A New Active Disturbance Rejection Control Tuning Method for High-Order Electro-Hydraulic Servo Systems
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors presented a novel ADRC tuning method tailored for high-order electro-hydraulic servo systems (EHSSs), validated through simulations and experiments. Their objective was to broaden the use of active disturbance rejection control in high-order EHSSs by implementing this innovative tuning approach. The original question is well-defined, advancing current knowledge and fitting the journal's scope. The results are significant, appropriately interpreted, and all conclusions are justified and supported. Hypotheses are clearly identified, the article is well-written, and data and analyses are presented with high standards. The paper offers an overall benefit, addressing a long-standing question with smart experiments, and the English is clear and understandable. Thus, I recommend its publishing.
Comments on the Quality of English LanguageN/A
Author Response
Dear Reviewer:
We feel great thanks for your professional review work on our manuscript. We would be glad to respond to any further questions and comments that you may have.
Best regards,
Yours sincerely
Junli Zhang
25-Jul,2024
Nanjing University of Science & Technology
Reviewer 2 Report
Comments and Suggestions for Authors1. The authors have discussed the model structure of the control system and the controller itself for the ESSS in a very accessible way. No comparison of the response to the forcing with the real object. Such a comparison would show where we are in reality. Showing the operator transmittance of the system is a bit too little. Transmittance T(s) and G(s).
2. A very laconic description of the experimental site. I have the impression that the authors of the article mono focused on simulation studies, omitting the experimental studies, and they would in particular show the validity of the adopted research method. One figure 12- is a bit too little. In it we see displacements with an amplitude of 10m for the system. How does this relate to the valve slide displacements shown in Figure 10.
3. What does figure 4 actually show? As it is, it might not be there at all.
4. No description of the operating parameters, components used and the like.
5. What does figure 11 really show that the error is strongly attenuated?
6. In many studies ( including this one), so-called comparative studies are performed with some "inferior" control system. There is no solid data for the comparison process with the proposed PID controller. What is this controller? Why is an integrating member used in a strongly integrating (astatic) system? What settings are used in it. No solid basis for determining which one is in fact the better tuned system. Is the waveform diagram alone sufficient. Tests are made under the thesis that something is better than another.
7. No information (Equation 33) as to the values of the coefficients k1, k2 - unless I have missed something.
8. Figure 1 is incorrectly described. Applying voltage to one coil of the proportional valve, probably not a good idea.
9. Table 3 lacks units for the different values -is this not relevant to the simulation process?
In conclusion, the article should be solidly supplemented with information on the experimental part or no such research should be shown. In this form it looks poor. The comparative studies presented in section 4.3 are insufficient. Although the authors write that these are simulation studies?
Author Response
Dear Reviewer:
We feel great thanks for your professional review work on our manuscript. As you are concerned, there are several problems that need to be addressed. According to your nice suggestions, we have made extensive corrections to our previous draft, the detailed corrections are listed below.
Comments 1: The authors have discussed the model structure of the control system and the controller itself for the EHSS in a very accessible way. No comparison of the response to the forcing with the real object. Such a comparison would show where we are in reality. Showing the operator transmittance of the system is a bit too little. Transmittance T(s) and G(s).
Response 1: Thank you for pointing this out. We agree with this comment. We have added the parameters of the third-order EHSS in table 1, and the main components of the experimental platform also are shown in table 2. And we also added some introduction of the experimental platform and the results analysis of the experimental results.
Comments 2: A very laconic description of the experimental site. I have the impression that the authors of the article mono focused on simulation studies, omitting the experimental studies, and they would in particular show the validity of the adopted research method. One figure 12 is a bit too little. In it we see displacements with an amplitude of 10×10-3m for the system. How does this relate to the valve slide displacements shown in Figure 9?
Response 2: Thank you for your suggestion. We have added the description of the experimental platform and also added the main components of the experimental platform in table 2-page 16, line 406-414. The experimental platform is the dynamic disaster simulation test system for deep underground rock engineering, preparation of test specimens is required for each experiment due to the fact that the test piece cannot be reused. The test piece is a rock/concrete block with a size of 1m×1m×1m. The cost of the test piece is high, and the cost of conducting an experiment also is high, so we only conducted one experiment, we will build a dedicated electro-hydraulic servo system test bench in the future for the verification of the controller. The figure 9 shows the displacement tracking performance of the third-order EHSS controlled by PID controller and the improved ADRC controller, mainly to verify the tracking performance of the controller, it has no relationship with the amplitude of 10×10-3m in figure 12.
Comments 3: What does figure 11 actually show? As it is, it might not be there at all.
Response 3: Thank you for this valuable comment. The figure 11 show the experimental platform of the third-order EHSS. It is a dynamic disaster simulation test system for deep underground rock engineering, and it also is the application of the improved ADRC controller. we have replaced the figure 11 to the experimental section – page 16, line 414.
Comments 4: No description of the operating parameters, components used and the like.
Response 4: We sincerely appreciate the valuable comment. The operating parameters are very important for the simulations and experiments. We have added the parameters in table 1 and added the components of the platform in table 2 – page 16, line 414.
Comments 5: What does figure 10 really show that the error is strongly attenuated?
Response 5: Yes, the displacement tracking error of the third order EHSS controlled by the PID controller and the improved ADRC controller shown in figure 10 is used to shown the tracking error of the improved ADRC controller is smaller than the PID controller and the tracking performance of the improved ADRC controller also is better than PID controller. We have added in the revised manuscript – page 15, line 391-395.
Comments 6: In many studies (including this one), so-called comparative studies are performed with some "inferior" control system. There is no solid data for the comparison process with the proposed PID controller. What is this controller? Why is an integrating member used in a strongly integrating (astatic) system? What settings are used in it. No solid basis for determining which one is in fact the better tuned system. Is the waveform diagram alone sufficient? Tests are made under the thesis that something is better than another.
Response 6: This comment is very professional, and we strongly agree and would like to improve. The purpose of proposing the new tuning method is to improve the control performance of the dynamic disaster simulation test system, due to the cost of experiments, we only compared the control performance with the original controller of the system—PID controller. And we compared the control performance with the ADRC controller tuned by the bandwidth tuning method in simulation. We added the parameters of the PID controller in the revised manuscript. —page 14, line 385.
Comments 7: No information (Equation 33) as to the values of the coefficients ,unless I have missed something.
Response 7: Thank you for pointing this out. I know you have reviewed our manuscript very carefully, the coefficients is the gain vector of the designed controller as equation (11). – page 7, line 209.
Comments 8: Figure 1 is incorrectly described. Applying voltage to one coil of the proportional valve, probably not a good idea.
Response 8: Agree, we think this is an excellent suggestion. The value used in the Figure 1 is a servo value, and we have made changes in Figure 1.
Comments 9: Table 1 lacks units for the different values, is this not relevant to the simulation process?
Response 9: Thank you for pointing this out. We feel so sorry for our careless mistakes. The units are important for simulation process, and we add the units in table 1.
Comments 10: In conclusion, the article should be solidly supplemented with information on the experimental part or no such research should be shown. In this form it looks poor. The comparative studies presented in section 4.3 are insufficient. Although the authors write that these are simulation studies?
Response 10: Thank you for this suggestion. We have added some experimental content.
We deeply appreciate all the valuable comments and suggestions of you, and look forward to hearing from you regarding our submission. We would be glad to respond to any further questions and comments that you may have.
Best regards,
Yours sincerely
Junli Zhang
25-Jul,2024
Nanjing University of Science & Technology
Author Response File: 
Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe paper is interesting. However, the mathematical model of the electrohydraulic system is very simplified. It is necessary to clarify the doubts that I have highlighted in the attached manuscript file. Also the conclusions need to be rethought and reformulated. As it stands, more than 2/3 of the Conclusion section is an abstract. Detailed comments are in the attached file.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer:
We feel great thanks for your professional review work on our article. As you are concerned, there are several problems that need to be addressed. According to your nice suggestions, we have made extensive corrections to our previous draft, the detailed corrections are listed below.
Comments 1: Avoid the use of abbreviations in the title. ADRC is not explained. Please change the title of the paper.
Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have changed the title to A New Active Disturbance Rejection Control Tuning method for High-order Electro-hydraulic Servo Systems.
Comments 2: The modelling and interaction of a hydraulic system with its environment is a complex issue. Also, determining reliable values for the coefficients of the equations of a mathematical model of a hydraulic system is not easy. The reliability of the obtained results of numerical solutions depends on this. A detailed description of the mathematical model of the electro-hydraulic system including the interaction with the environment is presented in the paper: Research of vibrations effect on hydraulic valves in military vehicles. An important problem in the operation of electro-hydraulic systems is the effect of mechanical vibrations which can disrupt the operation of the entire system. I suggest briefly mentioning this and quoting the paper.
Response 2: We sincerely appreciate the valuable comments. We have checked the literature carefully and added references on the effect of external mechanical vibration on hydraulic valves into the introduction in the revised manuscript. “And the impact of external mechanical vibration on hydraulic valve also is an important issue need to solve [12].”– page 1, and line 25.
Comments 3: Detailed analyses of the operation of the electro-hydraulic system with proportional distributor are presented in the paper: A Case Study of Open- and Closed-Loop Control of Hydrostatic Transmission with Proportional Valve Start-Up Process. In the paper, simulations and experimental studies were carried out for control signals of different shapes and for different feedback from the hydraulic system. The pressure signal and the dynamic excess depending on the structure of the control system were analysed. I suggest briefly mentioning and citing this paper.
Response 3: We are glad to accept the valuable comments. We have checked the literature carefully and added references on the detailed analyses of the operation of the electro-hydraulic system into the introduction in the revised manuscript. “Detailed analyses of the EHSS with proportional distributor are presented in [22], simulations and experimental studies were carried out for control signals of different shapes and for different feedback from the hydraulic system.” – page 1 and line 33-36.
Comments 4: Please correct the picture 1.
Response 4: We were really sorry for our careless mistakes. Thank you for your reminder. We have added the kinematic viscous damping coefficientand the load stiffnessin figure 1 as follows.
Comments 5: Total disturbanceis a force, please describe what elements are inside of the total disturbance.
Response 5: This is an important suggestion for our manuscript, we have added the elements of the total disturbance in the revised manuscript.represents the total disturbance including the unknown external load and uncertainties of mechanical dynamics such as the unmodeled friction effects and unconsidered effects of parameter deviations. – page 3 and line 118-120.
Comments 6: Aboutof the equation (2), has the volume of liquid contained in the lines between the directional control valve and the actuator been taken into account ?
Response 6: Thank you for pointing this out. We agree with this comment. And the locations of the flow sensors are the inlet and the outlet of the actuator in our test bed, so we do not consider the volume of liquid contained in the lines between the directional control valve and the actuator.
Comments 7: Aboutand of the equation (2),Bulk modulus should take into account the susceptibility of the pipes (if flexible pipes are used). Please comment.
Response 7: This is a very important point in our manuscript. The pipes we used are all steel pipes, the deformation of the pipes is small under pressure, we do not consider the Bulk modulus. But if the flexible pipes are used, the Bulk modulus must be considered.
Comments 8: Please check figure 2.
Response 8: We feel sorry for our carelessness. We have corrected the schematic diagram of ADRC as follows.
Comments 9: In figure 11, value or valve? Please check that.
Response 9: We feel really sorry for our careless mistakes. Thank you for your reminder. We have corrected in figure 4.
Comments 10: Please add the units in table 1.
Response 10: Thank you point this out, We have added the units in table 1.
Comments 11: These are not conclusions; they are the abstract. Conclusions should be related to the results presented in the paper and should explain the cause and effect relationships that determine the results obtained. I strongly suggest that the conclusions be rewritten.
Response 11: We think this is an excellent suggestion. We have rewritten the conclusion part in the revised manuscript. – page 17 and line 429-439.
We deeply appreciate all the valuable comments and suggestions of you, and look forward to hearing from you regarding our submission. We would be glad to respond to any further questions and comments that you may have.
Best regards,
Yours sincerely
Junli Zhang
25-Jul,2024
Nanjing University of Science & Technology
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for Authors
Thank you for your responses to my comments. However, there are still some points that need clarification.
Comment 1:
Is the valve "4/4 controlled directional valve, directly operated, with electric position feedback and integrated electronics (OBE)" (Table 2) the valve you used as a basis for modelling and simulation? If so, something is wrong here. There is still a misuse of symbolism in Figure 1.
In Figure 1 there is a 4/3 valve while in the table there is a 4/4 valve. For comparison, I give example symbols and drawings of the valve from the datasheet for the valve given in Table 3.
https://www.kanflu.com/assets/Uploads/SERVO-VALVE-4WRPEH10-DIRECT-OPERATED-OBE-AND-FEEDBACK-RE29037.pdf
Comment 2:
I also note that this type of valve also uses a regulator to control the spool position. The authors have completely ignored this in the modelling.
Comment 3:
I also pointed out how the control object is modelled (Figure 3, transmittance P(s) (equation 23). The authors state that this is a 3rd order object for EHSS. The use of this type of model for EHSS is, in my opinion, a mistake. It is not about the order of magnitude of the transmittance denominator. This type of object is a static object if it is stable. In fact, for this type of object (EHSS) in an open-loop EHSS control system, applying a constant voltage to the input of the EHSS results in an astatic response (please check this). In this case, with this type of P(s) modelling, a static (asymptotically stable?) response will be obtained. For simplicity, it would be good if the authors provided the values of the model coefficients a1, a2 , a3, b1, for fixed values without the need for complex calculations. Please clarify this situation.
Summary: The main comments from my side are unfortunately the insufficient reliability of the simulation and modelling process concerning the presented real EHSS system. Lack of a reliable control object identification process. Lack of comparative studies (showing waveforms) of the model and the real object) in the identification process. Even the best-designed controller will be dysfunctional for, a poorly identified control object, as to its structure and parameters. Then such a model shows its value and is useful in the context of expensive tests on the real object (answer 2). Please provide a more solid representation of what is being studied and which system is the model for.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer:
We feel great thanks for your professional review work on our manuscript. As you are concerned, there are several problems that need to be addressed. According to your nice suggestions, we have made extensive corrections to our previous draft, the detailed corrections are listed below.
Comments 1: Is the valve "4/4 controlled directional valve, directly operated, with electric position feedback and integrated electronics (OBE)" (Table 2) the valve you used as a basis for modelling and simulation? If so, something is wrong here. There is still a misuse of symbolism in Figure 1. In Figure 1 there is a 4/3 valve while in the table there is a 4/4 valve. For comparison, I give example symbols and drawings of the valve from the datasheet for the valve given in Table 3.
https://www.kanflu.com/assets/Uploads/SERVO-VALVE-4WRPEH10-DIRECT-OPERATED-OBE-AND-FEEDBACK-RE29037.pdf
Response 1: Thank you for pointing this out. You have reviewed our manuscript carefully, thank you very much. We think the electro-hydraulic servo system shown in Figure 1 is a general electro-hydraulic servo system, so we use a common servo valve. Because the experimental platform requires a large hydraulic oil flow rate, we use the servo valve shown in table 2. And the process of establishing mathematical model of the electro-hydraulic servo system, we have considered the characteristics of the servo value we used in our experimental platform – page 4, line 131-142.
Comments 2: I also note that this type of valve also uses a regulator to control the spool position. The authors have completely ignored this in the modelling.
Response 2: Thank you for your suggestion. And in the process of establishing mathematical model of the electro-hydraulic servo system, we consider the characteristics of the servo value shown in table 2 – page 4, line 131-141. We simplified the mathematical model of the servo and also explained the reasons for the simplification. And we use ADRC controller to optimize the control performance of the electro-hydraulic servo system, the ADRC controller do not need the precise mathematical model of the electro-hydraulic servo system.
Comments 3: I also pointed out how the control object is modelled (Figure 3, transmittance P(s) (equation 23). The authors state that this is a 3rd order object for EHSS. The use of this type of model for EHSS is, in my opinion, a mistake. It is not about the order of magnitude of the transmittance denominator. This type of object is a static object if it is stable. In fact, for this type of object (EHSS) in an open-loop EHSS control system, applying a constant voltage to the input of the EHSS results in an astatic response (please check this). In this case, with this type of P(s) modelling, a static (asymptotically stable?) response will be obtained. For simplicity, it would be good if the authors provided the values of the model coefficients a1, a2 , a3, b1, for fixed values without the need for complex calculations. Please clarify this situation.
Response 3: Thank you for this valuable comment and it also is very important for our manuscript. We feel so sorry that we do not explain this question clearly in our original manuscript. And we have added the closed-loop control system equation (24) we used for simulations and experiments in our manuscript. – page 10, line 314-315. And the model coefficients a1, a2 , a3, b1 of the mathematical model of P(s) contain uncertain parameters, and it is the reason we selected ADRC controller to improve the control performance of the electro-hydraulic servo system.
Comments 4: Summary: The main comments from my side are unfortunately the insufficient reliability of the simulation and modelling process concerning the presented real EHSS system. Lack of a reliable control object identification process. Lack of comparative studies (showing waveforms) of the model and the real object) in the identification process. Even the best-designed controller will be dysfunctional for, a poorly identified control object, as to its structure and parameters. Then such a model shows its value and is useful in the context of expensive tests on the real object (answer 2). Please provide a more solid representation of what is being studied and which system is the model for.
Response 4: We sincerely appreciate the valuable comment. According to your comments, we have added the closed-loop control system as equation (24) we used for simulations and experiments – page 10, line 314-315. And we feel so sorry we did not do not explain this question clearly in our original manuscript so that it may cause you to misunderstand. And we have revised section 4.3 carefully, made effort to explain the results clearly in this section.
We deeply appreciate all the valuable comments and suggestions of you, and look forward to hearing from you regarding our submission. We would be glad to respond to any further questions and comments that you may have.
Best regards,
Yours sincerely
Junli Zhang
28-Jul,2024
Nanjing University of Science & Technology
Author Response File: Author Response.pdf
