Abstract Techniques for predicting the trajectory of vulnerable road users are important to the development of perception systems for autonomous vehicles to avoid accidents. The most effective trajectory prediction methods, such as Social-LSTM, are often used to predict pedestrian trajectories in normal passage scenarios. However, they can produce unsatisfactory prediction results and data redundancy, as well as difficulties in predicting trajectories using pixel-based coordinate systems in collision avoidance systems. There is also a lack of validations using real vehicle-to-pedestrian collisions. To address these issues, some insightful approaches to improve the trajectory prediction scheme of Social-LSTM were proposed, such methods included transforming pedestrian trajectory coordinates and converting image coordinates to world coordinates. The YOLOv5 detection model was introduced to reduce target loss and improve prediction accuracy. The DeepSORT algorithm was employed to reduce the number of target transformations in the tracking model. Image Perspective Transformation (IPT) and Direct Linear Transformation (DLT) theories were combined to transform the coordinates to world coordinates, identifying the collision location where the accident could occur. The performance of the proposed method was validated by training tests using MS COCO (Microsoft Common Objects in Context) and ETH/UCY datasets. The results showed that the target detection accuracy was more than 90% and the prediction loss tends to decrease with increasing training steps, with the final loss value less than 1%. The reliability and effectiveness of the improved method were demonstrated by benchmarking system performance to two video recordings of real pedestrian accidents with different lighting conditions.
A number of existing centrifugal fans’ aerodynamic sketches and dimensionless characteristics are investigated and evaluated by means of statistical method. Based on the statistical data, the optimum curve of centrifugal fans is replenished and amended. The paper also puts forward the relation curve between exit width of blade and diametral quotient, and discusses its application in fans’ design and calculation.
The current study aimed to assess the protective performance of helmets equipped with a multi-directional impact protection system (MIPS) under various oblique impact loads. Initially, a finite element model of a bicycle helmet with MIPS was developed based on the scanned geometric parameters of an actual bicycle helmet. Subsequently, the validity of model was confirmed using the KASK WG11 oblique impact test method. Three different impact angles (30°, 45°, and 60°) and 2 varying impact speeds (5 m/s and 8 m/s) were employed in oblique tests to evaluate protective performance of MIPS in helmets, focusing on injury assessment parameters such as peak linear acceleration (PLA) and peak angular acceleration (PAA) of the head. The results demonstrated that in all impact simulations, both assessment parameters were lower during impact for helmets equipped with MIPS compared to those without. The PAA was consistently lower in the MIPS helmet group, whereas the difference in resulting PLA was not significant in the no-MIPS helmet group. For instance, at an impact velocity of 8 m/s and a 30° inclined anvil, the MIPS helmet group exhibited a PAA of 3225 rad/s2 and a PLA of 281 g. In contrast, the no-MIPS helmet group displayed a PAA of 8243 rad/s2 and a PLA of 292 g. Generally, both PAA and PLA parameters decreased with increasing anvil angle. At a 60° anvil angle, PAA and PLA values were 664 rad/s2 and 20.7 g, respectively, reaching their minimum. The findings indicated that helmets incorporating MIPS offer enhanced protection against various oblique impact loads. When assessing helmets for oblique impacts, the utilization of larger angle anvils and rear impacts might not adequately evaluate protective performance during an impact event. These findings will guide advancements in helmet design and the refinement of oblique impact test protocols.
Numerous studies, including epidemiological, experimental and simulation studies, have shown that helmets can provide good protection for the two-wheeler (TW) rider's head and reduce the casualty rate due to head injuries during an accident. The objective of this current study was to evaluate the protective performance of a helmet based on in-depth accident reconstructions of electric two-wheel (ETW) rider's head-to-ground impact validated by the video information that provide clear and complete kinematics of ETW rider. Furthermore, validated finite element (FE) models of the helmet and human head were used. Three real-world accident cases (Cases A, B and C) were evaluated, in which, the riders' head were injured by ground impact after collided by the vehicles. In Case A and Case B, the helmet could effectively reduce the risk of skull fracture to 46% and 4%, respectively; whereas the risk of a skull fracture was up to 94% in Case C. In addition, the helmet can slightly reduce the risk of DAI injuries to 39% in Case C, while the risk of concussion cannot be reduced in three cases. In the violent impact condition such as in Case C, the bottoming out of the liner foam makes helmet lose effective protection against skull fracture. The connection between the shell and liner foam largely affects the helmet's protection against the brain injuries such as DAIs and concussions. The findings point out the lack of protective performance of the helmet and further provide more comprehensive guidance on the safety design of the helmet.
The parameterized drafting technology an database, which is used in diagram drafting of centrifugal fan, is introduced in this paper. The parameterized drafting system for main parts of centrifugal fan is developed by VBA under the circumstances of AutoCAD 2000. The paper introduced the realizing process of drafting principle and system function in detail.
The correlation between vehicle front profiles and multiple head injury forms in accidents remains unclear. Three hundred simulations were conducted by considering five vehicle front-end variables: bumper centre height, Bonnet Length (BL), Bonnet Leading Edge Height (BLEH), Bonnet Angle (BA) and Windscreen Angle (WA). HIC15, angular acceleration, maximum principal strain and cumulative strain damage measure were calculated to evaluate Skull Fracture (SF), Sub-Dural Hematoma (SDH) and Diffuse Axonal Injury (DAI). Prediction models were developed and evaluated by using back-propagation neural network algorithms. Results reveal that BLEH exhibits the highest overall significance of 0.41, which was the most sensitive parameter affecting all three injury forms. SF was significantly correlated with BL, with an importance value of 0.12. Changing WA and BA demonstrates significant effects on SDH and DAI, with significance values of 0.29 and 0.33, respectively. The results can give a comprehensive reference for the design and optimisation of vehicle front profiles.
Objectives The aim of this study was to examine the effects of emergency avoidance behaviors on the kinematics and injuries of electric two-wheeler (ETW) riders.Methods Four typical riding postures of ETW riders before collisions, including one normal posture and three avoidance postures, were identified through analysis of 298 videos of vehicle to ETW accidents. Crash simulations were then performed using the Total Human Model of Safety (THUMS) occupant model, ETW and a sedan finite element (FE) model, and the kinematics of ETW riders were compared. The risk of head injury and lower extremity injury was also investigated.Results When the struck foot position of the ETW rider was lower than the ETW pedal, the lower extremity was struck by the sedan bumper and ETW frame from the right and left side respectively, and the upper body of the rider rotated around the hood leading edge. At a car velocity of 40 km/h, the rider was at high risk of head injury and the tibia was fractured. The medial cruciate ligament (MCL) was ruptured in both the 20 km/h and 40 km/h collisions. When the struck foot position of the ETW rider was higher than the pedal, the lower extremity was hit by the bumper and then rebounded. In this situation, the bending moments of the femur and tibia, as well as the bending angle and shear displacement of the knee joint were less than the injury threshold in all crash simulations. Furthermore, when the head was turned toward the colliding car, the risk of head injury varied with the emergency avoidance posture.Conclusions The height of the struck foot relative to the ETW pedal influenced the rider’s global kinematics, and head and lower extremity injuries risk. In the struck side foot landing and both feet landing postures, the lower extremity was restrained and compressed by the ETW frame, resulting in a high risk of tibia fracture and MCL rupture. Reducing the impact velocities could effectively mitigate the injury risk of the ETW riders; however, loading patterns remain an important factor influencing the risk of lower extremity injury.
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