  In this paper, we investigate the consensus problem of second-order
multiagent systems under directed graphs. Simple yet robust consensus
algorithms that advance existing achievements in accounting for velocity and
input constraints, agent uncertainties, and lack of neighboring velocity
measurements are proposed. Furthermore, we show that the proposed method can be
applied to the consensus control of uncertain robotic manipulators with
velocity and control torque constraints. We rigorously prove that the velocity
and control inputs stay within prespecified ranges by tuning design parameters
a priori and that asymptotic consensus can be achieved through Lyapunov
functions and fixed-time stability. Simulations are performed for symmetric and
asymmetric constraints to show the efficiency of the theoretical findings.
