Linear Actuators Used to Test Replacement Hearts of the Future

The uses of linear actuators is broad and varied, as they become more and more popular in a variety of motion related fields. Innovative uses for actuators appear regularly. Recently a linear actuator was applied to the problem of simulating the action of the human heart to eliminate the need for animal testing.

The University of Leeds, UK, has developed the iVAD, Intelligent Ventricular Assist Device, to control irregular heartbeats. However, they needed to test the device on healthy and diseased hearts. Faced with a large range of necessary conditions, they also developed a mechanical heart, powered by two linear actuators, which can duplicate any scenario.

An actuator produces motion, and by connecting a linear actuator to each side of the metal heart the alternating strokes of the right and left ventricles is mimicked. A linear actuator was required for this application rather than a rotary actuator. The iVAD consists of a set of bands which will surround the heart to produce contractions when powered by a small motor. For the mechanical test heart to respond to the iVAD, pressure sensors feed data back to a controller which adjusts the linear actuators actions as if it were modifying a real heart beat.

Mini actuators include stroke lengths up to 12 inches with up to 15 pounds of force, and for this mechanical heart simulator, mini actuators were perfect. The actuators were simply attached externally, out of the way of the iVAD bands. The mechanical heart is basically a spring cage, moved by controlling the mini actuators in a pattern that resembles a natural or diseased heartbeat. The actual iVAD that could one day be installed into human hosts does not include an actuator, but a complex and life-saving device like this one could not be tested without them. The test harness and linked control system was awarded the National Instruments Application of the Year for 2012.

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