Quaternion-based Trajectory Optimization of Human Postures for Inducing Target Muscle Activation Patterns

In exercise and rehabilitation, to effectively train the human body, human motion trajectory is essential because it induces muscle activity patterns. In this letter, we develop a novel framework for the trajectory optimization of human postures, including the head, the limbs, and the body to induce patterns of target muscle activities. Our framework has the following features: 1) a data-driven muscle-skeleton model for managing user-specific features; 2) quaternion-based state representation amenable for IMU sensors in human posture measurement; 3) joint optimization of human postures to replicate therapists who adjust not only paralyzed limbs but also patient's other limbs and body postures. We experimentally investigated the effectiveness of our framework with a shoulder joint assistive exoskeleton robot for rehabilitation.