m-hvosm

m-hvosm =McHenry Highway Vehicle Object Simulation Model

The HVOSM mathematical model consists of up to 15 degrees of freedom; 6 for the sprung-mass, and up to 9 for the unsprung-masses. The mathematical model is based on fundamental laws of physics (i.e., Newtonian dynamics of rigid bodies) combined with empirical relationships derived from experimental test data (i.e., tire and suspension characteristics, load deflection properties of the vehicle structure). The balance of forces occurring within and applied to components of the system are defined in the form of a set of differential equations which constitute the mathematical model of the system. The HVOSM includes the general three-dimensional motions resulting from vehicle control inputs, traversals of terrain irregularities and collisions with certain types of roadside obstacles.

In addition to the substantial effort in validation of the mathematical model, the HVOSM was also uniquely tested by designing an automobile stunt which was used both in a traveling auto-stunt thrill show and in the 1974 James Bond Movie, “Man with the Golden Gun” produced by United Artists Corporation. Please see below for additional information

McHenry Software licenses the m-HVOSM program to 3rd party graphics and animation vendors.

Background on HVOSM

In the mid-60's while at the Calspan Corporation (then Cornell Aeronautical Laboratory, Inc.), Raymond R. McHenry began development of a general mathematical model and computer simulation of the dynamic responses of automobiles under Contract CPR-11-3988 with the Bureau of Public Roads. The mathematical model, which was subsequently named the Highway Vehicle Object Simulation Model (HVOSM), includes the general three-dimensional motions resulting from vehicle control inputs, traversals of terrain irregularities and collisions with certain types of roadside obstacles (Ref. 3). The development of the HVOSM included an extensive validation effort within which a series of repeated full-scale tests with instrumented vehicles was performed to permit an objective assessment of the degree of validity of the computer model.

In 1976, after 10 years of development, refinement and applications of the HVOSM by Calspan as well as other research organizations, a Federal Highway Administration (FHWA) contract (DOT-FH-11-8265, (Ref. 4) was performed by Calspan to document all the various developments, refinements and validations of the HVOSM. Within that contract, two program versions were assembled, the HVOSM-RD2 version (Roadside Design) and the HVOSM-VD2 version (Vehicle Dynamics).

Since 1976 a number of further refinements and enhancements of the HVOSM-RD2 version have been developed and incorporated by McHenry Consultants, Inc.,(MCI) and utilized as a part of subcontracts with Jack Leisch and Associates (DOT-FH-11-9575, Ref. 5 - 10), Midwest Research Institute (DTFH-61-80-C-00146, Ref. 11), Calspan (DTFH61-83-C-00060, Ref. 12) and the Highway Safety Research Center of the University of North Carolina (DTFH61-84-C-00067, Ref. 13-14). A brief summary of the research performed as a part of these projects and additional extensive internal research performed by MCI is contained in papers by McHenry:

2011 "A Short History of Nearly Everything! (...about McHenry and Computers in Highway Safety)", Brian G. McHenry, Presented May 24, 2011 at the 2011 ARC-CSI conference in Las Vegas, published in Collision magazine Volume 6, Issue 2 - Fall 2011

1992 "Simulation Models of Vehicle Dynamics", B.G. McHenry, presented November 1987, National Conference on Future Improvements to and Supplemental Guidance for AASHTO Policy on Geometric Design of Highways and Streets; Published April 1992, Transportation Research Board Circular "Beyond the Green Book".

The Astro-Spiral Jump

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In addition to the substantial effort in validation of the mathematical model, the HVOSM was also uniquely tested by designing an automobile stunt which was used both in a traveling auto-stunt thrill show and in the 1974 James Bond Movie, “Man with the Golden Gun” produced by United Artists Corporation (References [i] and [ii]). The rationale for the development of the stunt was as follows:

As a part of the HVOSM development process, Calspan employed the services of professional stunt drivers in 1968 to perform maneuvers and stunts with an instrumented vehicle and, thereby, to generate vehicle response data in violent maneuvers for use in investigating the validity of the computer simulation. One of the included stunts was a fifty foot jump from a take-off to a receiving ramp. The degree of achieved correlation between analytical predictions and experimental measurements was found to be remarkably good in all of the included maneuvers and stunts. At the time, it was jokingly pointed out that Calspan had unintentionally developed a capability for the design and staging (i.e., via animated perspective displays on motion picture film) of auto thrill shows. A related, "far out" suggestion was the design of ramps to produce a combination of jump and rollover (i.e., a "spiral" jump), such that the stunt car would land on its wheels after passing over an obstacle in an inverted condition.

Subsequent to completion of development and validation of the HVOSM simulation in 1970, the thrill show ideas were given somewhat more serious consideration. Such an application would constitute both a challenging dynamics problem, similar in nature to a particularly violent single-vehicle accident, and an attention-getting demonstration of capabilities. It also had the appeal of a "fun" project to relieve a steady diet of crash protection studies.

In November of 1970 Raymond R. McHenry contacted Mr. W. J. Milligan, Jr., President, J.M, Productions, Inc., of Hamburg, New York, regarding his possible interest in the design of a new auto thrill show stunt and/or the establishment of speed and dimensional tolerances for existing stunts. The occasion of the contact was a newspaper item about Mr. Milligan's organization of a new national auto thrill show. As a result of subsequent discussions, J. M. Productions gave Calspan a purchase order to support an analytical study of the spiral jump stunt concept. The HVOSM simulation does not, of course, provide direct guidance for invention. Its application is equivalent to performing experiments with a fully instrumented-vehicle. Therefore, the analytical study of the spiral jump stunt concept consisted essentially of a trial and error process of exploratory changes in ramp configurations. The initial simulation study indicated that the combined needs to run both ends of the automobile over the same ramp profile in sequence and to generate a large roll acceleration in the 40 MPH speed range would create a serious problem in achieving acceptable pitch and yaw behavior. The limitation to the speed range of 40 MPH, which is based on space restrictions that generally exist for thrill show performances, produced a corresponding limitation on the time in the air that was available for the 360 degree roll- over. Thus, a large roll velocity (approximately 230 degrees per second) had to be generated to achieve a "wheels down" landing on the receiving ramp. The sequential traversal of the take-off ramp by the front and the rear wheels, when combined with the nonlinear suspension characteristics during the traversal (i,e., front suspension "bottomed out" throughout the roll impulse) was found to create a response sequence in which the rear wheels cleared or only lightly touched the "roll-impulse" end of the ramp.

As a result of this sequence, the initially predicted responses retained a "nose-up" attitude during the entire jump and were found to include excessive yawing. Attempts to achieve a corrective pitch impulse at either of the rear wheels were unsuccessful, The rear wheel that was moving up fastest cleared any ramp configuration that the "bottomed out" front suspension had traversed, An impulse sufficient for the desired pitch response, when applied at the other rear wheel, acted to excessively reduce the roll velocity. Therefore, it became necessary to consider minor vehicle modifications to achieve the desired combination of linear and angular velocities at the end of the take off ramp. The necessary vehicle modification consisted of an auxiliary contact point on the rear axle, for which the primary loading occurred on the last ten feet of the take-off ramp. The additional contact on the rear axle was also found to require a relatively low side-force capability to avoid unwanted yaw accelerations.

McHenry Software, Inc. (MSI) has created the McHenry-HVOSM (m-hvosm), a Win32 state-of-the art version of the HVOSM. MSI has also integrated the management of m-hvosm projects including creation, editing, submission of runs and evaluation of output, including 3-dimensional animations, into the m-edit environment which runs in Microsoft Windows.

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McHenry Software licenses the m-HVOSM program to 3rd party graphics and animation vendors.