# Research on Design and Control Method of Flexible Wing Ribs with Chordwise Variable Camber

## TL;DR

This paper introduces a new wing rib design and control method for morphing wings, improving bending performance and control precision.

## Contribution

A novel rigid–flexible coupled wing rib structure and a fuzzy-adjusted PI sliding mode controller for precise morphing wing control.

## Key findings

- The three-rib wing box achieves a 30° deflection with a deformation error of 7.6%.
- Steady-state error for 15° downward bending is 0.19° with an overshoot of 1.8%.
- Stresses remain within the allowable limit of 7075Al-T6 material.

## Abstract

To improve the continuous chordwise bending performance of morphing wings, this study proposes a rigid–flexible coupled wing rib structure and its control strategy. Initially, the optimal rigid–flexible hybrid configuration was optimized via the mean camber line parameterization and genetic algorithm. For the flexible segment, topology optimization was conducted using the load path method, followed by subspace-based shape–size alternating optimization; bionic “longbow” curved beams and ‘S’-shaped substructures were adopted to enhance deformability. Biomimetic pneumatic muscles were used as actuators, and a fuzzy-adjusted PI sliding mode controller was designed to address the issue that traditional PI sliding mode controllers cannot achieve precise control under non-optimal parameters or when there is a significant difference in deformation targets. Experimental results show that when the flexible rib deflects by 15°, the three-rib wing box achieves a 30° deflection, with stresses within the allowable limit of 7075Al-T6 (540 MPa) and a deformation error of only 7.6%. For the 15° downward bending control, the adjustment time is 6.06 s, the steady-state error is 0.19°, and the overshoot is 1.8%. This study verifies the feasibility of the proposed rigid–flexible coupled structure and fuzzy PI-SMC, providing a technical reference for morphing aircraft.