Adaptive Robust Admittance Control of Robots Using Duality Principle-Based Impedance Selection
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Round 1
Reviewer 1 Report
1- in eqn.1, the definition of \tau \in R^n should be clearly stated that it is equal to J*\tau where J is the Jacobian
2- Define pHRI in the line after eqn3.
3- In line 78 after eqn.6, is the D_d a constant or time dependent?
4- Define Proj function precisely in eqn 14. What is the \dot output?
5- The example uses a sole robot link. The impedance idea is to control both force and position simultaneously. It is not clear for me how the example is relevant to the impedance control idea.
Author Response
The authors would like to express their sincere appreciation to the reviewer for his/her constructive comments and suggestions, and his/her time and efforts spent in helping us to improve the quality and presentation of the paper.
Comment 1: in eqn.1, the definition of \tau \in R^n should be clearly stated that it is equal to J*\tau where J is the Jacobian
Response: Thank you for the helpful comment. We have added the stated definition after eq. (1).
Comment 2: Define pHRI in the line after eqn3.
Response: Thank you for the helpful comment. We have revised ‘pHRI’ into ‘robotenvironment
interaction’ after eq. (3).
Comment 3: In line 78 after eqn.6, is the D_d a constant or time dependent?
Response: The $D_d$ after eq. 6 is a constant. We have deleted the redundant ‘(t)’ after.
Comment 4: Define Proj function precisely in eqn 14. What is the \dot output?
Response: Thank you for the helpful comment. We have corrected the projection function into the right form in (14).
Comment 5: The example uses a sole robot link. The impedance idea is to control both force and position simultaneously. It is not clear for me how the example is relevant to the impedance control idea.
Response: Thank you for the helpful comment.
- We have added the performance of the impedance error $e_{im}$ defined in Remark 3 in Fig. 5 to show the obtainment of the desired impedance dynamics in (6).
- The desired impedance dynamics in (6) develops a dynamic relationship between the tracking error and the interactive force shown in Fig. 8.
Reviewer 2 Report
The work presented in this manuscript is about adaptive robust admittance control for robot-environment interaction. The work can be accepted for possible publication in this journal should the following points be clearly addressed or improved.
(1) The novelty of the work is not clearly stated. The mentioned adaptive robust admittance control strategy is well-known method. However it was highlighted as a novel method. Perhaps more detailed reasoning or evidences should be ammended to the context of the article to defend the novelty of the work.
(2) Simulations are conducted in this work to demonstrate the effectiveness of the proposed impedance estimation and adaptive robust admittance control. In addition to simplyu showing simulation results, it is highly suggested to include experimental results and validations to signify the contribution of the proposed method.
(3) Concluding remakrs should be icnldued in the conclusion session of the manuscript. However, it is missing in the present manuscript.
(4) To show the significance of the propsoed method, comparisons to exisitng and known methods are required.
(5) What are the pros and cons of the proposed method compared to other eixiting methods?
(6) What are the limitations of the proposed method?
Author Response
Comment: The work presented in this manuscript is about adaptive robust admittance control for robot-environment interaction. The work can be accepted for possible publication in this journal should the following points be clearly addressed or improved.
The authors would like to express their sincere appreciation to the reviewer for his/her constructive comments and suggestions, and his/her time and efforts spent in helping us to improve the quality and presentation of the paper. Thank you for the positive comment.
Comment 1: The novelty of the work is not clearly stated. The mentioned adaptive robust admittance control strategy is well-known method. However it was highlighted as a novel method. Perhaps more detailed reasoning or evidences should be ammended to the context of the article to defend the novelty of the work.
Response: Thank you for the helpful comment. We have revised the manuscript and compared with related results to show the contributions of this paper in Introduction and Conclusions.
Comment 2: Simulations are conducted in this work to demonstrate the effectiveness of the proposed impedance estimation and adaptive robust admittance control. In addition to simply showing simulation results, it is highly suggested to include experimental results and validations to signify the contribution of the proposed method.
Response: Thank you for the valuable comment. We agree with that experiments will add more important things to validate the control effectiveness, however, we don’t have the related experiment condition at present. We have added more simulation results and analysis to show the control effectiveness in Simulations.We will conduct the related experiment in the future.
Comment 3: Concluding remarks should be included in the conclusion session of the manuscript. However, it is missing in the present manuscript.
Response: Thank you for the helpful comment. We have added Conclusions in the revised paper.
Comment 4: (1)To show the significance of the proposed method, comparisons to existing and known methods are required.
(2)What are the pros and cons of the proposed method compared to other existing methods?
Response: Thank you for the constructive comment.
(i)At Conclusions, we have stated the disadvantages of the proposed method.
(ii)We have added comparison with the related results at the last paragraph of Introduction.
‘Compared with the environmental impedance estimation in [12–14], the projection modification-based adaptive impedance learning law can guarantee the estimated environmental stiffness and damping being constrained in prescribed sets, which is of significant value for the determination of the range of the desired robot impedance. Compared with the TDE-based SMC in [28] for position regulation, the designed adaptive robust admittance controller can make robots realize the desired impedance dynamics without serious chattering and without the requirement of the bound of the TDE error.’
Comment 5: What are the limitations of the proposed method?
Response: Thank you for the meaningful comment. At the last of Conclusions, we have added the limitations
‘Since admittance control is with position-controlled outer loop and force-controlled inner loop, the proposed adaptive robust admittance control is better suited for interaction with soft environments than stiff environments. The developed method is suit for interaction with the environment with constant or slowly-varying impedance owe to the limitations of the differential adaptation used in impedance learning.’
Reviewer 3 Report
Unfortunately the literature review, based on the abstract, introduction, and the methodology, is still missing important points some of which are provided here. Since it is a combination of different areas, the litereature reviw is very important and it is not good to refer 9 references by two sentences.
1) Variable Impedance Control and Learning—A Review
2) Adaptive Fuzzy Sliding Mode Controller Design for a New Hand Rehabilitation Robot
3) A historical review of robust control
4) Design and impedance control of a hydraulic robot for paralyzed people
5) different robot environment control book
6) Fuzzy sliding mode control of a wearable rehabilitation robot for wrist and finger
The formula and description was good
There is not enough discussion on the results and no conclusion!
Author Response
Comment 1: Unfortunately the literature review, based on the abstract, introduction, and the methodology, is still missing important points some of which are provided here. Since it is a combination of different areas, the literature review is very important and it is not good to refer 9 references by two sentences.
1) Variable Impedance Control and Learning—A Review
2) Adaptive Fuzzy Sliding Mode Controller Design for a New Hand Rehabilitation Robot
3) A historical review of robust control
4) Design and impedance control of a hydraulic robot for paralyzed people
5) different robot environment control book
6) Fuzzy sliding mode control of a wearable rehabilitation robot for wrist and finger
Responses: The authors would like to express their sincere appreciation to the reviewer for his/her constructive comments and suggestions, and his/her time and efforts spent in helping us to improve the quality and presentation of the paper.
- We have revised citations in Introduction.
- We have cited the stated important results in [15]-[17] and [26]-[28].
Comment 2: The formula and description was good.
Response: Thank you for the positive comment.
Comment 3: There is not enough discussion on the results and no conclusion!
Response: Thank you for the helpful comment. We have added more simulation analysis and added Conclusion part.
Round 2
Reviewer 2 Report
All my questions are clearly answered, which is now ready to proceed to the next step.
Reviewer 3 Report
In this work, an adaptive robust admittance controller based on time-delay estimation is designed for the robot to track the admittance trajectory. The topic is good and useful for further researches. The adaptive robust system is very useful and the conclusion and references now are good.
