Fig. 1. Schematic diagram of Risley-prisms-based beam steering system. (a) Description of system parameters; (b) system arrangement

Fig. 2. Control singularity problem at center zone of field of regard (FOR) for real-time target tracking. (a) Schematic diagram for target moving at center zone of FOR; (b) variations of M required by real-time target tracking as a function of θ; (c) variations of maximum M value M_m as a function of Φ

Fig. 3. Schematic diagram of target tracking in discrete time domain

Fig. 4. Required rotation angle of two prisms for tracking target from point A (ΦA=1°, ΘA=0°) to other points at center zone of FOR. (a) Required rotation angle Δϕ1 of prism I when adopting the same set of solutions; (b) required rotation angle Δϕ1 of prism I when switching solutions; (c) required rotation angle Δϕ2 of prism Ⅱ when adopting the same set of solutions; (d) required rotation angle Δϕ2 of prism Ⅱ when switching solutions

Fig. 5. Required values of M¯1 and M¯2 for tracking target from point A (ΦA=1°, ΘA=0°) to other points at center zone of FOR. (a) Required values of M¯1 when adopting the same set of solutions; (b) required values of M¯1 when switching solutions; (c) required values of M¯2 when adopting the same set of solutions; (d) required values of M¯2 when switching solutions; (e) required values of M¯max when adopting the same set of solutions; (f) required values of M¯max when switching solutions

Fig. 6. Required values of M¯max for tracking target from point A (ΘA=0°) to other points at center zone of FOR by applying optimal-solution method. (a) ΦA=1°; (b) ΦA=0.5°; (c) ΦA=0.1°; (d) variations of M¯M as a function of ΦA

Fig. 7. Sources of singularity problem for tracking target at center zone of FOR. (a) Schematic diagram for beam steering at center zone; (b) variations of difference between two sets of solutions as a function of Φ

Fig. 8. Schematic diagram of tracking blind zone for rotational double prisms