CAN controller paves a road

—edited by Richard Mandel

Every springtime in the state of Ohio, after snows have melted and the earth begins to warm, the “state flower” blooms, a ritual repeated and echoed at some time or another in the remaining 49 states of the Union. Along the highways sprouts flowers of brilliant orange that bear no scent. We refer, of course, to the traffic diverter barrel, foreshadowing the coming of days, weeks and months of road construction, of detours, bridge rebuilding and street resurfacing.

One manufacturer of highway servicing equipment, E.D. Etnyre & Co, Oregon, IL, has come a long way over the past 100 years, since the days when their bituminous distributor was powered by horses and controlled by hand. With the advent of motor-driven vehicles, the operator had to be very skilled at steering the distributor while controlling the rate of asphalt application.

Adding control

Today, Etnyre machines cover roads with a greater level of control and efficiency, aided by a controlled area network (CAN) system Etnyre engineers devised with HED Inc, Hartford, WI, a developer of mobile equipment control systems. The modular units comprising this system have higher current outputs, more rugged construction out on the road projects, and occupy less space than competitor’s control systems, all at lower cost.

From the cab of the Black-Topper asphalt distributor, the operator has full control over all spraying functions, applying just the right amount of asphalt to match road surface specs and conform to the lane width while driving the vehicle along the road. Even if a driver experiences fatigue, which could lead to a less consistent application of asphalt, the automated control system guarantees the road is covered within specifications.

The application process is precise because there is no by-pass valve in the circulating system. Material passing through the hydrostatic pump goes directly through the spray nozzles. The spray valve is fully pressurized for accurate application. The system provides balanced, dual-feed asphalt while spraying to insure uniform application across the full spray bar and wing width up to 24 ft, offering coverage for two full lanes.

From the driver’s seat, the operator manages and monitors asphalt spraying from an interface panel developed by Etnyre, controlling application rate and the spray in one-foot increments. The system maintains the pre-set application rate, regardless of operator changes in vehicle speed or adjustments in spray width, by matching pump output to distribution speed. Accurate information about ground speed and distance is fed to the system by way of a simple radar-sensing device. The solid-state design eliminates parts that could otherwise become damaged or require maintenance.

Handling the asphalt

Under the truck, the asphalt feeds to the spreader bar from the tank, heated either with single or dual flue burners using LPG or fuel oil, based on the type of asphalt selected to spray on the road. The operator dials in the temperature ranging from 150° to 400°F. Once reaching the desired temperature the system shuts off the burners. Two Etnyre-designed large cross-section “obstruction-less” spray bars provide better circulation, faster heating, faster starts and improved heating for special asphalts.

The operator can control the width of the spray through the computer. The bar responds by moving the two spray bars past one another to vary the width of the spray. When the bars overlap, the computer turns off the appropriate valves.

The operator can monitor the computer screen for application rate, gallons-per-minute of asphalt dispersion and distance traveled. Ten different application rates can be stored in memory and recalled with the push of a button. The system adjusts performance rates of the Black-Topper’s 400 gpm pump (designed and built by Etnyre exclusively for handling asphalt and asphalt emulsions) for loading and circulating without changing the desired application rates. A two-speed, high-torque hydraulic motor drives the pump through a planetary gearbox, enabling the handling of rubber-modified asphalts, minimizing cold start problems and permitting light tack shots. Meanwhile, a built-in self-diagnostic program monitors the control circuits.

CAN do

The vehicle’s closed loop CAN system permits the computer to communicate with modules controlling bar position and valve operation over a common pair of twisted wires. This approach means much simpler connections for more design options within the confined space of the vehicle body for easier production and higher reliability. For this type of vehicle, CAN communication also provides a robust signal that withstands high EMI/RFI interference from electrical devices in the surrounding environment, such as power lines, radio transmitters, electric motors, solenoids and other computers used on the jobsite.

As part of the control system, the recently introduced CL-401 input/output module from HED provides higher current through 16 outputs for a wider range of electro-hydraulic components, including the valves. HED software engineers programmed the system to provide more consistent pump control to reduce spray pulsing, reduced the operating set-up parameters, and simplified the setup screen. They also minimized costs by specifying two CL-401 valve driver modules under the control of a CL-402 input/output module on a CAN Bus system, instead of three slave modules as required by other manufacturers.

With heated asphalt coursing through the vehicle, the CAN components withstand temperatures at jobsites, even during the hot summer months. In addition, the modules along the communication system are waterproof and withstand any direct contact with the asphalt.

By making application calculations and controlling sprayer system functions, the Black-Topper electronic controls bring a higher level of consistency and efficiency to this final stage of road construction, without requiring a higher level of driver skill.