΩ four terminal-pair (4TP) coaxial calculable resistor (CCR) with simple structure and minimum AC/ DC resistance difference is developed. On basis of the theoretical calculation and the 3D electromagnetic field finite element simulation, the AC/ DC resistance difference introduced from the distributed capacitance, residual inductance, skin effect and eddy current loss are achieved. A high-precision 4TP AC resistance bridge based on the inductive voltage divider is developed, which could be utilized as the experimental validation of the frequency dependence for the 4TP CCR from 400 Hz to 10 kHz in comparison with two commercial 10 kΩ 4TP quadrifilar calculable resistors with the known frequency dependence. In addition, the 4TP CCR with the same 4TP AC resistance bridge can realize the quantity value transfer for the commercial AC standard resistors within the resistance range of 100 Ω, 1 kΩ and 10 kΩ from 400 Hz to 10 kHz, which has the best standard measurement uncertainty of 8×10 -8 for the 1 kΩ at 1 kHz.

Abstract:The traditional Mirau interference microscope based on the PZT phase shifter has problems of long sampling interval, environmental disturbance sensitivity and non-adjustable fringe contrast. To address these issues, a polarization Mirau interference microscope is proposed for transient microscopic profile testing. To meet the testing requirements for various tested objects with different reflectivity, a linear grid polarizer is employed as a polarized beam splitter in the system. In this way, the polarization splitting and adjustable fringe contrast is achieved. Four polarization phase-shifted interferograms are instantaneously obtained with a polarization camera. In which, the influence of environmental disturbance is effectively reduced. The measurement error introduced by the polarization components is modeled and analyzed, and the actual polarization aberration is obtained to eliminate the corresponding systematic error. To remove the field of view ( FOV) error in the polarization camera, the FOV error calibration method based on phase interpolation is also studied. Based on the analysis of the influence of system components on the measurement accuracy, the corresponding error calibration method is proposed. The accuracy and feasibility of the proposed polarization Mirau interference microscope are demonstrated by experiments. Experimental results show that the measurement accuracy and repeatability are better than 1 / 100λ and 0. 1 nm, respectively. The measurement system has advantages of adjustable fringe contrast, transient measurement and compact in structure, which provides a feasible method for online testing of micro profiles and micro structures of various components.

Abstract:The accuracy of the turbine meter is influenced by the measured medium and its changing kinematic viscosity. Predictability and consistency of calibrating meter factor against volume flow rate are unable to be achieved with various viscous liquids. The method of dimensional analysis is applied to derive Reynolds and Strouhal numbers to describe the performance of the turbine meter. A DN25 turbine meter is calibrated with five different mixtures of propylene glycol and water, respectively. The comparison results show that the calibration data for varied kinematic viscosity vary up to 0. 9% at Reynolds number lower than 7 400. The scattered calibration curves tend to be collapsed as the Reynolds number increases, and the calibration data vary less than 0. 1% . The rise of skin friction drag occurs at the boundary layer transition from laminar flow to turbulent flow on the rotor blade surface, which is responsible for a humpshaped calibration curve. When the kinematic viscosity is lower, the hump is flatter. The bearing static drag is the main reason for scattered meter factors, and the discrepancy tends to increase with decreasing Reynolds number. Therefore, the turbine meter should not be used for low Reynolds numbers when the kinematic viscosities of the calibration medium and the working medium are significantly different.

Abstract:Prestressed steel strands are key components of concrete structures. Once the prestress loses severely, the structure safety will be threatened. To precisely monitor the stress of the steel strand, a prestress monitoring method is proposed, which is based on the magnetic resonance and the magnetoelastic effect. A dual-coil magnetic resonating sensor is designed, the selection of the test frequency is analyzed, and a stress monitoring system is established. To evaluate the feasibility of this method, stress monitoring experiments are carried out. To be special, the galvanized steel strands and the epoxy-coated steel strands are tested under different design tensions. Experimental results show that the induced voltages change similarly with the tension under different batches of steel strands. The induced voltage nonlinearly is related to the stress. By using the three fit, the goodness of the fitting (R 2 ) is greater than 0. 96. In addition, the test sensitive reaches 0. 064 79% / kN. According to the fitting results and the measured induced voltage, the stress of the steel strand is calculated. When the tension is high, the test error is almost less than 4% . This demonstrated that a new stress monitoring method is proposed for prestressed steel strands.

Abstract:The guided wave EMAT detection of large metal plate components has the problems of low resolution and poor SNR of the EMAT, which is challenging to be used for small crack detection. A multi-physical field finite element model of Lamb wave EMAT detection process based on the Barker code pulse compression technology is established to solve this issue. Taking a 5. 6 mm thick steel plate with prefabricated cracks as the detection object, the effects of permanent magnet width and height, meander coil turns, the bit length of Barker code sequence, and subpulse duration on EMAT detection echo are studied by simulations and experiments. The beneficial effect of pulse compression technology in Lamb wave EMAT detection is evaluated. After optimization, results show that the SNR of the EMAT based on pulse compression technology is 9. 69 dB higher than that of the traditional tone-burst excitation method. A small crack 10 mm long and 0. 5 mm deep can be detected, and the SNR of the defect wave can reach 23. 47 dB. When the center frequency of the Barker code subpulse is 1 MHz, the Lamb wave packet after pulse compression presents mode separation. However, the SNR of the A0 mode defect wave can still reach 35. 23 dB, and it has essential engineering application value for improving the detection ability of the Lamb wave EMAT.

Abstract:The mechanical wear of adjustment mechanism in the conventional gene biochip imaging system caused by frequent adjustment of gene chip pose is a key problem. To address this issue, a gene biochip imaging scanner based on magnetic levitation is designed. According to genetic biochip imaging scanner work principle and structure characteristics of magnetic suspension technology, a system is established, which consists of electromagnetic parameters and the imaging resolution differential array. Through the theory of optimization, the structure parameters are determined. The finite element analysis is used to analyze the system structure of electromagnetic heat coupling, optimize analysis results and set up the experimental test equipment. The device is used to calibrate the parameters of the gene biochip imaging scanner, verify the magnetic levitation system structure design results of the scanner, and compare the experimental test data with the imported PCR instrument. Results show that when the number of turns of electromagnetic structure of the designed magnetic levitation genetic biological imaging scanner is 340 N, the effective electromagnetic area is 180 mm 2 , and the accuracy error of magnetic levitation system is less than 0. 15 mm. They are basically consistent with the simulation data. Compared with the data of T790M mutation detection by bio-RAD digital PCR system in the United States, CV is less than 5% . The precision of the designed gene-biochip imaging scanner based on magnetic levitation can meet the requirements of gene-biochip imaging detection, provide core technical support for improving the service life of the adjustment device, and play an important role in improving the gene-diagnosis technology of clinical tumor screening.

Abstract:The current electrocardiogram (ECG) collection mainly uses wet Ag / AgCl electrodes, which need to be closely attached to the skin surface to obtain high quality signal. However, the hardening of conductive gel, irritation or damage of electrodes may cause to skin and the discomfort during utilization, which make Ag / AgCl electrodes not suitable for long term ECG monitoring. The capacitance coupling PCB electrode presented in this article is equipped with an AC bootstrap circuit and has a super high input impedance about 100 GΩ. Experimental results show that the PCB electrode can maintain a high coupling ratio for signals of different frequencies through multilayer insulating medium, and the actual input impedance is about 87. 26 GΩ. The similarity between the ECG signals simultaneously measured by PCB electrodes and Ag / AgCl electrodes is more than 91% . Finally, the influence of the lead position of electrodes, the parameters of the coupling medium and the motion state of the body on non-contact ECG measuring is experimentally studied. The measurement results demonstrates the proposed non-contact ECG measurement method based on capacitance coupling electrodes can effectively detect the main components of ECG signal and heartbeat rhythm under various situation.

Abstract:For the exiting staging methods, the accuracy is limited by insufficient feature extraction and class imbalance. To solve the problem, the residual shrinkage network is applied to design a convolutional neural network to extract feature efficiently. Meanwhile, the idea of re-weighting is used to design the loss function to address the problem that N1 stage gets low accuracy due to less samples. Finally, experiments are designed based on data of the Fpz-Cz and Pz-Oz channel in the Sleep-EDF dataset. The accuracy rates are 85. 4% and 82. 2% , respectively. The MF1 values are 79. 6% and 75. 4% , respectively. Results show that the method achieves higher accuracy and MF1 than the benchmark algorithm and current advanced comparison algorithms. It proves the effectiveness and advancement of the proposed algorithm.

Abstract:The time-domain near-field simulation of electromagnetic compatibility has attracted more and more attention in industrial application. The physical characteristics of the automotive electronic fan drive circuit are complex, and the time-domain simulation has the problem of excessively long calculation time under the condition of steep pulse signal excitation. First, the waveform oscillation problem of time-domain finite element calculation is analysed and verified. The limitations of the classical time-frequency domain calculation method of radiated electric field in practical application are also considered. Secondly, the suppression effect of different window functions on the spectrum leakage of steep pulse signals under incoherent sampling conditions are compared and studied. The cubic spline interpolation is used to weaken the fence effect. Based on the Rife-Vincent ( Ⅲ) window Fourier transform and cubic spline, the time-frequency domain calculation method of radiated electric field is established. Finally, the rapid calculation of the timedomain radiated electric field of the car fan drive circuit is realized, which avoids the numerical oscillation problem in the initial stage of the time-domain calculation. Compared with the traditional time-domain calculation method, the calculation time is reduced by about 62% under the condition of non-parallel calculation. The method in this article provides conditions for parallel computing and has the potential to reduce computing time consumption by several to tens of times.

Abstract:As a part of the multi-source cooperative navigation scheme, data fusion has significant impact on the quality of state estimation. Because of its unique theoretical advantages in the nonlinear non-Gaussian system, the particle filter has gradually become the focus of many fusion methods. However, particle degradation and sample depletion restrict the application of particle filter in complex engineering. In this article, a robust cubature fission particle filter is proposed to solve the above problems. Firstly, in the framework of cubature rule, the Huber function is used to combine L2 norm with L1 norm to improve the importance density function, suppress the observation noise, and further optimize the proposed distribution by integrating Gaussian distribution with Laplace distribution. In this way, the particle degradation is alleviated. The particle swarm is fission derived before resampling, and the sample depletion is suppressed by fission of high weight particles and covering low weight particles to reconstruct particle weights. The vehicle experiment of multi-source cooperative navigation shows that under the same conditions, compared with extended Kalman filter, cubature particle filter and strong tracking particle filter, the root mean squared of the proposed algorithm is improved by 23. 04% , 42. 62% and 37. 74% , respectively. It provides a new idea for alleviating particle degradation and multi-source cooperative localization.

Abstract:To improve the signal noise ratio (SNR), it is important to enhance the intelligent analysis of MFL signal. If MFL data are processed directly, it usually has low precision due to the low and high frequency noise contained in MFL signal. It is discovered from the magnetic dipole model of infinite rectangular groove that there is a cross correlation between the original function and first derivative of the normal component and tangential component leakage magnetic field. Therefore, a MFL signal enhancement algorithm is proposed based on the cross correlation, which can enhance the signal near detect targets and suppress noise. Hence, the SNR of MFL signal is improved. The algorithm is validated and generalized by pipeline pull-through test data and in-service pipeline inspection data, respectively. Finally, some samples are collected from in-service pipeline inspection data and a signal quality estimation method is proposed which is suitable for evaluating the quality of the MFL signal. The enhancement algorithm is quantitatively evaluated by the samples and the estimation method. Experimental results show that almost all the samples are improved and most of the samples are improved by 10 dB at least.

Abstract:The micro-computed tomography (micro-CT) can achieve high-resolution imaging for objects completely contained in the field of view (FOV) by circular scanning. For the CT imaging of large objects beyond the FOV, the source translation based CT (STCT) is proposed, which collects data by moving the X-ray source along the straight trajectory. It has characteristics of simple structure and flexible application. But only part of the object can be illuminated at each source′s position during the STCT scanning, which causes the projection data truncated. For the enhancement of reconstruction efficiency and the processing of truncated projection data, the data rearrangement based filtered backprojection (rFBP) algorithm is proposed in this article. Based on STCT′s scanning characteristics and X-ray attenuation properties, this algorithm rearranges the truncated projection data into the global projection data by inverting the source sampling point and the detector unit, and the rFBP algorithm expression is deduced. Numerical simulations and practical experiments are performed. Results validate the effectiveness and practicability of the rFBP algorithm. The reconstruction time is reduced to 0. 6% of that of SIRT algorithm. The rFBP algorithm could accurately and efficiently reconstruct images of STCT.

Abstract:The aero-engine electrostatic monitoring technology shows a high fault warning capability. However, the raw electrostatic signal usually contains unexcepted noise. To improve the accuracy of the information extraction, the electrostatic signal should be denoised. This study firstly introduces the principle of electrostatic monitoring technology and analyzes the sources and principal components of the noise. To address the problem of coupling noise filtering of electrostatic signal, the theories of sparse signal representation and empirical mode decomposition are introduced. The basis and criteria for mode functions selection are investigated, and a joint denoising algorithm and process based on the mode function optimized reconstruction and sparse representation are proposed. The actual electrostatic signal acquired in the turbofan engine test run is used to evaluate the denoising effectiveness of the proposed algorithm. Meanwhile, it is compared with other classic methods. The results show that the proposed method can effectively remove the random noise and power frequency interference while remaining the useful particle signal to a large degree. The abnormal signal can be extracted well when the number of sparse iterations is set from 20 to 50.

Abstract:During the process of assisted walking or gait rehabilitation training, it is essential to recognize abnormal behaviors accurately in human-computer interaction on the basis of following user′s gait closely. This article proposes a non-contact recognition method which has advantages of universality, robustness, and convenience for multimodal walking intention. It can control the robot flexibly and accurately recognize various gaits. Firstly, the structure, functions, and kinematics models of the walking assist robot and the gait rehabilitation training robot are introduced, and an embedded airborne gait recognition system is established. It can accurately describe the gait and changing rule. Secondly, to effectively solve the problem of mark point loss, a new extended set membership filter is proposed to estimate the knee angle. Finally, a compliance control method based on walking speed compensation is established by combining with gait information. Experimental results show that the proposed method could effectively overcome the loss of marker points, identify the normal gait accurately in the interaction process, and flexibly control the robot movement. Meanwhile, it can effectively recognize the falling and drag-to-drop gait. The recognition rates are 91. 3% and 89. 3% , respectively. The non-contact walking intention recognition method can be applied to walkers with similar structures and their daily walking assistance or rehabilitation training

Abstract:To assist patients with upper limb motor dysfunction for rehabilitation training, an upper limb rehabilitation exoskeleton robot system is established and an augmented neural network adaptive admittance control strategy based on the barrier Lyapunov function is proposed. Firstly, the mechanical mechanism and control system of upper limb rehabilitation exoskeleton are introduced. Then, the design process of the controller is illustrated and Lyapunov stability is demonstrated. Finally, the passive training experiment of trajectory tracking with different inner control loops and the active interaction training experiment based on human-robot interaction force under different admittance parameters are carried out. Experimental results of passive training show that the effectiveness of the augmented neural network is close to human-robot dynamics, and the maximum trajectory tracking error is only 53% of that of fuzzy PID controller. The active interaction training experiment proves that different intensities of rehabilitation training can be achieved under the same training task by adjusting the admittance parameters to match patients with different levels of recovery.

Abstract:The pseudoinverse-type solution may exceed the physical limit of a manipulator. To address this problem, two kinds of jointvelocity constraint schemes of redundant manipulator based on the pseudoinverse algorithm are proposed. Firstly, according to the tracking task of the end-effector, the pseudoinverse algorithm is used to analyze the redundancy at the velocity level. Secondly, two constraint schemes are utilized to limit and compress the specified joint velocity. A new velocity solution is obtained to perform the specified trajectory-tracking task. Then, the error compensation function is designed to eliminate the position error of the end-effector to ensure the smooth execution of the tracking task. Finally, simulation results based on the MATLAB software are analyzed and discussed. The algorithm is further evaluated using a six-DOF manipulator which is controlled by the Arduino platform. These results show that the maximum tracking errors do not exceed 3×10 -4 m with two proposed constrained schemes. And the time-varying function constrained scheme can achieve better velocity stability when the joint velocity is limited.

Abstract:The accuracy of the phase locked loop of grid-connected inverter conditions is easily affected by grid-side voltage distortion in the weak grid, including frequency offset, three-phase voltage imbalance, and DC voltage offset. To address these issues, a decoupled double synchronous reference frame phase locked loop (DDSRF-PLL) optimization method for grid-connected inverter is proposed in this article. First, based on the formulation of the DDSRFR-PLL model, it is proved from a theoretical perspective that the grid voltage distortion and DC voltage offset are two key factors affecting the phase-lock accuracy of the conventional DDSRF-PLL. Secondly, a frequency adaptive phase discriminator based on sliding Fourier transform is proposed by using Fourier transform′s advantages of suppress harmonics and DC bias. Then, a phase locked loop suitable for grid-connected inverters is established under an improved decoupled double synchronous reference frame. When the grid voltage is distorted, the proposed PLL can re-track the voltage phase within 20 ms. In the case of a DC bias in the grid voltage, the PLL could quickly track the voltage phase within 10 ms. The phase overshoot is all within 1°. Experimental results show that the PLL can quickly and accurately extract the phase information of the grid voltage in the weak grid, which helps the grid-connected inverter to reduce harmonics of the output current under complex conditions, such as grid voltage imbalance and distortion.

Abstract:The inconsistency in airborne 28 V series battery group will reduce their energy utilization and life, which even leads to flight accident. In this article, an energy equalization method based on a new equalization topology is proposed to improve the inconsistency of airborne lithium series battery group. The equalization topology uses the isolated DC-DC converter with simple structure and resistor to realize “peak clipping” or “ valley filling” of any single cell in the battery group. Compared with the non-centralized equalization topology, the number of equalization components and system volume are reduced. By using state of charge as the equalization variable, the energy transfer between cells in the airborne 28 V battery power supply is realized quickly. Compared with the centralized DC-DC topology, simulation and experimental results show that the proposed new equalization method can improve the equalization speed by 13. 3% , reduce the voltage range to 32 mV and SOC range to less than 0. 4% , and have faster and better equalization effect.

Abstract:The runway has the problem of ice accumulation. To address this issue, an autonomous cooling device with a thermoelectric cooler as the core is designed to achieve active ice accumulation warning. Numerical analysis shows that the cold end of the device is affected by the small-scale meteorological environment of the runway and has non-linear characteristics. To realize the fast response and accurate following of the device temperature, a dual-loop active disturbance rejection control (ADRC) method is proposed to design an autonomous cooling controller for runway ice accumulation warning. Simulation results show that ADRC temperature control following and immunity performance are better than the nonlinear PID. The RMSE values are 0. 654 1 and 1. 152 6, respectively. Low-temperature experimental chamber temperature control performance test shows that the steady-state error of ADRC under different temperature control instructions is less than the nonlinear PID, and the highest is 0. 04℃ . The freezing point detection experiment under runway environment shows that the device can realize the runway freezing point detection function. The temperature control performance regulation strategy of this autonomous cooling device meets the demand of active warning of runway ice accumulation.

Abstract:In the biological micromanipulation experiment, it is of great significance to capture biological targets safely and stably. The traditional manual operation has problems of low efficiency and poor repeatability. To address these issues, a set of biological automatic capture system for micromanipulation is proposed. Through visual feedback and closed-loop control, the micropipette is used to automatically aspirate biological objects in a liquid growth medium. Firstly, the particle swarm optimization algorithm is used to optimize the traditional image segmentation algorithm to realize the synchronous real-time tracking of the biological target in the field of view and the position of the pipette. Then, the dynamic model of micropipette capture process is formulated, the nonlinear disturbance observer is used to suppress the uncertainty of model parameters and environmental disturbance, and the closed-loop control system is established. Finally, the performance of the system is evaluated by experiments. Results show that the average image segmentation time of the system is 81. 05 ms, the average capture time is 1. 85 s, the average maximum error of capture is 0. 34 mm, and the capture success rate is 94% . The experiments show that the system can accurately, quickly and undamaged capture biological objects in the environment with trace interference in different light sources and visual fields, which has good robustness. The potential applications of this method include vitrification of embryos, embryonic stem cell transplantation, blastomere biopsy, cell mechanical property detection, etc.

Abstract:To solve the tracking control problem for velocity curve of urban rail vehicle, an improved predictive function control algorithm IPFC is proposed. Step function and Morlet function are selected as two base functions. According to the change degree of target velocity curve, a strategy for basis function selection of predictive function control is given, which can switch wavelet and step basis function. In addition, an adaptive nonlinear online softening factor adjustment strategy based on the fuzzy satisfaction of system performance and optimization factor is proposed. This strategy can further improve the tracking control performance by using optimization factor. Taking the instance of velocity curve tracking control from Lvshun New Port to Tieshan Town pertain of the urban rail transit line No. 12 in Dalian as the test object, the hardware-in-the-loop test results show that the proposed IPFC can improve control performance of control system significantly. The quality indexes, such as energy conservation, accurate parking, punctuality and comfort, have obvious improvement effectiveness, especially for punctual and precise parking. Compared with the traditional improved algorithms widely used in practice, they are improved to be more than 55% .