Design and Research of Form Controlled Planar Folding Mechanism based on 4D Printing Technology

The use of non-smart materials in structural components and kinematic pairs allows for flexible assembly in practical applications and is promising for aerospace applications. However, this approach can result in a complex structure and excessive kinematic pairs, which limits its potential applications due to the difficulty in controlling and actuating the mechanism. While smart materials have been integrated into certain mechanisms, such integration is generally considered a unique design for specific cases and lacks universality. Therefore, organically combining universal mechanism design with smart materials and 4D printing technology, innovating mechanism types, and systematically exploring the interplay between structural design and morphing control remains an open research area. In this work, a novel form-controlled planar folding mechanism is proposed, which seamlessly integrates the control and actuation system with the structural components and kinematic pairs based on the combination of universal mechanism design with smart materials and 4D printing technology, while achieving self-controlled dimensional ratio adjustment under a predetermined thermal excitation. The design characteristics of the mechanism are analyzed, and the required structural design parameters for the preprogrammed design are derived using a kinematic model. Using smart materials and 4D printing technology, folding programs based on material properties and control programs based on manufacturing parameters are encoded into the form-controlled rod to achieve the preprogrammed design of the mechanism. Finally, two sets of prototype mechanisms are printed to validate the feasibility of the design, the effectiveness of the morphing control programs, and the accuracy of the theoretical analysis. This mechanism not only promotes innovation in mechanism design methods but also shows exceptional promise in satellite calibration devices and spacecraft walking systems.