A framework for multi-objective optimization of virtual tree pruning based on growth simulation

Highlights

• A framework for multi-objective optimization of virtual tree pruning is presented.

• Tree growth simulation is used to evaluate the long-term effects of pruning.

• The case study uses light intake of pruned trees as pruning objectives.

• NSGA-II builds better non-dominated solution sets than local search heuristic.

Abstract

We present a framework for multi-objective optimization of fruit tree pruning within a simulated environment, where pruning is performed on a virtual tree model, and its effects on tree growth are observed. The proposed framework uses quantitative measures to express the short-term and long-term effects of pruning, for which potentially conflicting optimization objectives can be defined. The short-term objectives are evaluated on the pruned tree model directly, while the values of long-term objectives are estimated by executing a tree growth simulation. We demonstrate the concept by using a bi-objective case, where the estimated light interceptions of the pruned tree in the current and the next season are used to define separate optimization objectives. We compare the performance of the multi-objective simulated annealing and the NSGA-II method in building the sets of non-dominated pruning solutions. The obtained Pareto front approximations correspond to diverse pruning solutions that balance between optimizing either objective to different extents, which indicates a potential for new applications of the multi-objective pruning optimization concept.