Fig 1.
The proposed kinetic model across the entire gait cycle.
The blue rod represents the left leg, and the gray rod represents the right leg during walking. The gray circle represent the trunk with the pelvis. The gait cycle is initiated at left heel contact (0%) and is normalized to 100%. The diagram depicts the double support phases and single support phases. The first double support phase (0-12%): the period when both the feet is in contact with the ground (for example, the right leg is the trailing leg); The first single support phase (13-50%): the period when only one foot is on the ground (the right leg is swing, and left foot contact the ground); The second double support phase (51-62%): the period when both the feet is in contact with the ground (the right leg is the dominant leg). The first single support phase (63-100%): The period when only one foot is on the ground (the right leg is supporting, and right foot contact the ground).
Fig 2.
Three-link dynamic model of a single support phase.
Fig 3.
Two-link dynamic model of the double support phase.
The limbs are assumed to be symmetrical.
Table 1.
Empirical parameters in the predictive model of the hip and knee in the sagittal plane.
Fig 4.
Measurement of the hip angle and knee angle in the sagittal plane of one subject.
The horizontal axis of the gait cycle is determined on the basis of the left foot. The orange red dashed line indicates the critical thresholds (t* = 168.662, α = 0.05). Regions of the gait cycle for which SPM {t} exceeded the critical threshold are considered as the predicting model is invalid.
Table 2.
Error evaluation of the joint angle prediction model.
Fig 5.
The GRF across the entire gait cycle.
The dashed line denotes the model-predicted value. The shadow region is composed of 8 walking trials of one subject. The orange red dashed line indicates the critical thresholds (t* = 250.126, α = 0.05). Regions of the gait cycle for which SPM {t} exceeded the critical threshold are considered as the predicting model is invalid.
Table 3.
Error evaluation of 4 testing subjects by the GRF prediction model.
Fig 6.
The joint moment across the entire gait cycle of one subject.
The measurement moment in the figure is obtained from the walking trials of the corresponding subject in the experiment. The orange red dashed line indicates the critical thresholds (t* = 334.678, α = 0.05). Regions of the gait cycle for which SPM {t} exceeded the critical threshold are considered as the predicting model is invalid.
Table 4.
Error evaluation of the joint moment prediction model.
Table 5.
Comparison of methods for estimating lower limb dynamics.