Abstract: A selectively self-locking actuator includes a threaded shaft having a first threaded portion and a second threaded portion. The first threaded portion includes a semicircular ball screw threadform and the second threaded portion includes a power screw threadform. The actuator further includes a ball nut mated to the first threaded portion, a split nut selectively mated with the second threaded portion, and a nut coupler plate configured to secure the ball nut and split nut at a fixed distance from each other. The split nut includes at least a first split nut portion and a second split portion each mated to a spring and a driver. The spring is configured to bias the first split nut portion and the second split nut portion either radially inward or radially outward with respect to the threaded shaft, and wherein the driver is configured to selectively oppose the bias of the spring.

Abstract: A selectively self-locking actuator includes a threaded shaft having a first threaded portion and a second threaded portion. The first threaded portion includes a semicircular ball screw threadform and the second threaded portion includes a power screw threadform. The actuator further includes a ball nut mated to the first threaded portion, a split nut selectively mated with the second threaded portion, and a nut coupler plate configured to secure the ball nut and split nut at a fixed distance from each other. The split nut includes at least a first split nut portion and a second split portion each mated to a spring and a driver. The spring is configured to bias the first split nut portion and the second split nut portion either radially inward or radially outward with respect to the threaded shaft, and wherein the driver is configured to selectively oppose the bias of the spring.

Abstract: A method of configuring a wing velocity profile includes segmenting a complete wingbeat cycle into a set of quarter-strokes including a first quarter-stroke, a second quarter-stroke, a third quarter-stroke, and a fourth quarter-stroke. The method further includes generating time-varying quarter-stroke wing position commands for each of a first and second wing planforms to produce wing flapping trajectories that generate non-zero, cycle averaged wing lift and drag and alter a cycle average center of pressure of each of the first and the second wing planforms relative to the aircraft. The wing position commands include velocities and positions with temporally symmetric and asymmetric quarter-stroke components for the first wing planform and the second wing planform. The first wing planform and the second wing planform produce controlled six-degrees-of freedom vehicle motion without using actuators in excess of the first actuator and the second actuator.

Abstract: A method of controlling wing position and velocity for a flapping wing air vehicle provides six-degrees-of-freedom movement for the aircraft through a split-cycle constant-period frequency modulation with wing bias method that generates time-varying upstroke and downstroke wing position commands for wing planforms to produce nonharmonic wing flapping trajectories that generate non-zero, cycle averaged wing drag and alter the location of the cycle-averaged center of pressure of the wings relative to the center of gravity of the aircraft to cause horizontal translation forces, rolling moments and pitching moments of the aircraft.

Abstract: A method, computer usable medium including a program, and a system for braking a vehicle during brake failure. The method and computer usable medium include the steps of determining a brake force lost corresponding to a failed brake, and determining a brake force reserve corresponding to at least one non-failed brake. At least one commanded brake force is determined based on the brake force lost and the brake force reserve. Then at least one command brake force is applied to the at least one non-failed brake wherein at least one of an undesired yaw moment and a yaw moment rate of change are limited to predetermined values. The system includes a plurality of brake assemblies wherein a commanded brake force is applied to at least one non-failed brake.