Fig. 4

Tracking task performance during multi-DOF IN-type tests. Exoskeleton knee and ankle joint angular positions are reported by means of a stick figure. The green figure represents the target multiple-joint position to be attained. The blue and red stick figures represent the subject’s voluntarily controlled exoskeleton trajectory obtained using low-gain (LG) and high-gain (HG) assistance levels, respectively. The target positions were changed automatically when the user was within ±5 degrees of the target position. Model-based estimates of joint moments are reported about both the knee flexion-extension and ankle plantar-dorsiflexion degrees of freedom (DOFs). Data are reported as averages across all tracking trials with standard deviations (shaded area). They are reported as a function of percent cycle, i.e., where 0 and 100%, respectively, represent the beginning and the end of the tracking trajectory (Target). The results are relative to tests inside of the exoskeleton, i.e., IN-type tests. Data are reported for two representative healthy subjects (Healthy 1–2), one stroke patient (Stroke 2) and one incomplete spinal cord injury (SCI) patient, as shown in Table 2. Recorded electromyograms (EMGs) are relative to muscles including the biceps femoris (BF), rectus femoris (RF), semimembranosus (S), vastus lateralis (VL) and vastus medialis (VM), soleus (So), gastrocnemius medialis (Ga) and tibialis anterior (TA), as presented in Table 1