In functional electrical stimulation, the time delay between an input voltage and the corresponding muscle force is a significant issue. This study revealed that the joint angle/voltage relationship can be modeled as a fourth-order system. This enables the inclusion of a time delay in the high-order phase delay of the force/voltage relationship, which may lead to delay recovery using a suitable controller. Accordingly, a full state feedback controller is proposed in this study, to recover the phase delays. Jerk measurement is mandatory for full state feedback controllers owing to the joint the fourth-order joint angle/voltage relationship. This issue can be solved by the recent development of high-resolution encoders. Finally, the validity of the proposed method was verified experimentally.
Bilateral control, a remote-control technique, is used to work at a distance. However, many existing bilateral control systems have two common problems: 1) it is difficult to create a system like a human hand, that has multiple degrees of freedom and 2) if the mechanism becomes too complicated, operators feel restrained and experience discomfort. Because, for these reasons, the bilateral control of fingers has not been accomplished to date, we aimed to overcome this by applying functional electrical stimulation~(FES). In our experiments, through an adhesive electrode pad, electrical stimulation was delivered to the muscles that flex and expand the metacarpophalangeal joints of the thumb and middle finger. Position-symmetrical bilateral control was implemented so that the deviation of the master's and slave's positions relative to each other was zero degrees. A sliding mode controller was used as a position controller. We found it possible to control multiple degrees of freedom; however, we found areas where the number of tracking errors was large. We speculated that the middle finger did not bend, because the arm rotates as the thumb was abduction, therefore the position of the motor point of the middle finger deviates from the position of the pad.
Background The Credibility Expectancy Questionnaire (CEQ) includes three items each on the credibility and expectancy subscales. Credibility indicates to what extent the treatment is reasonable, and expectancy indicates to what extent the treatment is expected to be effective. The CEQ has been assumed to have a two-factor structure: credibility and expectancy, among patients receiving psychotherapy. However, its internal structure has been unknown to patients receiving physical therapy for musculoskeletal disorders. This study aimed to explore the internal structure of the CEQ and preliminary investigate the construct validity of the CEQ among patients receiving physical therapy for musculoskeletal disorders. Methodology A multi-center prospective cohort study was conducted. Data from 100 patients receiving outpatient physical therapy for musculoskeletal disorders was collected using an anonymous paper-based survey. The initial survey was conducted immediately before the initial physical therapy session, and the second survey was conducted after the third to seventh physical therapy sessions. The Patient Specific Functional Scale 2.0 (PSFS 2.0) was collected in both surveys, and the CEQ and an 11-point global rating of change scale (GRCS) were collected in the second survey. Exploratory factor analysis was conducted for the CEQ, and internal consistency was assessed for each subscale and an identified factor structure. Convergent validity in construct validity was also assessed with the hypothesis that Pearson's r values of each CEQ factor score to the PSFS 2.0 change scores and GRCS would range from 0.4 to 0.6. Results An exploratory factor analysis revealed a one-factor structure, where the percentage of the variance for the extraction sums of squared loadings was 62.8%. Cronbach's alpha was 0.89 for all items, 0.91 for the credibility subscale, and 0.75 for the expectancy subscale. Hypothesized correlations to the PSFS 2.0 change score and GRCS were detected with the CEQ total score (r = 0.48 for the PSFS 2.0 change score and r = 0.59 for the GRCS) and each subscale score (credibility subscale, r = 0.48 for the PSFS 2.0 change score and r = 0.49 for the GRCS; and expectancy subscale, r = 0.43 for the PSFS 2.0 change score and r = 0.62 for the GRCS). Conclusion A single-factor internal structure of the CEQ was detected among patients receiving physical therapy for musculoskeletal disorders. Additionally, preliminary evidence of construct validity was detected with convergent validity between the CEQ and functional and perceived improvement.
