Development and evaluation of a robotic mechanism for automated palm crop harvesting

• A dynamic model of hybrid robots has been developed for agricultural applications. • The kinetic equations were derived using the Gibbs-Appell formulation. • Dynamic couplings between the parallel and serial manipulators were analyzed. • A complex hybrid robotic system with 15 degrees of freedom was simulated and fabricated. Date palm harvesting presents persistent challenges due to the hazardous nature of manual climbing and the technical limitations of current mechanized systems. This study introduces a novel hybrid robotic harvesting system that integrates a 4RRR parallel manipulator, a serial robotic arm, and a custom-designed end-effector for precision fruit collection. The research pursues three primary objectives: (1) optimizing the kinematic architecture for improved accuracy and expanded workspace, (2) formulating dynamic models for precise torque computation, and (3) experimentally validating system performance under realistic field conditions. Kinematic analysis was conducted using Denavit–Hartenberg (D–H) conventions, while dynamic modeling employed the Gibbs–Appell formulation for its computational efficiency in constrained multi-body systems. A fully functional prototype was developed and tested, with experimental data recorded for joint positions, velocities, and torques. Performance was evaluated across multiple circular trajectories (100 mm, 150 mm, and 200 mm radius) at varying heights (200 mm, 250 mm, and 300 mm), with three trials per configuration. The system achieved an average positioning error of 8 mm (maximum 11 mm) and a mean harvesting cycle time of 19.8 ± 1.1 s per fruit. Dynamic model validation showed less than 5% deviation between computed and measured joint torques. The hybrid design demonstrated superior precision and payload adaptability compared to conventional serial manipulators, effectively addressing the operational and safety constraints of date palm harvesting. These results establish a validated theoretical and practical foundation for automated orchard harvesting, with direct applicability to date palms and potential adaptability to other tree crops.