Figure 6 is a schematic illustration of the operational principle of a triboelectric sensor according to the embodiments of Figure 4; Figure 7 illustrates output signals from an embodiment of a triboelectric sensor; Figure 8 schematically illustrates the use of an embodiment of a triboelectric sensor for 3D control, and the output signals generated during the use; Figure 9 shows the block architecture of another embodiment of a triboelectric control system; Figure 10 illustrates use of the triboelectric control system for 3D motion control of a drone; Figure 11 shows a further embodiment of a triboelectric control system; Figure 12 shows signals generated by a sensor of the triboelectric control system of Figure 11; Figure 13 shows an embodiment of a triboelectric sensor and signals generated thereby; Figure 14 shows another embodiment of a triboelectric sensor and signals generated thereby; Figure 15 shows a yet further embodiment of a triboelectric sensor and signals generated thereby; Figure 16 shows a yet further embodiment of a triboelectric sensor and signals generated thereby; Figure 17 shows test results from the triboelectric sensor of Figure 1(b);