This　paper　proposes　a　predefined-time　null-space　behavioral　control　algorithm　based　on　a　time-base　generator　(PTNSBC-TBG)　for　multi-quadrotor　unmanned　aerial　vehicle　(UAV)　systems,　enabling　rigid　formation　control　with　collision　and　obstacle　avoidance　within　a　predefined　time.　First,　the　UAV　kinematic　model　is　incorporated　into　the　task　design　of　null-space　behavioral　control　(NSBC)　to　ensure　that　task　instructions　adhere　strictly　to　the　UAV＇s　motion　constraints,　overcoming　the　limitations　of　the　classical　NSBC　method,　which　relies　on　a　single　integrator　model.　Second,　a　predefined-time　null-space　behavioral　control　algorithm　is　designed　to　drive　UAVs　to　form　a　rigid　formation　within　a　specified　time　in　advance.　The　issue　of　excessive　initial　control　input　is　addressed　by　utilizing　a　time-base　generator　(TBG).　Additionally,　a　nonlinear　adaptive　sliding　mode　control　law　based　on　the　TBG　is　designed　to　ensure　the　predefined-time　convergence　of　the　UAVs＇　velocity　command　tracking　error.　Finally　Numerical　simulations　and　experiment　indicate　that　the　proposed　PTNSBC-TBG　can　form　a　rigid　formation　within　a　predefined　time.　Compared　to　the　algorithm　without　TBG,　the　initial　control　input　is　significantly　reduced,　by　at　least　60%.　　©　2026　World　Scientific　Publishing　Company.