Nonlinear feedback control algorithms for manipulators utilise the complete (coupled and nonlinear) dynamic model to decouple the robot joints. In this framework, we present a comparative evaluation of the computed-torque and direct-design control algorithms, and outline the practical problems introduced by modelling inaccuracies, unmodelled dynamics and parameter errors. We then formulate the α-computed-torque nonlinear feedback control algorithm which is robust in the presence of the aforementioned error sources. Numerical experiments with cylindrical robots confirm the robustness and applicability of our α-computed-torque algorithm.