A Variable Clutch Mechanism for Adjustable Stiffness Actuators Based on Bending and Torsion of Prismatic Beams
Round 1
Reviewer 1 Report
The authors present a clutch mechanisms based on the beams responding under bending and torsion.
- - The authors mentioned that this is an enhanced version of a previous work, but they do not provide enough information of the previous version. Can the authors provide a diagram or figure showing this previous version?
- - A more universal diagram is needed to represent the boundary conditions at which the FE models were tested. Figure 4a only works for those ANSYS-experienced users.
- - Which were the material properties used for FE?
- - As the performance of the clutch is based on beam mechanics response, the length is not the only parameter that can affect their resulting properties. Hence, a study in which the cross-section is varied might also be useful, no need for experimental testing, FEA and analytical suffices for this.
- - Quantify the maximum errors obtained between experiments, FE and analytical
Author Response
Response to Reviewer 1’s Comments
Point 1: The authors mentioned that this is an enhanced version of a previous work, but they do not provide enough information of the previous version. Can the authors provide a diagram or figure showing this previous version?
Response 1. A figure showing the previous version has been added to the article, the figure descriptions and text have been reorganized by this add-on. Please see pages 3 and 4.
Point 2: A more universal diagram is needed to represent the boundary conditions at which the FE models were tested. Figure 4a only works for those ANSYS-experienced users.
Response 2. Figure 4a has been revised to show more clearly the boundary conditions of the analysis, as suggested by the Reviewer. Please see page 7.
Point 3: Which were the material properties used for FE?
Response 3: The text below was added in the section “2.2. Numerical Analysis”
“The gears materials used in the analyses were assumed to be structural steel which has a modulus of elasticity 200 GPa, and Poisson's ratio is 0.30. The beam materials are assumed to be spring steel which has a modulus of elasticity 205 Gpa, and Poisson’s ratio is 0.30.” Please see page 6.
Point 4: As the performance of the clutch is based on beam mechanics response, the length is not the only parameter that can affect their resulting properties. Hence, a study in which the cross-section is varied might also be useful, no need for experimental testing, FEA and analytical suffices for this.
Response 4. We agree with the referee's views on this matter. In the design, cross-section, section moment of inertia, and modulus of elasticity also affect the stiffness of the elastic clutch. Clutch length (beam length) is the easiest parameter to actively control among these parameters. For this reason, beam length was chosen as the control variable in the stiffness adjustment design, and beam length was emphasized in the analyses. If the design is modified, the radial position of the beams can also be actively controlled and used for stiffness adjustment. To guide future studies, the effect of the radial position of the beams is also shown for three different positions in the study. Different beam sections were not tested in the study, as the beam section is difficult to control actively. An explanation of this preference has been added to the article. Please see page 10.
Point 5: Quantify the maximum errors obtained between experiments, FE, and analytical
Response 5: Figure 8 and related text were added to the results section to highlight the maximum error. Please see pages 7 and 8.
Reviewer 2 Report
1. The equations (1) and (2) denoting the relationship between torsion moment and torsion angle should be more clearly described and cited in the manuscript text.
2. Is the active clutch length L shown in Figure 1d? (in the manuscript text (lines 156, 157) it is written Figure 1c. Please check and correct.
3. The lines 223-226 describe the boundary conditions. Please explain more clearly why the output gear boundary condition has been set to the 1 Nm torque value.
Author Response
Response to Reviewer 2’s Comments
- The equations (1) and (2) denoting the relationship between torsion moment and torsion angle should be more clearly described and cited in the manuscript text.
Response 1: The text below has been added to the text. “The relationship between the torsion moment and the torsion angle can be derived from the theory of elasticity. As long as the beam remains elastic under the exerted moment, the linear relationship will be seen between the torsion moment and the torsion angle, as shown in Eq 1. The slope of the torsion moment-torsion angle curve will indicate the torsional stiffness (Eq 2)[22].” Please see page 4.
- Is the active clutch length L shown in Figure 1d? (in the manuscript text (lines 156, 157) it is written Figure 1c. Please check and correct.
Response 2: Corrected in the text. Please see page 4.
- The lines 223-226 describe the boundary conditions. Please explain more clearly why the output gear boundary condition has been set to the 1 Nm torque value.
Response 3: Actually, the torque of 1Nm was set in the pre-analyses to see if any plastic deformation would occur in the beams. After the ensure that the beams remain elastic under the 1Nm torque, conducted the main FEM analyses were where the torque was set to 0.5 Nm in compliance with the experiments The torque value written as 1 Nm incorrectly in the text has been updated to 0.5 Nm. Also, the von-mises stress value has been updated. Please see page 6.
Round 2
Reviewer 1 Report
Authors addressed the comments given; I identify no further issues.
