Robots are now frequently used to complete tasks more quickly, precisely, and reliably than people. Articulated manipulators are highly coupled, nonlinear, timevarying systems that are subject to a number of uncertainties, including changes in the parameters, friction at the joints, and external disturbances. For these reasons, robust trajectory tracking control design for such dynamics have drawn a lot of attention. The dynamic modeling of this robot is created using 3D-CAD(ComputerAided-Design) and all of its geometry can be easily found by exporting the robot's 3D-CAD model to MATLAB Simscape Multibody for simulation and control. For the sake of driving the robot joints, a PMDC(Permanent Magnet Direct Current) motor is used. Sliding mode control (SMC) was initially used, however it caused chattering in the response of the control input. Therefore, to reduce chattering and improve the trajectory tracking, PSO based Super Twisting Sliding Mode Control (PSO-STSMC) is designed. Furthermore, the controller parameters were automatically optimised using particle swarm optimisation (PSO) to obtain the best values and to avoid the tedious trial method of parameter setting using MATLAB/Simulink software. Comparative analysis were made between the proposed controller and to other controllers (i.e, standard STSMC, PSO-SMC, classical SMC). The numerical simulation revealed that the tracking error (RMSE) improvement is around 18:3303%, 16:6644% and 14:2857% due to PSO-STSMC compared to classical STSMC and 79:5027%, 78:041% and 25% compared to PSO-SMC for each joints under the ideal condition, respectively and simulation results have shown the ability of the controller to external disturbance, parameter variation and joint friction rejection capability and it is demonstrated that the proposed approach attenuates the jittering e ects of the control signal and is robust to such uncertainties. Keywords: Chattering; Particle swarm optimization; Robustness testing; Sliding mode control; Super-twisting algorithm; Trajectory tracking.