Search

Accurate accident reconstruction requires the knowledge of the mass properties of vehicles, namely the centre of gravity location, the mass and the inertia tensor. Such data are seldom available, especially in case of newly produced electric vehicles. In this paper, vehicle inertia measurements, performed at Politecnico di Milano, refer to a number of electric vehicles. In addition to the “simple” measurement of vehicle inertia, measured mass properties are analysed to derive the proper empirical formulae for the estimation of the centre of gravity height and the moments of inertia. Both internal combustion and electric vehicles are considered. Data show a significant difference in the mass properties of the two types of vehicles. The proposed formulae can be effectively employed to quickly obtain a reasonable estimation of the mass properties of any vehicle. The results show that electric vehicles are characterised by higher values of mass with respect to internal combustion vehicles, but they present a lower centre of gravity location and proportionally lower values of the moments of inertia.

According to accident case studies, one of the causes of accidents involving container ships was often the incorrectly declared weight of the container. For this reason, the International Maritime Organization introduced an amendment to the International Convention for the Safety of Life at Sea, requiring the verification of container weight declared in the transport document. It partially solved the problem of accurate determination of container ship stability, although an error of 5% by weight is accepted. In this study, using the Macs3 program, the weight of 100 containers was changed by 5% to assess how such a situation affects the ship’s stability. It was found that even a slight change in the weight can affect stability. There are other problems that have to be addressed, e.g., loading of the containers as per positions in the loading plan or sharing information about mass distribution inside. In the last part, Ishikawa’s diagram was used to determine the relationship between the causes and their effect on the accident of MSC Napoli in an attempt to determine other factors that may have contributed to the container ship’s accident and highlight the need to systematize the rules and tools connected to container ship weighing.

As an important spatial carrier of Hong Kong’s economic development, construction land provides a critical site for Hong Kong’s economic and social activities. The development of construction land directly affects the sustainable development of the city. Therefore, analysing the spatial and temporal evolution and driving mechanism of construction land in Hong Kong is of great significance in promoting sustainable urban development. This study aimed to evaluate the evolutionary characteristics and driving mechanism of construction land of Hong Kong in the period 1972–2020. Here, we extract construction land data from 1972 based on the historical map of Hong Kong. Then, we apply ArcGIS Pro and Fragstats software to calculate the rate of land expansion, land intensity, change in the centre of gravity, and landscape pattern index of construction land in Hong Kong from 1972–2020. Analysis shows the following: (1) The expansion of construction land in Hong Kong generally showed the characteristics of “rapid at first and then slowing down”, with 2010 as the peak of the 1970–2020 timeframe. (2) The sources of construction land transfer mainly came from cultivated land, sea areas, and forest land, which were mainly distributed in the New Territories. (3) The centre of gravity of construction land in Hong Kong showed the spatial characteristics of “slowly shifting to the northwest” during the study period, indicating that Hong Kong’s polycentric urban structure has been continuously strengthened. (4) The Spiltting index showed a tortuous upward trend, and the index of Mean Euclidean nearest neighbour distance showed a steady downward trend, which indicated that the landscape connectivity of city construction land steadily increased while the degree of fragmentation gradually increased. (5) The driving factors behind the expansion of Hong Kong construction land comes from population, economic, and traffic factors; the support factors come from location and policy factors; the elasticity factors mainly come from reclamation projects; the resistance factors mainly come from the restrictions of environmental protection departments, NGOs, and relevant laws on land reclamation.

This study aimed at analysing the influence of the position of the centre of gravity variability and the movement velocity on the demand for a torque and work time coverage of a wheelchair with an electromechanical drive. The variable parameter in the study was the configuration of the wheelchair, namely changes in the position of the batteries which changed the weight distribution. An analytical model describing the demand for torque was used in the analysis. The set of equations was introduced into the numerical calculation software. Simulations were carried out which allowed it to analyse selected parameters of the wheelchair dynamics. An increase in the torque demand was observed due to the increase in the mass of the system from 427.7 N to 533.1 N, ranging from 6.1% to 31.6% at the simulated velocity v7 = 4.2 m/s. The increase in the demand for torque due to the increase in velocity of the wheelchair from v2 = 1.05 m/s to v7 = 4.2 m/s ranged from 25.9% to 31.6% compared to the reference velocity v1 = 0.525 m/s. The centre of gravity of the wheelchair structure localization has a non-linear impact on the analysed values. At the same time, it was not possible to define its nature—this issue remains open and requires further research.

Floating devices under wave and current loads are typically designed based on numerical methods followed by a validation with experimental investigations. This allows an independent check due to the comparison of two different modelling approaches based on different assumptions. At an early stage of the project, numerical simulations are based on theoretical (ideal) values of the centre of gravity (CG) and moment of inertia (MI). The building process of a scaled model results very often in a requested simplification of certain parts, which can influence the CG and also the MI of the scaled model. Knowing those discrepancies allows us to improve the comparability of both approaches but the measurement of those values is connected with either a higher uncertainty or a high level of effort. A significant improvement of such measurements can be reached by the deployment of a specific experimental set-up. This paper presents the classification of the newly designed swing with a high accuracy inertial inclinometer, which was verified by the marker-based motion capturing system. The achieved experiences are useful for the future use of the set-up as well as similar investigations. The comparison with the theoretical values for the swing as well as an example model showed very good agreements and a high accuracy of few millimetres for the CG and an error smaller 1% for MI.

The paper presents a static lateral stability of a sub-compact tractor MT8-070 Mini in relation to a safe tractor operation. Axle weight distribution of the tractor was measured to calculate the vertical and longitudinal coordinates of a centre of gravity (COG). Experiments were aimed at the tractor equipped with no and four levels of rear wheel ballast weights (30.5, 61, 91.5 and 122 kg) at standard and extended overall width on tyres. A static overturning angle was calculated and experimentally measured when the tractor with right wheels touching the ground was in a state of unstable equilibrium. Comparing the experimental data with ISO 16231-2 (2015), the differences were 2.57%, 2.80%, 3.04%, 3.42% and 3.88% in the case of the standard overall width on tyres and 2.40%, 2.61%, 3.11%, 3.67% and 3.99% in the case of the extended overall width on tyres at 0, 30.5, 91.5 and 122 kg of the rear wheel ballast weight. Considering the vertical tyre deformation and the lateral shift of the tyre, the differences decreased to 0.95%, 1.11%, 1.29%, 1.85% and 1.42% (standard overall width on tyres) and 0.91%, 1.18%, 1.69%, 2.27% and 2.57% (extended overall width on tyres). The length of a rubber lug of a tyre contact patch did not change when the tractor was inclined at various ballast weights and did not affect the static overturning angle calculation according to ISO 16231-2 (2015). Results showed higher static overturning angle experimentally measured in comparison with calculated according to ISO 16231-2 (2015) due to the tyre deformation. Limiting the tractor operation on the basis of the static overturning angle calculated according to ISO 16231-2 (2015) avoids the tractor usage under dangerous operation conditions.