Temporal Analysis Method of Lower Limb Muscle Activation Based on OpenSim

The optimized control of knee exoskeletons based on electromyographic signals requires the explicit definition of specific muscle characteristics as objective functions. However, there are certain differences in leg muscle activation under different conditions. This paper proposes a method for analyzing the temporal activation of lower limb muscles based on OpenSim, studying the activation timing of lower limb muscles during the gait cycle under different conditions. Multiple conditions were set up in experiments, and human kinematic, kinetic data, including electromyographic data were collected. Using the raw kinematic and kinetic data, a human motion model under multiple conditions was constructed, and the accuracy of the model simulation results was verified using electromyographic data. Analysis of the simulation results reveals that during uphill walking, the biceps femoris, gastrocnemius medial and lateral heads, and gluteus maximus are primarily involved, while during downhill walking, the rectus femoris, vastus medialis, and vastus lateralis are primarily involved. In addition, significant involvement of the soleus muscle in all conditions is also noticed. The simulation results preliminarily provide the timing and activation level of muscle activation under different conditions. Based on this characteristic, corresponding muscles can be determined as optimization targets, providing guidance for defining objective functions in exoskeleton optimized control.