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Off-Road Tire Pressure & Temperature Monitoring

Skills Chart
Teaming Specifications, Schedules, Budgets, User-Interface issues
Technical Electronics & the Physics of mass, temperature, pressure, materials
Software C, C++, Motorolacopy; assembler, firmware, FoxPro© database
Hardware System & circuit design, layout, component selection, prototyping, testing

The guy standing in this tire's rim will attest that this industry involves some serious hardware.   These are not your father's tires!

They are hand-crafted, expensive (~$20KUS/ea) and (believe it or not) relatively fragile outside their load-range.    The contained-air mass is so large that their inflation pressure varies broadly with ambient temperature and loading.   This variation was the project's biggest challenge.

[A Minimg Vehicle]

The design goal was a hand-held instrument to measure and record vehicle tire pressures.   It was to be operable by relatively untrained personnel, dock to a telephone line for optional remote maintenance, and interact with a database located on a PC in a nearby office or Supervisor's line shack.

Under-pressure tires can self-destruct and over-pressures are a safety hazard.   But if you inflate a tire on a hot day, how do you know it's still correct a week later, when it's cold outside and the pressure reading is lower?   This issue led us to track temperature and implement software algorithms that correct the pressures according to the tire's internal temperature and inflation history.

[Handheld PC]  

To meet the project's tight schedule, we located and qualified an existing, industrially-hardened, hand-held personal computer with an internal 12-bit A/D measurement system and thermocouple signal-conditioning.   A perfect fit.

To this platform we added sensors, an armored cable containing support circuitry we designed, and a custom application we wrote in the "C" language, (state-based, event-driven, with interrupt-handlers for the measurement system and the communications interface).

Measurements are made in the field, when the vehicles pause to load or unload.   Each vehicle can have up to 12 tires and the software tracks their pressures, internal temperatures, location on the truck, rim, and various other factors.   The User Interface was carefully designed to lead the Operator through the measurement process with visual and audible prompts, to promote efficiency and avoid costly or dangerous pitfalls.   After gathering data, the Operator returns the unit to the Supervisor between shifts, for interaction with a custom database initially crafted by one of our associates, a sub-contractor.

The database was developed in FoxPro©, with an add-in communications package, to talk directly to the hand-held unit via serial cable.   It schedules (downloads) the day's work in the morning and retrieves (uploads) the results at the end of each shift.  It also prepares customizable maintenance reports and alerts the Supervisor to developing problems or out-of-spec maintenance conditions.

This system was so well-received that we developed a prototype of a next-generation Wireless, Real-Time data collection system for the same Client.   The new system features immediate results, reduced risk to field personnel, and provisions for an interface to mobile vehicle networks.   It is based on Micron© RF-ID tagging technology ( 2.4GHz ) and the development involved additional circuit design, low-level assembly language (firmware) coding and an application written in C++.

This work resulted in U.S. Patent #6,025,777: Off-the-road tire temperature and pressure monitoring system.

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