Advanced electronics keep military and emergency vehicles on the go.
Logistics is an often underappreciated, but key, aspect of national defense. Trucks and other vehicles play crucial roles in bringing personnel and equipment to the scene of an incident or troops into battle. Any malfunction in these important machines can, at best, slow response and, at worst, spell disaster.
A system using advanced computer-controlled, multiplexed electronics and control-area-network (CAN) technology will help these vehicles continually monitor internal systems and diagnose problems. Called the Command Zone system, it was recently introduced to the military market, starting with a Medium Tactical Vehicle Replacement (MTVR) wrecker. This technology provides applications with data integrity and data rates up to 250 kbs offering, among other things, constant system self-diagnosis.
Developed by Oshkosh Truck Corp., Oshkosh, Wis. (www.oshkoshtruck.com), in collaboration with HED Inc., Hartford, Wis., the J1939 CAN-based microprocessor vehicle-control system:
J1939 is a high-speed 250-kbs protocol that provides registered addresses and standard architecture, enabling vehicle components such as antilock brakes, engine, transmission, and various electronic and hydraulic systems to essentially talk to one another. The system sorts out and coordinates all of this action so each function delivers better overall performance.
The CAN microprocessor-based modules positioned throughout the vehicle monitor and manage a full range of functions, having a number of inputs and outputs to replace the volume of wiring harnesses, relays, and fuses these types of applications would otherwise need. In addition, the modules have configurable digital or analog/digital inputs, and PWM outputs.
Command Zone lets Oshkosh engineers offer many features within the confines of the truck chassis. In a system as large as that used within a fire truck from Oshkosh's Pierce subsidiary, a central-control module (CCM) coordinates information between CANLink I/O modules that handle load control, safety interlocks, engine-load control, soft limits for devices, programmable limits, and automated sequencing.
The CCM houses software for coordinating the entire CAN system. If the application calls for a high level of sophistication, a 40-meter CAN backbone can support up to 30 units, though currently the largest CAN system on one fire truck reaches 27 modules.
An example of this capability is the use of the engine controller unit (ECU) on the Detroit Diesel engine powering the Oshkosh four-axle Heavy Expanded Mobility Tactical Truck (HEMTT). The ECU generates an abundance of information on the 445-hp engine. One of the prime purposes of the ECU is to curb emissions while improving fuel economy, an important consideration in places where the nearest fill-up is miles away. The module sends performance information to other control modules to manage engine operation for better fuel use, letting the HEMTT travel roughly 300 miles on a full tank. In another case, a gage-driver module developed by HED translates the CAN messages and sends them over a twisted pair of wires to drive standard analog gages, indicator lights, and meters in the cab.
The compactness of Command Zone components lets Oshkosh engineers provide features that would be difficult with standard electronics. One example is All Steer electronic all-wheel-steering. All Steer provides three separate steering modes - front steer for conventional driving; coordinated steer which turns the rear wheels in the opposite direction of the front wheels, cutting the turning radius up to 30% at speeds between 2 to 35 mph; and crab steer that "walks" the vehicle around obstacles or into tight spots by turning the front and rear wheels in the same direction. The driver selects the mode by flipping a switch and Command Zone takes over. The system calculates the correct wheel angles and performs self-diagnosis while displaying system status in the cab.
The system controls these vehicles by performing intricate calculations based on the dimensions of the equipment and data trafficking necessary to protect the equipment from damaging the vehicle or itself. On the MTVR wrecker, for example, the system prevents the crane from deploying beyond certain angles so it doesn't tip while operating.
Oshkosh applies this same equipment protection with the "Snozzle" elevated waterway on their Striker aircraft rescue and fire-fighting (ARFF) truck. Command Zone controls Snozzle operation, making possible one button extension and retraction of the boom. Capable of aiming in any direction, the Snozzle delivers a high-powered spray of 1,250 gallons of water and foam per minute.
Along with letting operators control the vehicle, Command Zone keeps them informed about the operational status as well. Inside the cab of fire trucks, the system delivers real-time information on apparatus performance, vehicle operation, and diagnostics. This information displays on screens located in the cab, at the pump panel, and on aerial booms.
At vehicle start-up, the system automatically checks each electrical circuit to verify all systems are go. Troubleshooting is as quick and easy as simply scrolling through the screens on the display. Built-in diagnostic software developed by Oshkosh, Pierce, and HED engineers lets maintenance personnel target problem areas within minutes. The system also incorporates modems into control boards and systems, permitting remote monitoring of machine functions. Problems can be solved right at the vehicle or from miles away. If the problem is software, it can be fixed remotely as well.
Command Zone will give the HEMTT a number of other features for greater reliability in the unforgiving world of combat. To get a quick handle on the source of a problem, technicians can plug their laptop or PDA into the various electronic control modules through an RS-232 port to access system conditions.
Once plugged in, a Diagnostic/Service Tool software package lets field technicians locate problem areas within minutes and e-mail this information, if necessary, for consultation with other technicians. They can readily determine if the remedy is a quick fix to the software or if more extensive repairs are necessary. This Windows-based system doesn't require any special software knowledge or training.
The Service Tool locates system modules and displays their status on a screen. The user can click to open a module viewer that displays all the information about the module's inputs and outputs. Several viewers can be opened at a time to see if modules are working together to complete specific operations. The Diagnostic Tool manipulates module inputs and outputs during run time in a debug mode. This tool determines if the problem lies with the module itself, or if it's associated with wiring or an external device.
Expert technicians located elsewhere can constantly monitor vehicle condition via modems. This enhanced remote diagnosis can improve the military's "reach-back readiness," minimizing battlefield emergencies due to equipment malfunctions. The electronic-control modules included in Command Zone have "black-box capability" to deliver real-time operating information - known in the military as health and usage monitoring. These modules store performance data for all the truck's working systems. Analysis of the information will help improve driver training and preventative maintenance while providing a picture of vehicle conditions if there's an accident.
In addition, the CAN components are built tough for high-stress situations under demanding off-road conditions. The CAN communication method provides a strong signal with high EMI/RFI tolerance and message priority capability.
The environment where this equipment travels offers an abundance of electromagnetic and radio-frequency interference from radio transmitters, electric motors, solenoids, power lines, and a host of computers now used on the battlefield or at the site of a fire. To break through this clutter in the airways, HED uses ground planes on circuit boards, ferrites (inductors), capacitors, and enclosures.
These components are ready for whatever nature throws at them by housing the boards in a watertight case which resists temperature extremes from -46 to 85°C, and vibration. Additionally, the units resist a variety of fluids.
To further protect the truck's performance, Command Zone automatically manages the electrical system. This load-prioritizing feature prevents interruption of critical systems at peak loads. During system start-up, Command Zone eliminates line surges to minimize the likelihood that breakers and fuses will blow.
The collaboration of Oshkosh and HED engineers has developed a cumulative expertise that will let the building blocks of Command Zone technology be applied to other vehicles. In the course of this project, HED has developed an array of CAN modules that will easily adapt to other projects. According to Duane Pillar, chief engineer for corporate electronics at Oshkosh, "Developing a selection of modules to choose from means we can easily integrate the Command Zone concept into vehicles in all of our divisions with a minimum of development costs."
With Command Zone in these vehicles doing much of the thinking, the drivers can focus their attention to the task at hand. That attention, in turn, is less likely to be interrupted by equipment failures. The ongoing development to add this system to other vehicles means the equipment this country depends upon for Homeland defense and deployment internationally will be more reliable and ready to respond when needed.