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The research described in this paper aimed to study the cornering resistance and dissipation power on the tire contact patch, and to develop an efficient direct yaw moment control (DYC) during acceleration and deceleration while turning. A previously reported method [1], which formulates the cornering resistance in steady-state cornering, was extended to so-called quasi steady-state cornering that includes acceleration and deceleration while turning. Simulations revealed that the direct yaw moment reduces the dissipation power due to the load shift between the front and rear wheels. In addition, the optimum direct yaw moment cancels out the understeer augmented by acceleration. In contrast, anti-direct yaw moment optimizes the dissipation power during decelerating to maximize kinetic energy recovery. The optimization method proved that the optimum direct yaw moment can be achieved by equalizing the slip vectors of all the wheels.

Dynamic wind-tunnel tests of a simplified passenger car model were conducted using a two-degree-of-freedom model shaker. Time-resolved aerodynamic loads were derived from a built-in six-component balance and other sensors while the model underwent sinusoidal heaving and pitching motions at frequencies up to 8 Hz. The experimental results showed that frequency-dependent gains and phase differences between the model height/angle and the aerodynamic loads are in close agreement with those predicted by large-eddy simulation (LES) using an arbitrary Lagrangian-Eulerian (ALE) method. Based on these findings, transient aerodynamic loads associated with lateral motions were also estimated by LES analysis. Based on the above results, a full-unsteady aerodynamic load model was then derived in the form of a linear transfer function. The force and moment fluctuations associated with the vertical and lateral motions are well described by the full-unsteady aerodynamic load model.

Grip feeling is an important facet in vehicle dynamics evaluation from a driver satisfaction and enjoyment standpoint. To improve grip feeling, we analyzed the subjective comments from test driver's about grip feeling and an evaluated human sensitivity to lateral motion. As a result, we found that drivers evaluate transient grip feeling according to the magnitude of lateral jerk. Next, we analyzed what vehicle parameters affect lateral jerk by using theoretical equations. As a result, we found that cornering power is an important parameter, especially the cornering power of rear tires as they can be create larger lateral jerk than can front tires.

An understanding of human sensitivity is an important factor in enhancing vehicle dynamics. The purpose of this study was to evaluate human sensitivity to vehicle dynamics, especially visual and motion sensitivity. The first step of this study involved the development of a human sensitivity evaluation system composed of a highly responsive six-degree-of-freedom motion device and a visual device with high spatial frequency resolution. This system is able to apply sensory and visual information to a test subject corresponding to that experienced during driving. Perceptional characteristics with regard to single motions were evaluated using this system.

It is well known that the self-aligning torque decreases before lateral force is saturated. Focusing on this self-aligning torque change, an estimation method has been developed to detect the friction condition between steered wheels and road surface before the lateral force reaches the friction limit. The lateral grip margin (LGM) is defined based on the self-aligning torque change, which is obtained using the EPS torque and motor current information. The LGM is theoretically analyzed based on the tire model and experimentally verified through the full-scale vehicle test. Moreover, the estimated LGM is applied for the chassis control systems to improve the vehicle dynamics performance.

The long-term hypothesis of this study is that the patterns in uptake of certain nutrient species in the hydroponic nutrient solution can serve as an early-warning stress detector for specific hydroponically grown crops. This is a two-part hypothesis: first, it posits that the time variation in the uptake of specific nutrient species under a given nutrient regime shows fairly reasonable regularity; and, second, it posits that deviations from such regularity actually correlate with the occurrence of certain plant stress. Addressing the first part of the hypothesis, the objective of the current study was to determine the temporal variations in the concentrations of nitrate, potassium, and manganese under the following four nutrient regimes used for sweetpotato hydroponics: standard or control, elevated nitrogen by ammonium, elevated nitrogen by nitrate, and elevated potassium conditions.

The next-generation of plant hydroponic systems for advanced life support will most likely require a dynamic monitoring capability for their nutrient species in solution for two reasons: (1) to be able to optimize nutrient use, which would help to reduce the mass and volume of stored inorganic chemicals; and (2) to be able to dynamically correlate the fluctuations in uptake of individual nutrient species with the plant’s physiological state (e.g., stress) over time under microgravity conditions. The latter in turn will provide advanced physiological diagnoses for the crops and could help reduce the astronaut man-hours for crop maintenance. The results of this study suggested that a combination of inductively coupled plasma (ICP) spectroscopy and ion selective electrodes (ISEs) could be a competent strategy for designing a dynamic nutrient-monitoring capability for hydroponic systems.

Hybrid solar and electric lighting (HYSEL) systems constitute the latest generation of lighting systems for advanced life support, exhibiting continued potential for reducing the significant electrical power demand of current bioregenerative life support systems (BLSS). Two experimental HYSEL systems were developed: one employing xenon-metal halide (XMH) lamps and the other adopting light-emitting diodes (LEDs) as the electric-lighting components, and both using a mirror-based, fiberoptic-based solar collection system. The results showed that both the XMH and LED HYSEL systems effected reduced effective plant growing volume, indicating potential for a compact plant hardware design. The apparent electrical conversion efficiency of the LED HYSEL system exceeded that of the XMH HYSEL system by five-fold. Both the XMH and LED HYSEL systems provided reasonably acceptable spectral quality and lighting uniformity.

The Hybrid Solar and Artificial Lighting (HYSAL) system used in this study consisted of a mirror-based Optical Waveguide (OW) Solar Lighting System as the solar component and four 60-W xenon-metal halide illuminators as the artificial-light component. A reference (or control) system consisted of a conventional 250-W high pressure sodium (HPS) lamp. Solar irradiance was harnessed whenever available for the HYSAL treatment. During the course of the 30-day growth period for lettuce (Lactuca sativa), the HYSAL's solar PPF varied with the natural fluctuations of terrestrial solar irradiance, which changed dramatically within each day and between days. When averaged over the entire growth period, the average instantaneous solar PPF for the HYSAL treatment turned out to be 322 μmol m−2 s−1 for an average daily photoperiod of only 3.86 hours owing to numerous cloudy days.

Significant reductions in electrical-power demand as well as in related mass and physical volume might be achieved if available extraterrestrial solar irradiance could be utilized for plant production in a Bioregenerative Life Support System (BLSS) on Mars. Working estimates of the available photosynthetic photon flux (PPF) at Chryse Planitia (22.3° N, 47.9° W), landing site for the Viking Lander 1 (VL-1) on Mars and geographically near the Mars Pathfinder's landing site, were simulated based on the year-long actual irradiance measurements and downward spectral characteristics made by VL-1 in the 1970's. The results showed that the Wm−2 to µmol m2 s−1 conversion factors for Earth and Mars are essentially equal, being approximately 4.6 µmol m−2 s−1/Wm−2. For half of the total sunshine hours at Chryse Planitia for a whole Martian year, the incident PPF level is at least 400 µmol m−2 s.

The long-term supplemental terrestrial solar lighting made available to the Biomass Production Chamber (BPC) located in the Subterranean Plant Growth Facility (SPGF) at The University of Arizona was determined for two cases where two types of Solar Irradiance Collection, Transmission and Distribution System (SICTDS) were used for the facility. Databases for hourly solar irradiance incident upon Tucson, AZ compiled over a 12-year period from 1987 through 1998 were used to calculate the projected average instantaneous PPF within the BPC per hour and per day throughout the year. The results showed that replacing the available solar irradiance within the BPC as delivered by the Himawari SICTDS in June would require either 97.7 W m−2 of HPS lighting or 185.9 W m−2 of CWF lighting supplied continuously for 450 hrs. In energy terms, these would be equivalent to 44.0 kW-hr m−2 for the HPS lamp and 83.7 kW-hr m−2 for the CWF lamp.

This paper deals with a case where H∞ control is applied to a basic control logic of a rack-assisted Electric Power Steering (EPS) system. In the body, the following three key features are described: Construction of the target controlled model including a vehicle Controller design for the model H∞ controller performance verification In this paper, it has been confirmed that H∞ control is valid as a basic control logic for the EPS system.

A control law for integrating 4WS and 4WD systems is presented. It is based upon a non-linear vehicle model in which the lateral force acting on the tires changes according to the tire slip angle, slip ratio and the load. The purpose of the system is to make the actual yaw rate follow the desired yaw rate. A two-degree-of-freedom control structure has been devised and variable transformation is used to linearize the non-linear model so that H∞ control theory can be applied to design the feedback compensator. A new control theory is used to calculate optimum command values for the 4WS and 4WD actuators. Moreover, adaptive logic is added to reduce the desired yaw rate as the tires approach the limits of adhesion. Simulations and experiments prove the system greatly improves stability during cornering.