Boom stability control: A new solution to reduce oscillation

Picture yourself in the bucket of an aerial work platform, ascending 50, 75, 100 feet (15 to 30 meters) into the air. Or perhaps you’re climbing the ladder of a fire rescue vehicle. Imagine what it would feel like if the platform beneath your feet begins to bounce—a little at first, but in greater amplitude the further the boom extends or the closer you get to the top of the ladder.

Stability means everything at these heights. It means the ability to focus on the task at hand without the uneasiness—whether real or perceived—that your personal safety is in danger.

Two steps forward, one bounce back

The long booms on many types of mobile machinery—concrete pump trucks, telehandlers, sprayers and hydraulically controlled cranes, for example—are subject to boom oscillation.

Manufacturers have designed longer and lighter boom structures to reduce vehicle axle weight and enhance machine capabilities, but this has come at the expense of boom stiffness and stability. The boom tends to oscillate because of the mechanical flexibility of the boom and the compliance of the hydraulic oil in the cylinders. Pressurized oil in the cylinders holding the boom in position contributes to oscillation, as the oil compresses and induces more oscillation.

The implications of boom bounce vary by platform. They include reduced machine performance and productivity, and increased safety risks for operators and nearby workers.

Concrete pumping productivity

With boom lengths ranging from less than 65 feet (20 meters) to over 200 feet (60 meters), concrete pump trucks are an application where the effect of boom oscillation is pronounced, and particularly detrimental to productivity. In operation, as the boom is maneuvering and pumping concrete, the tip can oscillate 4 to 6 feet (1.5 to 2 meters). 

To manage the oscillation, additional workers are typically required to hold the boom tip hose, and concrete pumping speed may also be decreased. This reduces machine productivity and increases the potential risk to workers.

Boom stability control technology

In response to these challenges, the Eaton DMC team developed a solution called boom stability control (BSC). This technology reduces hydraulic boom oscillation by up to 75% and boom settling time by up to 90%.

The active damping technology is enabled by a proprietary control algorithm, which works in conjunction with the Eaton CMA advanced mobile valve. It uses the valve’s onboard sensing and independent metering capabilities to detect disturbances and automatically stabilize the entire boom structure.

The boom stability control algorithm is internal to the CMA valve and the additional hardware and wiring on the boom is minimal. It easily integrates with Eaton or original equipment sensors and controllers. It also maintains machine safety and manual override features common on most platforms, and is fully configurable and tunable to the desired feel and performance.

The chart shows the results of a simulated concrete pumping test, where a rope is tied to the tip of the boom and used to inject a cyclical disturbance on the boom structure. At the start of the test, the rope is pulled for 10 seconds and then released to measure settling time. 

In the baseline case (shown in blue), the pressure ripple, which correlates to boom movement, continues to grow in amplitude until the disturbance is removed. Even without the disturbance, the boom requires an extended period of time before it returns to the stable, starting condition.

The boom stability control system (shown in red) maintains a small pressure ripple throughout the disturbance stage, correlating to a significant reduction in boom tip movement. Additionally, any small vibrations present in the boom are quickly dampened once the disturbance is removed from the boom.

Boom stability control (BSC) enables end users to perform more work in less time. The technology can also reduce component wear and maintenance downtime. Together, these benefits can result in potential direct and indirect cost savings for the machine owner.