March 2021

motion control to tilt the bucket, for example, it would be far easier to run electrical wire to up the boom than hydraulic fluid transport tubing. This solution also removes potential concerns about fluid dripping into the environment. A designer of a tractor-hauled seeding unit might output hydraulic lines to the rear of the tractor to control the depth into which the planter cuts to deposit the seed. Replacing that fluid hose with an electric cable has many advantages, such as avoiding costly infrastructure and fluid leakage into a food crop. Shock loading Historically, hydraulic technology has been better able to handle sudden shocks, such as the impact of a snow-covered concrete barrier on a cylinder-guided plow blade. However, embedding this technology into electro-hydraulic actuators gives them shock-loading benefits on par with hydraulic cylinders, countering any advantage they might have previously had in this area. Another example of shock handling would be a mower deck running into a large rock. As with the snowplow example, the electro- hydraulic actuator would absorb the sudden energy spike instantly by redistributing the fluids throughout the internal valves and pump housing. Cost effectiveness Conventional hydraulic systems are most cost effective when they are already specified into a design already containing hydraulic elements, and it is just a matter of adding cylinders to the initial design. Otherwise, there is a cost in designing the support infrastructure and incorporating that into the overall system design. Eliminating fluid handling and storage, leak and spill management, and additional maintenance costs of identifying and repairing leaks can also reduce lifecycle costs for end-users. These benefits are marketable for OEMs and can easily be communicated as advantages to their customers. Conclusion For new application designs requiring handling of loads up to 2.180 kg and speeds up to 100 mm (4 inches) per second, electro-hydraulic actuators have significant advantages over hydraulic cylinder-based systems in power density, cleanliness of operation, versatility and lifecycle costs. They also match hydraulic systems in load and shock handling performance. www.thomsonlinear.com ! !"#$%&'()*)"'(+#,$- .%/,#*/"/0,1/* 2',)0$3-4"#$%&'()* %)0&%03$/* "#$!%&#'!(#)#(*+,! -./01!! ./!01! 2&345!'467*+,! 8*9:! 8*9:47+! ;%4#6%*6477!<!7#=4+,! >&3! 8*9:! ?''*+*&6#%!@#*6+46#6(4!! 8*9:! 1&64! >&(#+*&6!A457#+*%*+,! >&3! 8*9:! B:&(0!:#6'%*69! 8*9:! 8*9:! ;&7+!C!*6*+*#%!! 8*9:! >&3! ;&7+!C!4$)#6'*69!4$*7+*69!D6*+! >&3! >&3! ;&7+!C!%*=4(,(%4! 8*9:! >&3! Figure 2: Comparison of hydraulic cylinder-based systems and electro- hydraulic actuators. LEFT: The Thomson Warner Linear H-Track electro-hydraulic linear actuator provides the performance of hydraulics without the expansive space requirements nor the prohibitive cost of full- sized hydraulic systems. It handles force up to 21.350 N and features the smallest mounting envelope in its class. www.hpmag.co.uk HYDRAULICS & PNEUMATICS March 2021 21