Analysis of Non-Linear Dynamics and Control of a Three-Degree-of-Freedom Parallel Robot Manipulator for Micro-Assembly Applications

Parallel robot manipulators offer high stiffness, low moving mass, and fast dynamic response characteristics that are particularly advantageous for micro-assembly applications requiring sub-millimetre positioning accuracy, such as electronic component placement and biomedical device assembly. This study presents an analysis of the non-linear dynamics and control performance of a three-degree-of-freedom delta-configuration parallel robot manipulator designed for micro-assembly tasks in a Nigerian precision engineering research context. The complete non-linear dynamic model of the manipulator, including rigid body dynamics derived via the Lagrange formulation and flexible link effects for high-speed operation, is developed and implemented in MATLAB-Simulink. Three control architectures, computed torque control, adaptive computed torque control with parameter estimation, and a sliding mode controller with boundary layer smoothing, are derived, implemented, and comparatively evaluated in simulation. The manipulator prototype is fabricated with carbon fibre composite links and precision ball screw actuators, and the three controllers are implemented on a Beckhoff real-time EtherCAT controller. Experimental trajectory tracking accuracy is measured for point-to-point moves of 20 millimetre amplitude at 2 Hz cycle rate. The adaptive computed torque controller achieves the best tracking performance with a maximum position error of 0.08 millimetres, compared to 0.19 millimetres for the non-adaptive computed torque and 0.12 millimetres for the sliding mode controller. The study provides analytical insight into the coupling effects between the three manipulator axes under high-speed operation that are specific to the delta kinematic architecture. Keywords: parallel robot, non-linear dynamics, computed torque control, micro-assembly, delta manipulator