This paper investigates the problem of robust mixed control under input saturation constraints for a class of polynomial parameter-varying (PPV) systems subject to convex polytopic uncertainties, external disturbances, and unmeasurable states. By integrating finite-time boundedness with uniform exponential stability and utilizing a homogeneous polynomial Lyapunov function approach, a robust mixed stability criterion is established for the closed-loop system without input constraints, guaranteeing both satisfactory transient convergence and robust steady-state performance within a finite time interval. Subsequently,using the sum of squares (SOS) technique, the obtained criterion is reformulated into an efficiently solvable convex optimization problem. Based on these results, to address the local control problem subject to input saturation, the solvability conditions are derived via the S-procedure to ensure that the closed-loop system respects the input constraints and maintains robust mixed stability within a specified compact set of initial conditions. Finally, numerical simulations and comparative analyses are provided to demonstrate the effectiveness and superiority of the proposed approach.