Seohyun Jeon

Task allocation strategy of heterogeneous multi-robot for indoor surveillance

Multi-robot cooperation promises increased performance and fault-tolerance in large-scale environments. To achieve the goal with these features, dynamic task allocation algorithm is required to adapt changing environment. Whereas previous researches mostly have been done for simplifying the mission and emphasizing the task allocation algorithm, this paper addresses the needs to analyze the mission more concretely and introduces a strategy for the task allocation problem: off-line and on-line analyses. The off-line analysis takes the robot-working scenario into account statically before deploying the robots. The on-line analysis considers the real time task allocation algorithm while running the robots. Combining these two analyses, efficient task allocation is achieved with minimum cost.

Vehicle routing problem with pickup and delivery of multiple robots for hospital logistics

This paper considers multiple mobile robots for hospital logistics application. To increase the efficiency of using multiple robots, more than one delivery tasks can be assigned to a robot instead of delivering one package at a time. Since a robot can accept more than one task while delivering, a real-time routing method for visiting multiple pickup and delivery positions is required. This paper proposes an exhaustive search algorithm that reduces the computational resource for finding the shortest path while promising global minimum solution. This algorithm derives the shortest path that visits multiple positions by finding possible combinations with minimum iteration of the function while not allowing inversely visiting of pickup and delivery position. Applying distance matrix to the generated combination result, the total travel distance can be derived. The robot that provides the minimum total travel distance is selected for the new task. The algorithm is tested by the simulation and the result shows that the proposing method not only increases the delivery efficiency but also reduces the computational burden for exhaustive searching the shortest path of all robots for assigning the delivery task in real-time.

Cooperative Multi-robot Searching Algorithm

The problem of multi-robot for searching mission with fully communicative known environment is considered in this paper. Robots are required to maneuver every part of the given environment repeatedly until they find a target object. In order to increase the effectiveness of deploying the mult-robot, they need to be spread out sufficiently, not overlapping the searching area with other robots. To achieve this, we proposed an algorithm about deploying the multi-robot with maximizing the on-line coverage of the searching area. A shared dynamic map and its updating algorithm is proposed. Robots find next exploration area autonomously while updating the shared dynamic map. The algorithm is tested by simulation and the result is presented.

Framework and Modeling of a Multi-robot Simulator for Hospital Logistics

An autonomous mobile robot has opened a new era of hospital logistics. Mobile robots will substitute human courier by transporting goods within the hospital day and night. Multiple robots will be deployed at a hospital and coordinating these robots will increase the efficiency of delivery. This paper introduces the framework of the simulator which enables testing coordination algorithms of multiple robots. The simulator models hospital environment with the hospital-specific delivery demand as well as the specification of robots used for the delivery. The outcome of the simulator is the performance of applied task allocation algorithms, which includes overall delivery time and waiting time of delivery tasks.

Multi-robot multi-task allocation for hospital logistics

A number of materials are delivered inside a hospital, and a fleet of autonomous navigating mobile robots are applied to replace these heavy mobility works. To increase the efficiency of using multiple robots, more than one delivery tasks can be assigned to a robot instead of delivering only one package at a time. This multi-task allocation algorithm (MTA) is introduced in this paper and a simulator is developed to measure the performance of the algorithm. The simulator models the hospital environment and enables to compare the delivery productivity by changing the number of robot. It shows that the efficiency of MTA increases dramatically compared to the single task allocation when using the same number of robot.

Performance analysis of scheduling multiple robots for hospital logistics

A fleet of autonomous mobile robots are used in the hospital for the delivery service. To increase the efficiency of using multiple robots, an appropriate task allocation algorithm is required. This paper explains the task allocation procedure for multiple robots and introduces two multi-task allocation (MT) algorithms to be applied in the hospital delivery service. The algorithms are tested via simulation, and the performance are compared according to the criteria. The result shows that proposing combinatorial search algorithm with limited capacity performed better among others.

Multi-robot Control Architecture for Hospital Delivery Service in Unstable Network Environment.

This paper describes the problem about controlling multiple robots in a real world when the network connection is unstable. Robots are deployed at the hospital for delivery service. Robots navigate autonomously through the hospital-wide hallway while delivering items from point to point. The delivery task is assigned and sent to the robot by the server via wireless network. To increase the performance of using fleet of robots, online task assignment and fleet optimization is required. However, the robots are frequently disconnected with the network since the robot continuously moves and the mission area covers multiple floors. The online communication cannot be guaranteed at all times. Therefore, this paper proposes a control architecture to cope with such unstable network connectivity. The server has a specific message board to communicate with the robot. Task assignment of the server or status report of the robot are transferred through this message board. In general, the server uses a fixed IP address, whereas a robot uses a dynamic IP address. Therefore, the connection is always initiated from the robot’s side by the heartbeat message. With this architecture, the communication between the server and the robot can be achieved in a partially online network environment. And, the delivery performance of the fleet of robots can be increased by the scheduler assigning the task online.

The simulator for performance analysis of multiple robots for hospital delivery

Numerous materials are transported inside a hospital, which mostly relies on human porter. Mobile robots have been developed to substitute such human effort. These robots are able to navigate autonomously within a hospital. To estimate the number of robots to be obtained by a hospital, this paper introduces a simulator which enables comparison of the delivery performance according to the number of robots. The result shows the delivery performance by differing the number of robots which helps the management group to decide how many robots to afford by reviewing the performance report. One example of a delivery environment is tested and the result shows the estimation of delivery performance.

Multiple Robots Task Allocation for Cleaning and Delivery

This paper presents a mathematical formulation of the problem of cleaning and delivery task in a large public space with multiple robots, along with a procedural solution based on task reallocation. The task in the cleaning problem is the cleaning zone. A group of robots are assigned to each cleaning zones according to the environmental parameters. Resource constraints make cleaning robots stop operation periodically, which can incur a mission failure or deterioration of the mission performance. In our solution approach, continuous operation is assured by replacing robots having resource problems with standby robots by task reallocation. Two resource constraints are considered in our formulation: the battery capacity and the garbage bin size. This paper describes and compares the performance of three task reallocation strategies: All-At-Once, Optimal-Vector, and Performance-Maximization. The performance measures include remaining garbage volume, cleaning quality, and cleaning time. Task allocation algorithms are tested by simulation in an area composed of 4 cleaning zones, and the Performance-Maximization strategy marked the best performance. Hence, a delivery task is added to the cleaning task. The delivery request operates as a new perturbation factor for the reallocation. The task allocation procedure for the delivery task includes the switching of tasks of the delivery robot itself as well as exchanging among cleaning robots to meet the balance of the cleaning performance. The experiment was conducted with 9 robots with the software architecture that enables multi-functional of a robot and they performed both pseudo-clean and delivery task successfully.

Accurate fusing multiple RGBD sensors using geometry

This paper proposes an approach for fusing multiple RGBD sensors using geometry obtained from the captured image. We used Xtion Pro Live as the RGBD sensor. With the coupled line camera (CLC) method, the position of the camera is geometrically reconstructed when the size of a quadrilateral in the captured image is known. After roughly setting the hardware of multiple sensors on the frame, accurate calibration is proceeded by software using CLC. When positions of sensors are decided, the center of sensors can be derived. Input data of each sensors are reconstructed with this center point afterwards. Prior to the calibration, the method for connecting multiple sensors on a laptop is described and different square patterns used for calibration is discussed.