查看更多>>摘要：The Tethered Space Net Robot(TSNR)is an innovative solution for active space debris capture and removal.Its large envelope and simple capture method make it an attractive option for this task.However,capturing maneuverable debris with the flexible and elastic underactuated net poses significant challenges.To address this,a novel formation control method for the TSNR is proposed through the integration of differential game theory and robust adaptive control in this paper.Specifically,the trajectory of the TSNR is obtained through the solution of a real-time feed-back pursuit-evasion game with a dynamic target,where the primary condition is to ensure the sta-bility of the TSNR.Furthermore,to minimize tracking errors and maintain a specific configuration,a robust adaptive formation control scheme with Artificial Potential Field(APF)based on a Finite-Time Convergent Extended State Observer(FTCESO)is investigated.The proposed control method has a key advantage in suppressing complex oscillations by a new adaptive law,thus pre-cisely maintaining the configuration.Finally,numerical simulations are performed to demonstrate the effectiveness of the proposed scheme.
查看更多>>摘要：This paper proposes a measurement method related to the braking deformation of a complex motion.During the braking process,the deformation of the wheel includes large amounts of movement,vibration,warping,and distortion.A novel subset assignment and correlation method is proposed to measure the complex deformation.The proposed method can greatly improve the accuracy and stability of the calculation of complex deformations by simplifying the complex deformation into translational deformations in logarithmic coordinate system.According to the simulation and actual experiments,the proposed method can be utilized to measure the defor-mations of up to 100％tensile strain under complex deformation.According to the accuracy ver-ification experiment,the error of the proposed method is less than 50 με.The results show that the proposed method can effectively carry out structural deformation measurement in the complex motion and deformation process.The proposed method has great significance for structural perfor-mance analysis and optimization design considering complex motion and deformation.
查看更多>>摘要：A quantitative identification method for in-flight icing has the capability to significantly enhance the safety of aircraft operations.Ultrasonic guided waves have the unique advantage of detecting icing in a relatively large area,but quantitative identification of ice layers is a challenge.In this paper,a quantitative identification method of ice accumulation based on ultrasonic guided waves is proposed.Firstly,a simulation model for the wave dynamics of piezoelectric coupling in three dimensions is established to analyze the propagation characteristics of Lamb waves in a struc-ture consisting of an aluminum plate and an ice layer.The wavelet transform method is utilized to extract the Time of Flight(ToF)or Time of Delay(ToD)of So/B1 mode waves,which serves as a characteristic parameter to precisely determine and assess the level of ice accumulation.Then,an experimental system is developed to evaluate the feasibility of Lamb waves-based icing real-time detection in the presence of spray conditions.Finally,a combination of the Hampel median filter and the moving average filter is developed to analyze ToF/ToD signals.Numerical simulation results reveal a positive correlation between geometric dimensions(length,width,thickness)of the ice layer and ToF/ToD of Bf mode waves,indicating their potential as indicators for quantify-ing ice accumulation.Experimental results of real-time icing detection indicate that ToF/ToD will reach greater peak values with the growth of the arbitrary-shaped ice layer until saturation to effec-tively predict the simulation results.This study lays a foundation for the practical application of quantitative icing detection via ultrasonic guided waves.
查看更多>>摘要：As the elevator and rudder can be used actively for control,in addition to the rotors,Coaxial High-speed Helicopters(CHHs)have the problems of control redundancy and changing control authority in the transition mode.This paper presents a robust-augmentation transitioning flight control design for a CHH under the adverse conditions of parametric uncertainties and exter-nal disturbances.First,based on control characteristic analysis,an Adaptive Filtered Nonlinear Dynamic Inversion(AFNDI)controller is proposed for the angular rate to handle the effect of unknown unstructured uncertainties and external turbulence.Theoretical analysis proves that the presented angular rate controller can guarantee steady-state and transient performance.Further-more,the attitude angle and velocity controllers are also added.Then,an Incremental-based Non-linear Prioritizing Control Allocation(INPCA)method is designed to take into account control surface transition and changing control authority,which efficiently distributes the required moments between coaxial rotors and aero-surfaces,and avoids the control reversal problem of the yaw channel.In the proposed control architecture,the low-pass filter is introduced to alleviate the adverse influence of time delay and measurement noise.Finally,the effectiveness of the pro-posed controller is demonstrated through nonlinear numerical simulations,and is compared with existing methods.Simulation results show that the proposed control law can improve both capabil-ities of disturbance rejection and fast response,and works satisfactorily for the CHH transitioning control characteristic.
查看更多>>摘要：In this paper,a multi-bus distributed Power Conditioning Unit(PCU)is proposed for the Space Solar Power Station with large scale photovoltaic(PV)array and power levels reaching MW level.In this unit,there are multiple independent PV arrays.In each PV array,there are mul-tiple independent PV subarrays.In this paper,a V-P droop control method with adaptive droop coefficient is proposed,which modifies the droop intercept based on the bus voltage deviation and the power per unit value of the PV array.This method ensures the accuracy of bus voltage and achieves proportional distribution of power between PV arrays based on the proposed topology structure in this paper.When the load changes or the output power of the PV array fluctuates,this method can ensure that power is distributed proportionally.The principle and control method of the proposed droop control method is analyzed in this paper.The effectiveness of the method is verified through MATLAB/Simulink simulation and experiment.Simulation and experimental results show that the proposed method can achieve power distributed proportionally when load changes and PV output power fluctuates,reduce bus voltage error caused by line impedance and differences in rated power of different PV arrays,and improve the performance of PV power gen-eration system applied to space.
查看更多>>摘要：This study focuses on addressing kinematic singularity analysis and avoidance issues for a space station remote manipulator system(SSRMS)-type reconfigurable space manipulator.The manipulator is equipped with a non-spherical wrist and two lockable passive telescopic links(LPTLs),which enable it to have both active revolute and passive prismatic joints and operate in two distinct modes.To begin with the kinematic singularity analysis,the study derives the differen-tial kinematic equations for the manipulator and identifies the dominant Jacobian matrix that causes singularities.Subsequently,an in-depth analysis of singularities from multiple perspectives is conducted.Firstly,a kinematic singularity map method is proposed to capture the distribution of singularities within the reachable workspace.Then,the influence of the two LPTLs on singular-ities is thoroughly examined.Finally,a new method based on the matrix rank equivalence principle is introduced to determine singularity conditions,enabling the identification of all the singular con-figurations for the SSRMS-type reconfigurable manipulator.Notably,this method significantly reduces computational complexity,and the singularity conditions obtained have more concise equa-tions.For the singularity avoidance problem,a novel method is developed,which simultaneously addresses the requirements of real-time performance,high precision,and the avoidance of both kinematic singularities and joint limit constraints.Benefiting from these excellent properties,the proposed method can effectively resolve the singularity issues encountered separately by the SSRMS-type reconfigurable manipulator in its two operational modes.Several typical simulations validate the utility of all the proposed methods.
查看更多>>摘要：Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of deployable structures(e.g.,solar arrays and antennas).This paper investigates folding stable state of Bi-DCB through the analytical method.Based on Archi-medes'helix and energy principle,an analytical model for predicting folding stable state of Bi-DCB was presented.The failure index of Bi-DCB in folding stable state were analyzed using the Tsai-Hill criterion and the maximum stress criterion.Then,a 2400 mm long Bi-DCB was fabricated using autoclave method.The prediction results of the proposed model were compared with experiments and results of two other analytical models.It is shown that the proposed model shows good predic-tion accuracy.Finally,the effect of geometric parameters on folding stable state of Bi-DCB was fur-ther investigated with the aid of the proposed model.
查看更多>>摘要：Both experimental and simulation approaches were employed to investigate the laser ablation mechanism and performances of Glass Fiber Reinforced Phenolic Composites(GFRP).During the ablation process,the difference in thermal conductivities of the glass fibers and the resin matrix as well as their discrepant physical and chemical reactions form a conical ablation morphol-ogy.The formation of a residual carbon layer effectively mitigates the ablation rate in the thickness direction.A higher power density results in a faster ablation rate,while a longer irradiation time leads to a larger ablation pit diameter.To account for the variation in thermal conductivity between the fiber and resin,a macro-mesoscale model was developed to differentiate the matrix from the fiber components.Finite element analysis revealed that laser irradiation leads to phenolic decompo-sition,glass fiber melting vaporization,and residual carbon skeleton evaporation.The dual-scale model exhibits precise prediction capabilities concerning the laser ablation process of GFRP,and its accuracy is confirmed through the comparison of simulation and experimental results for the GFRP laser ablation process.This model provides a feasible method for performance evaluation and lifetime prediction of GFRP subjected to continuous wave laser irradiation.
查看更多>>摘要：Instrumented indentation is a promising technique for estimating surface residual stres-ses and mechanical properties in engineering components.The relative difference between the indentation loads for unstressed and stressed specimens was selected as the key parameter for mea-suring surface residual stresses in flat-ended cylindrical indentations.Based on the equivalent mate-rial method and finite element simulations,a dimensionless mapping model with six constants was established between the relative load difference,constitutive model parameters,and normalized residual stress.A novel method for measuring the surface residual stress and constitutive model parameters of metallic material through flat-ended cylindrical indentations was proposed using this model and a mechanical properties determination method.Numerical simulations were conducted using numerous elastoplastic materials with different residual stresses to verify the proposed model;good agreements were observed between the predicted residual stresses and those previously applied in finite element analysis.Flat-ended cylindrical indentation tests were performed on four metallic materials using cruciform specimens subjected to various equibiaxial stresses.The results exhibited good conformance between the stress-strain curves obtained using the proposed method and those from traditional tensile tests,and the absolute differences between the predicted residual stresses and applied stresses were within 40 MPa in most cases.
查看更多>>摘要：Gamma titanium-aluminum(γ-TiAl)intermetallic compounds are increasingly used in manufacturing key hot-end components(e.g.,blade tenon)in aero engines due to their high specific strength and lightweight properties.Creep feed profile grinding(CFPG)as a crucial precision pro-cess that is applied to produce the final profile of the blade tenon.However,sudden surface burns and microcracks of machined γ-TiAl blade tenon often occur because of its low plasticity and high strength during grinding processes,leading to poor surface integrity.In this work,CFPG experi-ments based on the profile characteristics of γ-TiAl blade tenon were performed and an associated undeformed chip thickness model considering grain-workpiece contact condition was established to explore the evolution of the surface integrity.Subsequently,the surface integrity was analyzed at different positions of the blade tenon in terms of surface roughness and morphology,metallo-graphic structure,microhardness,and residual stress.Results show that the profile characteristics of blade tenon have a significant influence on machined surface integrity because of the thermome-chanical effect at various detecting positions.The residual stress was established based on the unde-formed chip thickness model considering the profile structure,with a prediction error of 10％-15％.The thermomechanical effect is more obvious at the bottom area,where the surface roughness,work hardening degree,and subsurface plastic deformation range are the largest,while the values at the bevel area are the smallest.Based on the undeformed chip thickness model,a residual stress finite element simulation was conducted by employing thermomechanical coupled effects.In addi-tion,the error between the simulation and the experiment was between 10％-15％.Strain and strain rate equations were established through the relationship between material displacement and depth.The average strain and strain rate of the ground surface when ap is 1.0 mm are 18.8％and 33.2％larger than when ap is 0.5 mm,respectively.This study deepens the understanding of surface integ-rity under the influence of CFPG γ-TiAl and provides a practical reference and theoretical basis for realizing high-quality profile grinding of other complex parts.
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