A magnetically controllable valve to vary the resistance of hydraulic dampers for exercise machines

While the majority of exercise machines use weights, springs or spinning fans to generate motion resistance, a large number of machines also utilize linear fluid damping. Similar to a shock absorber, linear dampers are compact, extremely reliable, and produce "double positive" resistance (resistance to both directions of motion). However, they are difficult to adjust for higher or lower resistance. This paper illustrates a mechanism to vary the resistance of a linear damper, and illustrates with experimental data certain properties of the damper