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Wheel Force Transducer

This transducer could ensure better testing of off-road vehicles.

Aconcept wheel force transducer has been developed that can measure the forces and moments between a tire and a road on a High Mobility Multi-purpose Wheeled Vehicle (HMMWV or Humvee) driven under off-road conditions. The proposed wheel force transducer is an important step in correcting the gap in current tire testing and modeling knowledge to ensure that future off-road vehicle models and simulation efforts are conducted with confidence. In order to obtain tire characteristics over off-road terrain, cost-effective field test equipment was required.

This model shows the Force Transducer mounted to the modified rim. The load cell inner ring is mounted to the modified rim using 12 bolts.
There are many derivatives of the HMMWV, with large differences in mass. The gross weight of the vehicle used in this work is 12,100 pounds. The first important step in the concept design was to determine the space envelope, and therefore basic dimensions available to fit the transducer. Due to the suspension components on the inside of the wheel, the transducer had to be mounted to the outside of the standard rim.

The wheel force transducer had to replace part of the rim so that the rim was connected to the hub via the force transducer. To achieve this, the standard rim had to be modified. Modification involved cutting out the center portion of the outer part of the original rim to the same diameter as the unmodified inner rim. The load cell inner ring was mounted to the modified rim using 12 bolts. On the unmodified rim, these 12 bolts were responsible for holding together the two parts of the split rim. These bolts were part of the inner rim. In this application, the bolts were replaced and screwed in from the inside of the rim into the load cell inner ring. The nuts on the outside were not used, as the load cell inner ring served this purpose.

The load cell outer ring was mounted to the hub using the hub mounting adapter, which connected the load cell outer ring to the vehicle’s hub with the existing eight hub bolts and nuts. The hub mounting adapter was also bolted to the load cell outer ring. The load cell inner ring and outer ring were connected to each other via six individual tension-compression load cells. The load cells were mounted such that the three tire forces and three tire moments could be calculated from the six tension-compression forces measured with the individual load cells and the geometry.

The possibility exists to mount the wheel force transducer to other rim sizes and designs. The exact possibilities depend on the geometry of the different rims, but basically entail designing and manufacturing adapters to connect the load cell inner ring to the rim, and the load cell outer ring to the hub. This can also be turned around so that the load cell inner ring is mounted to the hub, and the load cell outer ring is mounted to the rim.

This work was done by P.S. Els of the University of Pretoria, South Africa, for the US Army International Technology Center-Atlantic. ARL-0124

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This Brief includes a Technical Support Package (TSP).
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Wheel Force Transducer Research and Development

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    Defense Tech Briefs Magazine

    This article first appeared in the April, 2011 issue of Defense Tech Briefs Magazine (Vol. 5 No. 2).

    Read more articles from this issue here.

    Read more articles from the archives here.

    Overview

    The document titled "Wheel Force Transducer Research and Development" is a first interim report authored by Prof. P.S. Els from the University of Pretoria, covering the period from September 16, 2010, to December 16, 2010. It details the development of a prototype wheel force transducer designed to measure the forces and moments between a tire and the road while a vehicle, specifically a High Mobility Multipurpose Wheeled Vehicle (HMMWV), is driven under off-road conditions.

    The primary objective of this research is to create cost-effective field test equipment that can accurately capture tire characteristics in real-world off-road scenarios. The report outlines four main objectives: developing a six-component wheel force transducer, creating mathematical models for the transducer, validating and calibrating the device, and manufacturing a set of four wheel load cells for vehicle installation.

    The document emphasizes the importance of obtaining accurate tire characteristics for off-road terrain, which poses significant challenges for traditional laboratory testing methods. The proposed wheel force transducer is a crucial step in addressing gaps in current tire testing and modeling knowledge, ultimately enhancing the reliability of future off-road vehicle models and simulations.

    Key design requirements for the transducer include a static vertical wheel load of 1600 kg, a maximum vertical load capacity of 4800 kg, and specifications for rim size and flange dimensions. The report also discusses the need to mount the transducer externally on the standard military HMMWV split rim due to space constraints imposed by suspension components.

    The research is supported by the U.S. Army International Technology Center-Atlantic (USAITC-A), highlighting its significance in military applications. The report serves as a foundational document for ongoing research efforts aimed at improving tire performance and vehicle dynamics in challenging terrains.

    In summary, this interim report outlines the initial stages of developing a wheel force transducer that will facilitate better understanding and modeling of tire behavior in off-road conditions, thereby contributing to advancements in vehicle testing and performance evaluation.

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