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The Size of Children's Strollers of Different Ages Based on Ergonomic Mathematics Design

Publicado en línea: 15 Jul 2022
Volumen & Edición: AHEAD OF PRINT
Páginas: -
Recibido: 18 Jan 2022
Aceptado: 28 Mar 2022
Detalles de la revista
License
Formato
Revista
eISSN
2444-8656
Primera edición
01 Jan 2016
Calendario de la edición
2 veces al año
Idiomas
Inglés
Abstract

By establishing common simplified model rules for strollers, the early planning of rapid modeling of new products is realized. We have ergonomically designed the shock-absorbing structure of the stroller. Studies have shown that the vibration damping of the stroller has the greatest relationship with the damping structure of the car body itself. The vibration acceleration monitoring of the cart with the frame damping system found that due to the frame damping system, nylon components are used for isolation between the frame connection parts and between the wheel and the seat pocket so that the nylon can effectively absorb the impact energy.

Keywords

MSC 2010

Introduction

Baby strollers have become one of the must-have items for young parents to take care of their babies. The innovation and development of baby strollers are also changing with each passing day. The main trend is diversified functions, beautiful appearance, and lighter quality. Since infants use the stroller with very weak self-protection ability, the safety of its use is directly related to the safety and health of the infants and children [1]. Therefore, the safety requirements for baby strollers are very strict in the standards of various countries in the world. Especially reflected in the aspects of structural safety, mechanical strength safety, flame retardancy, chemical toxicity, etc. However, an important factor has been neglected in the current standards: the harm control requirements caused by vibration. For this reason, the author researched the vibration damping structure of the baby stroller. The research purpose of this article is further to improve the vibration damping effect of the stroller.

Sources and injuries of baby stroller vibration

Consumers mainly use baby strollers to carry babies outdoors. When the road is bumpy, vibration excitation will be generated and transmitted to the baby's head and other body parts through the stroller. The unevenness of the road surface is the source of vibration. The wavelength can be divided into three types: long wave, short wave, and rough texture. Among them, the long wave causes the low-frequency vibration of the vehicle, the short wave causes the high-frequency vibration of the vehicle, and the rough texture causes the driving noise of the tire.

Vibration is serious to the human body, especially for newborn babies. Because its head is very fragile, the brain is in a period of rapid growth, and the damage to the brain caused by vibration may be irreversible [2]. According to the ergonomics point of view, it is found that the impact of vibration on the human body mainly depends on factors such as vibration frequency, vibration intensity, and vibration time.

Vibration frequency

The vibration frequency range that the human body can feel is from 1 to 1000 Hz. The human body feels low-frequency (below 20 Hz) vibrations by shaking and impact. The human body feels high-frequency vibrations with pain or even burning. See Table 1 for the impact of vibration at different frequencies on the human body.

The impact and harm of different frequencies of vibration on the human body.

Frequency/Hz Affected area harm
<1 overall Motion sickness, such as motion sickness, seasickness, etc.
1–30 Bones and joints Cause changes such as bone and joint displacement
30–300 Peripheral blood vessel and nerve function Cause changes in peripheral blood vessels and nerve function
300–1000 Blood vessel and nerve function Vascular contracture weakened
﹥ 1000 Hard to be subjectively felt by the human body
Vibration intensity

When the vibration frequency is constant, the greater the vibration intensity (amplitude or acceleration), the greater the impact or damage on the human body.

Vibration time

The impact of vibration is also related to the action time of the vibration. The vibration can be tolerated in a short period. The damage caused by the vibration will accumulate over a long period. The longer the vibration time, the greater the impact on the human body. Vibration action time is divided into continuous action and intermittent action. Among them, continuous long-term vibration is more harmful to the human body [3]. Appropriate short-term vibration is not only harmless but also has a good effect. For example, electronic massagers can be used to eliminate physical fatigue and increase muscle strength. When the vibration frequency is low, the vibration intensity plays a major role. Stroller vibration is mainly generated during the implementation of the caregiver. The speed of general pedestrians is 5km·h−1. This is a low-frequency vibration, so the harmful components of the vibration mainly come from the vibration intensity. Reducing the intensity of vibration, including amplitude and vibration acceleration, are very critical factors.

The main vibration damping methods used in baby strollers

The damping of the baby stroller is through a series of damping equipment to weaken or reduce the vibration and discomfort transmitted to the baby by the unevenness of the road surface. This increases the comfort and safety of the ride. The baby's head accounts for about 18% of the total body weight [4]. The shock of the vibration during the stroller's push is directly transmitted to the baby's head. This is likely to cause harm to the babysitting in the car.

The current damping methods and methods of baby strollers mainly imitate the damping technology of automobiles. But the driving speed of the stroller is very low, so the vibration damping does not need to be so complicated. The current damping measures adopted by baby strollers are mainly as follows.

Adopt dumping tires

Stroller tires mainly use foam tires. Some high-end baby strollers begin to use pneumatic tires. This has obvious vibration damping effects for large-volume and mass strollers. In addition, vibration reduction is related to the tire's material, and Therefore, the larger and wider the tire, the better its damping effect.

Adopt damping spring

The damping spring is an additional damping device. The stroller installs one or several sets of springs on the wheels or the frame, which can effectively reduce the vibration of the stroller. The vibration reduction effect of this method is relatively better, especially for baby strollers with a relatively large maximum load [5]. This vibration reduction measure will be adopted, such as three-wheel strollers, twin strollers, etc. The damping effect of this method is also related to the material of the spring itself. The spring material is good, and its vibration-damping effect will be relatively better.

Vehicle body vibration reduction

The vehicle body damping is mainly designed for the overall damping of the vehicle body, including the car body clearance and the buffer and damping mechanism design between the sitting or lying pocket and the frame.

Mathematical model analysis of the vibration transmission system of the baby stroller

To study the vibration damping characteristics of the stroller system is to analyze the system's frequency response of its input and output signals through vibration to reflect the system's signal transmission characteristics (amplitude-frequency characteristics and phase-frequency characteristics). This depends on the system's characteristics, as shown in Figure 1 (K is the system under study, x(t) is the input signal, y(t) is the output signal, and t is the time variable in the time domain equation).

Figure 1

Schematic diagram of system analysis

We use the stroller as a mechanical system. The above three damping methods constitute the three transmission processes of the system, and they are transmitted in series with each other [6]. The author selects the complete baby stroller (with pneumatic tires, frame damping spring system, and frame component damping system) as the research object to model the three transfer processes. We Laplace transform the function in the time domain into a transfer function (Figure 2).

Figure 2

Schematic diagram of the transmission of the damping system

The transfer function of the vibration system is as follows: G(s)=Xc(s)/Xr(s)=G1(s)G2(s)G3(s) G\left( s \right) = {X_c}\left( s \right)/{X_r}\left( s \right) = {G_1}\left( s \right)\,\,{G_2}\left( s \right)\,\,{G_3}\left( s \right)

G1(s) is the tire vibration damping system. G2(s) is the frame spring damping system. G3(s) is the frame damping system. Xr(s) is the Laplace converted signal input (frequency domain). Xc(s) is the Laplace converted signal output (frequency domain). s is the derivative of the variable concerning time in the complex domain state. Assuming that the road surface excitation x(t) is a continuous sinusoidal function of frequency f, then: x(t)=Asin(2πft+ϕ) x\left( t \right) = A\sin \left( {2\pi \,ft + \phi } \right)

f is the road excitation frequency. ϕ is the phase angle. A is the excitation amplitude of the road surface. The tire vibration reduction system can be regarded as a linear transfer system, and the tire transfer function is: FK1=K1(X1X2) {F_{{K_1}}} = {K_1}\left( {{X_1} - {X_2}} \right)

K1 is the elastic tire coefficient. X1 is the displacement of a certain point in the stroller. X2 is the displacement caused by the deformation of the frame spring at a certain point in the stroller. The function of the frame transfer system with spring damping structure is: FK2=KX2 {F_{{K_2}}} = K{X_2}

K2 is the elastic coefficient of the spring. X2 is the displacement caused by the deformation of the frame spring at a certain point in the stroller.

The damping system of each component of the frame is proportional to the speed, and its transfer function is: fB=B(dX1dtdX2dt) {f_B} = B\left( {{{d{X_1}} \over {dt}} - {{d{X_2}} \over {dt}}} \right)

B is the damping coefficient of the frame. The above mathematical model constitutes the analysis of the vibration transmission process of the road vibration to the baby stroller.

We select a typical cart for system analysis [7]. The article introduces the above transfer function into the computer program and uses the finite element analysis method. In the case of a road surface excited on the wheels, a computer simulates the vibration spectrum generated somewhere in the seat. Figure 3 shows the force diagram and finite element analysis diagram of the cart's typical horizontal and vertical frame.

Figure 3

Frame force and finite element analysis

Because the actual road conditions are more complicated, the incentives produced are also different. The excitation produced by the wavy road is mainly sinusoidal x(t) = A sin(2π ft + ϕ). The excitation generated by the stepped road pit is mainly a step excitation x(t) = STEP(time, 0, 0.5, 0.05). The displacement is assumed to be 5cm.

We separately input the transfer as mentioned above functions into the computer to analyze the vibration reduction system well [8]. After shielding the other systems, we simulated the vibration maps of the head points in the sitting pocket of the baby stroller (Figure 4). Among them, the vibration transmission coefficient of the damping spring is higher, but the damping effect is the worst (4a). The vibration transmission coefficient and damping effect of pneumatic tires are second (4b). The frame damping system has the lowest vibration transmission coefficient and the best damping effect (4c).

Figure 4

Vibration simulation output spectrum of different vibration damping systems of baby strollers

Verification of the maximum acceleration of different vibration reduction systems under extreme road conditions

Use machines to simulate road conditions under current conditions. We replaced the baby with a model and used an accelerometer to measure the maximum acceleration of the model's head. The excitation caused by the unevenness of the road mainly comes from the immediate impact caused by the bumps of the road surface [9]. It is mainly the impact caused by the excitation of obstacle blocks (Figure 5).

Figure 5

Schematic diagram of simulated road conditions (two types of obstacles) in national standards

We select several typical baby strollers on the market for testing: 1) Japanese Combi brand strollers with wheel damping springs (Figure 6a). 2) American brand carts with tire damping structure (Figure 6b). 3) British Silvercross cart with frame component damping system design (Figure 6c).

Figure 6

Several types of typical baby strollers for testing

The vehicle needs to be placed on the irregular surface testing equipment. Place and fix the test weight in the vehicle. We make the axis of 300mm at the center of the bottom of the cart. To keep the vehicle in the center of the irregular test equipment during the test, additional elastic bands should be connected to the sides of the vehicle's front wheel bracket and front-wheel bracket and the side of the test equipment [10]. The vehicle travels at a speed of (5±0.1) km·h−1. Fix the accelerometer on the model head (near the top) and test the vibration acceleration.

Figure 7 shows the vibration acceleration monitoring spectrum of a cart with a vibration-damping spring structure. There are many peaks. The maximum peak is more than 50m·s−2. These peaks are mainly caused by the step impact of the stroller passing through the obstacle block to the baby model. However, the shock-absorbing spring structure stores the impact energy, which will still be transmitted to the baby model after the energy is released. Therefore, the damping spring structure can delay the impact, but the energy is not absorbed by the car body and is still transferred to the baby model. This shows that the damping effect of the damping spring is poor.

Figure 7

Vibration acceleration output of the head of the cart model with damping spring structure

The acceleration monitoring spectrum of the vibration test of a typical pneumatic tire structure cart is shown in Figure 8. It can be seen that the vibration peak distribution is relatively uniform. The instantaneous acceleration of a step impact is close to 20m·s−2 each time the cart passes through an obstacle [11]. It can be seen that the damping effect of pneumatic tires is significantly better than that of the damping spring structure, mainly because the diameter of pneumatic tires is larger. When passing through obstacles, the impact of the car body is small, and it is converted into part of heat energy after being absorbed by the wheels. The energy delivered to the infant model has been significantly reduced.

Figure 8

Head vibration acceleration output of a cart model with pneumatic tire structure

A typical vibration acceleration monitoring graph of a cart with a frame damping system is shown in Figure 9. It can be seen that the peak acceleration generated under the same road surface excitation is significantly reduced. Due to the frame damping system, nylon parts are used for isolation between the frame connecting parts and the wheels and the seat pocket. As a result, the impact energy can be effectively absorbed by nylon, so the peak acceleration is lower than 13m·s−2.

Figure 9

The head vibration acceleration output of the frame damping cart model

Conclusion

(1) The damping of the baby stroller has the greatest relationship with the damping structure of the car body. Pneumatic tires and damping springs can have a certain damping effect, but it is mainly in the design of the damping structure of the car body itself. The content includes the connection between the frame and the cloth cover, the design of the frame linkage mechanism, and the design and installation points of the damping spring. (2) The test shows that the maximum instantaneous acceleration in the vehicle body can reach 5g (g is the acceleration due to gravity) when encountering obstacles, such as the standard value when the travel speed reaches 5km·h−1. The impact force 5 times that of the human body's gravity is very harmful to the baby. Therefore, it is recommended to formulate Chinese safety standards as soon as possible to regulate the requirements of the anti-vibration performance of baby strollers.

Figure 1

Schematic diagram of system analysis
Schematic diagram of system analysis

Figure 2

Schematic diagram of the transmission of the damping system
Schematic diagram of the transmission of the damping system

Figure 3

Frame force and finite element analysis
Frame force and finite element analysis

Figure 4

Vibration simulation output spectrum of different vibration damping systems of baby strollers
Vibration simulation output spectrum of different vibration damping systems of baby strollers

Figure 5

Schematic diagram of simulated road conditions (two types of obstacles) in national standards
Schematic diagram of simulated road conditions (two types of obstacles) in national standards

Figure 6

Several types of typical baby strollers for testing
Several types of typical baby strollers for testing

Figure 7

Vibration acceleration output of the head of the cart model with damping spring structure
Vibration acceleration output of the head of the cart model with damping spring structure

Figure 8

Head vibration acceleration output of a cart model with pneumatic tire structure
Head vibration acceleration output of a cart model with pneumatic tire structure

Figure 9

The head vibration acceleration output of the frame damping cart model
The head vibration acceleration output of the frame damping cart model

The impact and harm of different frequencies of vibration on the human body.

Frequency/Hz Affected area harm
<1 overall Motion sickness, such as motion sickness, seasickness, etc.
1–30 Bones and joints Cause changes such as bone and joint displacement
30–300 Peripheral blood vessel and nerve function Cause changes in peripheral blood vessels and nerve function
300–1000 Blood vessel and nerve function Vascular contracture weakened
﹥ 1000 Hard to be subjectively felt by the human body

Aghili, A. Complete Solution For The Time Fractional Diffusion Problem With Mixed Boundary Conditions by Operational Method. Applied Mathematics and Nonlinear Sciences., 2021; 6(1): 9–20 AghiliA. Complete Solution For The Time Fractional Diffusion Problem With Mixed Boundary Conditions by Operational Method Applied Mathematics and Nonlinear Sciences 2021 6 1 9 20 10.2478/amns.2020.2.00002 Search in Google Scholar

Vanli, A., Ünal, I. & Özdemir, D. Normal complex contact metric manifolds admitting a semi symmetric metric connection. Applied Mathematics and Nonlinear Sciences., 2020; 5(2): 49–66 VanliA. ÜnalI. ÖzdemirD. Normal complex contact metric manifolds admitting a semi symmetric metric connection Applied Mathematics and Nonlinear Sciences 2020 5 2 49 66 10.2478/amns.2020.2.00013 Search in Google Scholar

Koh, B. X., Nirmal, U., & Yuhazri, M. Y. Developments on baby strollers over the last decade. Current Journal of Applied Science and Technology., 2019; 33(6): 1–25 KohB. X. NirmalU. YuhazriM. Y. Developments on baby strollers over the last decade Current Journal of Applied Science and Technology 2019 33 6 1 25 10.9734/cjast/2019/v33i630105 Search in Google Scholar

Bondan, A. T., Nasruddin, N., & Andhika, R. PENGGUNAAN KAOLIN SEBAGAI FILLER BAN PADAT PADA STROLLER BABY ELLE MINI CAPSULE. Jurnal Dinamika Penelitian Industri., 2021; 32(1): 27–36 BondanA. T. NasruddinN. AndhikaR. PENGGUNAAN KAOLIN SEBAGAI FILLER BAN PADAT PADA STROLLER BABY ELLE MINI CAPSULE Jurnal Dinamika Penelitian Industri 2021 32 1 27 36 Search in Google Scholar

Kuo, T. C., & Wang, C. J. Integrating robust design criteria and axiomatic design principles to support sustainable product development. International Journal of Precision Engineering and Manufacturing-Green Technology., 2019; 6(3): 549–557 KuoT. C. WangC. J. Integrating robust design criteria and axiomatic design principles to support sustainable product development International Journal of Precision Engineering and Manufacturing-Green Technology 2019 6 3 549 557 10.1007/s40684-019-00036-1 Search in Google Scholar

Witte, A. M., De Moor, M. H., Van Ijzendoorn, M. H., & Bakermans-Kranenburg, M. J. Fathers today: design of a randomized controlled trial examining the role of oxytocin and vasopressin in behavioral and neural responses to infant signals. BMC psychology., 2019; 7(1): 1–11 WitteA. M. De MoorM. H. Van IjzendoornM. H. Bakermans-KranenburgM. J. Fathers today: design of a randomized controlled trial examining the role of oxytocin and vasopressin in behavioral and neural responses to infant signals BMC psychology 2019 7 1 1 11 10.1186/s40359-019-0356-2691597831843012 Search in Google Scholar

Cardoso Filho, C. A., Claudino, J. G., Lima, W. P., Amadio, A. C., & Serrão, J. C. Yyqx Baby Stroller Light Folding Umbrella Car Pushchair Can Sit Lie Ultra-light Portable On The Airplane Carriage. Revista Brasileira de Medicina do Esporte., 2019; 25(3): 252–257 Cardoso FilhoC. A. ClaudinoJ. G. LimaW. P. AmadioA. C. SerrãoJ. C. Yyqx Baby Stroller Light Folding Umbrella Car Pushchair Can Sit Lie Ultra-light Portable On The Airplane Carriage Revista Brasileira de Medicina do Esporte 2019 25 3 252 257 10.1590/1517-869220192503189675 Search in Google Scholar

Royo, M., Mulet, E., Chulvi, V., & Galán, J. Surveying the Perception of the Environmental Advantages of an Adaptable Product. Ingeniería e Investigación., 2020; 40(1): 50–59 RoyoM. MuletE. ChulviV. GalánJ. Surveying the Perception of the Environmental Advantages of an Adaptable Product Ingeniería e Investigación 2020 40 1 50 59 10.15446/ing.investig.v40n1.76048 Search in Google Scholar

Cardoso Filho, C. A., Claudino, J. G., Lima, W. P., Amadio, A. C., & Serrão, J. C. QXue Automatic Mechanical Watch Men Calendar Luminous Hands Dial Movement Design Stainless Steel Waterproof Wrist. Revista Brasileira de Medicina do Esporte., 2019; 25(3): 252–257 Cardoso FilhoC. A. ClaudinoJ. G. LimaW. P. AmadioA. C. SerrãoJ. C. QXue Automatic Mechanical Watch Men Calendar Luminous Hands Dial Movement Design Stainless Steel Waterproof Wrist Revista Brasileira de Medicina do Esporte 2019 25 3 252 257 10.1590/1517-869220192503189675 Search in Google Scholar

Churchill, E. F. Refactoring design to reframe (dis) ability. Interactions., 2021; 28(3): 24–26 ChurchillE. F. Refactoring design to reframe (dis) ability Interactions 2021 28 3 24 26 10.1145/3459094 Search in Google Scholar

van Loon, P., & Van Wassenhove, L. N. Transition to the circular economy: the story of four case companies. International Journal of Production Research., 2020; 58(11): 3415–3422 van LoonP. Van WassenhoveL. N. Transition to the circular economy: the story of four case companies International Journal of Production Research 2020 58 11 3415 3422 10.1080/00207543.2020.1748907 Search in Google Scholar

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