Takahide Nouzawa

CFD analysis of the flow in an automotive headlamp

Abstract In order to predict water condensation in an automotive headlamp at an early stage of the development process, CFD analysis of the flow in the headlamp was attempted. First, CFD analysis was conducted on the headlamp unit removed from a vehicle. The result was similar to the experimental result, thus the validity of this analysis was confirmed. Furthermore, water condensation in the headlamp on the vehicle was studied, based on the CFD analysis and the experiment. The results show that the water condensation in the headlamp is not only influenced by the velocity and temperature distribution in and around the headlamp, but also by the absolute humidity near the headlamp vents.

Evaluation of Aerodynamic Noise Generated in Production Vehicle Using Experiment and Numerical Simulation

Aerodynamic noise generated in production vehicle has been evaluated using experiment and numerical simulation. Finite difference method (FDM) and finite element method (FEM) are applied to analyze the flow field, and Lighthills analogy is employed to conduct acoustic analysis. The flow fields around front-pillar obtained by numerical simulations agree with those by experiment for two cases with different front-pillar shape. Moreover, the distribution of acoustic source predicted by FEM is consistent with that obtained by experiment. Present study ascertained the feasibility and applicability of FEM with SGS model towards prediction of aerodynamic noise generated in production vehicle.

A Subjective Force Perception Model of Humans and Its Application to a Steering Operation System of a Vehicle

The present study clarifies the human characteristics of motion and perception, and develops a force perception model in vehicle operation. As the first step, this paper analyzes experimentally human force perception properties during steering operation, in which multiple joint motions and large postural changes of arms are necessary. The experimental results reveal the following three points: a) force perception follows the Weber-Fechner law under the constant arm posture, b) force perception changes depending on the steering wheel angle and is affected by arm weight and force perception properties, and c) the same tendency of force perception properties is observed even if the steering direction changes. Finally, a force perception model in sending a steering wheel is proposed.

Active-steering control system based on human hand impedance properties

This paper proposes an active-steering control method that uses human hand impedance properties. In this method, the dynamic properties of a steering device manipulated by the upper limbs are automatically regulated according to the damping coefficient of the human-steering system. Human hand impedance in steering operations is measured and modeled depending on the steering angle and torque for use in the proposed control structure. The effectiveness of the proposed method was demonstrated by performing an emergency avoidance task using a stationary driving simulator.

Mechanical and perceptual analyses of human foot movements in pedal operation

A human can maneuver mechanical systems by adjusting his/her own body naturally and effectively according to a target task by utilizing the kinematical and dynamic characteristics of operating systems acquired through sensory organs. If such human sensory and motor characteristics changing in the task can be quantitatively described, it would be useful to design and develop a novel human-machine system so that humans can manipulate a machine more instinctively and comfortably. This paper investigates the interaction between human sensory and motor properties at the foot during the operation of an automobile pedal, as an example of human-machine systems, and demonstrates the close relationship between the perceptual properties of force resistance at the foot and the loads for foot joints much depending on the pedal layout. Finally, based on biomechanical and perceptual analyses, a human-inspired design method of pedal dynamic properties is discussed.

Investigation of the subjective force perception based on the estimation of the muscle activities during a steering operation

The models of motion and perception characteristics of humans are helpful to evaluate subjective efforts associated with intuitive, safe, and easy-to-use products. Traditionally, the muscle activity and/or the joint torque estimated by using a musculoskeletal model have been evaluated, whereas there are few studies that consider humans perception characteristics. In this paper, the perception characteristics of force are investigated based on the estimation of the muscle activities. Experimental analysis of human force perception characteristics in a steering wheel operation has revealed that the perceived force depends on the angle of the steering wheel and the direction of the load. This paper proposes the estimation model of the force perceived by a subject that considers humans posture- and direction-dependent perception characteristics in the steering operation. We estimate the muscle activity during the steering wheel operation by using a three-dimensional musculoskeletal model, develops a perception conversion model that follows the Weber-Fechner law, and describes the experimental results that confirm the feasibility of the proposed force perception estimation.

Effects of Transient Aerodynamics on Vehicle Stability: A Large Eddy Simulation analysis

The present study investigated the extent to which the results obtained from simple bluff body model, regarding pitching stability, can be applied to real vehicle aerodynamics. The investigation was carried out using a large eddy simulation method with vehicle-motionairflow dynamic coupling capability. The aerodynamic damping coefficient and mechanism obtained from realistic sedan-type vehicle model cases are found similar to the one for simple body model cases. These agreements deduce that the use of simple body model in automotive aerodynamic research is justifiable.

LES study on the aerodynamic stability of sedan-type road vehicle

In this paper, in order to investigate a fundamental mechanism of a high-speed aerodynamic stability of sedan-type road vehicle, Large-Eddy Simulations on two simplified vehicle models are conducted. The objective vehicle models were simplified from the real sedan-type road vehicle and they have the same characteristics of the shapes as the original road vehicles. In the numerical simulations, interaction between vehicle motion and the aerodynamics is treated by a moving boundary technique with the ALE method. The target vehicle motion is a pitch motion, which was indicated as the related factor of the vehicles running stability. Before the simulations with dynamic vehicle motion, steady and unsteady flow characteristics around each model in stationary conditions are extracted by the numerical simulations. The slight different shapes of the vehicle model generated a significantly different flow structure around the vehicles. The quasi-stationary responses of the aerodynamics are also simulated on two different steady pitch conditions. Then, in nonstationary conditions with forced pitch oscillation, the interaction between the vehicle motion and the aerodynamics are investigated. The unsteady aerodynamic moment is decomposed to approximation function by the least-square method. Considering each decomposed factor, the vehicle model with high running stability has been considered as a stable model for the pitch motion in the evaluations of stability based on a quasi-stationary manner. However, regarding the non-stationary component, the additional mass effect is rather high in the high stability model. Aerodynamic damping factor, which is another nonstationary component, has significant intensity in both two models though their intensities are the same level with each other.

Windshield Frame Shape and Awareness of the External World While Driving an Automobile

The vehicle windshield is supported and framed by the hood, roof, and pillars, which occlude the driver’s view of the outside. It has been previously shown that awareness of the external world changes according to differences in windshield shape. This directly affects the drivability of a vehicle. Thus, the windshield shape must be designed by considering driver’s visual performance so that it can be balanced with other performance measures such as weight and roominess to design the optimal cockpit. Visual performance during driving is affected by (1) bottom-up attention and (2) top-down attention, and (3) selection between them. This study focuses on Itti and Koch’s visual saliency that attracts bottom-up attention as a visual scene changes in shape and color around front windshield frame during driving. This paper aims to quantify the relationships between drivers’ gaze movements and visual saliency.

Design of steering wheel characteristics based on human arm mechanical properties

Human arm operation in driving motion can be classified into the two categories of steering wheel and gear stick manipulation. In this study, the operational characteristics of a human-steering system were experimentally analyzed in consideration of the mechanical properties of the human arm and related effects on muscle activity. The results highlighted three points in particular: (1) positioning to facilitate operation as well as the operational direction of the steering column angle and fore-and-aft positions can be determined on the basis of force manipulability in consideration of human joint-torque characteristics; (2) subjects feel that handling is easier when arm muscle activity is low during steering wheel operation; and (3) arm positioning and body pressure distribution have a very significant effect on arm muscle loads. Comprehensive consideration of these results is expected to be useful in the design of human-vehicle steering wheel systems.