Design And Simulation Research Of A Four-point Child Safety Belt With Looped Waist-belt

The safety of child occupants has been an important subject in the field ofvehicle crash safety gradually. The current equipped types of child safety belt are3-point belt,4-point belt and5-point belt. However, all of them have somedisadvantages. The traditional3-point belt is very easy to cause the shoulder andthorax injuries of child because of the incomplete growth of child skeleton. The4-point belt can cause the “diving” problem during vehicle crash. The five-point beltis not convenient to adjust to fit the child occupants in different ages according to theheight of the cushion. Meanwhile, the hip-belt of5-point belt is not very comfort forthe child.Aim at the disadvantages of child belt addressed above, a four-point child beltwith a looped waist-belt was proposed in this thesis. The belt is mounted in integratedchild safety seat, and is applicable for the children aged from3to10years. The childbelt can be handled easily to avoid the misusage. The belt can be adjusted accordingto the height of seat cushion to match children in different ages or body shapes. The“diving” can be prevented effectively with the structure of looped waist-belt. Astructural design and working principle of the four-point child belt with loopedwaist-belt was conducted in this thesis. A specimen of the belt is made. A frontalimpact of sled test on the specimen was conducted and the crash velocity was set to nomore than30km/h for the sake of safety.The MADYMO was used to develop the frontal impact model which includes thefour-point child safety belt with looped waist-belt based on6-year-old child dummy.The model was validated by the results of the sled test. Based on the validated model,the parameters of the structure of child safety belt, including the interval of the leftand right slip rings of shoulder-belt (W) and the height of the connection betweenshoulder-belt and waist-belt (H), were optimized by the uniform design, the stepwiseregression analysis and the genetic algorithm.In order to analyze the protective performance of the optimized model onchildren aged3-year-old to10-year-old,3-year-old,6-year-old and10-year-oldchildren dummies were chosen to be researched. According to the process of thesimulation model developed above, frontal impact simulation model based on3-year-old and10-year-old were developed. The acceleration-time history based on 50km/h crash velocity which matches the ECE R44regulation requirements was used.The injuries of3-year-old,6-year-old,10-year-old child dummies before and after theoptimization were compared, and the injury values were compared with theregulations values.It is indicated that there is an intermediate value between t the maximum andminimum values of W and H to provide the best protective performance. It is alsoobserved that the comprehensive injury value of the child dummies in the optimizedmodel is reduced by about12%compared with to the results of original model. Theprotection to the6-year-old dummy is improved significantly. Base on the set of ECER44, the protection to3-year-old,6-year-old,10-year-old child dummies are alsoimproved and the injury values are all match the regulation requirements and it isproved that effective protection can be provided to the children occupants ranged3to10years old by the four-point child belt with looped waist-belt.