Development of a precision heating strategy for smart frost management in apple orchards
Restricted (Penn State Only)
- Author:
- Hua, Weiyun
- Graduate Program:
- Agricultural and Biological Engineering (PHD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 22, 2024
- Committee Members:
- Suat Irmak, Program Head/Chair
Minghui Zhu, Outside Unit & Field Member
Long He, Co-Chair & Dissertation Advisor
Paul Heinemann, Co-Chair & Dissertation Advisor
Armen Kemanian, Major & Minor Field Member - Keywords:
- Frost management
Heating
Numerical simulation
Path planning
Cyber-physical systems - Abstract:
- Frost is one of the major causes of weather-related damage on crops, which has resulted in huge economic losses for growers in agriculture worldwide. This dissertation reviewed advanced technologies for high-efficiency frost management and developed precision heating methods for improving anti-frost effects. The studies included numerical models for understanding orchard-based heat transfer patterns under various scenarios, a multi-heater path planning algorithm with shortest path cost in multiple heating cycles, an estimation method of heater number according to orchard size, heater performance, and frost severity, and a smart cyber-physical heating system by perceiving environments and making corresponding heating decisions. First, a research gap toward effective heating-based frost protection was identified due to the lack of spatial temperature information. To simulate airflow and heat transfer in an apple orchard, computational fluid dynamics (CFD) models were developed. The effects of heater output intensity and output velocity, heating angle, ambient wind direction and velocity were analyzed. Additionally, quantitative comparisons between the mobile heating case and fixed heating cases were conducted. The second objective focused on the deployment of multiple heaters in multiple heating cycles in apple orchards. Traditional heating, either fixed or mobile, has limited heating capacity. Therefore, a precision heating strategy was proposed to prioritize applying heat to canopies with high heating demands in orchards. The precision heating experiments in a simulated orchard environment with dynamic multiple goal points were implemented by an improved A-Star path-planning algorithm, in which a path cost estimation-based linear optimization method was presented to find the optimal paths for multiple heaters and a conflict-based search (CBS) method was used to generate collision-free paths. In addition, an estimation method for the heater number based on the precision heating strategy was proposed and the heater number was determined by orchard size, heater performance, and frost severity. Finally, the difference in the heater number between precision heating and traditional heating was compared. The last part of the dissertation aimed to solve a research gap toward timely and autonomously implementing frost protection actions. Growers generally determine when and how to apply heat in orchards based on their experiences, leading to either insufficient heating or energy waste. Therefore, a frost protection cyber-physical system (CPCPS) was developed to make heating decisions based on real-time ambient temperature and wind direction data. The CPCPS consisted of a real-time temperature sensing system, an angle auto-adjusted heater, and an unmanned ground vehicle (UGV) to move the heating system. The results show that the CPCPS improved protection performance during the field tests. This dissertation provided the conclusions, implications, and future improvements at the end of each chapter. Overall, the outcomes of this dissertation provided important guidance for precision heating-based frost protection to mitigate frost damage on crops and could lead to promote agricultural sustainability.