This paper revisits the problem of asymptotic tracking for robot manipulators with actuator constraints and position measurements only. A new dynamic nonlinear filter is first proposed and then a saturated output feedback proportional-derivative (PD) control is constructed. Lyapunov's direct method is employed to show global asymptotic stability (GAS). Explicit conditions on control gains ensuring GAS and avoidance of actuator constraints are obtained. This is accomplished by selecting control gains a priori. Advantage of the proposed approach is that it can assure GAS and satisfy actuator constraints. Numerical simulations are presented to demonstrate the improved performance of the proposed approach.