Abstract:Visual servoing control is an effective means for robotic manipulator to complete complex tasks and the path planning method of the robotic manipulator autonomous operation in dynamic unstructured environment is the difficulty and key in the field of visual servoing control. Two types of constraints that exist in the visual servoing path planning in dynamic unstructured environment and the processing methods of constraints are analyzed. The relevant research progresses of path planning in visual servoing control of robotic manipulator at home and abroad are reviewed, and the deficiencies in convergence and stability of different methods of path planning are also analyzed. The future research direction is prospected based on current research progress.

Abstract:To service the internal payload of communication satellite, according to the main frame structures and main bearing structures of traditional satellite platforms, six kinds of repetitive variable configuration truss-type satellite platform structures is proposed, and the main indexes, including mass, inertia change rate, utilization rate of fairing area, deployed surface area ratio, vibration frequency in folded and deployed state, equipment layout effect and complexity of deployable mechanism, for evaluating the performance of variable configuration satellite platform are put forward. Then the main indexes of those six satellite platform structures are analyzed, the weights of those indexes are obtained by analytic hierarchy process method, and a scheme with better comprehensive performance is selected using fuzzy synthetic evaluation method. The mobility of the deployable mechanism of the optimal scheme is 1. The satellite platform structure of the optimal scheme is detailed designed, and a prototype is manufactured to demonstrate the process of variable configuration.

Abstract:To apply a negative temperation coefficient(NTC) thermistor to achieve high temperature detection in a fixed interval, a parameter optimization method of a temperature measurement system (TMS) is proposed based on an expected relative temperature tracking control strategy. First of all, the parameters of TMS are initially optimized for a target temperature range based on nominal values of a NTC thermistor. Then, using an expected relative temperature tracking control strategy ensures that the steady outputs of TMS are within a specific distance to the upper and lower boundaries. Thirdly, the actual temperature range, which is measured by a standard temperature measurement device, is determined if it meets the design requirements. If it does not, the resistances of NTC thermistor is calculated corresponding to the actual temperatures, the parameters of NTC thermistor is amended, and then the parameter readjustment of TMS is achieved. At last, experiments are carried out by means of a Fused Deposition Modeling platform and the results show that the proposed parameter optimization method is valid, which realizes the optimal design of TMS for the fixed interval, and is helpful to improve the measurement accuracy of TMS.

Abstract:To realize the assistance of transrectal ultrasound imaging in robotic prostatectomy, registration between ultrasound equipment and surgical robotic system needs to be established. The recognition and segmentation of minimally invasive surgery (MIS) instrument contour in ultrasound image is an important part of registration process, and its accuracy will directly influence the registration results. An improved parametric active contour algorithm (Snake) under global constraints is proposed, which can accurately segment surgical instrument contour in ultrasound images. The improved Snake method uses known instrument profile as prior knowledge, describes the information in normalized Fourier descriptors, and applies it in Snake external energy to constrain the segmentation result gradually near the desired contour. During the solving process, the Jacobian matrix of energy function relative to parameters is calculated to acquire the partial differential equation with minimum energy. Then the partial differential equation is discretized, deduced with Euler method to obtain segmentation result. The experiment shows that when using Snake method with prior knowledge, the segmentation result of surgical instrument contour in ultrasound image can be realized with high accuracy, and the contour result is similar with real instrument profile. Compared with traditional Snake method, the improved method constrains curves globally, and can avoid contour curve falling into local minimum, having a great application prospect.

Abstract:To fully understand the friction and wear mechanism of chemical mechanical polishing process, the effects of different processing conditions on the polishing process were simulated. Three-dimensional CFD model considering multiphase flow and discrete phase was established to obtain the speed and pressure distribution of the polishing liquid as well as that of the polishing abrasive particles between wafer and polishing pad under different processing conditions. It is found that the abrasive particle distribution density is smaller when the film thickness is smaller, and the greater the speeds of the polishing pad and wafer, the smaller the particle distribution density. Based on the distribution characteristics of fluid velocity, pressure and polishing particles, a model of material removal rate(MRR) was established, and the dynamic pressure caused by flowing polishing abrasive on the surface asperity of the wafer during polishing process was analyzed. By applying the energy-balance fracture theory, the MRR prediction model was established which could be used quantitatively for all kinds of materials. For silicon carbide polishing, its MRR curve under different processing conditions was obtained by Matlab programing. It is found that the MRR is greater when the polishing pad speed is greater and the gap film thickness is smaller. The MRR decreases as polishing continues, and the effect of film thickness on the removal rate is smaller compared with that of the polishing speed.

Abstract:To improve the loading amplitude of friction based electro-hydraulic load simulator in compact size by using existing friction material, a loading method using a large amplitude torque loading mechanism is proposed, the working principle of the mechanism is described and a mechanism is designed and developed. The mechanism's finite element model is established then thermal-mechanical coupling simulation of the mechanism is conducted using ABAQUS software, and the feasibility of the mechanism is validated. The friction heat production characteristics and the friction heat impact on the loading mechanism are studied, and the simulation results indicate that in practical applications the mechanism needs fully heat dissipation. Using the developed loading mechanism, the original one-way friction based electro-hydraulic load simulator prototype is transformed as a large amplitude load simulator. Based on the transformed load simulator, under the control of a PID controller, the large amplitude torque loading experiments are conducted, and the experimental results indicate that the transformed load simulator can accurately track up to 70 N·m torque, the mechanism can improve the original load simulator's torque loading amplitude by 3 times as expected i.e., the effectiveness of the mechanism is validated.

Abstract:To realize the innovative design of reconfigurable parallel mechanism, a design method of metamorphic parallel mechanism based on basic subchain configurations is proposed. Starting from the constraints acting on the moving platform of lower-mobility parallel mechanism, the basic subchains whose constraint is a force or a couple using characteristics of reciprocal screw are constructed. And according to configuration characteristics of the basic subchains, metamorphic subchains are constructed to realize the design of metamorphic parallel mechanism. The line vector force and couple subchains whose configurations are similar are combined to construct metamorphic subchains. The metamorphic subchains can transform between two types of basic subchains by locking different kinematic pairs, then the parallel mechanisms whose constrained type is variable can be constructed. According to the constrained screw direction characteristics of basic subchains, the force direction of subchain is changed by changing the axis direction of kinematic pairs, then the parallel mechanism whose constrained force direction is variable can be constructed. At the same time, using the proposed metamorphic parallel mechanism design method and Bricard linkage's single degree of freedom motion, a new type of parallel mechanism whose moving platform is Bricard linkage is constructed. Based on the basic subchains, the configurations of the metamorphic parallel mechanism are constructed. According to the constraint of the moving platform, the metamorphic subchains are combined and transformed, which realizes the type synthesis of metamorphic parallel mechanism and lays the foundation for innovation design of mechanism.

Abstract:To improve the efficiency of microalgae photobioreactor to reduce cultivation costs and carry out large-scale cultivation, an online measurement method was proposed to measure the radiative properties of microalgae at whole growth phase. Using a custom flate-plate photobioreactor, an online measurement scheme for the radiative properties of microalgae was presented and the limitation of traditional measurement method was studied. An improved scheme was proposed based on the characteristics of radiative properties of microalgae. Chlorella vulgaris was taken as an example and its radiative properties at growth phase was experimentally studied. The results show that the proposed online measurement scheme can be effectively applied to measure the time-dependent radiative properties of microalgae. The improved scheme of spectral absorption and extinction coefficient measurement are more accurately applied to measure the radiative properties of microalgae at different growth phase with varied cell concentration. The spectral absorption and extinction corss-sections of Chlorella vulgaris vary significantly with growth time in the visible spectral range. This work provides a convenient and feasible experimental scheme for the measurement of radiative properties of microalgae at different growth period.

Abstract:To improve the foil bearing performance, a novel foil journal bearing with top foil thickness variation in axial direction was proposed. A wide groove extending in circumferential direction, within micron magnitude, was manufactured in the mid-plane zone of top foil. To consider the top foil thickness variation, the 2D thick plate finite element model was employed to simulate the top foil deformation. Based on Newton-Raphson iterative method and finite difference method, the coupled pressure equation and foil deflection equation were solved, and the gas pressure distribution and load capacity of the novel foil bearing were obtained. The dynamic characteristics were solved using perturbation method and the influence of the wide groove depth on bearing performance was investigated theoretically. The results indicate that the novel foil bearing with top foil thickness variation axially can decrease the gas edge leakage and improve hydrodynamic pressure effectively, so the load capacity and dynamic characteristics are improved. Moreover, with the increment of the wide groove depth on top foil, the load capacity and direct stiffness are enhanced further. For the foil journal bearing with a wide groove depth of 8 μm, the load capacity and direct stiffness increase by about 11.8% and 12.1% respectively, compared with the traditional foil journal bearing.

Abstract:To investigate the effect of demineralization on Longkou oil shale, the oil shale was acid demineralised in three steps with HCl→HF→HNO₃, XRD and FT-IR was respectively used to analysis the compounds of minerals the change of chemical structure information before and after acid-treatment. The results show that oil shale mainly contains four oxygen-containing function groups, ether oxygen, carboxyl, hydroxyl and carbonyl, organic matter made by acid-treatment is really pure, the ash weight percentage is less than 1% after acid-treatment. acid-treatment has effect on the chemical structure in oil shale, hydrolysis reaction is occurred during the acid-treatment, alkyl ether and aromatic ether in the oil shale is decreased after acid-treatment; Carboxylic acid and phenolic hydroxyl are obviously increased, this is because acid-treatment breaks the ion exchange interaction between oxygen-containing groups and inorganic salts, then organic salts convert into organic acid; Hydroxyl structure both mainly contains structures of ring hydroxyl, OH-O and OH-OH before and after the acid-treatment, The acid-treatment has obvious effect on ring hydroxyl, OH-O, and has little effect on OH-OH; To the aliphatic structure, Acid-treatment makes the CH stretching vibration and CH₃ asymmetric stretching vibration convert to CH₂ asymmetric stretching vibration, the aliphatic chain is becoming longer.

Abstract:To analyze a problem of typical blade internal cooling, the periodic case and full spatial case were computed using RANS and large eddy simulation(LES) approaches. The precision of two types of numerical method in predicting flow and heat transfer was compared based on the experimental data published. Numerical research shows that the process of initiation and shedding of the small flattened vortex, which is on the top surface of the rib, was detected by using LES approach, and the phenomenon, that the shedding vortex mixes with other coherent structure when moving along the trace at the height of the top surface of the rib, is accordant with the trend of turbulence intensity variation. The detailed flow structures reflect the true characteristic of the flow and show that not only the parameters of flow condition, including the mean velocity distribution and the turbulent intensity, but also the distribution of enhance factor predicted by LES approach are accordant with experimental data. The prediction error of enhance factor of heat transfer by RANS approach is smaller than that by LES approach.

Abstract:In order to explore Zhundong ash deposition rules, the visualization of fly ash deposition test rig was used to study the deposition characteristics of Zhundong coal under different ashing temperatures. SEM-EDS, XRD and Particles Distribution Instrument were utilized to analyze ash particles. The results showed that the different ashing temperatures led to large differences in characteristics. Existence in the form of calcium is mainly CaCO₃, CaSO₄ at 500 ℃ and 650 ℃ cases, but CaO in the 800 ℃ case. At 800 ℃, NaCl is unable to be found in ash and Zhundong coal exists self-desulfurization. In terms of ash deposition characteristic, the 800 ℃ ash is the highest in fouling height because of larger diameter of particles. It is illustrated that the physical factors are the controlling factors at this experimental condition. The "uneven" phenomenon is also appeared at borders for 500 ℃ and 650 ℃ cases, because the particles form voids and are heated to become soft and easy to collapse. It is called "Boundary Roughening", which may be important reasons of fouling and slagging in boilers.

Abstract:To realize the NO oxidation at low temperature, the NO catalytic oxidation efficiency through Fenton reagent/AC coupled with microwave in the liquid system and within 23~65 ℃ temperature range was researched, in which the AC acts as wave absorption heating-spots based on its developed pores. At first, the invigorating effect of microwave on Fenton reagent was proved using compared experiment in detail, including thermal effect and sensitization effect. Then the effect of the microwave power, the initial pH value, the AC dose, the Fe²⁺ initial concentration and the H₂O₂ initial concentration on the NO removal efficiency was studied thoroughly, the optimal reaction parameters were reached at last. The results indicated that the AC combined with microwave could enhance the NO removal efficiency substantially. The optimal reaction parameters was that the microwave power was 400 W, the pH value was 3, the AC dose was 4 g, the Fe²⁺ initial concentration was 5 mmol/L and the H₂O₂ initial concentration was 0.3 mol/L. The NO removal efficiency under the optimal reaction conditions was up to 46.3%.

Abstract:Using a new kind of absorbent which is the mixture of aqueous ammonia and ethanol, a process of carbon capture by ammonia of low concentration with reinforced crystallization and lower energy consumption is presented. By the application of antisolvent crystallization to reinforce crystallization process, low energy consumption of regeneration could be achieved easily due to saving the energy to heat the water of carbonized ammonia in the desorption process. TGA is adopted to study the regeneration process of crystal product, and heating method pyrolysis and constant temperature pyrolysis are used respectively. What's more, if the waste heat from the power plant can be used as heat source of the regeneration process, the more energy can be saved for the technology. With the regeneration temperature between 40 ℃and 80 ℃, the active energy can be as low as 48.38 kJ/mol. The regeneration process is studied at the constant temperature of 60 ℃, 80 ℃ and 100 ℃. And if the rate of rising temperature is 5 K/min, the crystal product will be totally decomposed when the temperature reaches 80℃, not only can achieve low energy consumption but also have fast regeneration rate which have the advantage over the process of rich carbonated ammonia. For the mixed absorbent, the different proportion of the dissolved agent has little effect on the regeneration process, and the composition of the mixture is determined only by the absorption rate. The better regeneration rate can be obtained by the constant temperature of 80 ℃. After the calculation of 16 classical models, the model function was selected for the study of crystal products.

Abstract:To understand the enhancing process of autothermal glycerol steam reforming for high efficient hydrogen production, the effects of two enhancing approaches including hydrogen separation and carbon dioxide absorption are evaluated based on Gibbs free energy minimization method. The variation of hydrogen yield, deposited carbon and reaction heat varied with temperature and hydrogen separation fraction are analyzed. The results reveal that the hydrogen separation can promote the hydrogen yield and restrict the methane production, while this process leads to the increase of carbon formation. The hydrogen removal increases the reaction heat, and a higher oxide to glycerol feed ratio is required to achieve the autothermal condition. Calcium oxide absorbs carbon dioxide to generate calcium hydroxide below 750 K, which leads to reduction of hydrogen yield. When the temperature reaches above 800 K, the capacity of sorbents becomes weak owing to the decomposition of calcium carbonate. Hence, the temperature from 750 K to 800 K is suitable for absorption reaction. The autothermal process can be attained with the heat from absorption reaction.

Abstract:To further discover the flow resistance characteristics of liquid nitrogen in bellows in wider application range, dimensionless variables namely the ratio of wave-height over bellows-diameter (e/d) and the ratio of wave-pitch over wave-height (p/e) are introduced. CFD modeling has been conducted on the behaviors of both pressure drop and Darcy friction factor (f) at different geometries of the bellows, either with or without an insert. Effects on the f by different Reynolds numbers at certain ratios e/d or p/e in wide ranges were investigated. The results shows that the vortex forming inside the bellows trough is the main cause of the flow resistance increment. When the e/d and p/e remain unchanged, changing of the inner diameter of the bellows has little influence on the friction factor. If a rod is inserted into the bellows, the larger the rod diameter, the smaller the Darcy friction factor. When the diameter of the insert reduces to zero, the friction factor approaches that of the hollow bellows, which is consistent with the experimental results.

Abstract:To further study the rupture of droplet after its impacting and the influence of different parameters on the droplet evaporation and heat transfer, three dimensional numerical simulation is performed by using CLSVOF method and phase transformation model. The effect of wall temperature, contact angle and impact velocity on the evaporation and heat transfer of droplet are considered in the simulation and the results show that the rupture position is related to the impact velocity of the droplet. When the impact velocity is small, the rupture occurs at the center of the droplet. When the impact velocity is large, the rupture position deviates from the center of the droplet. It is also found that vapor vortexes are generated near the three-phase contact line and the rupture, which strengthen the heat transfer between the droplet and the wall, and increase the heat flux density of droplet side as well. In a short time, the wall temperature has little effect on droplet evaporation, but the impact velocity and contact angle have great effect on droplet evaporation. The smaller the contact angle and the greater the impact velocity, the greater the average heat flux density and the greater the droplet evaporation, which is beneficial to heat transfer between the droplet and the wall.

Abstract:To research the performance of gasbag used in bladder-type dispersal system, the fluid-structure interaction (FSI) model is established to simulate the inflating process of the metal gasbag (304 stainless steel) with a initially flat form. Then the dynamic response of bag's deformation and the changing law of internal flow field are acquired, and the results show a good agreement with the experimental results. Besides, the performances of gasbag with the change of its geometry and inlet conditions are investigated. The results show that the inlet diameter of gasbag and the inlet conditions are the key factor influencing the bullet's separating speed and overload. The larger the inlet diameter or the charge weight is, the greater the bullet's overload is. And when the bag's inlet diameter is different, there is an existence of the extreme separation speed of bullet with a certain amount of charge. The bag's initial area has a small impact on the change of speed (the difference is only 4%), while it affects the magnitude of the pressure of gas in the gasbag obviously. The larger the area, the smaller the pressure presents, which is beneficial to reducing the stress level of the wall of gasbag. So the calculation results can provide a mainly reference for the optimal design and engineering application of gasbag.

Abstract:To solve the problem of transverse torques on micro-nano satellites during orbital maneuver, the spin-stabilized method was selected to reduce velocity pointing error. Considering the effects of mass variation and jet damping, the spinning thrusting satellite model which subjected to constant force and zero axial torque was established. After that, the analytic solutions for angular velocity, angular momentum, asymptotic limits of angular velocity and Euler angle were obtained. The example was simulated and the results show that the analytic solutions are highly accurate. Besides, the transverse angular velocity and Euler angle are changing periodically, and the amplitude of transverse angular velocity decreases as the time is increasing. What's more, the curve of angular momentum vector pointing is a circle, and the radius is nearly equal to the satellite velocity increment pointing error. Also, the dynamic unbalance characters of the micro-nano satellite under high spin rate have little influence on the spinning maneuver process. As the micro-nano satellite becomes more disklike, the velocity increment pointing error can be decreased, and the accuracy of the orbit maneuver is raised.

Abstract:To calculate the contact pressure of friction pair, a 3-D finite element friction model of sintered bronze is established by simplifying the structure of clutch. Accurate contact pressure distribution of friction pair is obtained by the study of friction characteristics. The distribution results and main reasons of contact pressure are analyzed by evaluating the data of radial and circumferential directions. To verify the computation and confirm the contact pressure dynamic change under sliding friction condition, the dynamic friction element contact pressure experiment is designed. The experiment is based on the strain measuring technology, the measurement points are calibrated, the strain data is collected and the pressure curves are drawn. The simulation and experimental results show that the friction pair contact pressure is uneven on radial and circumferential directions. Radial direction distribution is influenced by loading structure. The influences of circumferential direction are elasticity modulus, groove and roughness etc. Dynamic measurement curves of contact pressure show obvious cyclic quality. Contact pressure tends to be more uniform along with load increase.

Abstract:To further increase the slider flying stability, thereby enhancing capacity of hard disk drives, the effects of DLC (diamond like carbon) layer roughness, function group ratio and the number of hydroxyl within one lubricant molecule on lubricant transfer and lubricant distribution on the disk surface are investigated by molecular dynamics simulation, and the results indicate that the lubricant transfer behavior can be improved by decreasing DLC layer roughness or increasing functional group ratio. The lubricant transfer can also be improved by increasing the number of hydroxyl within one lubricant molecule, when physically absorbed lubricant exists on the disk surface. However, the lubricant accumulation height on the disk surface can be increased by decreasing DLC layer roughness or increasing function group ratio on the DLC surface and hydroxyl number within one lubricant molecule simultaneously, resulting in the decreasing of slider flying stability. Therefore, considering the effects of lubricant transfer volume and the thickness of lubricant accumulation on the disk surface, it is better to decrease the DLC layer roughness to approximately 0.07 nm, increase the functional group ratio to about 80% and make the number of hydroxyl within one lubricant molecule less than eight.

Abstract:To investigate the influence of dynamics interaction between the driver body and miniature automobile, the driver model was connected to the miniature automobile with spring-damping elements. A handling stability dynamics model was constructed for the driver-vehicle system with 6 degree of freedom (DOF). Based on the parameter identification for stiffness and damping coefficients at human-seat interface, the numerical method was used to solve the handling stability dynamics model by Matlab/Simulink. The influences of human-vehicle dynamics interaction on the stable and transient responses of step steering were analyzed for the miniature automobile with different curb weight. Results show that the human-vehicle dynamics interaction affects the roll response obviously, and increases the steady stable values, peak values and overshoot. With the curb weight and size more and more close to the driver body, the influences will be more significant. The human-vehicle dynamics interaction has a little effect on the yaw rate, increases the tendency of understeering and enlarges the fluctuation of the yaw rate curve.

Abstract:Aiming at the biomechanical characteristics of upper leg impactor in the pedestrian protection collision test, THUMS(total human model for safety) model and upper leg impactor were compared and simulated. Firstly, the THUMS-SUV pedestrian accident is simulated, and the impact force and bending moment of THUMS model of upper leg were output. According to the initial condition and minimum energy status of pedestrian upper leg in the accident, two upper leg impactor collision models were established and simulated. The kinematic behavior, maximum bending moment and maximum impact force between THUMS upper leg and upper leg impactor were compared and analyzed. The result showed that the upper leg impactor had higher impact force, but lower bending moment compared to THUMS model. This paper indicates that, due to movement and contact of lower leg and upper body, the contact force and bending moment of upper leg is affected, which means the biofidelity improvement is needed for the upper leg impactor.

Abstract:To establish an accurate visual simulation system for offshore hoisting operations, the "Offshore Oil 201" crane ship was regarded as the research object, a mathematical model for hoisting operations was established with comprehensive considering the influence of sea conditions, the dynamic positioning system of the ship and the ballasting system of the crane ship. An interactive three-dimensional dynamic virtual scene was constructed by the comprehensive application of virtual reality technology, multi-channel data interaction technology, numerical solution technology and semi-physical simulation technology. The Bliss approximate integration was used to solve the mathematical model of the hoisting operation and the real-time data interaction of the visual simulation system was realized on the basis of guaranteeing the accuracy of the solution. The dynamic response of the ship displacements, the ship attitude angles, the swing angles and forces of the hoisting system and the reaction force of the crane ship were emphatically analyzed in the simulation system. The movement law of the ship and the hoisting system were obtained. The simulation system results were compared with the sea trial and the deviation of the simulation system was kept within 10%. The accuracy of the mathematical model of the hoisting operation is sufficient for the simulation system, and the simulation system can carry on the engineering rehearsal of the offshore hoisting operations with ensuring the system accuracy, which can effectively improve the safety of the offshore engineering operations.

Abstract:To improve the lubrication characteristics of cylinder/valve plate in the axial piston pump, the dynamic pressure support characteristics with the grooved flow distribution face is studied. A theoretical dynamic pressure model is established. According to the law of conservation of flow and by applying the finite volume method to numerical discretization, the distribution law of dynamic pressure and the effect of support with the grooved face are analyzed, and the change law of the friction coefficient under the whole film lubrication condition is obtained as well. A test rig is built to verify the test results. Under certain conditions, the auxiliary support belt with grooves is beneficial to dynamic pressure support characteristics. With the increase of numbers of grooves, the dynamic pressure support is improved. There is a feature inclination angle at which the dynamic pressure support characteristics with grooved flow distribution face is the same as with non-grooved flow distribution face. At a particular cylinder inclination angle, the corresponding groove depth at which the "feature inclination angle" is larger than the cylinder inclination angle could be selected, so that the dynamic pressure support characteristics of cylinder/valve plate pair could be improved by auxiliary support belt with grooves.

Abstract:To improve the calculation accuracy for the heat exchanger, this paper establishes a compressible flow model for the pressurized air side of the exchanger. Considering the heat exchanger in wheel type loader, the present model employs the change rate of cross-section, heat transfer amount and surface friction coefficient as variables. CFD(computational fluid dynamics) is used to validate the model and simulation results have shown that the deviation between the present compressible flow model and the traditional incompressible model increases with the increasing flow rate. Compared with experimental tests, the incompressible model predictions are only acceptable when the flow rate is low; whereas the present compressible model provides more accurate predictions for high flow rate zone. Results reveal that the maximum deviations between the present model and test on pressure and temperature are merely 6.5% and 7.5%, respectively. Therefore, the present model solves the problem of simulating the high flow rate zone due to the neglect of the compressibility. This model would further guide the optimal design of heat exchanger.

Abstract:A three-direction piezoelectric sensor parallel-type balance with four supporting points was designed for the dynamic load measurement of the all-movable rudder which withstands high-load and installed in narrow space. The piezoelectric quartz was selected to be the force sensing element, the spatial layout and measuring principle of this three-direction force sensor with four supporting points were discussed and the calibration method of parallel balance was studied. Static calibration and compound loading test were carried on this parallel balance. The generalized inverse static decoupling algorithm based on the solution matrix of calibration matrix was used to decouple. From the view of equivalent application points' offset, the error generation mechanism of parallel piezoelectric balance was analyzed using ANSYS finite element software. The experimental results showed that the maximum nonlinear error and repeatability error of the balance were 1.352% and 1.019% respectively. The largest interference coefficient was 2.865%. The influence of composite load on vertical force measurement accuracy was less, yet on the bending moment was obvious. The balance static calibration indexes satisfied the test precision requirements. However, due to the different effects of different load on the range interval between sensors and the superimposed impacts of the composite loading time interval, the balance measurement accuracy was reduced and not satisfied multi-directional load measurement.

Abstract:To solve the problem of multivariate time-delay synchronous selection on phase space reconstruction(PSR), a maximal independent cross-correlation(MICC) algorithm was proposed to select multivariate phase space reconstruction time-delays. Firstly, the response variate sequence was segmented, and then, the segment surfaces were fitted and the observational sequences were substituted into the fitting function. At last, the optimal time-delay was computed iteratively when the cross-correlation was minimal. The simulation results of the Lorenz system were used to compare the binary and ternary time-delay selections of MICC algorithm with genetic neural networks, maximal entropy algorithm and mutual information algorithm. Joint recurrence plot(JRP) and mutual nearest neighbor radio(MNNR) were applied to evaluate the selections, and MICC algorithm was superior to the others. Besides, the coal mine gas concentrations of four crucial undermine locations were chosen to be the one real coal mine system coupling variates. The contrast experiments between MICC and mutual information had been done and the time-delays computed using MICC were 16-3-10-11 respectively, meanwhile the MNNR and JRP densities were 0.58 and 0.34%. The results showed that the MICC algorithm had obvious advantages in selecting optimal time-delays of multivariate and could be applied on multivariate analysis in practical issues.

Abstract:To obtain the temperature distribution rules of steel structures under solar radiation and offer standard reference and reliable basis for related numerical research, temperature field test of a specially designed triangle space truss model was carried out under various conditions. Through the continuous measurements, abundance experimental data and distribution rules were obtained and analyzed in detail. According to the comprehensive test results, solar temperature distribution rules under different conditions were summarized initially. Laying angle has a great influence on temperature field of members in non-horizontal location, while it has little influence on horizontal ones, and the maximum temperature difference between different members can reach 13 centigrade. Then numerical simulation for solar temperature field of the test model was conducted contrastively considering the shadow effect. The results show that test results and simulation results are almost the same, in which the average error rate is not more than 6%. The proposed simulation methods are effective for structural non-uniform temperature field analysis, and the experimental study and conclusions can provide valuable references for other similar analysis methods of temperature field.