Abstract:To solve the problems of the spacecraft anchoring and sampling on the surface of small bodies which are micro-gravity and unknown characteristics, an integrated robot design scheme for anchoring and sampling is proposed. It fusions functions such as buffering, anchoring, sampling, and sample transferring as a whole. Based on the idea of reusing leg and arm, a multi-arm collaborating scheme having active and self-adaptive land buffering is proposed; Taking advantages of the ultrasonic drill with low drilling pressure and high drilling efficiency on the hard rock, an anchoring scheme using ultrasonic drill for the rocky small body is proposed; In response to the uncertain characteristics of the small body and high sampling adaptability, a dual-mode sampling scheme including grinding and brushing is proposed. Buffering and sampling performances are simulated. Prototype is developed and the whole process test of anchoring and sampling is carried out, and the core functions of the robot mechanical system are verified.

Abstract:Aiming at the slow convergence speed of traditional particle swarm optimization (PSO) algorithm in solving the geometric error calibration problem of industrial robots, a two-stage dynamic particle swarm optimization algorithm (LDPSO-BT) is proposed. First, the error model of the industrial robot is established by the Denavit-Hartenberg method, the geometric error calibration problem is converted into the solution of high-dimensional nonlinear equations, and then the number of particle swarms and the number of particles are linearly reduced in the algorithm solution process. In the late iteration of the improved particle swarm algorithm, an improved search mode is used to improve the speed iteration formula of the traditional particle swarm, and then the end positioning accuracy of the two algorithms before and after the geometric error calibration of the industrial robot is compared by simulation experiments. The experimental results show that the number of particle swarms has an important influence on the iteration time. Reducing the number of particles of the particle swarm linearly can effectively reduce the geometric error calibration of industrial robots. At the same time, the improved speed iteration formula can be used in the later stage of the particle swarm algorithm to ensure the accuracy of convergence. Compared with the traditional particle swarm optimization algorithm, using the improved particle swarm algorithm to obtain the geometric error revision data of the industrial robot can not only effectively reduce the positioning error of the industrial robot, but also has a more efficient iteration efficiency.

Abstract:To save the semi-active suspension electrical architecture and ECU development process, a new semi-active suspension sensor layout scheme is proposed, and the optimal IMU installation position is given. An accurate and complete formula for calculating the acceleration of four sprung positions by IMU signal is established. The proper angular rotation order and reference frame are selected to ensure the correctness of the method. The influence of sensor mounting position on soft sensing accuracy is given by using optimization theory and partial derivative method combined with different suspension weights, and the optimal mounting position with constraints is given. The experimental results show that the new sensor arrangement scheme and kinematics solution method can well predict the vertical acceleration of four sprung positions and have high stability, but the solution accuracy of different positions is quite different. The experimental results of the constrained optimal installation position obtained by the optimization theory are consistent with the theory (the root mean square error is about 0.6 m·s^-2). Compared with other installation positions, the experimental results of the optimal installation position have higher stability and measurement accuracy for different working conditions. Compared with the horizontal installation position, the vertical position of IMU has a greater impact on the final solution results and accuracy. An equivalent error ellipsoid of IMU installation position is given with combination of quantities and spatial forms, which can analyze the installation position more clearly and intuitively.

Abstract:To improve the average efficiency of hydrogen in fuel cell vehicles, an improved thermostat control strategy based on the aging state of fuel cell is proposed. Firstly, The polarization curves of fuel cell at different aging stages were fitted by least square method. Secondly, aiming at improving the average efficiency of hydrogen, the regular parameters of thermostat control strategy were optimized continuously by using genetic algorithm. Finally, the output power of the fuel cell was determined by the improved thermostat control strategy according to the battery SOC and the regular parameters, and the 800 hours of collected data of the fuel cell vehicle was used for simulation. The results show that the improved thermostat control strategy can maintain the average efficiency of hydrogen at different fuel cell aging stages at a higher level under different cycle conditions. Compared with the common thermostat control strategy, the average efficiency of hydrogen can be increased by 1.1% at most. According to the aging state and cycle condition of fuel cell, adjusting the regular parameters of thermostat in time is beneficial to improve the average efficiency of hydrogen in the vehicle.

Abstract:To solve the high temperature problem of new ratchet ultra-compact combustor, a full-coverage film cooling method was adopted. Based on the experiment and simulation of KJ-66 micro gas turbine, the original combustor was replaced with a ratchet ultra-compact combustor after scaling optimization. Then, according to the high temperature wall of the slope of the sudden expansion section and the inner ring in the secondary combustion zone, the influences of different arrangement modes, hole inclination angles and expansion film holes on the film cooling effect under actual combustion conditions were compared. The results showed that the film coverage of the cylindrical film holes on the slope of the sudden expansion section was not ideal, the comprehensive film cooling effect was not good, and different arrangements and hole inclination angles had little influence on the film cooling effect. The air film adhesion and cooling effects of the slope were greatly improved by expansion film holes. In the expansion film holes with 45° hole inclination angle and 0.6 mm outlet diameter, the comprehensive cooling effect produced by blowing off the high temperature flame surface and overlaying the air film was the best. Under the influence of the mainstream high centrifugal force field, the downstream of the secondary combustion zone could also obtain better adhesion effects of film when the blowing ratio was larger. The influence of the arrangements on the film cooling effects in the secondary combustion zone was more obvious than that of the hole inclination angles. On the whole, the full-coverage film cooling has good cooling effects on the wall of the ratchet ultra-compact combustor under actual combustion conditions. Expansion film holes can effectively improve the film cooling effects.

Abstract:To investigate the influence of different navigation parameters on the wave-making characteristics of submarines navigating in deeper density layers, based on viscous-flow theory, a multi-phase flow numerical model with user define function to specify the distribution of different fluid layers is established for analyzing the hydrodynamic characteristics of the submarine navigating in density-stratified fluid. The wake characteristics of the submarine navigating with different forward speeds and submerged depths in deeper density layer, which means the navigating position below the interface of internal wave, are numerically simulated. And the discussion is carried out by analyzing the results of wave profile, fluid-velocity distribution and wave pattern. The results show that the forward speed has a remarkable effect on the wake of the navigating submarine in the deeper density layer. The most significant wake on the bow and stern of the submarine is noticed when the submarine is advancing at a the mid-speed stage near Fr＝0.6. The submerged depth of the submarine affects the wave amplitude on both the free surface and the internal surface. Compared with the submarine navigating in the shallower density layer, the wave-making characteristics on free surface generated by the submarine navigating in the deeper density layer are similar, but the internal surface wake is significantly different. The change of the fluid-velocity distribution on the interfaces with different navigation parameters is consistent with the change of the wave-making characteristics. Revealing the characteristics of wave-making of submarines when navigating at a special position in the deeper density layer can enrich the analysis methods of hydrodynamic characteristics of navigating submarines at different positions, and provide a reference for submarine non-acoustic detection.

Abstract:This paper optimizes the thread profile of the planetary roller screw mechanism to improve the bearing capacity of the planetary roller screw mechanism. A meshing method based on convex-concave contact is proposed and the thread profile of screw and nut with a concave arc is designed. Based on the space meshing theory, the thread surface equation and the space meshing equation are derived, and the load distribution model is established based on the Hertz contact theory and the deformation coordination equation. The contact point position, the axial clearance and the contact stress are calculated by the numerical calculation method, and the law of the flank angle, pitch and other parameters on the contact point position, the axial clearance and the load distribution are revealed systematically. The contact stress between the standard and the convex-concave contact planetary roller screw mechanism is compared. The results show that the flank angle has the greatest influence on the axial clearance. The changes of the concave arc radius of the screw and nut make little difference to the contact point position and the axial clearance, but have a great impact on the bearing capacity. The bearing capacity of the convex-concave contact planetary roller screw mechanism is greatly improved compared with the planetary roller screw mechanism. The smaller the concave arc radius of the screw and nut, the more obvious the improvement of the bearing capacity. This research provides a basis for optimal design and analysis for the development of the planetary roller screw mechanism with high load capacity and long service life.

Abstract:To restrain the flow separation phenomenon on the airfoil surface and improve the aerodynamic performance of wind turbine blade, the blowing jet technology with high reliability is applied to the blade trailing edge of vertical axis wind turbines (VAWTs). The influence of different jet angles on the wind power coefficient, torque coefficient, single blade pressure and whole vorticity of the wind turbine was analyzed by numerical simulation. The results show that, when the optimum tip-speed ratio is 2.3,0° jet can reduce the shedding vortex frequency effectively and control the wake effect of blade with a better efficiency and operation stability than 0° jet. When the tip-speed ratio is lower, the peak torque of single blade is concentrated on the 120° phase angle, and 10° jet has a noticeable effect on improving the torque coefficient of the whole machine. When the tip-speed ratio is higher, there is a large positive pressure area on the pressure surface of the single blade airfoil, the wind energy utilization coefficient increases by 11% at most, and the aerodynamic performance is superior to that of the non-jet VAWT. The wind turbine reduces the axial load that the blade needs to bear and improves the output power of the wind turbine through trailing edge jet on the whole. The trailing edge jet of different angles reduces the flow loss on the blade surface and delays the flow separation effectively, which is particularly important to enhance the market competitiveness of VAWTs.

Abstract:To improve the flight efficiency and multi-mission adaptability of aircraft, a morphing wing framework for both high and low speed conditions is designed, and the position optimization and quantity arrangement of distributed drivers inside the morphing wing are studied. Firstly, based on a wing rib swing mechanism, a parallel linkage morphing wing mechanism with variable chord length, variable sweep, variable area, and variable aspect ratio was designed. Taking element size as the parameter, the aspect ratio and degree of wing rib swing were analyzed to obtain the variation curve of wing parameters. Then, a structure unit that contains the wing skeleton, actuator and flexible skin was chosen as the research object. Equivalent spring stiffness of the flexible skin was measured by an experimental method. Based on the principle of virtual work, a quasi-static mechanical analysis method was adopted to obtain the mechanical model of structure unit. Taking the deformation of the unit as the objective optimization function, the optimal driver position and initial state of the skin were obtained by the Matlab optimization toolbox fmincon function, and the experimental verification was carried out. Lastly, Ansys was used to simulate the coupling effect of multi-unit mechanism motion and elastic deformation, and the final equilibrium state of the mechanism under the layout of multiple drivers was obtained. The detailed structure of the morphing wing is designed and the prototype is fabricated and assembled. The results show that the balanced deformation of wing is related to the driver layout and structural stiffness. When the structural stiffness of the mechanism is enhanced, the deformation caused by distributed actuator and single actuator converges to the ideal value. The distributed drive will maximize the deformation, which is more suitable for the wing with low stiffness structure. Prototype of morphing wing can realize continuous deformation.

Abstract:To optimize titanium alloy beam seal with elliptical arc groove, based on ABAQUS software, the elastic-plastic contact finite element model of the beam seal was established, and the contact stress distribution and contact bandwidth of the two seals between the male and female connectors were obtained. Taking S index as the evaluation criterion of sealing performance, which considers both the macro geometry of the beam seal and micro morphology of the contact surface, the female connector with the best sealing performance is obtained by using ISIGHT software and multi-island genetic algorithm. The simulation demonstrates that its S index is 102.2% higher than that of the prototype, 53.1% higher than the maximum in the database, and its maximum contact pressure and contact bandwidth are remarkably increased, which means that the sealing performance of the optimized geometry is significantly improved. The S index of optimized beam seal is in good agreement with the prediction value of the optimization method, which verifies the effectiveness of the optimization method and the accuracy of the optimized geometry. Compared with the traditional method of evaluating the sealing performance only by contact stress or contact width, the S index comprehensively considers the macro and micro characteristics of the seal and provides a quantifiable sealing performance objective function for the optimization design of the beam seal. The application of ISIGHT software and multi-island genetic algorithm can improve the calculation efficiency and optimization accuracy.

Abstract:To explore the best lubrication strategy for the service process of high-speed rolling bearing under the condition of oil-gas lubrication, the lubrication performance of H7003C series angular contact ball bearing made of steel and Si₃N₄ ceramic rolling element materials at different wear stages was experimentally studied. The lubrication characteristics of rolling bearing in the early, middle and critical failure stages were simulated by standard condition test, accelerated wear test and limit wear test. The test results show that there are an optimal working condition range for H7003C series bearings in the initial stage of wear. As the oil air lubrication supply pressure is 1 Bar with quantity of 0.8-0.98 ml/min, the bearing temperature changes less than ±3.5℃ and the vibration velocity variance of the bearing in stable operation is less than 0.029, the lubrication performance of the bearing is the best under this condition. When the vibration value increases to 2-2.5 time of the initial value of wear, the lubrication condition of the bearing can be improved by adjusting the oil supply interval reasonably. Therefore, under the condition of oil-gas lubrication, the bearing has different lubrication requirements in different wear stages. The oil-gas parameters can be reasonably adjusted according to the changes of working conditions in different wear stages, so as to obtain the best lubrication strategy of rolling bearing under various working conditions.

Abstract:To reduce the influence of factors such as backpack load, clothing and environment on gait recognition rate, a full-body gait model fusing visual and tactile features was proposed. The model first took the support foot as the starting point, established the kinetic relationship between the mass of each body part and the ground support force according to the motion transfer process, and introduced visual features through acceleration. Then the model was parameter separated to obtain feature matrices representing different gait motion features, the visual and tactile features were extracted using visual image sequences and plantar pressure images obtained from Kinect and walkway-type plantar pressure meter. A database containing the three gait motion states of normal, backpack loaded and overcoat wearing was established. Finally the multi-classification method in support vector machine was selected to complete the gait recognition, and the classifier parameters were optimized by the K-CV method in the recognition process. The experimental results showed that the model recognition rate was improved by increasing the number of feature recognition points by means of plantar pressure partitioning. The average recognition rate of the model under normal gait motion conditions was 97.31%, and the recognition performance of the model decreased less in the case of backpack and wearing a coat. Fusion of visual and tactile features to build a full-body model including upper limb swing could effectively improve the robustness of the model under complex gait motion conditions and increase the gait recognition accuracy.

Abstract:To improve the dynamic response ability of unmanned vehicle tracking process and ensure that the vehicle can track the reference route quickly and stably, this paper firstly introduces the time-varying forward-looking distance into the traditional line-of-sight (LOS)guidance strategy based on the idea of fuzzy control, and proposes the improved adaptive LOS guidance strategy, which simplifies the tracking of target trajectory to the heading of the target point track. Secondly, a three degree of freedom dynamic model of vehicle is established, and the linear system mathematical model of path tracking is designed by combining the tracking error variable of adaptive LOS. Finally, multi-step prediction, rolling real-time optimization and feedback correction are used to solve the optimal feedback steering wheel control command, based on the principle of model prediction. To verify the effectiveness of the above-mentioned tracking strategy, the straight-line path and the curve path are used as the reference path in the Simulink simulation environment. The results show that the proposed adaptive LOS guidance strategy can make the tracking vehicle's lateral and heading errors converge to zero rapidly, which verifies that the adaptive LOS guidance algorithm can improve the response speed and stability of unmanned vehicle path tracking.

Abstract:The increasing demand for automatic picking robots of fruits and vegetables drives the study of the end-grabber realizing non-destructive picking. However, most traditional end grips are rigid structures, and the existing flexible grips also have shortcomings such as insufficient grasping force and poor coating. A new type of pneumatic four-blade soft grip was designed to realize the non-destructive picking of strawberry, which used the contour curve of strawberry as the design curve for the first time. Firstly, the structure of the software grip was simulated and optimized, thus an idea of safely attaching to the target surface was put forward. Then, both the minimum failure stress on surface of the strawberry and the end force of the software grip were test, and the feasibility of nondestructive grasping was verified based on these results. Thirdly, the bending deformation law of the soft grip leaf surface was studied using the dynamic capture technology. Finally, the soft gripper with arcs gas channel of strawberry grab was used to test the actual grasping ability. Results showed that the four blade pneumatic gripper soft could realize nondestructive fetching, the success rate was 90%, and the damage rate was 2%. It is proved that the developed four gripper for strawberry scraping blade soft has a good stability and practicability, and can be used to strawberry picking at the end of the actuator. This study can also provide theoretical basis and technical support for the picking technology of other fragile fruits and vegetables.

Abstract:To study the influence of positive and cosine control canard on the aerodynamic characteristics of rotating missile, the nested grid method is used to simulate the missile rotation and the deflection of the canard in CFD software. Based on the comparison with the wind tunnel test results and the verification of the accuracy of numerical simulation, numerical simulation was carried out on the aerodynamic characteristics of the rotating missile with positive and cosine control modes at different speeds, angles of attack and Mach numbers, and the following conclusions were drawn: When the same maximum canard deflection angle is used, the normal force coefficient of the missile is smaller than that of the static condition, while the lateral force coefficient and lateral moment coefficient are larger than that of the static condition. The lateral moment coefficient of the missile under the control of sines and cosines is smaller than that under the control of no control. The variation of rotational speed has relatively little effect on the normal force, lateral force and the normal force provided by the canard. The lateral force coefficient and lateral moment coefficient of the missile under subsonic condition are larger than those under supersonic condition. During the coning motion of the missile, the changes of the synthetic angle of attack Г have little effect on the periodic average lift coefficient and the lateral force coefficient, and the greater the Г makes the periodic average yaw force coefficient increase. The rotation effect is the reason for the lateral force of the rotating missile with positive and cosine control mode, and the lateral force of the canard and tail is dominant.

Abstract:To deeply understand the nature of trajectory correction mechanics of fixed canard dual-spin projectile, the angular motion characteristics and control stability under the control of fixed canard were studied. According to the knowledge of exterior ballistics of rocket and projectile, the complex attack angle motion equation of the fixed canard dual-spin projectile is established, the expressions of the specific solution corresponding to the control force term of canard surface and general solution corresponding to the resulting initial disturbance term are derived. It is theoretically explained that after the fixed canard takes control, the complex attack angle motion of a dual-spin projectile is composed of the forced angular motion of the complex dynamic equilibrium attack angle with the complex control equilibrium attack angle, and the free attack angle motion generated by the initial disturbance of the canard control. Based on this, the control stability condition of the fixed canard dual-spin projectile is proposed, and the mechanical nature of the trajectory correction of the fixed canard dual-spin projectile is analyzed by solving the complex velocity deflection angle caused by the control force of the canard surface and the complex disturbance attack angle. The numerical calculation results of the trajectory that the fixed canard is controlled at different roll angles show that the angular motion’s analytical solution deduced theoretically is consistent with the numerical calculation results in terms of frequency and amplitude. It’s verified that the complex attack angle motion equation under the control of fixed canard deduced in this paper and its analytical solution and the control stability condition are reasonable and feasible, which provides a theoretical basis and design reference for the development of this type of projectile.

Abstract:In order to accurately evaluate the bursting pressure of Cu-Ni alloy tube with groove defect, the prediction model of burst pressure was established and the bursting process was simulated, the correction function was determined by the least square method, and the hydrostatic blasting test was carried out. Both the numerical simulation and test results show that the error between DNV standard and numerical simulation results decreases first then increases with the increase of corrosion depth. The prediction formula established by the correction function containing defect depth parameter can effectively predict the burst pressure of the Cu-Ni alloy pipe, and the test proves that the formula has a high accuracy. Compared with the crack morphology of blasting test, the numerical simulation of pipe bursting process under the condition of only internal pressure is better. The ductile fracture occurs when the residual wall thickness is thin, while the brittle fracture occurs when thick. The study of burst pressure can provide theoretical basis for scientific maintenance of ship pipeline and has great significance to guide pipeline condition assessment.

Abstract:To solve the problem that the static service bill of material (service BOM, SBOM) cannot reflect the service process of dynamic maintenance, repair and overhaul (Maintenance, Repair and Overhaul, MRO) in real time, a SBOM evolution model in the product service life cycle for different management and service requirements in the dynamic MRO business is designed. By analyzing the difference of SBOM structure under the three management requirements of batch product, single product and single MRO service, from the perspective of assembly location, supplier and MRO tasks, the nodes and constraints of SBOM are classified and defined, and the evolution relationship model of different types of SBOM is established. Based on the influence of MRO service requirements on the changes of general SBOM and instance SBOM nodes, two types of SBOM changes in the dynamic service process and the node states under each type of changes are described, and the dynamic evolution model of SBOM changing with time is constructed. Finally, a locomotive bogie is taken as an example to prove the feasibility of the evolutionary model, and two MRO service traceability mechanisms are proposed according to the node traceability purpose, which greatly improves the management and traceability ability of dynamic data information in locomotive MRO service.

Abstract:The traditional crane automatic positioning method has low accuracy and poor stability, which can not form a real closed-loop control. The existing crane vision positioning methods generally have problems such as poor anti-interference performance, difficulty in convergence of vision error and difficulty in obtaining visual Jacobian matrix parameters. To solve the problem that the external disturbance affects the positioning accuracy and stability of visual servo system, this paper establishes the mathematical model of the position and attitude of the end effector under the disturbance condition, and proposes a visual servo disturbance suppressing method based on the Active Disturbance Rejection Controller. According to the characteristics of image projection, the relation between the parameters of Jacobian matrix and the differential of image feature is obtained, the adaptive updating rate of the parameters of Jacobian matrix is designed, and the closed-loop dynamic equation is established. According to the image feature error, the Lyapunov function is constructed and the system stability is proved. The simulation result shows that when the visual error converges, the position and velocity curves tend to zero. The method in this paper has satisfactory positioning accuracy in the case of visual uncertainty and external disturbance. It can ensure the positioning accuracy of the visual servo system and accelerate the convergence speed of the visual error under the disturbance condition. So, it is suitable for the control of the automatic positioning visual servo system of the hoisting crane.

Abstract:Aiming at the inability of existing instruments to comprehensively and rapidly measure the burr height, root thickness and morphology across entire regions of holes and the incapability to automatically use measurement data to calculate the evaluation indicators of burrs, a hole burr measurement system based on 2D laser displacement sensor was developed. First, the effects of stray light caused by multiple reflection, the tilting of laser imagining plane and the hole surface to be measured on measurement accuracy were discussed, followed by the proposition of a method to eliminate stray light and tilt correction. Next, the data of sensor measurements was utilized to develop an algorithm to calculate burr height and root thickness, fulfilling the visualization of burr height and root thickness extending around the hole circumference. Finally, evaluation indicators of median least square, arithmetic mean waviness and mean square root of waviness were used to describe the quantitative evaluation method of burr height and root thickness across the whole hole region. The experimental results show that the system can not only visualize the 3D morphology and 2D fluctuation of burrs across the whole hole region, but also give the quantitative values of burrs and their evaluation indicators. The repeatability precision of the system is less than 0.8 μm and the burr height accurate rate is 5 μm, which meets the requirements of accurate measurement of hole burr.

Abstract:In this paper, the lifting and drag characteristics, flow field structure and wake interference effects of two staggered wavy conical cylinders with center-to-center pitch ratios of L/Dm=4 and 5 and staggered angles of α=0~15° at Reynolds number 3900 are studied by large eddy simulation. The results show that the trailing vortex of the upstream wavy conical cylinder curls up and impacts on the side of the downstream wavy conical cylinder, which causes periodic coupling force on the surface of the downstream wavy conical cylinder, resulting in the increase of the fluctuating lift coefficient. At α=10° the fluctuating lift coefficient is 20.1 times and 21.4 times higher than that of single straight cylinder, respectively. Under the influence of two free ends of the upstream wavy conical cylinder and the backflow area generated by the interaction between the upstream wavy conical cylinder and the downstream wavy conical cylinder, the time-average drag coefficient of the downstream wavy conical cylinder is significantly reduced, and with the increase of the staggered angle, the time-average drag coefficient of the downstream wavy conical cylinder gradually approaches that of the upstream wavy conical cylinder. At α=10°, the time-average drag coefficient is 34.9% and 18.8% lower than that of a single cylinder, respectively. The flow around the staggered double wavy conical cylinders shows the flow structures of complete impact, side impact and wake disturbance et al. Because of the shape of the wavy conical cylinder, the flow field passing through the wavy conical cylinder presents strong three-dimensional characteristics, and the trailing vortex has obvious stratification, and the side impact condition provides a larger fluctuating lift coefficient than the other two. The results in this paper can provide theory support for the array layout of wind floating structure.