Design, Dynamics Analysis, and Real-Time Stiffness Control of a Variable Stiffness Joint
Round 1
Reviewer 1 Report
The paper presents a nice idea and a model which in itxself is correc t but misses to address some importzantz questions:
- when the stiffness is adjusted under high load the crank drive needs to generate the potential energy difference due to the different elastic deformation. That should be discussed in the paper
- Friction in the joints, particularly in the slider joint may play an important role for the actuator torque requirement and for the system behaviour
- The embodiment design according to Fig. 1 can be improved. Spring bar, guidance of sliding clamps and crank mechanism should be in one plane to avoid a complex deformation and unnecssary mechanical loads to the sliding clamp and the joints of the slider.
- The optimal choice of the system parameters, in particular of the main dimensions, L1, L2, L3, should be addressed, of course, in combination with statung the design optimzation criteria.
- The crank mechanism is an option. But why not adjusting the length l by a spindle which moves the slider joint in a linear guidance? Such a design reduces required space, gear ratio of the gear, and number of joints.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Interesting manuscript with detailed and useful modelling of this mechanism presented. A weakness is that no practical results are presented.
The authors present the modelling in great detail but the control information is lacking. Specifically:
- How did you choose the PID gains?
- What type of transient response were you aiming for?
- Did you consider any other methods other than PID control?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Dear authors,
I have reviewed your paper "Design, dynamic analysis and real-time stiffness control of a variable stiffness joint" and it is very interesting work. I can recommend it for publication after taking into account the following remarks:
Your introduction is well written but after reviewing the literature and a little bit of methodology, we wonder about the specificity of each publication and what AwAS means for example. Do you think a tab can be a good way to improve the preparation of the different methods and the way your work is positioned?
In the introduction, you write "according to the needs". In my opinion, the need is different for a dedicated application: industrial robot for machining and service robot for collaborative activities between humans and robots: can you readjust your specifications and the positioning of your work?
Finally but this aspect is probably related to the reviewed publication, I don't see any work on the quality of the identification and the predictability of the mechanism in terms of stiffness response. Furthermore, L281-L283, you talk about "accidental collision", does your mechanism offer a particularity on this subject?
To conclude the introduction, some objectives concerning the product specification could be provided.
The next section is dedicated to the structural model and a significant effort should be made to explain the design: different positions of the sliding clamp can be presented, the shape of the spring bar should be visible (it is a cylinder), the stiffness adjustment motor should be detailed, the spring bar bending should be detailed: this will help the reader to understand the system and the modeling you are doing. I wonder if providing a section explaining the different steps of the modeling with figures 5 and 10 right after the introduction could help us to better understand your approach.
Figure 2: Pivot points are not clear = > Improving figures 2 will help us
Can you delete "of MIT"(l31), modify According => according (l42), modify diskrete=>discrete(l44), delete MIT's (l51).
L120-121: external force: unclear = > Improving figures 2 will help us
L250-L256: you have spaces to delete
L276: is same => is the same
References: Numbers should be in square brackets; please use the correct format for all references.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Please find attached the report
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
This paper presents a desiogn concept and its analysis by a mathematical simulation. The reviewer does not think that this is an adequte embodiment of the principle design for the intended purpose. He does not repeat his basic criticism from the first round.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Dear authors,
Thank you very much for the change in your work. Could you take a look at :
1) "human-computer interaction": Why don't we talk about Human robot interaction which seems to fit better on your paper
2) Figure: Why is there no correspondence between the top and bottom image?
3) Please recheck the bibliography, you have nothing, p. and pp. for the number of pages for example
I recommand it for publication in MDPI
Author Response
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