An Efficient Scheduling Algorithm for Multi-Robot Task Allocation in Assembling Aircraft Structures

Abstract

Efficient utilization of cooperating robots in the assembly of aircraft structures relies on balancing the workload of the robots and ensuring collision-free scheduling. We cast this problem as that of allocating a large number of repetitive assembly tasks, such as drilling holes and installing fasteners, among multiple robots. Such task allocation is often formulated as a Traveling Salesman Problem (TSP), which is NPhard, implying that computing an exactly optimal solution is computationally prohibitive for real-world applications. The problem complexity is further exacerbated by intermittent robot failures necessitating real-time task reallocation. In this letter, we present an efficient method that exploits workpart geometry and problem structure to initially generate balanced and conflict-free robot schedules under nominal conditions. Subsequently, we deal with the failures by allowing the robots to first complete their nominal schedules and then employing a market-based optimizer to allocate the leftover tasks. Results show an improvement of 11.5% in schedule efficiency as compared to an optimized greedy multi-agent scheduler on a four robot system, which is especially promising for aircraft assembly processes that take many hours to complete. Moreover, the computation times are similar and small, typically hundreds of milliseconds.

Spatial–Temporal Load Balancing and Coordination of Multi-Robot Stations

“…An example presented in [8] assumes a constant duration between different groups of tasks and that robots can safely work simultaneously on these groups. Other examples that study the load balancing problem are presented in [9] and [10]: in the former the motion planning problem is disregarded and in the latter the workpiece is roughly a plane and thus the motions are easy to compute.…”

Dynamic Defender-Attacker Blotto Game

“…Dynamic resource/task allocation: Dynamical aspect of the resource allocation problem has been studied in different ways. Scheduling is one such formulation that considers tasks that must be completed in sequence [12]. On top of an efficient allocation algorithm, an adaptation mechanism is proposed in [12] which reacts to robot failures through a "market-based" optimizer to re-allocate the leftover tasks.…”

A Lean Robotics Approach to the Scheduling of Robotic Adhesive Dispensing Process

“…The literature review shows that there also exist studies that focus on industrial robot scheduling. These studies usually investigate several of the above-mentioned scheduling problems, and the effect of robot implementation is analysed in terms of its effect on the overall production process [12,15,21], robot task scheduling in specified jobs [16,22], and precise determination of robot end effector trajectory [6,23]. It should also be mentioned that the number of studies devoted Fig.…”

“…As far as task scheduling in specific production processes is concerned, previous studies usually provide in-depth analyses of robot movement parameters while neglecting the important aspect of robot task scheduling. Tereshchuk et al [21] proposed that the robot path planning problem should be described by means of the classic traveling salesman problem (TSP). This type of approach was adopted in numerous studies.…”