Trajectory control of a 3-dof robotic arm using proportional derivative computed torque control (PDCTC) / Nurul Aqilah Hermanud

Faculty of Electrical & Electronics Engineering Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang - 2026

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This study presents the modelling, simulation, and performance evaluation of a control strategy for a decoupled robotic manipulator mounted on a Small Unmanned Ground Vehicle (SUGV). Mobile manipulators are widely used in applications such as inspection, search and rescue, and hazardous environment operations. In conventional systems, the manipulator and the mobile platform are typically controlled as a coupled system, where the dynamics of the base and the arm are integrated. Although this approach reflects real operational conditions, it increases the complexity of the control design and makes it difficult to analyse the motion behaviour of the manipulator independently. To address this limitation, the present study adopts a decoupled modelling approach in which the robotic arm is treated as an independent subsystem. This allows the development of a control strategy that focuses specifically on the dynamic characteristics and trajectory tracking performance of the manipulator without interference from mobile base motion. A three-degree-of-freedom (DOF) articulated robotic arm was modelled using the Matrix Laboratory (MATLAB) /Simulink environment. The physical parameters of the system were obtained from Computer Aided Design (CAD) modelling and incorporated into the dynamic formulation. A Proportional Derivative Computed Torque Controller (PDCTC) was implemented as a model-based algorithm. The PDCTC combines model-based feedforward torque compensation with proportional-derivative feedback to improve tracking accuracy and system stability. A trapezoidal velocity profile was used as the reference trajectory to represent typical robotic motion consisting of acceleration, constant velocity, and deceleration phases. The performance of the proposed controller was evaluated based on several criteria, including joint-space tracking accuracy, motion smoothness, torque behaviour, and overall control stability. The results were also compared with conventional Proportional Derivative (PD) and Proportional Integral-Derivative (PID) controllers to assess the relative effectiveness of the PDCTC approach. Simulation outcomes indicate that the PDCTC provides improved trajectory tracking performance, reduced steady-state error, and smoother joint motion. The controller also demonstrates stable torque characteristics and efficient control effort within acceptable operating limits, indicating reliable dynamic behaviour of the system. This study was conducted entirely through MATLAB/Simulink simulation without physical hardware implementation, and the system was analysed under ideal operating conditions. Although experimental validation was not included, the findings confirm the capability of the PDCTC strategy to enhance the performance of a decoupled robotic manipulator. The proposed approach provides a useful reference for the design of high-precision control systems and establishes a foundation for future work involving real-time implementation and integration with mobile robotic platforms.