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Technical Paper

Failure Prediction for Robot Reducers by Combining Two Machine Learning Methods

2019-04-02
2019-01-0508
There are many production robots used at car manufacturing plants, and each of them is fitted with several reducers. A breakdown of one of these reducers may cause a huge loss due to the stoppage of all production lines. Therefore, condition-based maintenance is currently being used to predict failures by predetermined thresholds for average and standard deviations. However, this method can cause many false alarms or some false negatives. There are some ways of suppressing false alarms, such as detecting a change in the probability density function. However, when false alarms are suppressed using the probability density function in the operational range, some false negatives may occur, leading to a breakdown of a reducer and huge loss. A false negative is caused by overlooking an anomaly with slight changes and it is difficult to detect using only the probability density function.
Technical Paper

Evaluation of Equivalent Temperature in a Vehicle Cabin with a Numerical Thermal Manikin (Part 2): Evaluation of Thermal Environment and Equivalent Temperature in a Vehicle Cabin

2019-04-02
2019-01-0698
In the previous paper (Part 1), measurements of equivalent temperature (teq) using a clothed thermal manikin and modeling of the clothed thermal manikin for teq simulation were discussed. In this paper (Part 2), the outline of the proposed mesh-free simulation method is described and comparisons between teq in the calculations and measurements under summer cooling with solar radiation and winter heating without solar radiation conditions in a vehicle cabin are discussed. The key factors for evaluating teq on each body segment of the clothed thermal manikin under cooling and heating conditions are also discussed. In the mesh-free simulation, even if there is a hole or an unnecessary shape on the CAD model, only a group of points whose density is controlled in the simulation area is generated without modifying the CAD model. Therefore, the fluid mesh required by conventional CFD code is not required, and the analysis load is significantly reduced.
Technical Paper

Development of Plastic Region Tightening 1.6-GPa Ultra-High Strength Bolt with High Delayed Fracture Resistance

2019-04-02
2019-01-1116
A new variable compression turbo (VC-Turbo) engine, which has a multi-link system for controlling the compression ratio from 8:1 to 14:1, requires high axial force for fastening the multi-links because of high input loads and the downsizing requirement. Therefore, it was necessary to develop a 1.6-GPa tensile strength bolt with plastic region tightening. One of the biggest technical concerns is delayed fracture. In this study, quenched and tempered alloy steels were chosen for the 1.6-GPa tensile strength bolt.
Technical Paper

Aerodynamic Sensitivity Analysis of Wheel Shape Factors

2019-04-02
2019-01-0667
Wheels play an important role in determining the aerodynamic drag of passenger vehicles. This is because the contribution of wheels to aerodynamic drag comes from not only the wheels themselves, but also from the interference effect between wheel wakes and the base wake. As far as the authors are aware, there have been no reports about aerodynamic drag sensitivity to wheel shape factors for different vehicle types and different exterior body shapes. The purpose of this study was to clarify CD sensitivity to wheel shape factors for a sedan and an SUV, including different rear fender shapes. Many different wheel configurations were investigated in terms of the CD, base pressure and flow fields in wind tunnel tests. Multiple regression analyses were conducted to clarify CD sensitivity to each wheel shape factor based on the test data. This study revealed high CD sensitivity factors for both the sedan and SUV.
Technical Paper

Validation of Wireless Power Transfer up to 11kW Based on SAE J2954 with Bench and Vehicle Testing

2019-04-02
2019-01-0868
Wireless Power Transfer (WPT) promises automated and highly efficient charging of electric and plug-in-hybrid vehicles. As commercial development proceeds forward, the technical challenges of efficiency, interoperability, interference and safety are a primary focus for this industry. The SAE Vehicle Wireless Power and Alignment Taskforce published the Recommended Practice J2954 to help harmonize the first phase of high-power WPT technology development. SAE J2954 uses a performance-based approach to standardizing WPT by specifying ground and vehicle assembly coils to be used in a test stand (per Z-class) to validate performance, interoperability and safety. The main goal of this SAE J2954 bench testing campaign was to prove interoperability between WPT systems utilizing different coil magnetic topologies. This type of testing had not been done before on such a scale with real automaker and supplier systems.
Technical Paper

Evaluation of Equivalent Temperature in a Vehicle Cabin with a Numerical Thermal Manikin (Part 1): Measurement of Equivalent Temperature in a Vehicle Cabin and Development of a Numerical Thermal Manikin

2019-04-02
2019-01-0697
The present paper is Part 1 of two consecutive studies. Part 1 describes three subjects: definition of the equivalent temperature (teq), measurements of teq using a clothed thermal manikin in a vehicle cabin, and modeling of the clothed thermal manikin for teq simulation. After defining teq, a method for measuring teq with a clothed thermal manikin was examined. Two techniques were proposed in this study: the definition of “the total heat transfer coefficient between the skin surface and the environment in a standard environment (hcal)” based on the thermal insulation of clothing (Icl), and a method of measuring Icl in consideration of the area factor (fcl), which indicates the ratio of the clothing surface to the manikin surface area. Then, teq was measured in an actual vehicle cabin by the proposed method under two conditions: a summer cooling condition with solar radiation and a winter heating condition without solar radiation.
Technical Paper

Mechanism Analysis on the Effect of Fuel Properties on Knocking Performance at Boosted Conditions

2019-01-15
2019-01-0035
In recent years, boosted and downsized engines have gained much attention as a promising technology to improve fuel economy; however, knocking is a common issue of such engines that requires attention. To understand the knocking phenomenon under downsized and boosted engine conditions deeply, fuels with different Research Octane Number (RON) and Motor Octane Number (MON) were prepared, and the knocking performances of these fuels were evaluated using a single cylinder engine, operated under a variety of conditions. Experimental results showed that the knocking performance at boosted conditions depend on both RON and MON. While higher RON showed better anti-knocking performance, lower MON showed better anti-knocking performance. Furthermore, the tendency for a reduced MON to be beneficial became stronger at lower engine speeds and higher boost pressures, in agreement with previously published modelling work.
Technical Paper

Aerodynamics Development for a New EV Hatchback Considering Crosswind Sensitivity

2018-04-03
2018-01-0715
An electric vehicle (EV) has less powertrain energy loss than an internal combustion engine vehicle (ICE), so its aerodynamic accounts have a larger portion of drag contribution of the total energy loss. This means that EV aerodynamic performance has a larger impact on the all-electric range (AER). Therefore, the target set for the aerodynamics development for a new EV hatchback was to improving AER for the customer’s benefit. To achieve lower aerodynamic drag than the previous model’s good aerodynamic performance, an ideal airflow wake structure was initially defined for the new EV hatchback that has a flat underbody with no exhaust system. Several important parameters were specified and proper numerical values for the ideal airflow were defined for them. As a result, the new EV hatchback achieves a 4% reduction in drag coefficient (CD) from the previous model.
Technical Paper

Evaluation of an Open-grill Vehicle Aerodynamics Simulation Method Considering Dirty CAD Geometries

2018-04-03
2018-01-0733
In open-grille vehicle aerodynamics simulation using computational fluid dynamics, in addition to basic flow characteristics, such as turbulent flow with a Reynolds number of several million on the bluff body, it is important to accurately estimate the cooling air flow introduced from the front opening. It is therefore necessary to reproduce the detailed geometry of the entire vehicle including the engine bay as precisely as possible. However, there is a problem of generating a good-quality calculation grid with a small workload. It usually takes several days to a week for the pretreatment process to make the geometry data ‘clean’ or ‘watertight’. The authors proposed a computational method for complex geometries with a hierarchical Cartesian grid and a topology-independent immersed boundary method with dummy cells that discretize the geometry on a cell-by-cell basis and can set an imaginary point arbitrarily.
Technical Paper

NVH Development of a High Torque SUV Using a Novel Active Torque Rod System

2018-04-03
2018-01-0685
During the last decade, fuel economy mandates (CAFE regulations) have driven engine downsizing and down-speeding trends. More recently, downsized turbos are percolating down to heavier SUVs and trucks. Larger/heavier vehicles require high torque engines to provide attractive dynamic performance. While higher torque requirements can be satisfied with new innovations like the variable compression engine, larger and more upscale vehicles also need to deliver higher quietness requirements. For this, the vibration control system for combustion induced forces with high torque engines become very important. To address both dynamic performance and quietness requirements, active engine mounts have been previously adopted, however challenges for light-weighting, downsizing, and costs have still persisted.
Technical Paper

Application of 980 MPa Grade Advanced High Strength Steel with High Formability

2018-04-03
2018-01-0625
There are strong demands for vehicle weight reductions so as to improve fuel economy. At the same time, it is also necessary to ensure crash safety. One effective measure for accomplishing such both requirements conflicting each other is to apply advanced high strength steel (AHSS) of 780 MPa grade or higher to the vehicle body. On the other hand, higher strength steels generally tend to display lower elongation causing formability deterioration. Nissan Motor Corporation have jointly developed with steel manufacturers a new 980 MPa grade AHSS with high formability with the aim of substituting it for the currently used 590 MPa grade high-tensile steel. Several application technologies have been developed through the verifications such as formability, resistance spot weldability, crashworthiness, and delayed fracture.
Technical Paper

Real World Accident Analysis of Driver Car-to-Car Intersection Near-Side Impacts: Focus on Impact Location, Impact Angle and Lateral Delta-V

2018-04-03
2018-01-1328
In total, 865 intersection car-to-car crashes (NASS-CDS CY 2004-2014) are analyzed in detail to determine the injury level outcome based on different crash factors, such as delta-V, age, airbag deployment, number of events, impact locations (F,Y,P,Z,D,B-regions based on CDC codes), amount of compartment intrusion and impact angle. A multivariate logistic regression test was performed to predict the probability of MAIS3+ serious injuries using lateral delta-V, location of maximum deformation from B-PLR, age (0: <60/1: ≥60 years), number of events (0: single/ 1: multiple), intrusion (0: <16cm/ 1: ≥16cm), side airbag deployment (yes/no) and direction of impact (0: 9/ 1: 10 o’clock). It is found that direction of impact is one of the significant (p<0.05) parameters and 10 o’clock angle impact has more influence than 9 o’clock perpendicular lateral impact. Frequency of AIS3+ injuries was high in Y-region impact cases.
Technical Paper

Virtual Occupant Model with Active Joint Torque Control for Muscular Reflex

2018-04-03
2018-01-1316
Riding comfort on the seat is one of the important factors for vehicle comfort. To analyze riding comfort, there were some models for predicting human vibrations in the past studies. On the other hand, it is strongly affected by human body motion caused by vehicle excitation during driving especially low frequency, but it is difficult to predict human motion due to an unclear mechanism of muscle reflex. The purpose of this study is to construct virtual riding comfort testing simulation based on virtual prototyping of the seat. In this study, a virtual occupant model that predicts occupant motion on the seat against external excitation including muscle reflex for maintaining sitting posture constructed. The whole body was modeled as 15 segments biomechanical model (1D) with wobbling mass. Each joint has passive elastic torque and damping torque springs. Human body surface was modeled as rigid shape.
Technical Paper

Development of a New 2L Gasoline VC-Turbo Engine with the World’s First Variable Compression Ratio Technology

2018-04-03
2018-01-0371
A new 2L gasoline turbo engine, named KR20DDET was developed with the world’s first mass-producible variable compression turbo (VC-Turbo) technology using a multi-link variable compression ratio (VCR) mechanism. It is well known that increasing the compression ratio improves gasoline engine thermal efficiency. However, there has always been a compromise for engine designers because of the trade-off between increasing the compression ratio and knocking. At Nissan we have been working on VCR technology for more than 20 years and have now successfully applied this technology to a mass production engine. This technology uses a multi-link mechanism to change the top and bottom dead center positions, thereby allowing the compression ratio to be continuously changed. The VC-Turbo engine with this technology can vary the compression ratio from 14:1 for obtaining high thermal efficiency to 8:1 for delivering high torque by taking advantage of the strong synergy with turbocharging.
Technical Paper

High Performance Motor and Inverter System for a Newly Developed Electric Vehicle

2018-04-03
2018-01-0461
This paper describes a newly developed motor and inverter system with maximum torque of 320 Nm and maximum power of 110 kW for a 2018 model year EV. The system achieves this performance with no increase in size from the previous 2013 model year system with maximum torque of 254 Nm and maximum power of 80 kW. The specific features of the new system described in this paper are summarized below. A new inverter power module that adopts a direct cooling structure produces higher current density than the previous model. The designs of components experiencing structural and electrical variation that affects heat generation by the power semiconductors were confirmed. Furthermore, the motor temperature is estimated for thermal protection. These features allow for control logic that can optimally manage the temperatures of the power semiconductors and the motor to facilitate the high torque performance of the system.
Technical Paper

Effects of Fuel Properties Associated with In-Cylinder Behavior on Particulate Number from a Direct Injection Gasoline Engine

2017-03-28
2017-01-1002
The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.
Technical Paper

Development of the New V6 3.5L Gasoline Direct Injection Engine

2017-03-28
2017-01-1022
1 The new V6 3.5L gasoline direct injection engine, VQ35DD, was developed for the midsize premium SUV segment. This engine is the newest descendant of the VQ engine family and incorporates the latest technologies focused on enhanced driving performance, combined with high-level of environmental performance. Additional improvements include torque and power increase as well as improved fuel economy and emission performance. Simultaneous realization of both throttle response and smoothness are also in focus. To achieve these features, direct injection system, high response motor-driven intake Continuously Variable Valve Timing Control (e-Motor VVT), individual spark timing, mirror bore spray coating on the cylinder block, and various friction reduction technologies, such as variable displacement oil pump, are applied. Maximum engine power and torque are increased by 8 to 10%. Minimum BSFC is improved by 6%, combined with a wider spread of lower BSFC range considering CVT applications.
Technical Paper

A Study of Drag Reduction Devices for Production Pick-up Trucks

2017-03-28
2017-01-1531
This paper describes a study of drag reduction devices for production pick-up trucks with a body-on-frame structure using full-scale wind tunnel testing and Computational Fluid Dynamics (CFD) simulations. First, the flow structure around a pick-up truck was investigated and studied, focusing in particular on the flow structure between the cabin and tailgate. It was found that the flow structure around the tailgate was closely related to aerodynamic drag. A low drag flow structure was found by flow analysis, and the separation angle at the roof end was identified as being important to achieve the flow structure. While proceeding with the development of a new production model, a technical issue of the flow structure involving sensitivity to the vehicle velocity was identified in connection with optimization of the roof end shape. (1)A tailgate spoiler was examined for solving this issue.
Journal Article

Coupled 6DoF Motion and Aerodynamic Crosswind Simulation Incorporating Driver Model

2017-03-28
2017-01-1525
Because of rising demands to improve aerodynamic performance owing to its impact on vehicle dynamics, efforts were previously made to reduce aerodynamic lift and yawing moment based on steady-state measurements of aerodynamic forces. In recent years, increased research on dynamic aerodynamics has partially explained the impact of aerodynamic forces on vehicle dynamics. However, it is difficult to measure aerodynamic forces while a vehicle is in motion, and also analyzing the effect on vehicle dynamics requires measurement of vehicle behavior, amount of steering and other quantities noiselessly, as well as an explanation of the mutual influence with aerodynamic forces. Consequently, the related phenomena occurring in the real world are still not fully understood.
Journal Article

Silicon Carbide Inverter for EV/HEV Application featuring a Low Thermal Resistance Module and a Noise Reduction Structure

2017-03-28
2017-01-1669
This paper presents the technologies incorporated in an electric vehicle (EV)/hybrid electric vehicle (HEV) inverter built with power semiconductors of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) instead of conventional silicon (Si) insulated gate bipolar transistors (IGBTs). A SiC inverter prototype of 2.9 L in size for driving an 80-kW motor was fabricated and evaluated on a motor test bench. The SiC inverter prototype attained average efficiency of 98.5% in the Worldwide harmonized Light-duty Test Cycle (WLTC) driving mode. The two main technologies achieved with this SiC inverter prototype are described. The first one is a new direct-cooled power module with a thick copper (Cu) heat spreader located under the semiconductors that improves thermal resistance by 34% compared with a conventional direct-cooled power module.
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