This study proposes a chattering-free non-linear sliding-mode controller for interior permanent magnet synchronous motor drive systems. First, the input-output feedback linearisation technique is used to derive a linearisation model. Next, the upper bounds of the modelling uncertainties are considered, and then a new non-linear sliding-mode control algorithm is proposed to obtain a chattering-free controller. Finally, the stability of the proposed controller is derived based on Lyapunov theory and Barbalat's lemma. A digital signal processor, TMS320LF2407, is used to realise the proposed control system. The experimental results show that the proposed system can effectively reduce the chattering phenomenon and achieve satisfactory performance, including fast transient responses, good load disturbance rejection responses and good tracking responses.