PID-Based Design of Automatic Control System for a Travel Speed of the 4UM-120D Electric Leafy Vegetable Harvester

Round 1

Reviewer 1 Report

The authors developed a PID-based automatic control system for travel speed based on the

analysis of the entire machine structure of the 4UM-120D electric leafy vegetable harvester to enhance the operation quality of the harvester and lessen the workload of operators. This is a very useful and interesting system. Thus, I would like to suggest to accepting this article with a minor revision.

1.     The display diagram of this system is not very clear. So, I cannot clear understand the composition of the system and the role of each part.

2.     What are the advantages of this compared to other similar works?

3.     Will the 4UM-120D damage the plant when we use it to collect leaves?

Author Response

Response to Reviewer 1 Comments

Point 1: The display diagram of this system is not very clear. So, I cannot clear understand the composition of the system and the role of each part.

Response 1: Thank you for your valuable suggestions. I apologize that the display diagram of the PID-based automatic control system for travel speed is not very clear. The modified and clearer display diagram of the system is shown in Figure 2. The PID-based travel speed automatic control system included a Kunlun Tongtai touch screen, computer, S7-200SMART PLC, DC48V lithium battery, travel motor and its driver, and Hall speed sensor. The Kunlun Tongtai touch screen was used to enter the desired travel speed and adjust the initial value of the travel motor drive voltage. The computer was used to write PLC programs. The S7-200SMART PLC made a difference between the current value of the travel speed and the set value and derived the deviation amount, which was calculated by the PID control algorithm to get the bus voltage value at both ends of the travel motor. The DC48V lithium battery was used to power the entire system. The travel motor and its driver adjusted the speed according to the size of the bus voltage at both ends to realize the travel speed automatic control function, and real-time measurement of the travel motor speed was made using a Hall speed sensor.

Figure 2. Travel speed automatic control system.

Point 2: What are the advantages of this compared to other similar works?

Response 2: Thank you for your valuable suggestions. With each basket of leafy vegetables collected throughout the harvesting process, the load on the harvester grows. The travel speed will decrease if the power output isn't increased. The harvester's travel speed will be slower when it climbs hills or navigates bumps during harvest if the leafy vegetable planting monopoly surface (bed surface) doesn't fulfill agronomic standards. All of the aforementioned scenarios call for manual speed modification, yet there are drawbacks such as imprecision and huge adjustments being made easily. Inefficient harvesting is caused by excessive travel speed adjustment, which expands the missed cutting zone. However, in the actual harvesting operation, the operator's professionalism is generally lacking, making it challenging to keep the leafy vegetable harvester in stable working condition for a long time. As a result, the harvester runs too slowly or too quickly, which not only intensifies the operator's work but also has a greater impact on the efficiency and quality of leafy vegetable harvesting. Based on this, this paper takes the self-developed 4UM-120D electric leaf vegetable harvester as the research object and focuses on the research status at home and abroad, and designs an automatic control system of travel speed of electric leaf vegetable harvester based on PID. When the deviation between the current value of the harvester's travel speed and the set value exceeds ±2%, the automatic control system of the travel speed of the electric leaf vegetable harvester based on PID will automatically adjust the travel speed to keep it within the range of ±2% of the set value. Compared with manual speed regulation, the system has shorter adjustment time, better stability and stronger resistance to disturbance. The system provides a way to improve the working efficiency and quality of leaf vegetable harvester and reduce the working intensity of operators.

Point 3: Will the 4UM-120D damage the plant when we use it to collect leaves?

Response 3: Thank you for your valuable suggestions. When 4UM-120D electric leaf vegetable harvester harvests leaf vegetables, it will not harm the leaf vegetables themselves, because the harvester harvests the mature stems and leaves on the top of the leaf vegetables. After the mature stems and leaves on the top of leaf vegetables are harvested, a new batch of mature leaf vegetables will appear after a growth cycle, realizing sustainable harvest and development.

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Author Response File: Author Response.pdf

Reviewer 2 Report

In this study, a PID-based automatic control system for travel speed based on the analysis of the entire machine structure of the 4UM-120D electric leafy vegetable harvester was developed to enhance the operation quality of the harvester and lessen the workload of operators. I think that the work described in the manuscript is interesting. In general the work is well structured; however, I believe that minor revisions are necessary before the manuscript can be published. The authors presented an interesting work with a clear methodology of system development and implementation.

Comments:

1.      What are the technical data of the DC motor used, such as revolution, speed, torque etc.? If you can add these information in the article, I believe that the readers will be able to get information about the structure of the machine more easily.

2.      Although the authors presented good detail about the development process in the methodology section, the result section lacks essential information.  What was the PLC response time during validation? Sensor data accuracy? What driving speed the system was tested? Effect of forward speed to PLC response time? Response time caused any sync problems? Accuracy of position control or speed control for cutting units using the PLC? What are the key contributions of this paper? Any loss of sensor data? Any faults and warnings indicated by PLC during validation? Limitations of this study? As a suggestion, I think the article will be enriched if a small paragraph is added to the article as an answer to the above questions.

3.      I think the work is very important and impressive. Thank you for contributing to the scientific literature on the subject.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 Comments

Point 1: What are the technical data of the DC motor used, such as revolution, speed, torque etc.? If you can add these information in the article, I believe that the readers will be able to get information about the structure of the machine more easily.

Response 1: Thank you for your valuable suggestion. The travel motor of 4UM-120D electric leaf vegetable harvester is a DC brushless motor, with a revolution range of 0~2000rpm, a reduction ratio of 1:42.5, and an output revolution range of 0~47rpm. The rear wheel of 4UM-120D electric leafy vegetable harvester is a traveling driving wheel with a diameter of 35cm, so the traveling speed of the harvester is 0~0.86m/s. The set revolution of DC brushless traveling motor is 1000rpm, so the set traveling speed of the harvester is 0.43m/s. The electromagnetic torque coefficient of DC brushless traveling motor is 0.1697. The three-phase winding resistance of DC brushless traveling motor stator is 0.01391. The self inductance of three-phase stator windings of DC brushless traveling motor is 5.82. The rotor moment of inertia of DC brushless traveling motor is 0.001677. The viscosity friction coefficient of DC brushless traveling motor is 0.02.

Point 2: Although the authors presented good detail about the development process in the methodology section, the result section lacks essential information.  What was the PLC response time during validation? Sensor data accuracy? What driving speed the system was tested? Effect of forward speed to PLC response time? Response time caused any sync problems? Accuracy of position control or speed control for cutting units using the PLC? What are the key contributions of this paper? Any loss of sensor data? Any faults and warnings indicated by PLC during validation? Limitations of this study? As a suggestion, I think the article will be enriched if a small paragraph is added to the article as an answer to the above questions.

Response 2: Thank you for your valuable suggestion. The response time of PLC was 33ms~48ms during validation. The Hall speed sensor has a linear accuracy of ±3% and a resolution of 12 bits. The driving speed of the PID-based travel speed automatic control system under test was 0.43m/s. Because the sampling time of Hall speed sensor was set as 0.5s in this study, the forward speed of 4UM-120D electric leaf vegetable harvester had almost no influence on PLC response time. Response time did not cause synchronization problems in this study. Using PLC to control the speed of cutting units was more accurate, which could make the cutting motor change in the speed range of 0~300rpm. This paper developed a PID-based automatic control system for travel speed based on the analysis of the entire machine structure of the 4UM-120D electric leafy vegetable harvester to enhance the operation quality of the harvester and lessen the workload of operators. Taking the system adjustment time during the process of starting and maintaining the travel speed of the harvester within ±2% of the set value as the main evaluation index, the Box-Benhnken test method was applied based on the single-factor test, and the proportional coefficient Kp, the integral coefficient Ki and the initial value U of the travel motor drive voltage of the PID control algorithm were used as the test factors, and the PID-based 4UM-120D electric leafy vegetable Harvester travel speed automatic control system operating parameters based on PID was studied in a three-factor, three-level experiment, and a multiple regression model of evaluation indexes on each factor was established to analyze the influence of each factor on system rapidity and to obtain the optimal operating parameters. The results of the study could provide a way to improve the operation quality of leafy vegetable harvesters and reduce the work intensity of operators. The sampling time of the Hall speed sensor was set to 0.5s, and almost no sensor data was lost. During the validation process, PLC did not show any fault and warning, indicating that the stability of the PID-based automatic control system for travel speed was better. This paper only designed and studied the automatic control system of travel speed of 4UM-120D electric leaf vegetable harvester based on PID control strategy, without comparing and analyzing the dynamic response performance and stability of the automatic control system of travel speed under various other control strategies.

Point 3: I think the work is very important and impressive. Thank you for contributing to the scientific literature on the subject.

Response 3: Thank you very much for taking time out of your busy schedule to make invaluable suggestions to me. Thank you for your recognition and support of our work. "Sustainability" magazine is a very good journal. It is my honor to have my manuscript accepted by "Sustainability", and I also hope that my manuscript can be accepted by it. Please also kindly contact me if you have any suggestions during the review of my manuscript. Thanks again for the suggestion you gave me during your busy schedule.

Please see the attachment