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Some manufacturers of off-highway equipment have replaced hydraulic cylinders with electric actuators in order to eliminate pumps, hoses and valves, and make vehicles smaller, lighter and quieter. They have taken advantage of the flexibility in interfacing with control systems to provide a wide range of new features and capabilities.

Electric actuators can interface with a vehicle controller for complex motions such as cycling for a specified number of times at various positions, resulting in improved machine performance and productivity.

Today the benefits of electric actuators can be realized in applications with static loads up to 5,000 lbs and dynamic loads up to 3,000 lbs., with load ratings increasing each year. Hydraulic cylinders are required for higher loads or when moving loads at 100% duty cycle.

Certain myths have arisen about electric linear actuators that have slowed their adoption in applications where they potentially offer substantial OEM and end-user advantages. This article will take a look at these myths and discuss the opportunities for integrating electric linear actuators in machinery including recreational vehicles, sprayers and turf equipment.

Myth No. 1: Electric actuators can't handle a harsh environment

Hydraulic technology has been used in off-road vehicles for many decades, and engineers have become familiar with its ruggedness in tough environments. Hydraulic actuators have also historically enjoyed a lead in power density over their electric counterparts, which enhance their performance in the most difficult applications. But many off-highway engineers aren't aware that over the past decade the power density and ruggedness of electric actuators has substantially improved.

The power density of hydraulic actuation is largely dependent upon the pressure of their systems, and for safety and cost reasons these pressures have plateaued over the past decade. On the other hand, the power density of electric motors has substantially increased over the same time frame because of advances in magnetic materials, lead/ball screw efficiency, construction, manufacturing techniques and electronics. One of the most significant benefits is the ability to deliver substantially more power while maintaining high levels of efficiency. Additional improvements have come in the power transmission, largely through gearbox designs that are optimized to the requirements of electric linear actuator applications. As a result, electric actuators provide superior power density in many applications resulting in simplified installation and appreciable vehicle weight savings.

Today, electric linear actuators designed for off highway applications are engineered to withstand harsh environments. Castings use finite element analysis to optimize their load handling capabilities. Electric actuator design has migrated from an approach that uses modular assemblies to one in which the key components are encapsulated in a clamshell that protects them against shock and vibration.

Multi-axis vibration testing and analysis prove the ability of electric linear actuators to withstand real-world mechanical loading. Improvements have also come from eliminating the wiring harness previously used to connect to the motor control and instead molding a connector into the housing that the control system cable can be plugged into. This approach provides a better seal and takes the motor connection out of harm's way. Today's electric linear actuators designed for off-highway applications are every bit as rugged as hydraulic actuators.

Myth No. 2: Electric linear actuators aren't as reliable

The myth that hydraulic actuators are more reliable may also be due to the fact that many engineers are familiar with a previous generation of electric linear actuators that did experience reliability problems. But electric linear actuators have benefited from dramatically improved reliability of all electronic and electrical products. Consisting solely of a motor, gearbox, lead or ball screw and often a clutch, electric linear actuators are simple. Based on highly reliable electronic technology and with minimized possible points of failure, the life of electric linear actuators has improved in recent years to the point that, in the vast majority of applications, they will outlast the equipment they are installed on.

Electric linear actuators provide maintenance-free operation and are therefore much less prone to fail due to lack of maintenance. Today's electric linear actuators require zero maintenance, not even lubrication. Electric linear actuators run independently with every axis being powered by a different motor, so a failure in an electric application affects only that single actuator, which makes it much easier to troubleshoot and repair.