The normal vehicle forces effects of a two in-wheel electric vehicle towards the human brain on different road profile maneuver
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Noise, harshness and vibrations are a non-trivial aspect of ride or human comfort, and car manufacturers often sought to improve the aforesaid comfort level. In previous studies, human biodynamic model and vehicle model are often modelled separately. Human model is used to study human alertness level and health while vehicle model is used to study on the car vibration to specifically understand the impact of vibration towards the model independently. In this study, a twelve degrees of freedom (12 DOF) human biodynamic model is incorporated with a two in-wheel electric car model to investigate the effect of vertical vibration towards the human brain based on different types of road profile and maneuver. MATLAB simulation environment is used to carry out the investigation, and it was established from the present study that the proposed model is able to provide significant insights on the impact experienced by the human brain to the skull based on the given vertical input of different road profile. The impact on the human brain to the skull is often associated with human alertness while driving where vibration exposure towards human driver influence the sleepiness level, human reaction times and lapses of attention which may lead to road accidents.
KeywordsVibration Electric vehicle Human biodynamic model Comfort
The increasing usage of vehicle worldwide has motivated the car manufacturers to produce a vehicle that is safe, comfortable, optimized fuel consumption as well as have a minimal impact on the environment. Human beings are exposed to vibration through different mediums such as driving and working conditions amongst others in their daily life. It is worth noting that when travelling, both the driver as well as passengers are exposed to vibrations which originate primarily from the vehicle due to the interaction between the vehicle and the road. Studies have shown that prolonged vibrational exposure leads to harmful effects towards human health such as reducing the alertness level, increase in heart rate and also back problem [1, 2]. Moreover, sudden manoeuvre or braking also could cause injury and decrease the human comfort level when travelling [3, 4]. This is due to the vibration transmitted through the supported vibrated surface that, to some extent, affects the comfort level of the human body.
Researchers have developed human biodynamic models as a lumped masses that are connected with springs and dampers which represent the body joints and muscles to represent the human body in order to study the impact of vibration towards human health and comfort [5, 6, 7]. By using this model, the effect of vibration exposure towards human health and comfort can be obtained and verified. Similarly, the lumped mass approach has also been employed to vehicle models. Such models are able to provide insights on the ride comfort and road handling that could quantify the effect of different road profiles [8, 9]. In addition, a study by Sezgin and Arslan had demonstrated that the comfort level experienced by the driver or passenger is significantly reduced by travelling at rate a of 72 km/h for 5 to 6 h journey on a smooth road with passive suspension systems, suggesting that vehicular condition, as well as road profile, does affect its users .
More often than not, the study on human biodynamic models is investigated independently without coupling it with any vehicle model. Moreover, it has been reported in the literature that the vibration effect on the human body considers the vibration effect attained from the vehicle seat without considering the vehicle conditions on different road profile while travelling [1, 2, 7, 10]. In a recent study, the effect of vibration towards human comfort, particularly towards the brain was investigated by exciting the human model that consists of lumped masses with varying input values . In addition, a two in-wheel electric car model that considers the effect of both lateral and longitudinal forces of the vehicle was investigated in . The forces were computed by means of the Dugoff’s model as the weight shift, and the tire stiffness are considered independently for both lateral and longitudinal directions. Therefore, this paper attempts to investigate the effect of vertical vibration towards the brain of twelve degrees of freedom (12 DOF) human biodynamic model [7, 13] coupled with the aforesaid two in-wheel electric car model.
2 Premilinary section
m1 = 27.174, m2 = 5.906
m3 = 0.454, m4 = 13.626
m5 = 32.697, m6 = 5.470
m7 = 5.297, m8 = 2.002
m9 = 4.806, m10 = 1.084
m11 = 3.500, m12 = 1.500
c1 = 37.8, c2 = 29.8
c3 = 29.8, c4 = 29.8
c5 = 365.1, c6 = 365.1
c7 = 365.1, c8 = 365.1
c9 = 365.1, c10 = 365.1
c11 = 1 800 000.0
c12 = 156 000.0
c59 = 365.1
k1 = 2550.0, k2 = 89.41
k3 = 89.41, k4 = 89.41
k5 = 5364.0, k6 = 6885.0
k7 = 6885.0, k8 = 5364.0
k9 = 5364.0, k10 = 5364.0
k11 = 450.0, k12 = 340.0
k59 = 5364.0
The vehicle tire receives major forces and moments that acts on the vehicle. As the properties of tires are deformable, Dugoff’s model (Eqs. 1–7) is employed as it considers the tire stiffness as independent values for both lateral and longitudinal directions. Thus, the forces acting on each tire can be determined independently and be used as the vibrational input on the 12 DOF human model. Besides that, this model is developed from force balance equation, which is analytically derived.
3 Result and discussion
From the preliminary investigation, it could be established that the forces arising from different road profile conditions of a moving vehicle do affect parts of the human body to a certain extent. Although the value of displacement is small, nonetheless, upon prolonged exposure, it could pose detrimental effect towards the driver as well as the passengers [10, 15].
In conclusion, the forces that acting of the vehicle tire does affect the parts of the human body to a certain extent when the vehicle is moving. This may reduce the comfort level of human while travelling at a prolonged duration which, in turn, could also affect human health in the long term. Further study on the effect of vertical vibration towards the human body due to the normal forces acting on different tires of the vehicle shall be investigated. Also the frequencies generated by the forces, shall also be scrutinized to observe, if the natural frequencies of the body parts or organs coincides as prolonged exposure could have an adverse effect on one’s health.
The authors are grateful to Universiti Malaysia Pahang in providing the financial support for this study via RDU190104 and RDU190328.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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