Fluid power actuator utilizing a screw and nut assembly

A fluid power actuator comprising:

• a housing comprising:
• a cylinder,
• an end cap to seal a blind end of the cylinder, and
• a rod end cap to guide a piston rod relative to the cylinder;
• a piston rod assembly comprising:
• a piston that travels within the cylinder in response to fluid pressure within the cylinder, the piston having a nut, and
• the piston rod connecting the piston to an external load using a piston rod end, the piston rod being hollow to allow a screw to be partially or fully located inside the piston rod;
• and
• a screw and nut assembly comprising:
• the screw that couples the blind end of the cylinder to the nut, wherein the screw extends in part or in whole inside the piston rod, the screw and nut assembly being constructed to be non-self-locking and arranged to control movement of the piston relative to the housing, and
• a brake that controls a position of the nut relative to the screw;
• a load cell that measures an axial load that the screw imposes on the housing;
• and
• a controller that adjusts the fluid pressure on at least one side of the piston to adjust the axial load, wherein the controller is constructed and arranged to:
• receive, from the load cell, a measurement of the axial load that the screw imposes on the housing, and
• based on the measurement, direct an increase in the fluid pressure on a particular side of the piston, the increase in the fluid pressure on the particular side decreasing the axial load that the screw imposes the housing.