An Effective Optimization Method for Integrated Scheduling of Multiple Automated Guided Vehicle Problems

Automated Guided Vehicle(AGV)scheduling problem is an emerging research topic in the recent literature.This paper studies an integrated scheduling problem comprising task assignment and path planning for AGVs.To reduce the transportation cost of AGVs,this work also proposes an optimization method consisting of the total running distance,total delay time,and machine loss cost of AGVs.A mathematical model is formulated for the problem at hand,along with an improved Discrete Invasive Weed Optimization algorithm(DIWO).In the proposed DIWO algorithm,an insertion-based local search operator is developed to improve the local search ability of the algorithm.A staggered time departure heuristic is also proposed to reduce the number of AGV collisions in path planning.Comprehensive experiments are conducted,and 100 instances from actual factories have proven the effectiveness of the optimization method.

Research of Dynamic Material Handling in an Automobile General Assembly Line Based on Real-time Information

The status of material delivery of an automobile general assembly line is analyzed, and the technique to achieve the real-time tracking of assembly status information is proposed based on RFID（ Radio Frequency Identification）. Thus the consumption of line-side buffer is obtained dynamically, then the type and quantity of needed material are fed back to the subsystem of material handling; the algorithm for determining the best time departure time of delivery driver based on minimizing of total time penalty function is proposed. This approach makes the material amount of a single delivery trip maximized and improves the efficiency of delivery drivers significantly in the case of does not affect the assembly line normal throughput. Additionally, although this dynamic material handling method is developed for the automobile assembly plant, it should be pointed out that this method is also applicable to other mixed model assembly plants such as electronics, semiconductor and aerospace industry.

Local temperature and El Niño Southern Oscillation influence migration phenology of East Asian migratory waterbirds wintering in Poyang,China

Temperature is a critical factor influencing avian phenology,due to its direct impact on food and water availability.Most previous studies have focused on the timing of spring migration and the arrival of birds at breeding grounds along the European and American flyways;little is known about migration ecology at the wintering sites along the Asian flyways.Using linear regression models,this study investigates how local temperature variation and EI Niño Southern Oscillation(ENSO)influences the arrival and departure timing of 9 waterbird species breeding in Mongolia or Siberia and overwintering in Poyang,China from 2002 to 2013.Birds mainly arrive at Poyang in October and depart for their breeding sites in March.Out of the 9 species,6 show a strong negative relationship between departure time and overwintering temperature in Poyang.Departure dates also show a negative association with overwintering ENSO and March ENSO for two species.Both local and large-scale climate indices show no influence on the arrival timing of waterbirds.We suggest that birds react to the annual variation of overwintering temperature:an earlier departure of waterbirds is facilitated by a warmer overwintering period and vice versa.The long-term accumulated temperature effect is more pronounced than ENSO and the short-term local temperature effect.Our findings could help quantify the potential impact of global warming on waterbirds.