Design and Test of a Cone Dielectric Elastomer Actuator Driving Hopping Robot

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

It  is fair study, however, Introduction is short and reference is alittle.

Author Response

Comments 1: It is fair study, however, Introduction is short and reference is a little.

Response 1: Thank you for pointing this. We agree with this comment. We increased the references from 15 to 33. Accordingly, we supplemented the content of the introduction. So the introduction is revised as follows:

Dielectric elastomer actuator (DEA) is a kind of electromechanical transducer that convert electrical energy to mechanical energy. DEAs are widely used in the field of robotics and electromechanical systems, such as DEA-driven robots [1–4]; fast and accurate tunable optics [5]; and miniature DEA pump and valves [6,7]. These functions are contingent on the deformation mechanisms of the DEA. Most DEAs are composed of compliant electrodes sandwiching a thin layer of pre-stretched elastomer and preload mechanisms. The DEAs^’ benefits are lightweight, low-cost, high energy density properties, reliable, and easy to manufacture because it uses easily accessible material. So DEA has a bright future in the engineering field because of the above advantages.

DEA actuation characters similar to artificial muscles, it has a large energy conversion efficiency of 80 % and a volumetric energy density of 3.4 J/cm³ [8]. DEA is capable of stroking [9], bending [10] or rotating [11] under the influence of electric field. The current research on DEA actuation applications is mainly focused on the field with small power requirements for soft robot actuations, for example FLEX 1, FLEX 2, Skitter robot et al [12-15]. There is less research on the application of devices with high output power requirements. To get high-power output actuators, multi-layer DEA film stacking is usually developed [16]. But due to the great elasticity of pre-stretched elastomer films, it is difficult to ensure its manufacturing process. A four-legged robot driven by trapezoidal multi-stacked DEAs is realized [17]. The DEA of the article is fabricated by synthetic acrylonitrile butadiene rubber elastomer that does not need to be pre-stretched. Response of the angle of the femur under different voltage frequencies are studied. Presently, many different configurations of DEAs have been developed to drive robots. The conical configuration DEA has been widely used due to its large stroke and great output force [18-20]. Cone DEA consists of a piece of elastomer membrane bonded to a rigid circular ring with a disk in the center. Some of them have been used to developed to drive rigid legged robots. The antagonistic cone DEAs are adopted to drive three-segment leg that is able to move up and down by 17.9 mm [21]. Conn et al fabricated a cone DEA with multi-degree-of-freedom (DOF) [22]. In order to improve the perforce of the cone DEA, the negative-stiffness preload mechanism is designed. The preload mechanism designing usually ignores the problem that adds DEAs’ mass and lows DEAs’ power density. That will limit their application.

Although many robots have been driven by DEAs, they have limited mobility. As a moving way for mobile robots, hopping movement can cross obstacles several times of its own height [23-24], and can be widely used in the movement of unstructured ground environments that cannot be reached by traditional mobile robots. They can be used in emergency rescue, disaster search and rescue, military reconnaissance, information gathering, planet exploration and other fields. However, hopping robots need output high power density actuators. At present, the actuation modes for hopping robots include electromagnetic actuators [25], hydraulic actuators [26], combustion actuators [27], and shape memory alloy actuator [28]. Electromagnetic actuation is susceptible to the influence of environmental temperature. Due to the limitation of magnetic saturation of magnetic materials and battery energy-to-mass ratio, electromagnetic actuation power density is small. For promoting its ability of driving hopping robots, complex energy accumulation and releasing mechanism are designed, that will make the structure complex. Hydraulic (pneumatic) and combustion actuations have high power-to-mass ratio, which is suitable for directly driving the fields with high immediate power requirements, but their noise is too large and they have an influence on the environment. Shape memory alloy is usually used as a kind of smart material for driving micro-miniature robots. Recently, the hopping robots driven by DEA are studied. To increase DEA output force for hopping robots, 20-layers films are stacked. It can output 30 N force. A 530 g robot can jump 45 mm [29]. Du et al used rotation vibration of DEA to drive a robot with soft bristles via hopping locomotion [30].

In this paper, one hopping robot with mW-level cone DEA is designed and tested. This innovative design offers several significant advantages. Firstly, the structure of designed cone DEA with negative stiffness preload mechanism is lightweight, large force and displacement output, which make it fit for driving hopping robot. Secondly, the integration of the constant torque cam ensures that the applied torque during the energy storage phase remains consistent, which is crucial for reliable and predictable energy storage. Thirdly, the compact and lightweight nature of the robot, facilitated by the use of DEAs, makes it suitable for various applications where space and weight are critical considerations.

 

The references are revised as:

1. Manaswi, D.K.; Cao, C.; Guo, J.; Andrew, C.; Jonathan, R. Multi-Directional Crawling Robot with Soft Actuators and Electroadhesive Grippers. In Proceedings of the First IEEE-RAS International Conference on Soft Robotics, RoboSoft 2018, Livorno, Italy, 24–28 April 2018.
2. Pei, Q.; Rosenthal, M.; Stanford, S.; Prahlad, H.; Pelrine, R. Multiple-degrees-of-freedom electroelastomer roll actuators. Smart Mater. Struct. 2004, 5, 86.
3. Nguyen, C.; Phung, H.; Jung, H.; Kim, U.; Nguyen, T.; Park, J.; Moon, H.; Koo, J.; Choi, H. Printable monolithic hexapod robot driven by soft actuator. In Proceedings of the 2015 IEEE International Conference on Robotics and Automation (ICRA), Seattle, WA, USA, 26–30 May 2015.
4. Carpi, F.; Frediani, G.; Turco, S.; de Rossi, D. Bioinspired tunable lens with muscle-like electroactive elastomers. Adv. Funct. Maters. 2011, 21, 4152–4158.
5. Shian, S.; Diebold, R.; Clarke, D. Tunable lenses using transparent dielectric elastomer actuators. Optics Express. 2013, 7, 8669–8676.
6. McCoul, D.; Pei, Q. Tubular dielectric elastomer actuator for active fluidic control. Smart Mater. Struct. 2015, 10, 105016.
7. Ghazali, F.; Mah, C.; AbuZaiter, A.; Chee, P.; Ali, M. Soft dielectric elastomer actuator micropump. Actuators A Phys. 2017, 263, 276–284.
8. Wang H M.; Zhu J Y.; Ye K B. Research on Linear Dielectric Elastomer Actuator, Journal of Mechanical Engineering. 2009, 45, 291-296.
9. Pfeil, S.; Henke, M.; Katzer, K.; Zimmermann, M.; Gerlach, G. A Worm-Like Biomimetic Crawling Robot Based on Cylindrical Dielectric Elastomer Actuators. Front. Robot. AI 2020, 7, 9.
10. Cho, K.H.; Kim, Y.; Yang, S.Y.; Kim, K.; Park, J.H.; Rodrigue, H.; Moon, H.; Koo, J.C.; Choi, H.R. Artiffcial musculoskeletal actuation module driven by twisted and coiled soft actuators. Smart Mater. Struct. 2019, 28, 125010.
11. Minaminosono, A.; Shigemune, H.; Okuno, Y.; Katsumata, T.; Hosoya, N.; Maeda, S. A deformable motor driven by dielectric elastomer actuators and ffexible mechanisms. Front. Robot. AI 2019, 6, 1.
12. Huang P.; Wang Y.W.; YE W.J.; WU J.D.; SU C.Y.; Design, Modeling and Motion Control of Soft Robots Based on Dielectric Elastomer: A Survey. Control Engineering of China. 2023, 30: 1389-1401.
13. Li Q.; LI X.; Yu F. Dielectric Elastomer-driven Frog-shaped Bionic Soft Robot[J]. Acta Armamentarii. 2022, 43, 140-147.
14. Duduta M, Berlinger F, Nagpal R. Tunable multi-modal locomotion in soft dielectric elastomer robots[J]. IEEE Robotics and Automation Letters. 2020, 5, 3868-3875.
15. Zhao J.; Zhang J.; McCoul D. Soft and fast hopping–running robot with speed of six times its body length per second[J]. Soft robotics. 2019, 6, 713-721.
16. Mert C.; Wayne W.; Kathleen L.Ke. Implementation of Soft-Lithography Techniques for Fabrication of Bio-Inspired Multi-Layer Dielectric Elastomer Actuators with Interdigitated Mechanically Compliant Electrodes. 2018, 7, 73-86.
17. Nguyen, C.; Phung, H.; Nguyen, T.; Lee, C.; Kim, U.; Lee, D.; Moon, H.; Koo, J.; Choi, H. A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators. Smart Mater. Struct. 2014, 6, 065005.
18. Wang H, Zhu Y, Zhao D, Luan Y, Performance Investigation of Cone Dielectric Elastomer Actuator Using Taguchi Method. Chinese Journal of Mechanical Engineering. 2011, 24: 685-692.
19. Cao, C.; Conn, A.T. Performance Optimization of a Conical Dielectric Elastomer Actuator. Actuators 2018, 7, 32.
20. Bruch, D.; Willian, T.P.; Schäfer, H.C.; Motzki, P. Performance-Optimized Dielectric Elastomer Actuator System with Scalable Scissor Linkage Transmission. Actuators 2022, 11, 160.
21. Cao, C.; Conn, A. Elastic actuation for legged locomotion. In Proceedings of the SPIE Electroactive Polymer Actuators and Devices (EAPAD), Portland, OR, USA, 17 April 2017.
22. Conn, A.T.; Rossiter, J. Towards holonomic electro-elastomer actuators with six degrees of freedom. Smart Mater. Struct. 2012, 3, 035012.
23. Meng X Y.; Ge W.J. Actuator Configuration of Optimal Motion Posture for Underactuated Hopping Robots[J]. China Mechanical Engineering. 2017, 28, 1765-1770.
24. Wang K D.; Chen S.; Tang W. A Bionic Bouncing Robot Design and Made Inspired by Locusts[J]. China Mechanical Engineering. 2023, 34, 2946-2951.
25. Kovac M.; Fuchs M.; Guignard A. A miniature 7g jumping robot[C]// 2008 IEEE International Conference on Robotics and Automation，Pasadena，CA，USA, May 19-23， 2008.
26. Semini C.; Tsagarakis N.;, Guglielmino E. Design of HyQ–a hydraulically and electrically actuated quadruped robot[J]. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 2011, 225, 831-849.
27. Bartlett N.; Tolley M.; Overvelde J. A 3D-printed, functionally graded soft robot powered by combustion[J]. Science, 2015, 349, 161-165.
28. Mao T.; Peng H.; Zha Z.; Continuous Jumping Soft Robot Driven by Shape Memory Alloy [J]. Continuous Jumping Soft Robot Driven by Shape Memory Alloy. 2021, 41, 447-452.
29. Luo, B.; Li, B.; Yu, Y.; Yu, M.; Ma, J.; Yang, W.; Wang, P.; Jiao, Z. A Jumping robot driven by a dielectric elastomer actuator. Appl. Sci. 2020, 10, 2241.
30. Du, Y.; Wu, X.; Wang, D.; Zhao, F.; Hu, H. Multimodal Resonances of a Rectangular Planar Dielectric Elastomer Actuator and Its Application in a Robot with Soft Bristles. Biomimetics. 2024, 9, 488.
31. Luan Y G.; Wang H M.; Zhu Y L. Design and Implementation of Cone Dielectric Elastomer Actuator with Double-slider Mechanism. 2010, 7, s212~s217.
32. Chan K., Dong-J.L., Sun P., Jung, G., Wang P.J., Dipo: a miniaturized hopping robot via lightweight and compact actuator design for power amplification[J]. Bioinspiration & Biomimetics. 2023, 18, 046006.
33. Pope M H . Elastic mechanisms in animal movement[M]. Cambridge University Press,1988, pp: 35-39.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Comments

Overall – Interesting work on DEAs.  Novelty of the paper does not revolve around the DEAs but the mechanical mechanism for hopping.

1. Lit Review – missing key work in the field

2. Cone Design – This statement is difficult to follow…. The preload mechanism can be analysed as opposing vertexes double-sliders mechanism on the top [13]. For analysing conveniently, one double-sliders mechanism shown in figure 1(b) is analysed in detail.

3. Is the preload from the spring or was it pre-stretched to 375% and if so how?

4. This sentence is unclear. “The testing stretching forces of DE film under 7.5kV and 0V voltages are showed in Figure 3.”

5. This sentence is unclear. “Whether the two points is proper directly affects the performance of the DEA.”

6. Remove firstly. “To test the performance of DEA, its displacement is measured firstly”

7. Results – Table 3.  How many tests were performed and what was the standard deviation?

Comments on the Quality of English Language

The English should be improved.  Some sections were very difficult to understand. 

Author Response

Comment 1. Lit Review – missing key work in the field

Response 1: Thank you for pointing this. We agree with this comment. We increased the references from 15 to 33. Accordingly, we supplemented the content of the introduction. So the introduction is revised as follows:

Dielectric elastomer actuator (DEA) is a kind of electromechanical transducer that convert electrical energy to mechanical energy. DEAs are widely used in the field of robotics and electromechanical systems, such as DEA-driven robots [1–4]; fast and accurate tunable optics [5]; and miniature DEA pump and valves [6,7]. These functions are contingent on the deformation mechanisms of the DEA. Most DEAs are composed of compliant electrodes sandwiching a thin layer of pre-stretched elastomer and preload mechanisms. The DEAs^’ benefits are lightweight, low-cost, high energy density properties, reliable, and easy to manufacture because it uses easily accessible material. So DEA has a bright future in the engineering field because of the above advantages.

DEA actuation characters similar to artificial muscles, it has a large energy conversion efficiency of 80 % and a volumetric energy density of 3.4 J/cm³ [8]. DEA is capable of stroking [9], bending [10] or rotating [11] under the influence of electric field. The current research on DEA actuation applications is mainly focused on the field with small power requirements for soft robot actuations, for example FLEX 1, FLEX 2, Skitter robot et al [12-15]. There is less research on the application of devices with high output power requirements. To get high-power output actuators, multi-layer DEA film stacking is usually developed [16]. But due to the great elasticity of pre-stretched elastomer films, it is difficult to ensure its manufacturing process. A four-legged robot driven by trapezoidal multi-stacked DEAs is realized [17]. The DEA of the article is fabricated by synthetic acrylonitrile butadiene rubber elastomer that does not need to be pre-stretched. Response of the angle of the femur under different voltage frequencies are studied. Presently, many different configurations of DEAs have been developed to drive robots. The conical configuration DEA has been widely used due to its large stroke and great output force [18-20]. Cone DEA consists of a piece of elastomer membrane bonded to a rigid circular ring with a disk in the center. Some of them have been used to developed to drive rigid legged robots. The antagonistic cone DEAs are adopted to drive three-segment leg that is able to move up and down by 17.9 mm [21]. Conn et al fabricated a cone DEA with multi-degree-of-freedom (DOF) [22]. In order to improve the perforce of the cone DEA, the negative-stiffness preload mechanism is designed. The preload mechanism designing usually ignores the problem that adds DEAs’ mass and lows DEAs’ power density. That will limit their application.

Although many robots have been driven by DEAs, they have limited mobility. As a moving way for mobile robots, hopping movement can cross obstacles several times of its own height [23-24], and can be widely used in the movement of unstructured ground environments that cannot be reached by traditional mobile robots. They can be used in emergency rescue, disaster search and rescue, military reconnaissance, information gathering, planet exploration and other fields. However, hopping robots need output high power density actuators. At present, the actuation modes for hopping robots include electromagnetic actuators [25], hydraulic actuators [26], combustion actuators [27], and shape memory alloy actuator [28]. Electromagnetic actuation is susceptible to the influence of environmental temperature. Due to the limitation of magnetic saturation of magnetic materials and battery energy-to-mass ratio, electromagnetic actuation power density is small. For promoting its ability of driving hopping robots, complex energy accumulation and releasing mechanism are designed, that will make the structure complex. Hydraulic (pneumatic) and combustion actuations have high power-to-mass ratio, which is suitable for directly driving the fields with high immediate power requirements, but their noise is too large and they have an influence on the environment. Shape memory alloy is usually used as a kind of smart material for driving micro-miniature robots. Recently, the hopping robots driven by DEA are studied. To increase DEA output force for hopping robots, 20-layers films are stacked. It can output 30 N force. A 530 g robot can jump 45 mm [29]. Du et al used rotation vibration of DEA to drive a robot with soft bristles via hopping locomotion [30].

In this paper, one hopping robot with mW-level cone DEA is designed and tested. This innovative design offers several significant advantages. Firstly, the structure of designed cone DEA with negative stiffness preload mechanism is lightweight, large force and displacement output, which make it fit for driving hopping robot. Secondly, the integration of the constant torque cam ensures that the applied torque during the energy storage phase remains consistent, which is crucial for reliable and predictable energy storage. Thirdly, the compact and lightweight nature of the robot, facilitated by the use of DEAs, makes it suitable for various applications where space and weight are critical considerations.

The references are revised as:

1. Manaswi, D.K.; Cao, C.; Guo, J.; Andrew, C.; Jonathan, R. Multi-Directional Crawling Robot with Soft Actuators and Electroadhesive Grippers. In Proceedings of the First IEEE-RAS International Conference on Soft Robotics, RoboSoft 2018, Livorno, Italy, 24–28 April 2018.
2. Pei, Q.; Rosenthal, M.; Stanford, S.; Prahlad, H.; Pelrine, R. Multiple-degrees-of-freedom electroelastomer roll actuators. Smart Mater. Struct. 2004, 5, 86.
3. Nguyen, C.; Phung, H.; Jung, H.; Kim, U.; Nguyen, T.; Park, J.; Moon, H.; Koo, J.; Choi, H. Printable monolithic hexapod robot driven by soft actuator. In Proceedings of the 2015 IEEE International Conference on Robotics and Automation (ICRA), Seattle, WA, USA, 26–30 May 2015.
4. Carpi, F.; Frediani, G.; Turco, S.; de Rossi, D. Bioinspired tunable lens with muscle-like electroactive elastomers. Adv. Funct. Maters. 2011, 21, 4152–4158.
5. Shian, S.; Diebold, R.; Clarke, D. Tunable lenses using transparent dielectric elastomer actuators. Optics Express. 2013, 7, 8669–8676.
6. McCoul, D.; Pei, Q. Tubular dielectric elastomer actuator for active fluidic control. Smart Mater. Struct. 2015, 10, 105016.
7. Ghazali, F.; Mah, C.; AbuZaiter, A.; Chee, P.; Ali, M. Soft dielectric elastomer actuator micropump. Actuators A Phys. 2017, 263, 276–284.
8. Wang H M.; Zhu J Y.; Ye K B. Research on Linear Dielectric Elastomer Actuator, Journal of Mechanical Engineering. 2009, 45, 291-296.
9. Pfeil, S.; Henke, M.; Katzer, K.; Zimmermann, M.; Gerlach, G. A Worm-Like Biomimetic Crawling Robot Based on Cylindrical Dielectric Elastomer Actuators. Front. Robot. AI 2020, 7, 9.
10. Cho, K.H.; Kim, Y.; Yang, S.Y.; Kim, K.; Park, J.H.; Rodrigue, H.; Moon, H.; Koo, J.C.; Choi, H.R. Artiffcial musculoskeletal actuation module driven by twisted and coiled soft actuators. Smart Mater. Struct. 2019, 28, 125010.
11. Minaminosono, A.; Shigemune, H.; Okuno, Y.; Katsumata, T.; Hosoya, N.; Maeda, S. A deformable motor driven by dielectric elastomer actuators and ffexible mechanisms. Front. Robot. AI 2019, 6, 1.
12. Huang P.; Wang Y.W.; YE W.J.; WU J.D.; SU C.Y.; Design, Modeling and Motion Control of Soft Robots Based on Dielectric Elastomer: A Survey. Control Engineering of China. 2023, 30: 1389-1401.
13. Li Q.; LI X.; Yu F. Dielectric Elastomer-driven Frog-shaped Bionic Soft Robot[J]. Acta Armamentarii. 2022, 43, 140-147.
14. Duduta M, Berlinger F, Nagpal R. Tunable multi-modal locomotion in soft dielectric elastomer robots[J]. IEEE Robotics and Automation Letters. 2020, 5, 3868-3875.
15. Zhao J.; Zhang J.; McCoul D. Soft and fast hopping–running robot with speed of six times its body length per second[J]. Soft robotics. 2019, 6, 713-721.
16. Mert C.; Wayne W.; Kathleen L.Ke. Implementation of Soft-Lithography Techniques for Fabrication of Bio-Inspired Multi-Layer Dielectric Elastomer Actuators with Interdigitated Mechanically Compliant Electrodes. 2018, 7, 73-86.
17. Nguyen, C.; Phung, H.; Nguyen, T.; Lee, C.; Kim, U.; Lee, D.; Moon, H.; Koo, J.; Choi, H. A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators. Smart Mater. Struct. 2014, 6, 065005.
18. Wang H, Zhu Y, Zhao D, Luan Y, Performance Investigation of Cone Dielectric Elastomer Actuator Using Taguchi Method. Chinese Journal of Mechanical Engineering. 2011, 24: 685-692.
19. Cao, C.; Conn, A.T. Performance Optimization of a Conical Dielectric Elastomer Actuator. Actuators 2018, 7, 32.
20. Bruch, D.; Willian, T.P.; Schäfer, H.C.; Motzki, P. Performance-Optimized Dielectric Elastomer Actuator System with Scalable Scissor Linkage Transmission. Actuators 2022, 11, 160.
21. Cao, C.; Conn, A. Elastic actuation for legged locomotion. In Proceedings of the SPIE Electroactive Polymer Actuators and Devices (EAPAD), Portland, OR, USA, 17 April 2017.
22. Conn, A.T.; Rossiter, J. Towards holonomic electro-elastomer actuators with six degrees of freedom. Smart Mater. Struct. 2012, 3, 035012.
23. Meng X Y.; Ge W.J. Actuator Configuration of Optimal Motion Posture for Underactuated Hopping Robots[J]. China Mechanical Engineering. 2017, 28, 1765-1770.
24. Wang K D.; Chen S.; Tang W. A Bionic Bouncing Robot Design and Made Inspired by Locusts[J]. China Mechanical Engineering. 2023, 34, 2946-2951.
25. Kovac M.; Fuchs M.; Guignard A. A miniature 7g jumping robot[C]// 2008 IEEE International Conference on Robotics and Automation，Pasadena，CA，USA, May 19-23， 2008.
26. Semini C.; Tsagarakis N.;, Guglielmino E. Design of HyQ–a hydraulically and electrically actuated quadruped robot[J]. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 2011, 225, 831-849.
27. Bartlett N.; Tolley M.; Overvelde J. A 3D-printed, functionally graded soft robot powered by combustion[J]. Science, 2015, 349, 161-165.
28. Mao T.; Peng H.; Zha Z.; Continuous Jumping Soft Robot Driven by Shape Memory Alloy [J]. Continuous Jumping Soft Robot Driven by Shape Memory Alloy. 2021, 41, 447-452.
29. Luo, B.; Li, B.; Yu, Y.; Yu, M.; Ma, J.; Yang, W.; Wang, P.; Jiao, Z. A Jumping robot driven by a dielectric elastomer actuator. Appl. Sci. 2020, 10, 2241.
30. Du, Y.; Wu, X.; Wang, D.; Zhao, F.; Hu, H. Multimodal Resonances of a Rectangular Planar Dielectric Elastomer Actuator and Its Application in a Robot with Soft Bristles. Biomimetics. 2024, 9, 488.
31. Luan Y G.; Wang H M.; Zhu Y L. Design and Implementation of Cone Dielectric Elastomer Actuator with Double-slider Mechanism. 2010, 7, s212~s217.
32. Chan K., Dong-J.L., Sun P., Jung, G., Wang P.J., Dipo: a miniaturized hopping robot via lightweight and compact actuator design for power amplification[J]. Bioinspiration & Biomimetics. 2023, 18, 046006.
33. Pope M H . Elastic mechanisms in animal movement[M]. Cambridge University Press,1988, pp: 35-39.

The revision part have been marked in red.

Comment 2. Cone Design – This statement is difficult to follow…. The preload mechanism can be analysed as opposing vertexes double-sliders mechanism on the top [13]. For analysing conveniently, one double-sliders mechanism shown in figure 1(b) is analysed in detail.

Response 2. Agree.  “The preload mechanism can be considered as two double-sliders mechanisms. One mechanism consisted of slider 1, slider3 and linkage between of them. The other mechanism consisted of slider2, slider3 and the linkage between of them. The forces of the two mechanisms are outputted by slider 3 along with y direction. Now we choose the double-slider mechanism with slider 1 and slider3 shown in figure 1(b) to analyze in detail.” This explanation was added in ‘2.3 Design of Preload Mechanism’. 

Comment 3. Is the preload from the spring or was it pre-stretched to 375% and if so how?

Response 3. This part didn't explain well. To make it clear, we add '2.1 Fabrication' section. There we introduce the roles of pre-stretching device and preload mechanism.

Comment 4. This sentence is unclear. “The testing stretching forces of DE film under 7.5kV and 0V voltages are showed in Figure 3.”

Response 4.  To make the principle clear, we add this part ‘To design the parameters of the preload mechanism, the force changing with displacement curves of DE film under power on and power off are tested. The measurement equipment consisting with force sensor, stretching plate and high voltage module (DW-P103-1ACD8) is shown in Figure 5. The rigid outer ring frame is fixed on the stretching plate, and inner frame is fixed on the force sensor (BK-5D，Sensor701). NI PCI-6221 DAQ card is used to measure the output force of DEA. When the stretching plate is moving slowly (0.2 mm/s), the force sensor can obtain the output force with displacement. The stretching forces of DE film under 7.5 kV and 0 V voltages are showed in Figure 6.‘ this part was added on page 5.

Comment 5. This sentence is unclear. “Whether the two points is proper directly affects the performance of the DEA.”

Response 5. To make it clear, we add  '2.2 Working Principle ' section. The content is as follows :

The working principle of DEA is shown in Figure 3. When power is on, the DE film contracts in thickness and expands in area under Maxwell pressure. When power is off, the film will return to its initial dimension. During the two processes, the curves of film force-displacement are f_on and f_off respectively. If a preload mechanism can provide suitable preload force f_p, there exists two balance positions A, B. The stroke of DEA is the displacement change between A, B. The output forces during stroke and return process are the resultant force between f_p and f_on and between f_off and f_p.

Comment 6. Remove firstly. “To test the performance of DEA, its displacement is measured firstly”.

Response 6. We removed the word of ‘firstly’ from our manuscript.

Comment 7. Results – Table 3.  How many tests were performed and what was the standard deviation?

Response 7. 

Every test was conducted 5 times. The results are shown in Table 4.

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

 

The research article deals with developing cone dielectric elastomer to be used as the actuator for the hopping mechanism. Although the article is really promising, it is poor written, its English is poor, it is hard to understand, units are not correctly written, not all symbols that are used are explained, experiments are poorly explained, and results are not completely clear. I encourage the authors to really improve the methods, equations, units, writing, experiments and results to be suitable to be published in scientific journal. More comments in the attached file.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Both English and sentence formation must be corrected.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Comments

This manuscript presents an innovative design of a jumping robot driven by a conical dielectric elastomer actuator (DEA), with potential scientific research and applications. The advantages of this paper are its detailed design process, rational mathematical modeling and experimental validation, and a discussion of the relationship between the torsion spring precompression angle and the robot jump performance, which provide valuable insights for further studies. However, this paper has shortcomings in innovative elaboration, experimental design and verification of reproducibility of the results. Furthermore, more experimental data are needed to support these conclusions and conduct in-depth discussions to improve the academic depth of the paper. Detailed comments can be found below.

 

Scientific issues

1.    Although the principle and the application of DEA are mentioned, the research and application of DEA can be further expanded in similar jumping robots.

2.    It is suggested to add more charts and images to clearly demonstrate the structure and movement mechanism of the robot.

3.    Whether the selection of materials and parameters used in the DEA design has sufficient theoretical basis and experimental support.

4.    In the design part of the experiment, the number of replicates, the experimental condition control and the methods used for data analysis should be clearly stated.

5.    The article can increase the performance comparison with other types of jumping robots or driving mechanisms (e. g., electromagnetic, hydraulic, etc.) to highlight the advantages and limitations of DEA.

6.    It is recommended to proofread the article to eliminate grammatical or typos and ensure readability and professionalism of the manuscript.

7.    The paper mentions changing the jump height of the robot by changing the precompression angle of the torsion spring, but there is no detailed data analysis to demonstrate this change, and the authors provide more detailed data to verify these changes.

8.    For DEA-driven jumping robots, response time is an important performance indicator, so it is suggested that the authors increase the time of measuring DEA from receiving the electrical signal to the beginning of the jump response and analyze it.

9.    This paper mainly studies the single jump performance of the robot, and recommends the authors to perform repeated experiments and determine the number of tests to obtain enough data to evaluate the durability and reliability.

10. Despite mentioning the use of a combination of torsion spring and DEA to drive the jumping robot, the innovative description of the design is not clear and needs to be further strengthened in the abstract and text.

Comments on the Quality of English Language

The English writing quality of this article is generally good, the language is clear and professional. However, some sentence structures are slightly complicated, and further simplification is recommended to improve readability. At the same time, it is necessary to pay attention to the consistency of tense, and maintain accuracy and uniformity in the use of some technical terms. A thorough round of proofreading is recommended to correct any grammatical errors and typos and to ensure fluency and professionalism.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

In this manuscript, the authors developed a cone DEA driven hopping robot. The mechanism of the robot was modelled, the DEA output performance was tested and the hopping robot was demonstrated in the end. Overall, the novelty of this paper is clear, however, the reviewer has the following comments:

1.       It is suggested to include more state-of-the-art DEA driven robots and hopping robots driven by other principles in the introduction section. In its current form, the papers in the introduction section are mostly out-of-date and were very briefly listed without any discussion.

2.       Introduction section should have been numbered as 1, not 0.

3.       The English writing of this paper is poor and must go through proper English editing in its revision stage. It is very clear that the contents were translated from Chinese by using some sort of translation software. However, some contents lost their true meanings during translation. For example, ‘driver’ should be ‘actuator’ if the authors mean ‘Qu Dong’, ‘joystick’ should be ‘rocker’ if the authors mean ‘Yao Gan’. These mistakes must be corrected to improve the readability.

4.       Figure 3, legend part is too small to read.

5.       The DEA testing part should be described more clearly. What is the experimental setup, what is the model of the high voltage amplifier and the force sensor? How is the DEA stretched and at what stretch rate? How are the forces measured in Figure 6?

6.       Table 2, what is ‘DEA a’?

7.       Please discuss possible strategies to reduce the weight of the robot.

 

 

 

 

Comments on the Quality of English Language

The English writing of this paper is poor and must go through proper English editing in its revision stage. It is very clear that the contents were translated from Chinese by using some sort of translation software. However, some contents lost their true meanings during translation. For example, ‘driver’ should be ‘actuator’ if the authors mean ‘Qu Dong’, ‘joystick’ should be ‘rocker’ if the authors mean ‘Yao Gan’. These mistakes must be corrected to improve the readability

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

A big progress have been made by the authors to improve the quality of the research. No further comments on the work.

Comments on the Quality of English Language

It would be advisable if one native English speaker could read the work to improve the quality of English.

Author Response

Comment 1: [It would be advisable if one native English speaker could read the work to improve the quality of English.]

Response 1: We invited an native English  speaker to looked throughout our manuscript and corrected the manuscript. All changes are marked in red.

Reviewer 4 Report

Comments and Suggestions for Authors

Comments

The details of the design, experimental data of the DEA driven jump robot and factors influencing jump performance are described in more detail in the revised manuscript. However, after reading the revised manuscript, we believe there is room for further improvement to enhance the academic value of the article and the rigor of the experimental data. Here are some specific feedback and suggestions:

 

Scientific issues

1.    The authors are advised to provide data on the DEA response time and explain its improvement in the overall system performance.

2.    It is recommended that the authors add DEA changes in output power, response time and jump height after multiple cycle jumps to verify the performance stability and durability of DEA.

3.    The authors have added some charts, but some of the illustrations can still be clearer, such as indicating key parameters or analysis points in the working principle and experimental data charts, so that the reader can better understand them.

4.    The language expression in the revised draft is recommended to ensure the accuracy and overall fluency of the term.

Comments on the Quality of English Language

The English expression of the manuscript is clear overall, but there is room for improvement to enhance its academic rigor and readability. Authors are advised to note the consistency of the terminology. It is recommended to optimize the sentence structure in long sentences to enhance the fluency of the text. Some of the expression is relatively lengthy, so it is recommended to simplify and avoid duplication. There are also some spelling errors and punctuation problems in the manuscript that require careful inspection.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

Most comments have been addressed by the authors, however, English writing still requires improvements.

Comments on the Quality of English Language

The authors are suggested to use professional English editing services to improve their English writing. To the reviewer's knowledge, MDPI provides such services.

Author Response

Comment 1: [The authors are suggested to use professional English editing services to improve their English writing. To the reviewer's knowledge, MDPI provides such services.]

Response 1: Thank you for your suggestion . We invited an English native speaker to looked throughout our manuscript and corrected the manuscript. All changes are marked in red.