Multi-Objective Evolutionary Algorithm with Soft Constraints

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Solution Overview

Problem

Multi-objective Evolutionary Algorithms (MOEAs) face difficulties in large-scale value-based non-linear models with numerous decision variables and constraints, leading to computationally intensive feasibility checks and challenging convergence to optimized solutions due to vast infeasible search spaces.

Innovation Solution

The implementation of a multi-objective evolutionary algorithm system that employs soft constraints to differentiate between feasible, soft infeasible, and hard infeasible solutions, allowing for the persistence of soft infeasible solutions to navigate through infeasible regions and efficiently reach pareto-optimized solutions by prioritizing feasible solutions and allowing soft infeasible solutions to propagate for a limited number of generations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional MOEA is used to evaluate constraint feasibility, then solution feasibility can be determined, but computational bandwidth consumption is excessively high

Engineering Contradiction:
Improveconstraint feasibility determinationVSAvoidcomputational bandwidth
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent segments constraints into two categories: hard constraints and soft constraints. Hard constraints are evaluated with strict feasibility checks, while soft constraints allow for gradual penalty applications. This segmentation reduces computational overhead by avoiding exhaustive evaluation of all constraints for every candidate solution, thereby resolving the contradiction between reliable feasibility determination and computational bandwidth consumption.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces a penalty parameter that can be dynamically adjusted during the evolutionary process. Instead of binary feasible/infeasible classification, the system uses continuous penalty values that change based on the degree of constraint violation. This parameter change approach allows for more efficient computational evaluation while maintaining reliability in identifying viable solutions.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If strict feasibility checks are performed for all constraints, then solution validity is ensured, but convergence to optimized solutions is significantly delayed

Engineering Contradiction:
Improvesolution validityVSAvoidconvergence time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

By dividing constraints into hard and soft categories, the patent applies strict validity checks only to hard constraints while using softer evaluation for soft constraints. This selective validation ensures solution validity where critical while reducing time-consuming checks for non-critical constraints, thereby improving convergence speed without sacrificing essential solution validity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies partial feasibility checking by not evaluating all constraints with the same strictness level. Soft constraints are evaluated with partial enforcement, allowing the algorithm to make progress toward optimized solutions without waiting for complete validation of all constraints, thus reducing convergence time while maintaining necessary solution validity.

Inventive Principle:
Principle #16Partial or excessive action

3Adaptability or versatility

If the search space includes vast infeasible regions, then comprehensive solution exploration is possible, but navigation to feasible optimized solutions becomes extremely difficult

Engineering Contradiction:
Improvesolution space explorationVSAvoidconvergence difficulty
Core Design Contradiction:
Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent introduces penalty functions as intermediaries between the search space and feasibility evaluation. These penalty functions guide the evolutionary algorithm through infeasible regions by providing gradient information that gradually steers solutions toward feasible areas. This intermediary mechanism makes navigation through vast infeasible spaces more manageable while maintaining comprehensive exploration capability.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful effect of infeasible solutions into a beneficial guidance mechanism. Instead of discarding infeasible solutions outright, the system uses their penalty values to guide the search direction. Infeasible regions thus become informative rather than obstructive, helping the algorithm navigate toward feasible optimized solutions more efficiently.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS10387779B2Systems and methods for multi-objective evolutionary algorithms with soft constraints
Publication Date: 2019.08.20 AEROSPACE CORP
  • US10387779B2 patent drawing
  • US10387779B2 patent drawing
  • US10387779B2 patent drawing

AI summary

Systems and methods are provided to engage in multi-objective optimization where there may be one or more constraints. At least one of the constraints may be soft constraints, such that if a potential solution to the multi-objective optimization problem violates only soft constraint(s), then that potential solution may be allowed to persist in a population of potential solutions that may be used to propagate child potential solutions. Potential solutions that violate soft constraints may be tested for non-domination sorting against other potential solutions that violate soft constraints and based at least in part on values associated with the soft constraint violations.