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2011 IEEE International Conference on Automation Science and Engineering Trieste, Italy - August 24-27, 2011 FrC4.6 Development of Robotic Laboratory Automation Platform with Intelligent Mobile Agents for Clinical Chemistry Byung June Choi 1 , Won Suk You1 , Seung Hoon Shin 1 , Hyungpil Moon1 , Ja Choon Koo 1 , Wankyun Chung 2 and Hyouk Ryeol Choi ∗1 Abstract— In this research, we propose an innovative robotic platform for clinical tests suitable for small or medium sized laboratories using small-sized multiple mobile robots and a robotic arm. The proposed robotic platform is referred to as “BioRobot platform”. The BioRobot platform not only provides flexibility in test process by carrying out various clinical tests simultaneously through multiple mobile agents, but also increases productivity by having controllable throughput according to amount of tests. Therefore, the various algorithms which are related to robotic technologies have been applied in this platform to operate the entire hardware and several mobile agents simultaneously. To evaluate the performance of the BioRobot platform, various control methods are implemented, which provides parallel processing and scalability. The feasibility of the BioRobot platform with three mobile robotic agents is validated through preliminary experiments. I. INTRODUCTION Automated machines are becoming indispensable in today’s laboratory environments, and new technologies employing robotic automation are rapidly incorporated in the clinical laboratory. However, typical Total Laboratory Automation(TLA) systems used in large hospitals have been optimized for rapid tests of a large number of samples by adopting conveyor belts. The conveyor belt systems are difficult to setup in small or medium sized hospitals since the size of system is enormous, and a large amount of investment is needed to introduce related facilities. Therefore, in small or medium sized hospitals clinical tests are performed manually, or the samples are sent to the institutions with dedicated facilities for clinical tests. Moreover, the existing systems still take time to complete the ordered tests because most of tests are conducted sequentially. In order to realize the medical diagnosis for patients, an innovative laboratory system is required to support high flexibility. Up to now, many researches on analytical techniques or innovative devices have been reported [1]- [18]. Among them, personalized clinical tests with robotic automation appears to be attractive as an alternative to the TLA system [4]. Robotic automation is defined as a dedicated robotic system capable of performing selective laboratory tasks. In general, robotic automation is flexible and requires less footprint and financial investment than the TLA system. Shortcomings of throughput compared to the TLA are compensated with flexibility of operation under minimum overhead. Robotic automation systems designed for selective analytical tasks may better meet the needs of small- or medium-sized laboratories because these systems can either operate stand alone, or be integrated to form work cells [5]- [7]. Also, the robotic system can be customized or personalized based on needs and budgets of individual laboratory [8]- [10]. In this paper, a robotic laboratory automation system called the “BioRobot platform” is proposed that can be used for clinical chemistry tests. In past researches, the issue of hardware implementation and the characteristic of platform were presented [11] [12] [13]. In this work, the operation method of the platform with various machines that is based on parallel processing, scalability and fault tolerance is introduced. The platform can carry out various tests simultaneously via parallel processing. Also, the mobile agents can be easily added or removed because the Immediate PlugIn/Out (IPIO) functionality using Bluetooth communication. In addition, the platform has the advantage of fault tolerance because the entire system remains unaffected, even if one of the mobile agents break down [13]. Also, the various algorithms which is related to robotic technology has been applied in this “BioRobot platform”, such as localization method for mobile agents, path planning algorithm for each mobile agent, and job scheduling algorithm. This work is financially supported by the Ministry of Knowledge Economy (MKE) and Korea Institute for Advancement in Technology (KIAT) through the Workforce Development Program in Strategic Technology. H. R. Choi is with Professor of School of Mechanical Engineering, Sungkyunkwan University, Suwon, The Republic of Korea. hrchoi@me.skku.ac.kr W. K. Chung is with Professor of Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, The Republic of Korea. wkchung@postech.ac.kr 978-1-4577-1732-1/11/$26.00 ©2011 IEEE 708 For the automation robotic platform and realization parallel processing… Mobile agent Microplate loading module Incubator tor (with hotometer) ter)) spectrophotometer) Localization problem of mobile agents Docking module Reagent tray Miniature arm m Path planning Sample tray Loading of sample blood Identification of sample Test planning & scheduling Movement of mobile agents Results & removing of microplate on the mobile agent Microplate loading module Fig. 1. Loading ading of of croplate oon n microplate he mobile age h geent g nt the agent Microplate loading module ule Detection using spectrophotometer Incubator Incubation Dispensing of sample and reagent Job scheduling ure arm Miniature Requirement of algorithmic solution for BioRobot platform This paper is organized as follows. In section II, the TABLE I operating procedure of BioRobot platform is presented. Also, the algorithmic problems such as localization method, and path planning algorithm for multiple mobile robots, job scheduling algorithm for platform are presented in section III. In section IV, experimental procedures for evaluating the performance of the Mobile Agents are discussed and the paper is concluded with summary in section V. S PECIFICATION OF B IO R OBOT P LATFORM Hardware components Miniature arm Sample tray II. OPERATING PROCEDURES OF BIOROBOT PLATFORM As depicted in Fig. 1, the BioRobot platform is composed of mobile agents, miniature arm for handling samples and reagents, microplate loading module to supply microplates on the mobile agents, sample tray module, reagent chamber module, incubator module, and photometry scanner [13]. The basic functions of the BioRobot platform are enlisted as loading of the microplate on the mobile agent, test scheduling, dispensing of the sample and reagent, planning and control of mobile agents, incubation, and detection. First, the samples and reagents are loaded into individual tubes. Then, the samples and reagents are identified at each tray using RFID tags. The user determines the test sequences using the provided scheduler software. Now, the BioRobot platform is automatically operated according to the job schedules. The microplates are loaded on the mobile agents in the microplate loading module. The mobile agents transfer the microplates from the loading module to the miniature robotic arm which is equipped with the liquid handler. The miniature robotic arm takes a pipette tip to absorb the samples or reagents from each of the sample or reagent tubes, and the liquid handler dispenses each sample or reagent into the well of the microplate. Then, the mobile agents with the microplate that contains the mixtures of samples and reagents navigate to the inside of the incubator module. After the scheduled incubation time, the spectrophotometer in the mobile agents scans the sample and provides the test results to the platform controller via wireless communication. Finally, the mobile agents with the microplate return to its initial position for reloading (in the microplate loading module). In addition, the absorbance sensor integrated multiple mobile agents can reduce the clinical test procedure and the test time owing to their parallel processing capability. Therefore, the clinical test process in the proposed system achieves a parallel procedure rather than a sequential one. The efficiency and the speed of a test are to be optimized depending on the number of operated mobile agents, and flexible scheduling and robust operation of the entire clinical test are achievable. III. ALGORITHMIC SOLUTION FOR BIOROBOT PLATFORM Whenever several mobile agents are deployed in the same environment on the platform, there is the need for coordinating their movements to prevent the undesirable situations such as collision, congestions or deadlocks. Also, if the initial pose of the mobile agent is unknown or the mobile agents have been kidnapped, the mobile agent is difficult to estimate its current position directly from the general position Reagent tray Accuracy of liquid handler Expected throughput Dimension(W×D×H) 2×Microplate loading module, 8×Recharging and docking module, 1×Miniature arm, 1×Dispensing channel, 1×Sample tray, 1×Reagent tray, 1×Incubator, 2×Spectrophotometer, Mobile Agents 4-DOF SCARA type 7mL tubes, 21 sample tubes (with exclusive pipette tips) 40mL tubes, 70 reagent tubes (with exclusive pipette tips) 1.0mL pipette, 1.0µL resolution 240 photometric tests/hour 1,560×1,100×1,200(mm) (from the ground to the base plate (workspace of Mobile Agents)) tracking method. Therefore, in order to solve these problems, unique algorithmic approach for BioRobot platform is necessarily required. In this section, a new strategy for global localization and path planning algorithm of each mobile agent is presented. In addition, a scheduling algorithm called RIT (Reduced Idle Time) algorithm is presented, which can minimize the delay time of the job and provide the parallel processing. A. Localization method for multiple mobile agents in BioRobot platform Coordinate of mobile robot Coordinate of magnetic landmark Y y3 y3 y3 y2 x1 y2 x2 y2 x3 x1 x2 y1 x3 x2 x3 y1 x1 y1 X Global coordinate of the platform Fig. 2. Concept of proposed localization method using magnetic landmarks A new strategy for global localization using several patterns of magnetic landmarks is presented in this section. The basic concept of the global localization based on magnetic landmarks is to measure the magnetic field between the coordination of the hall sensors of the mobile agent and the coordinate of the magnet set, as shown in Fig. 2 [14]. For one set of landmarks is composed of four magnetic bars in rectangular configuration as shown in Fig. 3 where total six patterns can be obtained. When the mobile agent is located at the center of the four-magnets landmark, it can easily read 709 Current position of mobile robot : (xi,yi,θ) y 3 yi 2 4 2 3 2 4 2 2 5 3 5 3 3 3 4 2 4 5 1 3 3 2 1 2 1 1 4 5 4 1 4 O (a) Arrangement of four magnetic bars in rectangular configuration xi 2 1 4 2 x Equations for pose compensation Patterns Landmark 1 Landmark 2 Landmark 3 Landmark 4 Landmark 5 Landmark 6 t l +t l t l +t l  t l −t l   −t l + t l  xe = 2 2 2 4 ye = 1 1 3 3 θ e = sin −1  1 1 3 3  = sin −1  2 2 4 4  d 2 2    d  −l + l −l + l  −l − l  l +l  ye = 1 3 θ e = sin −1  1 3  = sin −1  2 4  xe = 2 4 2 2  d   d  (t1 = −1, t2 = −1, t3 = 1, t4 = 1) Fig. 4. Global localization method for finding current position information of mobile agent on the platform (Distribution of magnetic landmarks, generation of virtual map, and Sequence of localization method) −l + l l2 + l4  −l − l   −l + l  ye = 1 3 θ e = sin −1  1 3  = sin −1  2 4  2 2  d   d  (t1 = −1, t2 = 1, t3 = 1, t4 = 1) xe = −l − l −l2 + l4  −l + l  l +l  ye = 1 3 θ e = sin −1  1 3  = sin −1  2 4  2 2  d   d  (t1 = −1, t2 = −1, t3 = −1, t4 = 1) xe = l +l l2 + l 4 ye = 1 3 2 2 (t1 = 1, t2 = 1, t3 = 1, t4 = 1) xe =  l1 − l3  −1  −l2 + l4    = sin   d   d  θ e = sin −1  −l + l l2 − l 4  −l − l   −l − l  ye = 1 3 θ e = sin −1  1 3  = sin −1  2 4  2 2  d   d  (t1 = −1, t2 = 1, t3 = 1, t4 = −1) xe = l −l −l2 + l4 l +l  l +l  θ e = sin −1  1 3  = sin −1  2 4  ye = 1 3 2 2  d   d  (t1 = 1, t2 = −1, t3 = −1, t4 = 1) xe = (b) Equations for compensation of pose errors about six magnetic landmarks Fig. 3. Generation of six magnetic landmarks, (a) Arrangement of four magnetic bars in rectangular configuration, (b) Equations for compensation of pose errors about six magnetic landmarks one of four hall sensors is placed in the center region of the magnetic field which is generated by four magnetic bars [14]. Once this is done, the mobile agent can be controlled to a location where four hall sensors are properly located on top of magnetic bars. The mobile agent identifies the pattern of magnetic landmark by reading the sequence of the magnetic polarities while rotating, and it obtains the current global position information. At this point, there still is ambiguity in current location of the robot because the number of patterns is not large enough to cover the entire grid-like map. However, once the mobile agent recognizes the pattern of the current landmark, position tracking can be done afterward, thus the mobile agent can move to the one of the neighboring grid with very small tolerable pose error [14]. B. Path Planning Algorithm the polarity of the magnets while making a complete turn in one direction. In this paper, the patterns of magnetic landmarks are distributed in such a way of forming a grid-like global map as shown in Fig. 4 where the number inside of the grid stands for the type of the landmark pattern. It should be noted that once the pattern is identified, position tracking is easily done in this proposed framework. The first step for global localization is to control the mobile agent so to be situated on the range of magnetic landmarks. When fairly large size of magnets is used, the range of magnetic field is large enough. In this case, a simple random walk algorithm may situate the mobile agent onto a proper location where the mobile agent can read the four magnetic fields and begin the procedure of identifying the pattern of the landmark. Another approach is to use a gradient descent algorithm for one hall sensor so that Since the BioRobot platform consisted of the several mobile robots that are called mobile agents, the moving trajectories for the individual robots have to be computed such that collisions between the robots and static obstacles as well as between the robots among themselves are avoided. To obtain the moving paths of each mobile agent, The D ∗ lite search algorithm is applied in the proposed BioRobot platform. It produces an optimal path from the start position to the goal in the sense of minimizing a pre-defined cost function. D∗ lite algorithm can guarantee the least cost paths between a start point and any number of goal points as the cost of edges between change of point [15]. The basic principle of D∗ lite algorithm calculates a least cost path from a start point Sstart ∈S to a goal point S goal ∈S, where S is the set of point(node) in some finite state space, as shown in Fig. 5 [16]. To do this, it stores an estimate g(s) of the cost 710 from each state s to the goal [17]. It also stores a one-step lookahead cost rhs(s i ), sstart (Start point) 10 9 f (si ) = = 8 rhs(si ) + h(sstart , si ) mins′ ∈Succ(s) (c(si , s′ ) + g(s′ )) + h(sstart , si ) 7 (1) rhs(s) =  0 i f s = sgoal mins′ ∈Succ(s) (c(s, s′ ) + g(s′)) otherwise, (2) 6 h1 5 h2 4 h3 s1 s2 s3 3 2 where Succ(s) ∈ S denotes the set of successors of s, f (s i ) denotes evaluation function to determine the shortest path, and c(si , s′ ) denotes the cost of moving from s i to s′ (the edge cost), g(s′ ) denotes the operating cost function that actual operating cost have been already traversed, h(s start , si ) denotes the heuristic function that estimates the cost of an optimal path from state s start to si , and rhs(si ) is the onestep lookahead cost. As with D ∗ Lite uses a heuristic and a priority queue from f (s i ) to focus its search and to order its cost updates efficiently. As shown in Fig. 5, starting with the goal point (node), it maintains a priority queue of nodes to be traversed. The lower f (s i ) for a given node s i has the higher its priority. At each step of the algorithm, the node with the lowest f (si ) value is removed from the queue, the f and rhs values of its neighbors are updated accordingly, and these neighbors are added to the queue [16] [17]. The D ∗ algorithm continues until a start point (node) has a lower f value than any node in the queue. The set of lowest f values is then the shortest path from start point (node) to goal point (node). Therefore, D ∗ Lite expands nodes from the queue in increasing priority, updating their g-values and rhs-values of their predecessors, until there is no node in the queue with a key value less than that of the start point. 1 0 0 1 2 3 4 5 6 7 8 9 sgoal (Goal point) 10 hi(sstart,si) : Heuristic function Basic principle of D∗ lite algorithm Fig. 5. Machine number 1 211 2 122 231 223 3 4 131 114 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Time 14 15 Time (a) Gantt chart of the SPT algorithm Machine number 1 211 C. Job Scheduling algorithm 2 122 Independent n jobs should be processed according to a predetermined procedure using m machines for the minimization of total processing time. Solutions of this problem have been studied extensively in the operational research field and this problem is normally referred to as a “job shop” problem [18]. The popular methods for the job shop scheduling problem are loading rules, heuristic rules, integer linear programming, complete enumeration, sampling methods, and learning techniques. The loading rule and the heuristic rule are briefly reviewed here because those algorithms are used for the present work. The loading rule progresses by selecting the next process of the individual machine. The selected processes have to be feasible for the fixed sequence of tests and have to be finished with the least amount of idle time for each machine. If many processes are to be done, the job sequence is to be determined by the so-called shortest processing time (SPT), which is one of the heuristic rules. The SPT is usually regarded as the basic algorithm [19]. 3 4 131 231 223 114 1 2 3 4 5 6 7 8 9 10 11 12 13 (b) Gantt chart of the proposed RIT algorithm Fig. 6. Gantt chart of scheduling algorithm by the SPT and RIT algorithm, (a) Gantt chart of the SPT algorithm, (b) Gantt chart of the proposed RIT algorithm Although the SPT may provide the shortest job schedule for simple cases, this method cannot be applied to a case such that a single job uses a particular machine more than twice [20]. An exemplary case shown in Fig. 6 explains the limitations of the SPT algorithm. The algorithm distributes jobs to corresponding machines using information stored in array M. When a situation happens at the middle of 711 (1) (a) The part of Gantt chart, with which 10 clinical tests are scheduled by algorithm using one mobile agent. The processing time is 2,670 seconds (b) The part of Gantt chart, with which 10 clinical tests are scheduled by algorithm using three mobile agents. The processing time is 1,091 seconds Recognition of magnetic landmark 1 (3) a scheduling process such that job 131 is to be inserted, the only option for the SPT is locating the job at the end of sequence. Regarding job number 131, 1 stands for job number 1, 3 is for process number 3 in job 1, and 1 represents machine number 1 that is used for process 3 of job 1. Although job 131 can be allocated between job 211 and job 231 to minimize the idling time, the SPT algorithm routinely assigns the job at the end of sequence because a job uses a particular machine more than once. The basic principle of RIT algorithm is to be improved the SPT algorithm by left-shifting, as shown in Fig. 6. If 131 operation is assigned at machine 1, the 131 operation is rearranged at the feasible range of the idle time by searching ranges of the entire idle time, after the completing time of the previous operation of the same job as the operation (for example, 122 operation) [20]. Therefore, the RIT algorithm can reduce the total processing time and tardiness. IV. EXPERIMENTS AND DISCUSSIONS In previous research work, the BioRobot platform was fabricated, and it was tested with the frequently applied clinical chemistry test items to confirm the merits of the parallel processing and the scalability using multiple mobile agents. Through further research, the various methods that were related to robotic technology had been applied and verified in this BioRobot platform, such as the global localization technique, the path planning algorithm and job scheduling algorithm. In the first experiments, the proposed RIT algorithm was simulated in the operation conditions of 10 chemistry tests for job schedule. Figure 7 shows the Gantt charts of simulation results. When one mobile agent on the BioRobot platform carried out 10 chemistry tests (ALT, total cholesterol, AST, glucose, TG, total protein, lactate dehydrogenase, BUN, Creatine, IP), the scheduled processing time had taken 2,670 seconds, as shown in Recognition of magnetic landmark 2 (4) Recognition of magnetic landmark 3 Fig. 7. Comparison of the Gantt chart, with which 10 clinical tests are scheduled by algorithm using multiple mobile agents (2) Determination of current global position and moving direction Fig. 8. The experiments to prove the performance of global localization method using various patterns of magnetic landmarks Fig. 7. However, when three mobile agents on the BioRobot platform simultaneously carried out 10 chemistry tests, the scheduled time had taken 1,091 seconds. It was possible to confirm that the total processing time could be minimized in clinical chemistry tests. In the second experiments, in order to evaluate the performance of global localization technique of mobile agents, the experiments were carried out as shown in Fig. 8. The mobile agent was placed in an arbitrary position on the platform, and then four hall sensors of mobile agent looked for the changes of magnetic poles during the rotation. They then identified the magnetic landmark. The mobile agent moved to the two neighboring landmarks, and identified the pattern of the neighboring landmarks using the four hall sensors. Based on these information, the robot compares the measured three neighboring patterns with the map information that is saved in advance, the robot then estimates its current position and moving direction, as shown in Fig. 8. Finally, the overall BioRobot platform was operated by reproducing the chemistry tests, as shown in Fig. 9. First, the mobile agents moved towards the microplate loading module. Then, the microplates were loaded into the each mobile agent. Next, the mobile agents moved to the pneumatic pipettor of miniature arm, and then each sample or reagent was dispensed to the well of microplate on the mobile agent. The microplate containing the mixtures of the sample and the reagents was transferred to the incubator module by the mobile agent, and the results of tests were read with a spectrophotometer inside of incubator module. Finally, the mobile agents that had completed the work returned to the initial position for the next clinical test. According to the experiments, the mobile agents could perform the 712 ordered clinical tests by means of distributed robotic system. Therefore, it was possible to confirm that the BioRobot platform can be used in chemistry tests. (1) Preparation of the tests (waiting time, localization) (3) (2) Loading of the microplate on the mobile agent 1 (4) Movement of the mobile agent 1, and addition of mobile agent 3 (5) Completion of tests of mobile agent 2, and movement of mobile agent 2 from incubator to microplate loading module (7) Movement of mobile agent 1 and 3, and movement of mobile agents from miniature arm to incubator Dispensing of samples and reagents on the mobile agent 1 and 2 (6) Movement of mobile agent 1, and removal of mobile agent 2 that is caused by abnormal operation (8) Incubation and detection Fig. 9. Operation of BioRobot platform that reproduces the sequence of the real clinical tests V. C ONCLUSIONS In this research, we propose an innovative robotic platform for clinical tests suitable for small or medium sized laboratories using small-sized multiple mobile robots and a robotic arm. To evaluate the performance of the BioRobot platform, RIT(Reduced Idle Time) scheduling is implemented. 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