Search Results

Through inverse dynamics-based modeling and computer simulations for a 6×6 Unmanned Ground Vehicle (UGV) - a 6×6 truck - in stochastic terrain conditions, this paper analytically presents a coupled impact of different driveline system configurations and a suspension design on vehicle dynamics, including vehicle mobility, and energy efficiency. A new approach in this research work involves an estimation of each axle contribution to the level of potential mobility loss/increase and/or energy consumption increase/ reduction. As it is shown, the drive axles of the vehicle interfere with the vehicle's dynamics through the distribution of the wheels' normal reactions and wheel torques. The interference causes the independent system dynamics to become operationally coupled/fused and thus diminishes vehicle mobility and energy efficiency. The analysis is done by the use of new mobility indices and energy efficiency indices which are functionally coupled/fused.

An open-link locomotion module, comprising a driving wheel with an electric motor, a system of electro-hydraulic suspension, and an electro-hydraulic power steering system, is presented in this paper as the basis for the modular design of unmanned (robotic) ground vehicles. The open-link-type configuration allows the module to be functionally integrated and engineered with a system of similar modules and thus virtually allows to compile vehicles with any required number of driving wheels. The overall dimensions and carrying capacity of the tire used in the module, as well as technical characteristics of the suspension and power steering systems make possible to employ the module for commercial ground vehicle applications. This paper considers technical issues related to designing the locomotion module.

This paper presents an analysis of coupled longitudinal and lateral dynamics of a 4×4 hybrid-electric off-road vehicle (HEV) with two passive driveline systems, including drivelines with (i) an interaxle open symmetrical differential in the transfer case and (ii) a locked transfer case, i.e., positive engagement of two axles. The axle differentials are open. As the study proved, lateral dynamics of the 4×4 HEV, characterized by the tire side forces, vehicle lateral acceleration, yaw rate and tire gripping factors can be impacted by the tire longitudinal forces, whose magnitudes and directions (positive-negative) strongly depend on the driveline characteristics. At the same time, the tire side forces impact the relation between the longitudinal forces and tire slippages.

An alternative to the current drum brakes, with the increased requirements of todays daily service are disc brakes, in that they offer, in contrast to the drum brakes, the following technical advantages and in turn enhance the active safety of modern commercial vehicles when braking: Enhanced brake pedal-feedback and actuation Improved efficiency Little performance losses when high thermal loads occur (fading). In order to be able to determine the improvement potential of disc brakes they will be compared to the commonly employed Simplex drum brakes. Both wheel brake systems (disc-/drum brakes and all variations) were tested on a computer controlled brake dynamometer and in field tests using a heavy duty commercial vehicle (class 8). The results are compared and conclusions drawn regarding “advantages/disadvantages”.

Hydrogen is considered one of the most promising future energy carriers and transportation fuels. Because of the lack of a hydrogen infrastructure and refueling stations, widespread introduction of vehicles powered by pure hydrogen is not likely in the near future. Blending hydrogen with methane could be one solution. Such blends take advantage of the unique combustion properties of hydrogen and, at the same time, reduce the demand for pure hydrogen. In this paper, the authors analyze the combustion properties of hydrogen/methane blends (5% and 20% methane [by volume] in hydrogen equal to 30% and 65% methane [by mass] in hydrogen) and compare them to those of pure hydrogen as a reference. The study confirms that only minor adjustments in spark timing and injection duration are necessary for an engine calibrated and tuned for operation on pure hydrogen to run on hydrogen/methane blends.

The lost foam casting (LFC) process offers unmatched versatility for producing near-net shape complex components for the automotive industry. Castings made by the LFC process can replace numerous individually-manufactured parts through part consolidation, have little or no draft, and have minimum machining stock. However, the filling behavior of lost foam castings is very different from that of open-cavity castings, so methods to reduce casting anomalies are not intuitive. Casting simulation codes have been in use for the past three decades and they are reasonably successful in predicting porosity in steel and other ferrous castings. The prediction of porosity in aluminum alloys is difficult because of long freezing ranges and lack of accurate thermo-physical property data. Also, for lost foam castings, large thermal gradients are created by slow mold filling, which further complicates porosity prediction.

Two characteristics of terrain mobility are essential in designing an unmanned ground vehicle (UGV): (i) the ability of a vehicle to move through terrain of a given trafficability and (ii) the obstacle performance, i.e., the ability to avoid, interact with and overcome obstacles encountered on a preset route of a vehicle. More attention has been given to the vehicle geometry including selection of the angles of approach and departure, radii of longitudinal and lateral terrain mobility, and the steering system configuration. An essential effect is exhibited by the tire properties in their interaction with the support surface; this, in turn, affects traction properties of the wheel and, thus, vehicle terrain mobility. However, the influence of power distribution between the driving wheels together with vehicle steering system on the two above-listed characteristics of terrain mobility has not been considered in depth.

Contaminating microorganisms pose a serious potential risk to the crew's well being and water system integrity aboard the International Space Station (ISS). We are developing a gene-based microbial monitor that functions by replicating specific segments of DNA as much as 1012 x. Thus a single molecule of DNA can be replicated to detectable levels, and the kinetics of that molecule's accumulation can be used to determine the original concentration of specific microorganisms in a sample. Referred to as the polymerase chain reaction (PCR), this enzymatic amplification of specific segments of the DNA or RNA from contaminating microbes offers the promise of rapid, sensitive, quantitative detection and identification of bacteria, fungi, viruses, and parasites. We envision a small instrument capable of assaying an ISS water sample for 48 different microbes in a 24 hour period.

Given the legal requirements for quality assurance of passenger car exhaust emissions worldwide we define our quality assurance system and present the emission laboratories of the Mercedes-Benz assembly plants Sindelfingen and Bremen. We developed a hierarchically structured, multi-level computer system, which enables us to automize emission test procedures, calibration, maintenance of measurement systems and documentation of exhaust data. Test cell computers coordinate the different components of the test cells and perform maintenance and calibration of measurement devices, thus guaranteeing a high measurement quality with reasonable economy. The coordinating level computer, the emission host system (EHS), processes test parameters, controls and supervises the test sequences and evaluates the test results on a statistical basis.

The monitoring of spacecraft life support systems for the presence of health threatening microorganisms is paramount for crew well being and successful completion of missions. The union of the molecular biology techniques of DNA probe hybridization and polymerase chain reaction (PCR) offers a powerful method for the detection, identification, and quantification of microorganisms and viruses. This report is an evaluation of the state of PCR science as it applies to the needs of NASA to develop a microbiology monitor for use aboard spacecraft, and a set of recommendations as to the design of a PCR-based microbial monitor for recycled water aboard the ISS.

Automotive collision data from the National Accident Sampling System database (compiled by the National Highway Traffic Safety Administration) was analyzed in regard to occupants who sustained major pelvic injuries during 1980-1992. These injuries included pelvic fracture, pelvic dislocation, pelvic separation, pelvic crush, and pelvic fracture/dislocation. All collisions analyzed were required to have a computed change in velocity during the collision, as well as data concerning injuries sustained by the occupants. The purpose of this research was to retrospectively analyze motor vehicle crash data to establish incidence of major pelvic injuries within automotive collisions. From the study, 1.8% of all collisions evaluated resulted in major pelvic injuries. Twenty-two percent of all crashes were side impact collisions and 8% of these side impact collisions resulted in occupants sustaining major pelvic injuries.

The Federal Motor Vehicle Safety Standards (FMVSS) require rear seat, lap/shoulder belts to “fit” Hybrid III dummies ranging in size from a 6 year old child (H3-6C) to a 95th-percentile-male (H3-95M). No dynamic performance FMVSS, however, exist for rear seat belt systems. Variations in the three-dimensional “fit” of the same lap-shoulder belt positioned around these extreme dummy sizes suggest a possible difference in performance. The purpose of this study was to assess the performance of two production lap-shoulder belt designs in a large SUV buck on a rebound sled using instrumented H3-6C, 5th-percentile-female (H3-5F) and H3-95M dummies. Sled velocities were approximately 35 kph. Test instrumentation included: lap and shoulder belt load transducers, triaxial accelerometers at the center of gravity of the head, triaxial accelerometers and a deflection gauge in the chest, and six-axis force (and moment) transducers in the neck of the dummy.

Catastrophic head and spinal injuries have been reported to older children, properly restrained in the back seats of motor vehicles. The interaction of small stature occupants in contemporary, rear restraint systems has not yet been reported in controlled frontal oblique sled test conditions. Such data is fundamental to understanding potential mechanisms of injuries and effective countermeasures. The purpose of this study was three fold: (1) to conduct a series of controlled sled tests to determine the critical angle at which torso roll-out from the shoulder belt occurs in 6 year old Hybrid III (H3-6C) and 5th percentile female Hybrid III (H3-5F) dummies, (2) to compare dummy injury measures to the standard Injury Assessment Reference Values (IARVs) as a function of impact angle, and (3) to assess the influence of belt pretensioners and anchorage geometry as countermeasures to submarining and torso rollout dummy kinematics.

The purpose of this research was to present and analyze a previously unreported mechanism of injury within the automotive crash environment - spinal burst or compression fractures due to a vertical force component. Spinal burst fractures are comminuted fractures of the vertebral body which are often associated with retropulsed bone fragments into the spinal. Compression fractures are less traumatic fractures of the vertebral body with minimal comminution. Both fracture types can have varying degrees of neurologic deficit. The mechanism of injury is hypothesized to be a high energy compressive load along the axis of the spine initiated through the buttocks and pelvis or through torso augmentation (inertial loading of the lumbar spine by the torso). Four crashes are presented as evidence of this injury mechanism within the automotive crash environment: two in the United States and two in Germany.

Robotic technology has begun to play an essential role in ground automotive applications. Utility trucks are among the first responders in extreme climate and severe weather conditions, comprised of two systems: a mobile platform and an articulated robotic morphing arm. The conventional industrial manipulators are mounted on stationary bases, while a mobile manipulator is dynamically coupled on a mobile platform. Such trucks with morphing manipulator can increase the possibility of road accidents in many ways and, additionally, create dangerous situations on the roads, and off-road conditions, while moving, and performing tasks. Large boom equipped trucks for reaching elevated heights can become unstable due to drastic variation of the boom equipment moment of inertia causing the extreme weight re-distribution among the wheels. The morphing capabilities of the utility trucks need to be investigated together with the vehicle-road forces in order to hold the truck safe on the roads.

In the absence of a physical driveline between the wheels powered by individual electric motors, in this paper, a concept of the virtual driveline system was applied to a small skid-steering unmanned ground vehicle (UGV) for the purpose of controlling its maneuverability, i.e., for fulfilling desired maneuvers in terrain zones constrained by natural and man-made objects. The virtual driveline concept supposes that the UGV driving wheels are connected via a virtual driveline that is a computational code to manage the power split among the wheels by using characteristics of a mechanical driveline system. The kinematic discrepancy factor (KDF) as a mechanical driveline characteristic is utilized to mathematically link the angular velocities and the drive torques of the electrically driven wheels.

When a vehicle moves over uneven ground, motion of the sprung and unsprung masses causes dynamic shifting in the load transmitted to the ground, making the normal reaction in the tire-soil patch a continuously changing wheel parameter that may affect vehicle performance. At high loads, sinkage of the wheel can become high as the wheel digs into the soil. At low loads, the wheel can have difficulty acquiring sufficient traction. Additionally, steerability of the wheel can be diminished at very low loads. Controlling the damping forces in the suspension that is usually used to improve ride quality and stabilize motion of the sprung mass can result in an increase in the dynamic variation of the wheel normal reaction and cause vehicle performance deterioration. In this paper, a method is developed to establish boundary constraints on the dynamic normal reaction to maintain reasonable tire-terrain mobility characteristics.

An open-link locomotion module (OLLM) is an autonomous energy self-sufficient locomotion setup for designing ground wheeled vehicles of a given configuration that includes drive/driven and steered/non-steered wheels with individual suspension and brake systems. Off-road applications include both trucks and trailers. The paper concentrates on the module's electro-hydraulic suspension design and presents results of analytical and experimental studies of a trailer with four driven (no wheel torque applied) open-link locomotion modules. On highly non-even terrain, the suspension design provides the sprung mass with sufficient vibration protection at low level of normal oscillations, enhanced damping and stabilized angular movements. This is achieved by the introduction of two control loops: (i) a fast-acting loop to control the damping of the normal displacements; and (ii) a slow-acting control loop for varying the pressure and counter-pressure in the suspension system.

In-wheel electric motors open up new prospects to radically enhance the mobility of autonomous electric vehicles with four or more driving wheels. The flexibility and agility of delivering torque individually to each wheel can allow significant mobility improvements, agile maneuvers, maintaining stability, and increased energy efficiency. However, the fact that individual wheels are not connected mechanically by a driveline system does not mean their drives do not impact each other. With individual torques, the wheels will have different longitudinal forces and tire slippages. Thus, the absence of driveline systems physically connecting the wheels requires new approaches to coordinate torque distribution. This paper solves two technical problems. First, a virtual driveline system (VDS) is proposed to emulate a mechanical driveline system virtually connecting the e-motor driveshafts, providing coordinated driving wheel torque management.

The lost foam casting process (LFCP) is a near-net shape casting process. This process is the most energy efficient casting process available. “Foundry Management and Technology” magazine analyzed the lost foam process and reported a 27% energy savings, a 46% improvement in labor productivity and 7% less material usage compared to other casting processes. The LFCP produces high value parts by combining multiple components into single castings, improving energy efficiency by achieving better metal yields, reducing materials consumption by eliminating cores, providing minimal post casting processing and improving as-cast dimensional accuracy. All of these process features reduce the total energy consumed during manufacturing.