Abstract: A hydraulic propulsion system is disclosed which includes an input interface configured to receive mechanical power from a power source, a pressure source comprising one or more fixed or variable displacement pumps coupled to the input interface and adaptable to convert mechanical power to hydraulic power and controlling outlet pressure of the pressure source (system pressure), one or more variable displacement motors coupled to the pressure source via a corresponding high-pressure line configured to be mechanically coupled to one or more aerodynamic rotors of an aircraft and comprising a closed loop speed control arrangement in response to a commanded rotor speed, and a controller configured to control the speed of one or more variable displacement motors by providing a control signal for controlling the system pressure.

Abstract: A hydraulic pump is disclosed, which includes an input crank shaft configured to be interfaced with a shaft of a power generating device, one or more connecting rings coupled to the input crank shaft with an eccentric interface such that when the input crank shaft is rotating causes the connecting ring to rotate with an eccentricity, a fixed annular frame, and a plurality of hydraulic actuators annularly disposed between the one or more connecting rings and the fixed annular frame, each hydraulic actuator of the plurality of hydraulic actuators having a piston disposed within a cylinder and each further including a hydraulic input and a hydraulic output, the eccentricity between the connecting ring and the input crank shaft causes the plurality of hydraulic actuators to i) pump hydraulic fluid out of the hydraulic output, or ii) cause suction of hydraulic fluid from the hydraulic input.

Abstract: A piston and cylinder assembly of an axial piston machine is disclosed which includes a cylinder having a uniform internal diameter, a cylindrical bushing press-fit against the inner surface of the cylinder and extending at least partially therein, the bushing comprising at least one circumferential groove formed on an outer surface of the bushing against the inner surface of the cylinder, a piston reciprocably disposed within the cylindrical bushing, generating a piston-bushing-interface, the piston and the bushing defining a diametrical clearance therebetween, the diametrical clearance defining a lubrication gap and a fluid-dynamic seal between the piston and the cylindrical bushing.

Abstract: A hydraulic propulsion system is disclosed. The system includes one or more input interfaces configured to receive mechanical power from a power source, four or more variable displacement pumps coupled to the one or more input interfaces adaptable to generate a controlled variable quantity of fluid to be pumped out of each of the variable displacement pumps in response to a control input from a corresponding control interface, and four or more positive displacement motors each fluidly coupled to a corresponding variable displacement pump and configured to receive the pumped fluid, wherein each motor is configured to be mechanically coupled to one or more aerodynamic rotors of a multi-rotor vertical take-off and landing aircraft to control thrust and attitude.

Abstract: A piston and cylinder assembly of an axial piston machine is disclosed which includes a cylinder having a uniform internal diameter, a cylindrical bushing press-fit against the inner surface of the cylinder and extending at least partially therein, the bushing comprising at least one circumferential groove formed on an outer surface of the bushing against the inner surface of the cylinder, a piston reciprocably disposed within the cylindrical bushing, generating a piston-bushing-interface, the piston and the bushing defining a diametrical clearance therebetween, the diametrical clearance defining a lubrication gap and a fluid-dynamic seal between the piston and the cylindrical bushing.

Abstract: A hydraulic propulsion system is disclosed which includes an input interface configured to receive mechanical power from a power source, a pressure source comprising one or more fixed or variable displacement pumps coupled to the input interface and adaptable to convert mechanical power to hydraulic power and controlling outlet pressure of the pressure source (system pressure), one or more variable displacement motors coupled to the pressure source via a corresponding high-pressure line configured to be mechanically coupled to one or more aerodynamic rotors of an aircraft and comprising a closed loop speed control arrangement in response to a commanded rotor speed, and a controller configured to control the speed of one or more variable displacement motors by providing a control signal for controlling the system pressure.