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In recent years, an innovative underactuated robot was developed, named as underactuated cable-driven truss-like manipulator (UCTM), to be suitable in aerospace applications. However, there has been strong consensus that the stabilization of planar underactuated manipulators without gravity is a great challenge since the system includes a second order nonholonomic constraint and most classical control methods are not suitable for this kind of system. Furthermore, the complexity of the truss-like structure results in tremendous difficulty of computational complicacy and high nonlinearity during dynamic modelling in addition to controller design. It is paramount to solve these difficulties for UCTM’s future applications. To solve the above difficulties, this paper presents a dynamic modelling method for UCTM and a trajectory tracking control method based on partial feedback linearization (PFL) that fulfills the control goal of moving UCTM from its original position to a desired position by tracking a given trajectory of the joint angles. To achieve this, a model equivalent method is proposed to make UCTM equivalent with a three-link manipulator in the sense of dynamic behavior. Then the Lagrangian equation combined with complex vector method is proposed in the dynamic modelling process of UCTM, which simplifies the derivation procedure. Based on the established dynamic model, a coordinate transformation method is proposed to transform the control force matrix into the conventional form of an underactuated system, so that the control force can be separated from the unactuated term. The PFL method in combination with the LQR control method is then proposed to realize the targets that the joint angles can track given desired trajectory. Simulation experiments are conducted to verify the correctness and effectiveness of the proposed methods.

To provide theoretical basis for square honeycombs used as crashworthy structures, energy-absorption properties of metal square honeycombs and the size optimization were performed. Specific energy absorption (SEA) was defined as the energy absorbed by the honeycomb structure per unit volume. This parameter was often used for determining the crashworthiness of thin-walled structures. In order to find the most optimized metal square honeycomb structure with the maximum SEA and the lowest peak stress, the cell length and the foil thickness of the metal honeycombs were optimized, with a low peak stress and a high SEA set as the two primary objectives. The pre-processing software Patran was used to build FE models, and the explicit solver LS-DYNA was employed to perform the crashworthiness analyses. The results show that the square honeycomb exhibits good energy absorption performance in some cases. The geometry is effective using 16.8% less buffer structure volume than the hexagonal honeycombs with a peak stress limitation of 1.21 MPa.

Both the friction caused by the preload in locked joints and the impact caused by clearance in unlocked joints cause energy dissipation in jointed deployable structures. The energy dissipation of locked joints is studied by analyzing the force on the infinitesimal body of the joint. The jointed beam with an unlocked joint is simplified into an impact mass-spring model with clearance, which considers the coefficient of restitution of impact. The energy dissipations of the joint caused by friction and clearance are transformed into damping ratios by Taylor expansion. Then, the effects of pressure, clearance and the dynamic parameters on the damping of joints are analyzed by utilizing the damping ratio formulation. The damping ratio increases with the preload and the clearance. To validate the damping ratio formulation of joints, experiments on a single jointed beam with preload and double jointed beams with clearance are conducted. Comparison between the experimental results and the model simulation results shows that the friction and impact damping models are accurate for the dynamic calculation of deployable structures. Furthermore, the damping ratio formulations can be directly introduced into the design and dynamic analysis of deployable structures.

The dynamic equivalent continuum modeling method of the mast which is based on energy equivalency principle was investigated. And three kinds of mast dynamic model were established, which were equivalent continuum model, finite element model and simulation model, respectively. The mast frequencies and mode shapes were calculated by these models and compared with each other. The error between the equivalent continuum model and the finite element model is less than 5% when the mast length is longer. Dynamic responses of the mast with different lengths are tested, the mode frequencies and mode shapes are compared with finite element model. The mode shapes match well with each other, while the frequencies tested by experiments are lower than the results of the finite element model, which reflects the joints lower the mast stiffness. The nonlinear dynamic characteristics are presented in the dynamic responses of the mast under different excitation force levels. The joint nonlinearities in the deployable mast are identified as nonlinear hysteresis contributed by the coulomb friction which soften the mast stiffness and lower the mast frequencies.

In order to study dynamic response of train collision based on the theory of multi-body dynamics, a multi-body dynamic model of two trains of high-speed trains was established by using MATLAB software. The numerical method is used to simulate the collision process of 6 marshalling trains. This paper studies the influence of the configuration of energy absorber, such as buffer, crushing tube and anti-creeper at different speeds of trains and strength gradient of crushing tube and anti-creeper on impact characteristics of train connected. The results show that the rational allocation of energy absorption components can effectively control the average energy absorption of the train.

Thin-walled tubes have been widely used as energy absorption structure. In this paper, the energy absorption properties of straight circular tube, straight sinusoidal tube and conical sinusoidal tube under oblique load were studied based on simulation analysis. The simulation model was validated by comparing with experiment. According to the simulation results, the straight circular tube is found to have the best crashworthiness performance under axial load. The crashworthiness performance of the conical sinusoidal tube is least influenced by the oblique load angle. The straight sinusoidal tube has the worst crashworthiness performance both under axial and oblique load.

Although much literature is available on the statics and grasp stiffness analysis of underactuated mechanisms, little research has been done on them of the underactuated cable-truss mechanism. The underactuated cable-truss mechanism grasps the target in the form of envelopment. Considering the grasping characteristics of the mechanism, the research on the relationship between the grasping force and the driving force is extremely important, as well as the study of the grasp stiffness. The statics analysis of an underactuated cable-truss mechanism, constituted by five cable-truss units, was given by means of combining with the vector method and the principle of virtual work in this paper. To prove the correctness of the analysis, the simulation was presented. The stiffness of the cable-truss unit was defined and the curve, showing the influence of the proportion relationship between the essential parameters to the stiffness, was obtained. Then, the stiffness of the mechanism was discussed.

Computer vision builds a connection between image processing and industrials, bringing modern perception to the automated industrials. At the same time, defect detection based on deep learning has played an important role in automated detection. In this paper, an improved convolutional neural network CU-Net for fabric defect detection is proposed. In this method, the classical U-Net network was improved. On the basis of network size compression, attention mechanism is introduced and a new compound loss function is used for training. Using the public AITEX defect fabric data set as the test sample, the experimental result shows that the accuracy and recall of the proposed method are 98.3% and 92.7%, respectively. Compared with the highest scores of other detection methods, they are improved by 4.8% and 2.3%, which improves the detection accuracy of fabric defect significantly.

The core algorithm of digital image processing has mainly involved three aspects: random theory, wavelet analysis and partial differential equations. This paper presents a new algorithm, which takes the digital image as a pixel grid, and then establishes the dynamic equation that has solitary wave solutions. Moreover, the solution can become analytic so it can be applied to the image directly. Meanwhile, due to the elastic collision properties of the solitary wave, pixel of the same size can produce the same kind of solitary wave, which facilitates a further processing of pixel. The interplay between pixels can be further studied in terms of collision property on account of the nonlinear effect. Analysis of the algorithm shows that solitary wave amplitude characterizes the effect between adjacent pixels, and the phase change of solitary waves provide the azimuth information of image.

As the development of space structures is increasing fast, analysis on the characteristics of those deployable structures deserve to be paid enough attention to ensure a reliable deployment on orbit. For a deployable truss structure, more than one position can be chosen as the driving positions, especially when the structure has not only 1 degree of freedom (DOF), an available choice of the driving positions shows significant importance on the performance of the space deployable structure. This paper mainly deals with a planar deployable support truss structure for space antenna by means of the closed loop equations and the Kane equation to discuss the deployment characteristics by comparison of the driving torque needed over time. A full comparison of all the possible examples of deployment analysis results under different driving modes is presented. The results show the importance of the choice of driving movements and the design of parameters and also provide a useful reference to other related truss structures.