Maintaining stable operation of battery swapping stations under time-varying demand is a critical issue in Advanced Air Mobility (AAM). This study proposes a stepwise capacity expansion strategy in which pre-secured standby swapping channels are sequentially activated when either queue length or longest waiting time reaches a predefined threshold. The main comparison was conducted between a two-channel fixed-capacity configuration (Fixed-2) and the stepwise expansion configuration (Stepwise), while a three-channel fixed-capacity configuration (Fixed-3) was additionally used as a benchmark. Using common random numbers, 100 simulation replications were performed under identical demand and operating conditions. Compared with Fixed-2, Stepwise reduced average waiting time by 88.48%, waiting probability by 50.80%, and average queue length by 88.76%, while throughput remained nearly unchanged. In the paired comparison, Stepwise showed a lower average waiting time in 99 of 100 replications and the same value in one replication. Sensitivity analysis showed that lower threshold values activated channels earlier and improved waiting performance, but increased the number of active channels. These findings indicate that stepwise activation can effectively mitigate congestion under model-based time-varying demand, although the threshold values should be interpreted as operating reference conditions rather than universal optima.

Abstract
1. 서 론
2. 시스템 구성 및 단계적 설비 확장 구조
    2.1. 시스템 정의 및 운영 범위
    2.2 운영 상태 모델 및 성능 지표
    2.3 운영 안정성 및 설비 확장 규칙
3. 시뮬레이션 설계 및 분석 조건
    3.1 수요 및 기본 운영 조건
    3.2 단계적 설비 확장 운영 로직
    3.3 반복 시뮬레이션 및 분석 방법
4. 시뮬레이션 결과 및 분석
    4.1 주요 성능지표 비교
    4.2 운영 안정성 분석
    4.3 운영 기준 변화에 따른 민감도 분석
5. 결 론
    5.1. Fixed-2의 운영 성능 특성
    5.2. Stepwise 적용에 따른 운영 성능 변화
    5.3. Stepwise의 채널 활성화 및 민감도 특성
    5.4. 설비 확장 전략의 적용 가능성
후 기
References

• 이우람(Division of Unmanned Aerial Vehicles, Kyungwoon University, Professor) | Wooram Lee Corresponding author