Kinematic-Based Multi-Objective Design Optimization of a Grapevine Pruning Robotic Manipulator

Annual cane pruning of grape vineyards is a time-consuming and labor-intensive job, but no mechanized or automatic way has been developed to do it yet. Robotic pruning can be a perfect alternative to human labor. This article proposes a systematic seven-stage procedure to design a kinematically optimized manipulator, named ‘Prubot’, to manage vineyards’ cane pruning. The manipulator structure was chosen, resulting in a 7R (Revolute) manipulator with a spherical shoulder and wrist. To obtain the design constraints, the manipulator task space was modeled. The robot’s second and third link lengths were determined by optimizing the global translational version of the measure of manipulability and the measure of isotropy of the manipulator arm section. Finally, simulations confirmed the appropriateness of the manipulator workspace. Furthermore, sampling-based path planning simulations were carried out to evaluate the manipulator’s kinematic performance. Results illustrated the impressive kinematic performance of the robot in terms of path planning success rate (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>≅</mo><mn>100</mn><mo>%</mo></mrow></semantics></math></inline-formula>). The simulations also suggest that among the eight single-query sampling-based path planning algorithms used in the simulations, Lazy RRT and KPIECE are the best (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>≤</mo><mn>5</mn><mo> </mo><mi mathvariant="normal">s</mi><mo> </mo><mo>&</mo><mo> </mo><mo>~</mo><mn>100</mn><mo>%</mo></mrow></semantics></math></inline-formula>) and worst <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mfenced><mrow><mo>≥</mo><mn>5</mn><mo> </mo><mi mathvariant="normal">s</mi><mo> </mo><mo>&</mo><mo>≤</mo><mn>25</mn><mo>%</mo></mrow></mfenced></mrow></semantics></math></inline-formula> path planning algorithms for such a robot in terms of computation time and success rate, respectively. The procedure proposed in this paper offers a foundation for the kinematic and task-based design of a cane pruning manipulator. It could be promisingly used for designing similar agricultural manipulators.