Transmission Comparison for Cooperative Robotic Applications
Round 1
Reviewer 1 Report
This is a fine paper and reflects appreciable technical efforts by the authors to address this important issue. Results were supported by some experimental work, the facts that adds to the paper content value.
My only remark is the fact that the authors did not explicitly highlight overall estimated power consumption of both systems (NB: some info on expected delivered rather than consumed max power were included).
I recommend the the authors shed some light or add a note on the expected power consumption and what drive/battery supply system they propose for usage.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
your work deals with an interesting theme and offers a surprising conclusion, which is why I read it with great interest. Unfortunately, there are some setup problems, or at the very least, the explanation of the method used is unclear.
In detail:
a) in equation (1) is K_tau a constant (as the text says), or not? The values ​​measured experimentally for K_tau (figure 5), are anything but constant and treating K_tau as a constant leads to quite gross errors, such as to question the conclusion of the work;
b) on line 214 you say that you have extrapolated the torque values ​​for 15A, but don't say with which approximant function. Since, again, the curves are not linear, it would be interesting to know how you got the extrapolation and with what uncertainty;
c) if I understand correctly, you have considered the motor torque constant (0.071 Nm / A) valid over the entire operating range and you have deduced the efficiency of the gearbox from the experimental calculation of the isometric torque. This means having strong variations in the efficiency of the reducer as the absorbed current varies regardless of the operating speed. This is an unacceptable deduction from a theoretical point of view. Have you wondered how this is possible? If so, you should include your own considerations;
d) how did you get the data in figure 6? By measuring the current absorbed as the no-load speed varies? Why do the experimental points present, at some speeds, such a great dispersion? Furthermore, the sentence on lines 217-219 is not understood: "While the trend line for the harmonic passive resistance decreases at high speed, this is not what happened in the recorded data. "What does that mean? Are recorded data not the points represented in the figure?
e) the calculation of the compensation current in which operating conditions takes place? Is it an active load case or a passive load case? Since we are talking about passive resistance perceived by the user, I understand that it is an active load case, ie that the patient's muscle moves the system and the reducer opposes resistance due to its internal friction. Well, if that's the case, you can't possibly proceed as you did. In general, all mechanisms have different efficiency values ​​(even very different ones, up to, in some cases, self-braking conditions) in case of active load. You cannot use resisting torque values ​​measured under passive load conditions.
f) you have reported the harmonic drive reducer model but not that of the planetary reducer, why? This makes independent verification of your work very difficult; g) in any case, it must be clearly specified that your comparison is between a specific model of planetary gearbox and a specific model of harmonic drive. It is absolutely not possible to generalize the results to all gearboxes based on these two technologies;
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The current paper proposes two electromechanical actuators that were developed to determine the effect of two candidate transmission
implementations for an exoskeletal joint. The theory was validated using simulations.
Comments to authors:
- Please add more details regarding paper’s novelty, it is not very clear what are the novelties of this paper.
- Please add more details of how the theory from the first sections is applied in the results section.
- The authors can add the steps of implementing the algorithms. The theoretical part can be better detailed. The steps will be in the benefit of the readers, maybe they’ll help the readers to implement the proposed algorithm.
- The state of the art it is very poor regarding representative papers, maybe the author could add the following publications:
o Hybrid Data-Driven Fuzzy Active Disturbance Rejection Control for Tower Crane Systems, European Journal of Control, doi https://doi.org/10.1016/j.ejcon.2020.08.001, pp. 1-11, 2020.
o Event-Triggered Adaptive Fuzzy Control for Stochastic Nonlinear Systems with Unmeasured States and Unknown Backlash-Like Hysteresis, IEEE Transactions on Fuzzy Systems, doi 10.1109/TFUZZ.2020.2973950, pp. 1–19, 2020.
- Please add more details regarding the obtained results.
proposed method. In the proposed manuscript just the advantages are presented.
Author Response
Please see attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Dear Authors,
thanks for your answers, your work is now much clearer and although I would explain some aspects in somewhat different terms, I consider your work worth publishing.
I just ask you to make small corrections.
The correct quote from the paper [38] is: T. D. Tuttle and W. P. Seering, "A nonlinear model of a harmonic drive gear transmission," in IEEE Transactions on Robotics and Automation, vol. 12, no. 3, pp. 368-374, June 1996, doi: 10.1109 / 70.499819.
At line 207 the K_tau symbol should be corrected with the Greek letter.
Author Response
Thank you for your feedback throughout this process. The submitted file has the requested changes.
Reviewer 3 Report
The current paper has been seriously improved. The authors answered to all my concerns with explicit answers and from my point of view the paper deserves to be published in Actuators journal.
Author Response
Thank you for your feedback and guidance throughout this process.
