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In order to study the uniaxial compression properties of closed-cell metal foam, three different modeling methods were used in this paper to establish 2D random cell, 3D Kelvin and 3D voronoi metal foam model. Based on the LS-DYNA software, the differences of the compressive mechanical properties of the closed-cell metal foam under three different models were analyzed. The deformation mode and the stress strain response of the metal foam under three models were studied. The results show that 2D random cell model is more suitable for the study of the compression regularity of metal foam, and the 3D model is more suitable for the prediction and optimization of the compression response of metal foam. The 2D random cell model is restricted by its plane geometry, it can only simulate the closed-cell metal foam with low porosity in most cases. The Kelvin model and Voronoi model can simulate the closed- cell metal foam with high porosity. Compared with the Kelvin model and 2D random cell model, the voronoi model is more realistic and reasonable, and it is able to better characterize the compressive mechanical properties of closed-cell metal foam.

Accurate material model is the basis of UAVs numerical simulation. In this paper, for different types of airframe structural materials of light and small UAVs, material mechanical performance tests with different strain rates and numerical simulation are carried out, to obtain reliable structural materials’ elastoplastic constitutive model and failure model.

The accuracy estimation of the peak power can guarantee the battery’s safety, and make full use of the battery performance during the allowed safe range, thus improving the safety, power and quick charge performance. Up to now, the peak power in the electric vehicles is usually acquired by the peak power, SOC and temperature map, thus requiring a lot of offline experiments, and not taking the real-time polarization into account. Besides, the map method is strongly influenced by the accuracy of SOC and battery aging. In response to these circumstances, this paper has developed a model-based method for peak power online estimation. Firstly, the one order resistance-capacity equivalent circuit model has been employed to model the battery; Secondly, the parameters of the model have been on-line estimated by the particle swarm optimization (PSO) method; Thirdly, through the model-based method, the peak power of the battery has been obtained; Finally, a simplified version of the federal urban driving schedule (SFUDS) with inserted pulse experiment has been conducted to verify the peak power estimated. The result indicates that the proposed method is accurate and reliable with the 25 W maximum absolute error of the peak power.

Child neck injuries in motor vehicle crashes (MVCs) result in high morbidity and mortality rates. Estimating a statistical cervical vertebrae geometric model and quantifying the variations of the size and shape with age are very important for investigating the dynamic response and injury risk to a child's cervical spine, as well as for providing a geometric basis for developing child anthropomorphic test devices (ATDs) and finite element models (FEMs) of different ages. In this study, spatial geometric points were automatically extracted from the cervical vertebrae computed tomography (CT) scans of 30 children aged 10 to 18 years old (YO), and a statistical geometric model was estimated for the cervical vertebrae as a function of age and neck circumference/neck length according to the method of principal component analysis and regression (PCAR). Based on this statistical model, geometric point sets representing cervical vertebrae geometries at different ages and percentiles were generated and formed to envelope surfaces. Meanwhile, the size changes of the cervical vertebrae with child growth from 10 to 18 YO were quantified. In general, the anteroposterior length (APL), transverse process width (TPW), vertebral body height (VBH), and vertebral body depth (VBD) of the cervical vertebrae increase with age; the VBH and VBD increase faster than the APL and TPW. Compared with other vertebrae, the APL of C7 is larger, and the rate of increase of C1 with age is evidently slower. The TPWs of C1 and C7 are greater than those of C2 to C6. C7 has higher average values for the VBH and VBD than C3 to C6.

Most of the garbage bins in public places are traditionally fixed, which are limited by the number of garbage bins, limited capacity, untimely cleaning and uneven placement, and other factors, causing inconvenience for people to use garbage bins [1]. This paper designs an intelligent garbage bin. Based on NB-IoT communication technology, it realizes the functions of self-moving and collecting garbage, self-detecting garbage capacity in the bin, temperature and humidity monitoring and so on. The design is divided into three parts: intelligent robot module, sensor circuit module and NB-IoT communication module. The intelligent robot module is mainly responsible for the mobile and obstacle avoidance function of the intelligent garbage bin, and realizes traversal and surround in the setting environment scene [2]. The sensor module is the core of the hardware system, which realizes the functions of obstacle avoidance evaluation, capacity monitoring, heat source induction and so on. The platform establishes contacts to feedback the contents of barrels, temperature, humidity, electricity and other information in a timely manner. This design combines convenience and practicability, and can improve the sanitary condition of public places.

The high-precision modeling and collision simulation of UAVs should be conducted to achieve the dynamic response of UAV and assess UAV safety. In this paper, a high-precision finite element model of small rotor logistics UAVs on the market was built in LS-DYNA. The process to model the connection structure between a range of parts of a UAV was elucidated in detail. The bolt, damping spring and rivet & thread were respectively simulated with “NRB + beam”, “NRB + discrete” and “spot weld”. By a series of static and dynamic material tests, the constitutive parameters of main materials of UAV structure were determined. Besides, a reasonable explicit time step was set by regulating the mass scaling of local elements. To verify whether the finite element model of UAV is accurate, UAV underwent a developed full-scale crash test. As revealed from the experimentally achieved results, the trend of impact load over time in collision simulation significantly complied with the experimentally achieved results, and the discrepancy between the maximum impact load peak and the experimentally achieved results only took up 6.54%. Moreover, the vital damaged parts, damaging process and failure mode of the UAV structure in the crash test were accurately characterized in the collision simulation. Thus, the UAV modeling and collision simulation was verified to exhibit feasibility. Lastly, with the verified UAV high-precision model, the impacting process, possible damaged parts and failure modes of UAV at the variety of angles and speeds were assessed. Accordingly, the proposed high-precision modeling and collision simulation of small rotor UAV is capable of saving the physical and time resources of UAV structural strength experiments, as well as effectively assessing the structural safety and improving the design of small rotor UAVs.

Nowadays the multi-rotor UAVs are used a lot in military and civilian fields and which are playing an increasingly important role. However, the fixed support frames made of metal or composite material acting as landing gears are widely used on the multi-rotor UAVs, which have shortages and can’t be applied to the landing environment with uneven terrain. So a new kind of terrain-adaptive bionic landing gear is proposed in this article with the function of adapting complex terrains and makes the multi-motor UAVs landing on rough terrain, great slope and step floor. The composition and designing principles of the system are introduced at first. Based on the working process, the design method of one-leg system is detailed described as a basic part, and the kinematic solution of multi-leg system is also based on this through coordinate transform. And through virtual simulation, laboratory debugging and flight test, the feasibility and correctness of the design are shown at last. From the jobs in this article, the terrain-adaptive landing gear can be successfully used on multi-rotor UAVs when landing on some complex terrain through adjusting the orientation of the legs. Compared to the traditional design forms, the design has important engineering application value.

Unmanned Aerial Vehicles are widely used in aerial photography, exploration, logistics and other fields for their low cost, low take-off and landing requirements and many other advantages. With the deep application of UAVs, their safety problems have become increasingly prominent. The frequent occurrences of collision events have attracted the public attention. This paper reviews the UAVs weight threshold estimation test, UAVs impact aircraft windshield test and aircraft horizontal stabilizer test, and compares the results with bird collision results, discusses the impact safety challenges of light and small UAVs. This paper puts forward what should focus on about UAVs designing.

In the dynamic mechanics analysis of light and small unmanned aerial systems (UAS), The importance of the high-precision modelling of UAS is unquestionable. Modelling can be classified into 3D geometric model modelling and finite element model modelling, of which the finite element model modelling is mainly divided into four parts: discretization, connection modelling, contact modelling and material attribute definition. This review summarizes the existing modelling methods of light and small UAS, and provides the basic methods and modelling methods for the simulation calculation of light and small UAS. Implications for practice and future research are provided.

In order to carry out the researches on the static and dynamic stability characteristics of power system under large wind power capacity, PSD-BPA transient stability simulation program widely used in the Chinese power system has introduced system-oriented electromechanical transient simulation models of wind turbines with various types. However, the existing applications and discussions are focused on the encapsulation models of the old version with obvious lack of the researches of the newgeneration wind turbine models. In this paper, the overall wind turbine models of PSD-BPA are systematically arranged and analyzed. In addition, the technical characteristics are verified by comparisons with PSS/E and the actually measured data. It also serves as a second interpretation of PSD-BPA official data, which helps to deepen the understandings of PSD-BPA new wind turbine models and improve the level of wind power system modeling.