In this article we are concerned with the implementation of a dither signal for a closed-loop DC motor system. Experimental studies show that the system contains two nonlinearities that are saturated with dead zone and backlash. Parameter estimation techniques are used to identify the unknown system parameters with special care due to the existence of system nonlinearities. An analytical method is then presented to deal with the closedloop DC motor system with two nonlinearities in the loop. Self-excited oscillations are found to exist in the system. A good correlation between the theoretical and experimental results indicates the success of the system identification and modelling process. Also the ability of dither to quench the limit cycle is demonstrated from these results.