The conventional sliding-mode control (SMC) technique requires that the perturbation upperbounds are known a priori to achieve a robust control process. This requirement creates some difficulties, at the least causing the controller to be over-conservative. introduced mode sliding perturbation estimation (SMCPE) philosophy removes this condition and replaces it with a continuous perturbation estimation process. It is shown that, for precise state measurements and high-speed control-loop closures, SMCPE manifests much smaller tracking errors than those of SMC. So far nonlinear systems in canonical form have been studied, and in the present paper the domain of application of SMCPE is extended to a more general class. For this extension, an I/O linearisation technique is utilised first, and then the SMCPE steps are followed for an output tracking control. Simulation results prove the strength of the technique for a satellite attitude control problem.