Showing papers on "Vehicle dynamics published in 1971"

A closed-form solution for the optimal error regulation of a string of moving vehicles

Abstract: A closed-form solution to the Riccati equation for the optimal error regulation of a string of moving vehicles is found. The use of lead and follow vehicles to prevent drifting of the string is included in the solution.

The relationship of vehicle paths to highway curve design

Abstract: CURRENT DESIGN PRACTICE FOR HORIZONTAL CURVES ASSUMES THAT VEHICLES FOLLOW THE PATH OF THE HIGHWAY CURVE WITH GEOMETRIC EXACTNESS. TO EXAMINE THE ADEQUACY OF THIS ASSUMPTION, PHOTOGRAPHIC FIELD STUDIES WERE CONDUCTED OF VEHICLE MANEUVERS ON HIGHWAY CURVES. RESULTS OF THE FIELD STUDIES INDICATE THAT MOST VEHICLE PATHS, REGARDLESS OF SPEED, EXCEED THE DEGREE OF HIGHWAY CURVE AT SOME POINT ON THE CURVE. FOR EXAMPLE, ON A 3-DEGREE HIGHWAY CURVE, 10 PERCENT OF THE VEHICLES CAN BE EXPECTED TO EXCEED 4.3 DEGREES. A NEW DESIGN APPROACH IS PROPOSED. THIS APPROACH IS DEPENDENT UPON SELECTING: AN APPROPRIATE VEHICLE PATH PERCENTILE RELATION; A REASONABLE SAFETY MARGIN TO ACCOUNT FOR UNEXPLAINED VARIABLES THAT MAY EITHER RAISE THE LATERAL FORCE DEMAND OR LOWER THE AVAILABLE SKID RESISTANCE, AND A MINIMUM SKID RESISTANCE VERSUS SPEED RELATIONSHIP THAT THE HIGHWAY DEPARTMENT WILL PROVIDE ON ALL PAVEMENTS. /AUTHOR/

The Dynamic Performance of Articulated Highway Vehicles - A Review of the State-of-the-Art

Abstract: THIS PAPER REVIEWS THE STATE OF THEORETICAL AND EXPERIMENTAL TECHNOLOGY RELATIVE TO THE DYNAMIC PERFORMANCE OF ARTICULATED HIGHWAY VEHICLES. THE REVIEW CONTAINS THREE MAJOR SECTIONS CORRESPONDING TO THE TRADITIONAL BREAKDOWN OF VEHICLE PERFORMANCE: DIRECTIONAL PERFORMANCE, BRAKING PERFORMANCE, AND COMBINED DIRECTIONAL AND BRAKING PERFORMANCE. AN ATTEMPT IS MADE TO TAKE A FRANKLY EVALUATIVE POINT OF VIEW AND TO POINT OUT KNOWLEDGE GAPS AND UNANSWERED QUESTIONS, IN ADDITION TO DOCUMENTING PREVIOUS ACCOMPLISHMENTS AND PROGRESS. THE PAPER CONCLUDES WITH SOME RECOMMENDATIONS FOR FUTURE RESEARCH CONSISTENT WITH THE FINDINGS OF THE REVIEW. /AUTHOR/

Influence of vehicle and distributed guideway parameters on high speed vehicle-guideway dynamic interactions

Abstract: MODAL ANALYSIS TECHNIQUES ARE USED TO STUDY THE DYNAMIC INTERACTIONS BETWEEN A ONE-DIMENSIONAL HIGH SPEED GROUND TRANSPORT VEHICLE MODEL AND A GUIDEWAY CONSISTING OF MULTIPLE INDEPENDENT SPANS RESTING FREELY ON RIGID DISCRETE SUPPORTS THE STUDY INCLUDES AN EVALUATION OF THE EFFECTS OF VARIATIONS IN THE FUNDAMENTAL VEHICLE AND GUIDEWAY PARAMETERS ON SPAN MAXIMUM DYNAMIC DEFLECTIONS AND VEHICLE HEAVE ACCELERATIONS RESULTS INDICATE THAT VEHICLE-GUIDEWAY DYNAMIC INTERACTIONS STRONGLY INFLUENCE BOTH VEHICLE SUSPENSION AND GUIDEWAY SPAN DESIGN FOR THE RANGE OF PARAMETERS OF INTEREST IN HIGH SPEED SYSTEMS (200-300MPH), GUIDEWAY SPAN DYNAMIC TO STATE DEFLECTION AND STRESS RATIOS, OR IMPACT FACTORS, MAY APPROACH VALUES OF 20 FOR A SINGLE VEHICLE PASSAGE, AND VEHICLE HEAVE ACCELERATIONS MAY EXCEED THE LEVELS OF 005G DESIRED FOR GOOD RIDE QUALITY UNLESS VERY STRONG CONSTRAINTS ARE PLACED UPON VEHICLE SUSPENSION REQUIREMENTS AND GUIDEWAY STIFFNESS, WEIGHT, AND SPAN LENGTH SPECIFICATIONS /AUTHOR/

General aspects of the lateral dynamics of railway vehicles

Abstract: Recent developments in research into the lateral dynamics of railway vehicles are reviewed with particular reference to dynamic stability, dynamic response, and curving. Two engineering aspects of this work are stressed - namely, the advantages of applying linear theory to a comprehensive study of vehicle dynamics, and the choice of basic assumptions required to make such studies realistic for design purposes.

Guardrail performance and design

Abstract: BARRIER INSTALLATIONS ARE WARRANTED (OR JUSTIFIED) ONLY AT HIGHWAY LOCATIONS WHERE THE CONSEQUENCE OF AN ERRANT VEHICLE LEAVING THE ROADWAY IS JUDGED TO BE MORE HAZARDOUS THAN THE IMPACT WITH THE BARRIER INSTALLATION. A SIX DEGREE-OF-FREEDOM MATHEMATICAL MODEL WAS FOUND TO BE USEFUL IN DESCRIBING DYNAMIC BEHAVIOR OF A VEHICLE DURING IMPACT. PREDICTIONS OF VEHICLE AND BARRIER BEHAVIOR CORRELATED WITH RESULTS OBTAINED FROM FULL-SCALE CRASH TESTS. CRASH CONDITIONS SIMULATED WITH A COMPUTER WERE USED TO IDENTIFY AND EVALUATE VEHICLE STATIC AND DYNAMIC AS WELL AS BARRIER PARAMETERS. VEHICLE WEIGHT, YAW MASS MOMENT OF INERTIA, AND DEFORMATION CONSTANT WERE FOUND TO BE SIGNIFICANT. AS EXPECTED, SUCH VEHICLE DYNAMIC PARAMETERS AS IMPACT SPEED AND ANGLE WERE THE MOST IMPORTANT FACTORS IN VEHICLE-GUARDRAIL INTERACTION. THE SIGNIFICANT BARRIER PARAMETERS WERE ASCERTAINED TO BE THOSE RELATED TO POST STRENGTH, VEHICLE-BARRIER COEFFICIENT OF FRICTION, SOIL MODULUS, AND BEAM TENSION; THESE APPRECIABLY INFLUENCE THE ACCELERATION INTENSITIES INDUCED IN THE VEHICLE DURING REDIRECTION. FOR THE SYSTEMS EXAMINED, IT WAS FOUND THAT VEHICLE LATERAL ACCELERATIONS WERE HIGHER WITH RESPECT TO SUGGESTED HUMAN TOLERANCE LEVELS THAN THE LONGITUDINAL ACCELERATIONS WITH RESPECT TO THEIR CORRESPONDING SUGGESTED LEVELS. FOR A STANDARD TEST (I. E., 4000-LB. VEHICLE, 60 MPH, AND 25-DEGREE IMPACT), THE VEHICLE ACCELERATION PREDICTIONS WHEN COMPARED TO SUGGESTED HUMAN TOLERANCE LEVELS INDICATE THAT OCCUPANTS NEED BOTH LAP BELT AND CHEST HARNESS RESTRAINTS TO AVOID SERIOUS INJURIES. TO FACILITATE COMPARISONS OF BARRIER SYSTEMS ON THE BASIS OF DYNAMIC PERFORMANCE, THE ORDER IN WHICH THE THREE MOST SIGNIFICANT FACTORS NEED BE CONSIDERED WAS ESTABLISHED AS BEING: (1) BARRIER STRUCTURAL INTEGRITY AS DETERMINED WHETHER OR NOT A SYSTEM CAN REDIRECT A SELECTED ERRANT VEHICLE, (2) VEHICLE ACCELERATIONS DURING REDIRECTION, AND (3) POST-IMPACT TRAJECTORY OF THE VEHICLE. FOR SYSTEMS THAT SATISFY THIS BASIC REQUIREMENT THE EVALUATION PROCEDURE NEXT CONSIDERS VEHICLE ACCELERATIONS; THESE VEHICLE ACCELERATION VALUES SERVE AS INDICATORS OF THE SEVERITY OF REDIRECTION AND MAY BE USED IN PROJECTING POSSIBLE INJURIES OR FATALITIES AMONG VEHICLE OCCUPANTS. FINALLY, WHEN THE FIRST TWO FACTORS ARE EQUAL OR ACCEPTABLE, VEHICLE EXIT TRAJECTORY BECOMES A CRITICAL CRITERION AS IT REFLECTS THE HAZARDS PRESENTED TO OTHER TRAFFIC. THE REBOUNDING VEHICLE CAN BE THE CAUSE OF A MULTICAR COLLISION, ALTHOUGH THE INCIDENCE OF THIS IS CONJECTURED TO BE QUITE SMALL /NCHRP/

Digital computer simulation of railroad freight car rocking

Abstract: A mathematical model for the simulation of railroad freight car rocking is presented. The equations of the model are developed into a digital computer program. The model response is validated by two series of test results, and the model is considered reliable for engineering predictions.

On vehicle longitudinal dynamics

Abstract: The longitudinal dynamics of a highway vehicle are frequently represented by a first-order, constraint-coefficient, differential equation with two fixed parameters. It is well-known that this representation is not valid in practice, for these parameters vary erratically with time both within and across vehicles; however, in some studies, particularly those dealing with the determination of macroscopic traffic characteristics such as flow versus speed, the parameter variations - both within and across vehicles - are effectively averaged out and will cause little or no effect on the final results. The opposite is true when individual vehicle control is considered; here, the selected model must realistically represent the vehicle dynamics or the derived results will be of limited practical value. In the research reported, the quantitative limitations of the commonly used first-order model were experimentally determined for steady- state driving conditions. Subsequently, a more realistic model was developed and experimentally validated.

Friction requirements for high-speed passing maneuvers

Abstract: This research determined the tire-pavement friction demands of vehicles performing high-speed passing maneuvers. These frictional demands were found by photographing and analyzing passing maneuvers performed under actual highway conditions. Critical frictional requirements are proposed for application to skidding accident prevention programs that incorporate minimum skid resistance levels and wet weather speed limits.

Dynamics of Wheeled Vehicles. Report 2. Implementation of Wiener-Bose Theory and Application to Ride Dynamics

Abstract: WIENER-BOSE THEORY IS A STRATEGY FOR IDENTIFYING NONLINEAR SYSTEMS IN TERMS OF "CHARACTERIZING COEFFICIENTS." THESE ARE OBTAINED THROUGH THE AGENCY OF A CERTAIN PROBING PROCESS CARRIED OUT ON EACH SYSTEM. ONCE THE COEFFICIENTS HAVE BEEN DETERMINED THEY MUST BE USED IN A RATIONAL SYNTHESIS PROCEDURE TO PREDICT RESPONSES TO INPUTS OF INTEREST. THE WIENER-BOSE THEORY REQUIRES VERY LITTLE KNOWLEDGE OF THE PHYSICS OF THE SYSTEM, WHICH IS INCORPORATED INTO THE CHARACTERIZING COEFFICIENTS. SO THIS PROPERTY MAKES ITS APPLICATION TO VEHICLE RIDE DYNAMICS ATTRACTIVE. THE PRESENT STRATEGY FOR RIDE DYNAMICS STUDIES USES OF STRUCTURE-ORIENTED MASS-SPRING-DASHPOT MODELS BASED ON RIGID BODY MECHANICS. THESE MODELS ARE CHARACTERIZED BY THE NEED FOR REPEATED "TUNING" IN WHICH MODEL PARAMETERS ARE ALTERED IN A BASICALLY IRRATIONAL WAY WHEN COMPARISONS MADE TO DIFFERENT SETS OF ACTUAL VEHICLE RESPONSES. A COMPUTER STUDY WAS CONDUCTED TO DISCERN PROBLEMS OF IMPLEMENTATION OF THE THEORY. SEVERAL SYSTEMS OF INCREASING COMPLEXITY WERE STUDIED AND A PRACTICAL FORM OF WIENER-BOSE THEORY EVOLVED. THE SYSTEMS STUDIED WERE: (A) A ZERO-MEMORY SYSTEM, (B) RATE-INDEPENDENT HYSTERESIS, (C) A SECOND-ORDER SYSTEM WITH SATURATION, AND (D) A FOURTH-ORDER MECHANICAL SYSTEM WITH NONLINEAR COMPLIANCES. THE EXPERIENCE GAINED HERE WAS SUMMARIZED IN A SET OF GUIDELINES FOR WIENER-BOSE MODEL CONSTRUCTION. TESTING WAS CARRIED OUT TO ASCERTAIN THE PRACTICALITY AND UTILITY OF WIENER-BOSE THEORY FOR RIDE DYNAMICS STUDIES. A MILITARY M37, 3/4-TON TRUCK WAS SELECTED FOR CHARACTERIZATION USING A WIENER-BOSE MODEL HAVING 1024 COEFFICIENTS, WHICH WERE OBTAINED BY UTILIZING THE VEHICLE RESPONSES RECORDED DURING TRAVERSAL OF A SPECIALLY CONFIGURED OBSTACLE COURSE WHOSE TOTAL LENGTH WAS 2.5 MILES. ONCE THE COEFFICIENTS WERE OBTAINED, THEY WERE USED TO SYNTHESIZE RESPONSES TO SPECIFIC TERRAIN PROFILES. THESE PREDICTED RESPONSES COMPARED FAVORABLY WITH COUNTERPART RESPONSES OF THE VEHICLE TRAVERSING THE SAME PROFILES. IT WAS CONCLUDED THAT WIENER-BOSE THEORY IS CAPABLE OF SATISFACTORY PERFORMANCE IN MANY NONLINEAR SYSTEMS ANALYSIS. THE PRINCIPAL DIFFICULTY IN ITS PRACTICAL APPLICATION LIES IN THE EXTENSIVE PROBING EFFORT REQUIRED FOR CHARACTERIZING THE SYSTEM. /AUTHOR/

The Effect of Aircraft Lateral Dynamics on Aircraft Positioning Accuracy When Using Loran-C

Abstract: The dynamics of an aircraft following a fixed course line using Loran-C for position fixing are shown to interact with Loran-C receiver dynamics to result in cross-track aircraft positioning errors that are smaller than cross-track Loran receiver errors. In a particular case considered, this error reduction is on the order of 50 percent.