An Adaptive Fast Terminal Sliding Mode Controller of Exercise-Assisted Robotic Arm for Elbow Joint Rehabilitation Featuring Pneumatic Artificial Muscle Actuator

Round 1

Reviewer 1 Report

The paper presents a rehabilitation system of the elbow joint actuated by a pneumatic muscle.

Overall, the novelty of this work is quite limited. The significance of this work is not well described in the paper. The design and control of the rehabilitation system are the main objectives of the paper. However, the innovation of the design is not significant. It is not clear what the novelty of the proposed control diagram is.

The constructive solution presented in the paper is a fairly simple one, its innovative character being questionable. The general drafting of the paper is unsatisfactory.

The authors may consider the following comments for revising the paper.

• An thorough revision of the English language used in the paper is required. The current wording is nearly unintelligible.
• Row 79-81 need rephrasing: “Section 2 presents the structure and dynamic model of the robotic arm. Section 3 introduces…..”.
• Row 91: replace “Festo Cooperation” (incorrect) with “Festo Corporation” or “Festo AG & Co”.
• The reference source should be specified for equations (1), …, (4).
• Pay attention to equation (18) end the subsequent notations: λ has indices between 2 and 4 or between 1 and 3?
• The notations following equation (26) are not clear, unknown characters are used. The same for equations (28), (29), (30).

Author Response

Dear Reviewer

First of all, we would like to thank very for comments from reviewers concerning our manuscript entitled “An adaptive fast terminal sliding mode controller of exercise-assisted robotic arm for elbow joint rehabilitation featuring pneumatic artificial muscle actuator”. We think that all these comments are really valuable and helpful for revising and improving our paper. We have studied carefully these comments and have made correction which we hope to meet with approval. In revised version, all changes or corrections are marked with red highlight tool. Additionally, all the comments from the reviewers have been responded point by point. Please see the attachment file. 

Finally, we appreciate for valuable recommendations and comments from reviewer

Thanh Danh Le

On behalf of all authors

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors demonstrate a control scheme that can control pnematic actuators (in a bending arm configuaration) fairly acuartely. I believe the work is intresting. However, the following comments should be addressed before I can reassess its suitability for publication in the journal of Actuators.

“In addition, the pneumatic artificial muscle actuator offers currently promising application in robot-assisted rehabilitation.”

One of PAM actuators’ fairly recently proposed application is in respiratory management (10.1063/1.5140760). I recommend the authors include this very important application as well.

“Although PAM actuator offers significant merits such as compliant behavior, soft and flexible structure, high power to weight ratio, lightweight, etc. it exists nonlinear dynamics and hysteresis characteristics [16-17].”

PAM actuators are indeed among the most promising actuators for industrial applications and devices where long cycle-life performance is needed. However, they suffer from two significant drawbacks, nonlinear dynamics and hysteresis (on the control side) and reliance on compressor valves, pressurized gas tanks, and compressors (on the physical structure side). The latter is addressed to some extent by using phase transition liquids such as 10.1126/scirobotics.aaz4239 and 10.1038/s41467-017-00685-3. I recommend the authors briefly discuss this limitation and the proposed solutions for it as well.

There is an odd symbol on the equations in lines 213, 219, 222, and 224. Please fix it.

The angular position steady-state tracking error looks like to be less than 5 degrees. How does this error would compare to other control schemes? It would be extremely helpful if the authors can highlight the advantages of their control scheme in the text.

Author Response

Dear Reviewer

First of all, we would like to thank very for comments from reviewers concerning our manuscript entitled “An adaptive fast terminal sliding mode controller of exercise-assisted robotic arm for elbow joint rehabilitation featuring pneumatic artificial muscle actuator”. We think that all these comments are really valuable and helpful for revising and improving our paper. We have studied carefully these comments and have made correction which we hope to meet with approval. In revised version, all changes or corrections are marked with red highlight tool. Additionally, all the comments from the reviewers have been responded point by point. Please see the attachment file. 

Finally, we appreciate for valuable recommendations and comments from reviewer

Thanh Danh Le

On behalf of all authors

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Almost all of my comments were taken into consideration.

 

Reviewer 2 Report

Good work.