Nonlinear Control of a Hydraulic Exoskeleton 1-DOF Joint Based on a Hardware-In-The-Loop Simulation

Round 1

Reviewer 1 Report

The presented article contains the results obtained from the theoretical model combining the basic kinematic and hydraulic relationships and the control system of the hydraulic exoskeleton system. Unfortunately, as a result of the authors' decisions on a very wide range of analyzes, significant simplifications were introduced to the models of components. For example, the division of friction forces in the actuator into static and dynamic friction was not taken into account, using a simple model of viscous friction. Moreover, it seems that it was assumed that the dynamic characteristics of the hydraulic control elements (servo valves) are based on the basic dynamic relationships, disregarding the types of frictional forces and hydrodynamic forces. Therefore, as a result of implementing the control model in the control model, the results were obtained that can only be treated as preliminary system analysis. These results are not supported by real tests and probably have a very significant margin of error in relation to reality. The authors also tend to unjustifiably extend the model, e.g. they quote formulas no. 8 and 9 to prove the truth of the obvious formula no. 10. Therefore, it seems that the presented article is a work on a significant level of generality and requires significant supplementation with any real tests.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The authors of the article deal with the control of an exoskeleton with hydraulic drive. The topic of the article is current and the article is a valuable contribution to the topic. The article is well organized with an appropriate scientific style.

I would like to see a well-developed discussion comparing and contrasting solutions/results presented in the work with existing work and then a subsection of it presenting contributions to theory/knowledge/literature and followed by a subsection on Implications for practice. In these paragraphs authors should compare their research approach with previous research, citing references to others' research.

There are missing links in the work that need to be corrected (lines 445; 457; 480; 488).

After considering the comments, I recommend publishing.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thank you for responding to the review and making changes. I leave the decision to publish the article to the editorial office.