The simple and low cost manipulator system for the use in small workspace of nuclear laboratories is presented. The system is designed for remote translocation of radioactive sources and other applications increasing staff safety during processing of radioisotope materials. The described cable-pulley manipulator is controlled by a very simple PC set-up

Baczyński, Janusz

Baczyński, Michał

English

University of Maria Curie-Skłodowska (UMCS): Scientific e-Journals / Uniwersytet Marii Curie-Skłodowskiej: e-czasopisma naukowe

Annales UMCS Informatica AI IX, 1 (2009)191–199; DOI: 10.2478/v10065-009-0015-ySimple cable–pulley manipulator system for remotetranslocation of radioactive materialsJanusz Baczyn´ski1∗, MichaÃl Baczyn´ski2†1 University of Lodz, Faculty of Physics and Applied Computers Science,149/153 Pomorska St., 90-236 ÃLo´dz´, Poland2 Technical University of Lodz, Institute of Automatic Control,18/22 Stefanowskiego St., 90-924 ÃLo´dz´, PolandAbstractThe simple and low cost manipulator system for the use in small workspace of nuclear labo-ratories is presented. The system is designed for remote translocation of radioactive sourcesand other applications increasing staff safety during processing of radioisotope materials. Thedescribed cable-pulley manipulator is controlled by a very simple PC set–up.1. IntroductionRadioactive materials (that is, the substances that emit nuclear radiation)are often used for various purposes in different medical or academic researchlaboratories. It is well known, that the materials can be extremely hazardousto human health or life. The nuclear materials can produce four different kindsof radioactive rays: alpha particles (electrically charged nucleus of a heliumatom composed of two protons and two neutrons), beta particles (electrons),neutrons and gamma (short wave-length electromagnetic rays). All kinds of therays are dangerous for human organisms, of course only when radiation doses∗E-mail address: bacz@uni.lodz.pl†E-mail address: mbaczyn@p.lodz.plPobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCS192 Janusz Baczyn´ski, MichaÃl Baczyn´skiare relatively high. Biological results of radiation exposures depend on the doseof absorbed radiation and the type of radioactive particles [1, 2].The alpha particles are the least penetrating. In practice, the reasonable thinsheet of paper is able to totally absorb the alpha particles - also they are totallystopped by a few centimeters of air.The beta particles are more penetrating. They can travel a few meters inair or a few millimeters through aluminum before being totally absorbed. Inpractice, the human skin can stop alpha or beta radiation inside the upper layerof the body tissue.The gamma rays are the most penetrating. The gamma radioactivity has thesame nature as x-rays but it comes from the nucleus and usually the gammaradiation is somewhat higher in energy than x-rays. The gamma rays are able topenetrate large thickness of absorbing material - for example, a few centimetersof lead. Practically, the human body is transparent to the gamma rays.The conclusion is that, the gamma and beta radiation is the most externaldanger for workers employed in radioisotope laboratories. Of course, specialsafety standards and procedures are applied in each laboratory to protect theworkers from health hazard. Usually they require exceptionally high accuracyand precision from workers. In such cases there is always a risk of radiationexposing the staff of the laboratory to hazard.Only the use of automatic or teleoperator systems allows for total eliminationof radiation hazardous for staff employed in workspace of nuclear laboratories.Below the simple cable–pulley manipulator system for small academic re-search laboratories is presented. To be more specific the system is designedfor manipulation of gamma radiation samples in neutron sources. The idea ofthe described system is that the human operator is physically separated froma place where the manipulation with radiation materials is to be done. For ex-ample, a thick lead wall or only a suitably long distance from the radioactivitysources reduces radiation to the absolutely safe level.2. ManipulatorsThe manipulator systems have been used in nuclear laboratories since 1940when the Goertz’s group [3, 4] constructed the first one. Since then the ma-nipulators are employed in the places of sources of nuclear radiation in twomodes: as off-line automatic systems or for on-line operations. The first one isso called ”robot mode”. The second one is often called the teleoperation mode.A human operator of the teleoperator system can perform all the risk tasks inreal time at a distance, well isolated from the hazardous area.Pobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCSSimple cable-pulley manipulator system for . . . 193Fig. 1. 5–DOF robotic arm with the gamma radiation detector – the example of theuse of the standard manipulator arm for manipulations in radioactive environmentsThe teleoperator systems [5]–[7] are especially functional for the remote ma-nipulation in dynamically changing environments where routine procedures (au-tomatically performed) cannot be used.Regardless of the operation mode used automatic systems or remote con-trolled systems require proper manipulators for adequate manipulation of ra-dioactive materials in laboratory workspace. The standard solution is the usedof a commercially available type robot arm – see Fig. 1.The basic disadvantage of this approach is that, generally the basis of the armis not moveable. Thus the workspace of the robotic arm is relatively small. Theadaptation of the arm for its relocation in laboratory space requires advancedmechanisms and it is usually very expensive. The use of the cable–driven ma-nipulator [8] can eliminate the substantial disadvantage and the manipulatoris relatively simple and low cost.Thus, it seems that the relatively simple and low cost cable manipulatorsystems are more adequate for small academic or medical nuclear laboratories.3. Cable manipulator systemThe presented cable–pulley manipulator system designed for small nuclearlaboratories consists of a mobile platform and six cables. The cables attachedto the platform are pulled by six separate motors that can extend or retractthe cables - the schematic form is displayed in Fig. 2.Pobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCS194 Janusz Baczyn´ski, MichaÃl Baczyn´skiFig. 2. Simplified scheme of the cable-driven manipulator systemIt is similar to NIST RoboCraner [9]. Practically, the manipulator is asix degrees of freedom inverted Stewart platform [10] which uses gravity tomaintain tension in the cable. The cables are attached to pulley mechanismslocated in three vertices of an about 4–metre equilateral triangle. In fact theangular points of the triangle are placed on the tetragonal aluminium gantry –the scheme is displayed in Fig. 3. Each vertex contains two pulley mechanismsfor two steel cables of a 1.5 mm diameter.Fig. 3. Axonometric projection of the cable-driven manipulator systemPobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCSSimple cable-pulley manipulator system for . . . 195The platform has a form of the circle circumscribed in the equilateral triangle.The cables are attached to the grapples located in the angular points of thetriangle.The construction of the gantry is adapted to install the mobile cable–pulleymechanisms. In this way the layout of the manipulator cables can be changedto adjust it to workspace. Thus the laboratory workspace accessible for theequipment placed on the manipulator platform is about 12 square metres.The space position and orientation of the manipulator platform can be changedby proper drawing out or reducing the length of the cables. The aligning pro-cess is controlled by a PC computer interfaced with the proper control circuit- see Fig. 4. Each of the six pulley mechanisms consists of a winch driven by aseparate electric 24V DC motor.The winches are equipped with incremental encoders to determine changesof the manipulator cable lengths. Each set–up of the motor and the encoderis linked to its separate controller. The controllers are interfaced with thepersonal computer by the RS–232 serial port. In fact, the controllers are linkedto the USB computer port by the standard USB-to-Serial Hub. In this way,employing only one USB port of the PC is enough to control all six cable–pulleymechanisms.4. Test applicationsThe cable–pulley manipulator system has been tested for different appli-cations in the university nuclear laboratory. The laboratory is designed foreducational purposes. Its relatively small area is like a standard radioisotopelaboratory in the medical center.The cable manipulator can be used for inspection and localization of radioac-tive impurities in the laboratory workspace. During different manipulationswith radioisotopes in nuclear laboratories, the radiation pollution is alwayspossible. For example: hazardous radiation liquid can be spilt on a laboratorydesk or single particles of radioactivity powder can be dropped on a floor and soon. Therefore each workday of the laboratory staff includes special proceduresfor examination of the workspace to detect possible radiation pollution. Theprocedures require an exceptionally high accuracy and precision and they areusually time–consuming.The problems can be solved by using the above described cable manipulatorsystem and an additional simple equipment. Fig. 5 shows the work platformof the cable manipulator equipped with a common Geiger–Mu¨ller (G-M) de-tector [11, 12]. The G-M detector is able to detect gamma and beta rays.Pobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCS196 Janusz Baczyn´ski, MichaÃl Baczyn´skiFig. 4. Electronic system of the cable manipulatorIt is absolutely sufficient to detect and localize radioactive pollutions in mostradioisotope laboratories.The G-M detector produces a single pulse for each particle entering its tube.The pulses are counted by an electronic counter interfaced with the PC by theparallel port - see Fig. 4. When the platform with the G-M detector is movedalong the monitored surfaces, the PC reads periodically the counter valuesto determine the radiation rate expressed in counts per fixed time interval.Pobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCSSimple cable-pulley manipulator system for . . . 197When the tip of the G-M detector is placed on the gamma source then theregistered pulse rate increases largely. It indicates that the system just detectsthe radiation impurities and the tip of the G-M points on the polluted place.The scanning process of the examined objects can be supervised by the humanoperator but it can also be automatically performed in a ”robot” mode.Fig. 5. Work platform of the cable manipulator equipped with the Geiger–Mu¨llerdetectorGenerally, a lot of various operations with radioisotope materials must beperformed in nuclear laboratories when they are produced or processed andprepared for further use. They must be often moved between different workplaces. The action of passing is not always simple since the transferred ma-terials can be strong sources of nuclear radiation threateniny health and lifeof laboratory workers. In those cases, employing the manipulator is the bestsolution. For those purposes the platform of the presented cable manipulatorcan be optionally equipped with a low cost end–effector to grasp tiny objects –see Fig. 6. The miniature 5–DOF robot arm is installed on the work platform.The light plastic robot arm is ended by the gripper and its operation reach is upto 35 centimetres. The mass and size of the radiation samples used in academicnuclear laboratories are like common medicine tablets, thus the power lift of thefiddly robotic arm is absolutely enough. The employed robot is a commerciallyavailable educational tool called the ”ARM-1”.The arm and the gripper are driven by seven analogue servos exactly thesame as those applied in hobbyist remote control devices. The servo motors arepositioned by the PWM signals generated by the ARM-1 controller accordinglyto the commands obtained from the PC by the serial port RS-232 via USBPobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCS198 Janusz Baczyn´ski, MichaÃl Baczyn´skiFig. 6. Educational robotic arm as the end-effector of the cable manipulatorhub - see. Fig. 4. The positioning precision is limited by the unsophisticatedservos used. Of course, there are many kinds of manipulations with radioactivesubstances where higher precision is required. However, the ARM-1 accuracyis absolutely enough to use it as the gripper of the radiation samples for theirtranslocation into laboratory workspace by the cable manipulator.5. ConclusionsThe described cable cable-pulley manipulator system is relatively low-costand very simple. The two presented applications based show that the manip-ulator can be very useful in many kinds of nuclear laboratories. The roboticmode allows for saving a lot of work-time of the laboratory staff. In this modeand also in the teleoperator manner the use of the manipulator increases con-siderably the safety level during works with radioactive materialsAcknowledgmentThe presented work has been financed by the Polish State research budget asdevelopment project R01 009 03 in the years 2007–2010.References[1] Nias IA. H. W., An Introduction to Radiobiology, 2nd. ed., John Wiley & Sons, New York1998.[2] Shleien B., Birky B., Handbook of Health Physics and Radiological Health, LippincottWilliams & Wilkins, 1997.Pobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCSSimple cable-pulley manipulator system for . . . 199[3] Goertz R. C., Fundamentals of General-Purpose Remote Manipulators, Nucleonics, 10,11 (1952) 36.[4] Goertz R. C., Manipulators used for handling radioactive materials, Human Factors inTechnology, Chapter 27, Ed. E. M. Bennet, McGraw-Hill, 1963.[5] Sheridan T. B., Telerobotics, Automation and Human Supervisory Control, MIT Press -1992.[6] Proceedings of the 10th Ann. Symp. on Haptic Interfaces for Virtual Environments andTeleoperator Systems, ASME/IMECE, Orlando - 2002.[7] Baczyn´ski J., Baczyn´ski M., Simple Teleoperator System for Gamma Radiation Decon-tamination, Proc. of the ISIE 2005 (IEEE International Symposium on Industrial Elec-tronics), 2005, Dubrovnik Croatia, 20th - 23th June.[8] Bosscher P. M., Disturbance Robustness Measures and Wrench-Feasibile Workspace Gen-eration Techniques for Cable-Driven Robots, Ph.D.Thesis, George W. Woodrur Schoolof Mechanical Engineering Georgia Institute of Technology, November 2004.[9] Bostelman R. V., Albus J. S., Dagalakis N. G., A Robotic Crane System Utilizing theStewart Platform Configuration, Proc., ISRAM 1992, Conference, Santa Fe, N.M., Nov.10-12, 1992.[10] Fichter E. F., A Stewart Platform-Based Manipulator: General Theory and PracticalConstruction, Int. J. Robot. Res. 5(2) (1986) 157.[11] Glenn F. Knoll, Radiation Detection and Measurement, 3nd. ed., John Wiley & Sons,New York 1999.[12] Baczyn´ski J., Baczyn´ski M., Simple robotic system for detecting and marking gammaradiation impurities, Proc. of the 11th IEEE International Conference on Methods andModels in Automation and Robotics - August 29, 2005 Mie¸dzyzdroje.Pobrane z czasopisma Annales AI- Informatica http://ai.annales.umcs.plData: 04/08/2020 20:47:17UMCSPowered by TCPDF (www.tcpdf.org)

Simple cable-pulley manipulator system for remote translocation of radioactive materials

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Simple cable-pulley manipulator system for remote translocation of radioactive materials

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