Three degrees of freedom rigid-soft coupling biomimetic hip joint driven by dielectric elastomer

Dielectric elastomer (DE) has an attractive combination of high energy density, large strain, and fast response. A growing number of DE actuators are being used as driving materials in rigid-soft coupling joints. For better structural design, the mapping relations from the musculoskeletal system of the human hip joint to the biomimetic hip joint mechanism have been established. Inspired by the human musculoskeletal system, the configuration of the three-degree-of-freedom rigid-soft coupling hip joint based on DE is proposed. The configuration includes six soft-driving limbs and one passive rigid limb. The soft-driving limb driven by the fiber-constrained dielectric elastomer actuator (FCDEA) does not contain passive rigid joints. Based on the Gent material model, the electromechanical coupling model of FCDEA is established. A mapping model is established between the voltage applied to the soft-driving limb of the biomimetic hip joint and the posture of the moving platform in the case of deflection and torsion. A single FCDEA is prepared and its electro-responsive deformation performance is tested through experiments. As a demonstration, a prototype of the biomimetic hip joint is developed. After applying voltage, the deflection angle and the torsion angle of the biomimetic hip joint are tested and the curve of voltage and rotation angle is drawn. The experimental results agree well with the theoretical predictions. This article can provide theoretical references for improving the performance of rigid-soft coupling hip joints.