## 6 Conclusions  
This paper focuses on the investigation of the accurate control of force/displacement caused by friction loss and elastic deformation in the process of flexible exoskeleton Bowden cable-fabric force transfer. We conducted a kinematic analysis of human lower limbs, force transfer analysis, and transmission displacement analysis of the Bowden cable-fabric and presented a friction model of the Bowden cable-fabric system. Based on the fric  
Figure 16: Experimental output of impedance control under different peak values. **(a)** The actual output force when the peak value is 50 N; **(b)** the force error when the peak value is 50 N; **(c)** the actual output force when the peak value is 60 N; **(d)** the force error when the peak value is 60 N.  
tion/displacement compensation method, a simulation and experiment based on the Bowden cable-fabric force transfer control were conducted to evaluate the performance under different settings. Our conclusions are as follows:  
1. To account for the friction loss in the force transmission of Bowden cable-fabric, a tension model under quasi-static conditions was derived, which can be used as feedforward force compensation in the control system;
2. The stiffness model of the transmission system and the inherent displacement model of the leg swing were introduced to express the displacement hysteresis in the process of Bowden cable-fabric transmission, and impedance control was added to improve the flexibility of human-machine interaction;
3. The force/displacement compensation was introduced into the system control model, and the output force with impedance control was compared to the force without impedance control. In addition, an in vitro Bowden cable-fabric force transfer experimental platform was built to evaluate the effectiveness of the force/displacement compensation and impedance control presented in this paper. The experimental results show that the relative root-mean-square errors of friction/displacement compensation for Bowden cable-fabric force transfer control are 2.53%, 2.16%, and 2.07% when the peak values are 40 N, 50 N, and 60 N, respectively. These results suggest good effectiveness of the force/displacement compensation and impedance control methods we proposed in this paper.  
Conceptualization, D.W. and X.L.; methodology, D.W.; software, G.M. and D.W.; validation, X.L., G.M. and D.W.; formal analysis, X.L.; investigation, G.M. and D.W.; resources, X.L.; data curation, G.M. and D.W.; writing--original draft preparation, G.M. and X.L.; writing--review and editing, X.L.; supervision, X.L.; funding acquisition, X.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Natural Science Foundation of China under Grant 62103007, Beijing Natural Science Foundation under Grant L202020, and the Launching Scientific Research Funds of North China University of Technology under Grant 110051360023 XN224-32.  
Ethical review and approval were waived for this study, due to no enforced nor uncomfortable restriction to the human wearer during the study period.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The data presented in this research are available from the corresponding author on reasonable request.  
The authors declare no conflict of interest.