US Patent 10953284 Apparatus and method for controlling fluid propulsion

A system, methods and apparatus for powered monofin that propels a swimmer through water uses one of two modes of power: 1. An electric-assist mode, in which the propulsor responds to a swimmer's kick by multiplying the work of the swimmer; 2. Inverse mode, in which the propulsor deactivates when the swimmer is working. In this mode, propulsion is inversely related to the work of the swimmer. As the swimmer does more work, power from the monofin is reduced, to a predetermined, average level of propulsion. As the swimmer does less work propulsion increases to the predetermined level.