Schwung and Lunze Table 3. Parameters of the Method Description Maximum speed vmax Event thresholdeG Event thresholded Safety distance s Maximum separations Rotor limitations n; n Angle limitations f; f; #; # Value 2 m s 1:1m 0:45m 0:4m 9m 0; 398 60 establishment of coordinate systems can be found in [30]. The UAVs are able to measure their local positions with respect to this coordinate system. In all cases the quadrotors move in a constant height of 3m. The stand-on object has the start position pSð0Þ¼ ð053ÞT and moves on the red trajectory in Figure 8, which is initially sent to the give-way object. It reaches its end point pSð16Þ¼ð16 6 3 ÞT at time t ¼ 16 s. The give-way object starts from pGð0Þ¼ ð013ÞT and follows the blue trajectory to its destination pGð16Þ¼ ð 16 1 3 ÞT. As the quadrotors are moving quite close to one another the time delays are nearly constant and given by ~tmaxðdð~tiÞÞ ¼ 227ms. CASE 1: NO CONSIDERATION OF PACKET LOSSES IN THE CONTROL METHOD Figure 8 shows the trajectories of the quadrotors in the xy-plane for the first case. The gray beams state the communication time instants tc;k, while the black beams indicate an event time instant tk. The light gray area corresponds to the distances for an event generation resulting from the event-based method for an ideal network. The dark gray area extends the distanceed to consider the time delays. Both areas together give the condition in (11). It can be seen that a consideration of the delay reduces the allowed movement space of the stand-on object. As a result, events are generated more often. In Case 1, in the control method time delays are considered but not the occurrence of packet losses. Hence, the event eG2 will be not triggered if a packet gets lost. The stand-on object changes its trajectory from the dashed line to the solid line directly after the communication time instant at t ¼ 4:1s.At t ¼ 5s and at t ¼ 5:4s two consecutive packets get lost. As the event eG2 is not triggered the give-way object continues following its initial trajectory while the stand-on object gets close. First, at t ¼ 5:9s the next information is received by the give-way object. The AUGUST 2022 Figure 8. Event generation of the give-way object for case 1. CASE 2: GUARANTEE OF COLLISION AVOIDANCE WHEN PACKET LOSSES ARE CONSIDERED IN THE CONTROL METHOD The difference to the first case is that now the occurrence of packet losses is considered in the method. The trajectories of the quadrotors are shown in Figure 9 in the xy-plane. The stand-on object changes its trajectory again at t ¼ 4:1s from the dashed line to the solid line. Two event eG1 is directly generated and the give-way object evades the stand-on object. This replanning manoeuvre happens too late and the stand-on object violates requirement (1) as illustrated by the flash in Figure 8. Hence, the collision cannot be avoided if packet losses occur and they are not taken into account in the control method. Figure 9. Event generation of the give-way object for case 2. IEEE A&E SYSTEMS MAGAZINE 31