Research on Miniaturization Design of Floor-standing Pole Electric Slewing Mechanism

This study is dedicated to investigating the downsizing design and ensuring the structural robustness of pole-mounted slewing mechanisms, aligning with the dynamic requirements of the power industry. The research encompasses critical facets, including the intricacies of mechanical structure design, meticulous motor selection, and a thorough finite element analysis. The outcomes reveal a noteworthy safety factor of 2.08, surpassing the standard requirement of ≥ 2, albeit without factoring in stress concentration. This study underscores the paramount importance of downsizing design in meeting the evolving demands of the modern power industry. It offers invaluable insights into the structural integrity and stability of the mechanism, thereby ensuring its reliability and safety in practical applications. The implications of these findings are poised to catalyse significant technological advancements in the realm of pole-mounted electric slewing mechanisms.


Introduction
With the rapid growth of the power industry, the application of floor-standing poles has become increasingly widespread [1][2][3].However, modern power equipment places higher demands on these structures, including the need for downsizing, enhanced efficiency, and adaptability to diverse application environments.Consequently, downsizing design has become a focal point of research and development [4][5][6][7].
This paper focuses on the study of downsizing design for pole-mounted electric slewing mechanisms, aimed at meeting the emerging demands in the power industry.Downsizing design not only requires reducing the physical footprint of the mechanism but also demands increased flexibility and cost efficiency [8,9].Simultaneously, the structural integrity, stability, and performance of the mechanism must remain outstanding.
In the pursuit of downsizing design, various critical factors come into play, including the optimization of mechanical structure and the selection of suitable motors.Engineering considerations such as strength verification, fatigue analysis, and safety assessments are indispensable to ensure the mechanism's reliability under diverse working conditions [10][11][12].
This paper delves deep into the essential elements of downsizing design for pole-mounted electric slewing mechanisms, addressing key aspects such as the optimization of mechanical structures, motor selection, and strength verification.Our objective is to provide insights and methodologies for the power industry on how to adapt to evolving demands and drive technological progress.

The Design Principles for Lightweight and Compact Electric Rotary Mechanisms
To achieve the downsizing design of the floor-standing pole electric slewing mechanism, meeting the requirements for pole-mounted power rotation and full inverting assembly, this paper proposes a design solution using an internal tooth ring rotation method.An AC motor drives a gearbox, the gearbox drives a small gear, the small gear drives the rotating support tooth ring, ultimately achieving the pole-slewing joint rotation, as shown in figure 1.The power rotary mechanism employs an internal gear engagement method, with the drive motor positioned beneath the rotating support, as depicted in figure 2. However, the integration of the motor within the mechanism compresses the internal space of the rotating support, causing potential interference between the variable amplitude rope and the hoisting rope as they pass through the rotary mechanism.Therefore, it is essential to optimize the spatial arrangement of the components within the rotary mechanism.By establishing a three-dimensional simulation model and conducting multiple animated simulations, the optimal layout of the key components of the power rotary mechanism and the path of the steel cables have been determined, as illustrated in figures 2 and 3.

Model of Pole-Mounted Slewing Mechanism
The load on the pole-mounted slewing mechanism primarily originates from the mast and the jib, specifically represented by the forces transmitted through the mast's primary material and the jib's primary material, as indicated in figure 4. Based on the actual load analysis of the pole-mounted structure, it is observed that the highest forces are exerted by the mast-connected primary material during unbalanced lifting under the rated lifting load.Conversely, when operating at the smallest working radius under the rated lifting load, the jib-connected primary material experiences the highest forces.Table 1 provides the extracted axial forces in the joint components of the slewing node, which can be utilized for finite element analysis of the pole-mounted slewing mechanism.

Simulation Result Analysis
Simulation calculations were performed on the slewing joints of working Scenarios 1, 2, and 3 respectively, and the stress cloud diagram and deformation results were obtained (the deformation ratio was enlarged 150 times), as shown in figures 5 and 6.Based on the results obtained from the comprehensive simulation analysis, several critical findings have been highlighted, shedding light on the structural integrity and safety of the pole-mounted slewing mechanism.In the analysis of three distinct scenarios, stress concentrations were observed, with peak localized stresses recorded at 221.88MPa, 219.21MPa, and 385.84MPa.Notably, in Scenario 3, the highest stress, reaching 170MPa, was identified at the root connection of the jib connection base.
It is imperative to emphasize that the material choice for the lifting mechanism, Q355B, featuring a yield strength of 355MPa, was a pivotal consideration.The calculated safety factor of 2.08, without accounting for the effects of stress concentration, is a crucial validation of the structural strength of the pole-mounted mechanism.This figure underscores the mechanism's ability to endure loads safely, meeting and even exceeding the industry-standard safety requirement of a safety factor greater than or equal to 2.
The identification of stress concentration areas within the mechanism underlines the significance of further engineering considerations.These include stress redistribution, the potential for structural reinforcement, and enhanced design modifications to mitigate the localized stresses.The findings not only serve as a testament to the structural robustness of the pole-mounted slewing mechanism but also provide a foundation for future design enhancements and optimization to ensure the highest levels of safety and performance under diverse operational Scenarios.

Conclusion
This study underscores the significance of downsizing design in pole-mounted slewing mechanisms to meet the demands of the power industry.Through a comprehensive approach encompassing mechanical design, motor selection, control systems, and finite element analysis, the following conclusions have been drawn: (1) Downsizing design is a pivotal element in addressing the requirements of the power industry.It offers enhanced flexibility, cost reduction, while concurrently maintaining structural stability.
(2) Finite element analysis has unveiled areas of stress concentration under specific working Scenarios.However, even without accounting for these scenarios, the mechanism attains a safety factor of 2.08, complying with safety standards.
This research provides valuable insights into pole-mounted slewing mechanism design, fostering technological advancements and offering practical references for power equipment design.

Figure 1 .
Figure 1.Diagram of loadings on the ground derrick.

Figure 2 .
Figure 2. Main components of electric slewing mechanism.

Figure 4 .
Figure 4. Schematic of the load positions on the slewing mechanism.

Table 1 .
Axial forces in the pole-mounted slewing node components (kN).