Axial-Pressure-Adjustable Macro-Fiber Composite Bimorph Actuator Based on Twisted and Coiled Polymer Actuator

Compared with the electric servoactuator, the macrofiber composite precompressed bimorph actuator (MFC-PBA) can be embedded into the airfoil to drive the deformation, thus saving the layout space and ensuring aerodynamic performance. However, the axial pressures of existing PBAs cannot be adjusted, which prevents MFC bimorph from achieving higher actuating performance under external load. Additionally, long-term high axial pressure causes permanent deformation and fracture of bimorph structure. Thus, an actuator using a twisted and coiled polymer actuator (TCPA) to regulate the axial pressure of MFC-PBA is proposed in this article, which can be referred to as the TM-PBA. First, a thermally driven tension gray-box model is established to obtain the tensile force of the TCPA under fixed boundary conditions at both ends. The thermally driven tension model is then combined with a finite-element model of the MFC bimorph to establish a complete mechanical model of the TM-PBA. Subsequently, the output tensile force of the TCPA and the actuation performance, frequency response, and hysteresis behavior of the TM-PBA were tested. The results show that the thermally driven tension gray-box model of the TCPA and the complete mechanical model of the TM-PBA can accurately predict the actuation capability of the TCPA and the TM-PBA; the output tensile force of the TCPA increased with increasing temperature and pre-elongation; and the actuation performance of the TM-PBA is 130% higher than that of the MFC-PBA. The control bandwidth of the TM-PBA is more than 10 Hz. Additionally, the TM-PBA hysteresis is related to load and driving frequency. Finally, the TM-PBA was applied to drive a rudder and its actuating capability was verified to be superior to MFC-PBA, but lower than that of the micro servoactuator. In future, the actuation capability can be increased by parallel multilayer TM-PBAs.