Multi-Body Dynamics Modeling and Straight-Line Travel Simulation of a Four-Tracked Deep-Sea Mining Vehicle on Flat Ground
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsAuthors used multibody dynamics simulations in RecurDyn to analyse the start, drive and brake motions of a four-tracked deep sea mining vehicle. Design of tracked vehicles with multibody dynamics simulations is not new as there are 'standard' tools for that in e.g. Adams ATV or Recurdyn, as mentioned by the authors. The novelty of this work is in sophistication of the soil-structure interaction models.
The authors propose empirical relations from different sources in literature and integrate them as soil-structure interaction force in the multibody dynamics simulations. The equations are presented in a clear manner. They have not been verified for their correctness by the reviewer. The multi-pass effect is described in much detail including background considerations. It is acknowledged that the validity of these is site-specific.
The main deficit of this work is in the lack of (experimental) validation of the integrated model(s). With elaborate empirical and analytical models, and their integration into a single simulation framework, it is rather easy to make minor mistakes that will propagate through the simulations into the results. The authors are encouraged to present validation/verification of their sub-models for those where insufficient public literature and validation is available.
Overall an interesting exercise that is reported in sufficient detail for others to follow-up on this work, with the addition that validation/verification of the models is deemed essential. Please consider verification of correctness of models and report on this in the paper.
Author Response
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Reviewer 2 Report
Comments and Suggestions for AuthorsThe article details the simulation of an underwater mining machine. It is an extensive work and analyzed in detail. However, despite the fact that it is necessary work, it only shows a simulation and the implementation in it of forces characterized in a laboratory test. Therefore, it is not possible to extract from the simulation results more information than expected, since the simulation behaves as it has been programmed. Mainly for this reason, the article does not contribute novelties to the state of the art, which is why it does not seem to me that it should be accepted in its current form.
In addition to this, the modeling of the vehicle is quite superficial and it would be convenient to detail it a bit, especially the topology of the suspensions or the arms that join the tracks to the chassis. The data on masses and inertia of the elements are also of special relevance, as well as indicating where they were obtained from. In the event that they are not reliable, it would greatly reduce the confidence of the simulation results.
It should also be clarified whether vehicle weight and water buoyancy are used, or whether underwater weight is used instead. It would be convenient to clarify that the thrust that is applied at the centroid of the vehicle and the real weight at the center of gravity. If there are variations in the density of the vehicle, they do not have to coincide.
Other minor aspects must be addressed:
On p. 2, line 70, it is convenient to clarify if the “simulated” sediments are real (physical) sediments that are used for an experimental study that recreates the sediments of the seabed.
Consider whether photos rather than diagrams of vehicle types would provide more information about the vehicles (idea of size, suspension detail, etc.)The introduction should also provide more detail on what is expected from the simulations, what is the object of the study, especially if the validation of the simulations is not presented.
Pg. 8, line 206. Sinkage, z, should be unequivocally defined.In figure 10, other parameters that are being referred to in the text (direction of movement, zc, h, etc.) could be added.
Equation (15) is not related to the force scheme presented in figure 10.
On page 13, line 368, it is striking that Ce=(0.1-0.2) Cc if Ce has more slope than Cc.
Page 15, line 421, L and d are not unequivocally defined either in the text or represented in any figure.
Page 15, line 431, the coordinate system used and the location of the origin, etc., should be established much earlier.
In equation (29) the parameter zd, which is referred to in the following line, does not appear.
Page 17, line 488. From what is indicated, the origin of these changes in speed is uncertain. If they are not validated, it is not admissible to say that they are more similar to reality.
Page 17, line 491. Align the heading to the left.
Table 2. It would be convenient to add what each parameter is.
In epigraph 3 the figures referred to are very poorly placed. The first alluded to is figure 24, which is 12 pages later. Please check the placement of all the figures. Reference is made simultaneously to figures 15 and 19. Wouldn't they be better located together?
Table 4. Add the units of the indicated magnitudes
Page 24, line 658. Without validating the model (comparing the simulation results with a real experiment) it cannot be affirmed that the validity of the dynamic model is verified. At most it can be said that the result is realistic.
Page 24, line 667. In the simulations, what has been programmed in the simulation must occur.
Page 24, line 683. Without detailing the suspensions or the connections between the tracks and the chassis, it is not easy to conclude about the different behavior of one axle and the other.
Page 29, lines 814-815. Speed control has not been detailed, so it is not easy to assess that statement.
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsIt is interesting to note that the addition of various variables to the simulation model is in this paper. Still, in its current state, it is not much about the scientific contribution of the proposed method but rather about application research. The following suggestions should be considered by the authors.
1. The scientific contribution of the manuscript should be clarified.
2. It is needed to add some information about the extent to which the proposed equations improved the accuracy compared to the previously known equations.
3. It would be good to show how much each resistance force contributes to the accuracy.
4. on line 169, please review that Figure 6 should not be Figure 7(a).
5. on line 206, please review PHI’s uppercase and lowercase letters.
6. on line 312, please review that Figure 9 is not Figure 11
7. on line 380, it is recommended to add a definition of Residual Shear Characteristics of Soils
8. line 527, please explain how the rotatable design is configured (the reviewer thought that the idler can rotate around the center of rotation of the sprocket, so it moves up and down)
9. line 737, confirmation that the description is consistent with what is shown in Fig20. From the graph, internal and water resistance do not appear to increase initially.
10. limitations of this study and future work should be added.
Author Response
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Reviewer 4 Report
Comments and Suggestions for AuthorsYou worked hard to write your paper.
1. Your paper is about the multi-body dynamic analysis of the tandem-tracked vehicle on cohesive soft soil. What do you think is the originality of this paper? In my opinion, It was extracted from reference papers that most of the theories used in the paper. I don't know what the originality of the paper is. Please describe the originality of your paper.
2. The accuracy of the numerical simulation results has not been checked. How are you going to validate the results of your numerical analysis?
3. Please check Figure number on line 570.
4. Please identify the source of the coefficient values used in your paper.
Author Response
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Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsComments have been sufficiently addressed.
Author Response
Thank you very much for your comments.
Reviewer 2 Report
Comments and Suggestions for AuthorsMost of the observations that I had previously indicated have been satisfactorily corrected. However, my main objections to the article still largely remain. Specifically:
1. The simulation itself is not new and it is not conclusive proof for other formulations either. A characteristic of a simulation that does not occur in reality is that, given the same inputs, the same result is always obtained, as many times as the simulation is executed. This is independent of the goodness of the programmed functions. For this reason, perhaps the objectives of the document should be focused on two aspects: a) determine, among two possible vehicle designs, the most suitable for its function through realistic simulations. This would entail a more detailed analysis of the two proposed options. b) introduce some original functions of the authors to estimate the resistance of the soil. This other objective would mean, at least, comparing the values of this estimate with others that have already been verified, such as those carried out by the program. I believe this comparison is essential to guarantee the quality of the estimates.
2. It must be indicated that the physical magnitudes of the model have been obtained using design software. If the vehicle includes items with different physical properties (eg batteries, motors, etc.) it should be specified. Sometimes these elements significantly influence the dynamic behavior of the vehicle.
3. Part of the article should be rewritten according to the objectives described in point 1.
Finally, in line 887 of the new wording there must be some error. A sprocket cannot has the velocity of an angel.
Author Response
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Reviewer 4 Report
Comments and Suggestions for Authors1. Please change the description of γs in Table 1 from "unit weight" to "specific weight"
2. The simulation time was set to 45 seconds on page 21. According to the simulation conditions in Table 4, the angular velocity function was composed of two step functions. Angular velocity was set to zero after 45 seconds. It is important to look at the analysis results, after the angular velocity becomes zero. Please add the analysis result with the simulation time longer than 45 seconds.
3. What is the meaning of Vehicle Body, Vehicle Body-Fixed in Fig. 17.
4. Why is the fluctuation of the pitch angle of the rear track so large in Fig. 17 ? What is the reason?
5. In your paper, the total sinkage consists of static sinkage and dynamic sinkage. By the way, how did you apply dynamic sinkage model? The dynamic sinkage is caused by the tracks shearing the sediment. In your paper, how did you apply dynamic sinkage model as a numerical analysis model?
Author Response
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Round 3
Reviewer 2 Report
Comments and Suggestions for AuthorsThe modifications made seem satisfactory to me. I would like to thank the authors for their efforts and encourage them to perform a validation of their results as soon as possible.
