Accurate drone positioning is challenging because pilots only have a limited position and direction perception of a flying drone from their perspective. This makes conventional joystick-based speed control inaccurate and more complicated and significantly degrades piloting performance. We propose PinpointFly, an egocentric drone interface that allows pilots to arbitrarily position and rotate a drone using position-control direct interactions on a see-through mobile AR where the drone position and direction are visualized with a virtual cast shadow (i.e., the drone’s orthogonal projection onto the floor). Pilots can point to the next position or draw the drone’s flight trajectory by manipulating the virtual cast shadow and the direction/height slider bar on the touchscreen. We design and implement a prototype of PinpointFly for indoor and visual line of sight scenarios, which are comprised of real-time and predefined motion-control techniques. We conduct two user studies with simple positioning and inspection tasks. Our results demonstrate that PinpointFly makes the drone positioning and inspection operations faster, more accurate, simpler and fewer workload than a conventional joystick interface with a speed-control method.

Scan tree architecture has been proposed to reduce the test application time of full scan chain by placing multiple scan cells in parallel. Most existing techniques rely on non-compact test pattern sets to construct the scan tree. However, they produce inefficient scan tree when highly compact test sets with few don't cares are used. In this paper, the depth of the scan tree based on approximate compatibility relation for completely specified test data set is analyzed probabilistically by modeling its construction as a vertex coloring problem. The upper bound of edges-per-vertex is computed and demonstrated to be a prime factor that limits the efficiency of scan tree construction based on both compatible and approximately compatible test data between two flip-flops. Inverse compatibility and aggressive approximate compatibility are then proposed to increase the edges-per-vertex for vertex coloring. The Q'-SD connection between two adjacent scan cells is exploited to implement the inverse compatibility with no cost or timing impact. To maintain the fault coverage, the missing faults under the tree scan mode can be detected by switching the same base architecture into the linear scan mode with negligible hardware overhead as shown by the experimental results on ISCAS89, ISCAS99 and LGSynth93 benchmark circuits. On average, the scan tree generated by our method reduces the test time of the full scan chain by 56.65 percent, and that of the scan tree designed by the approximate compatibility method by 39.18 percent under the same compact test sets.

Full scan design is usually time-consuming. Scan tree-based architectures can be applied to reduce test time, but few of them are power-efficient. Many low-power techniques have been proposed for scan chain design, while they are not applicable to scan tree architecture. To achieve a time-efficient and low-power scan design, in this paper, we propose a scheme to reduce the test power consumption of scan tree design by exploiting the Q' ports of scan flip-flops. As the structure of scan tree is not affected, the scheme resembles the time-efficiency of scan tree design. The modification for low power maintains the order of scan cells. It thus avoids the consequent design overhead due to scan reordering. Furthermore, no extra hardware is introduced. Experimental results on ISCAS'89 benchmarks show that 8.38% weighted transitions during test application can be reduced on average.