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Robotic Manipulators Mechanical Project For The Domestic HERA

Conference Paper · April 2019

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Marina Gonbata Fabrizio Leonardi University Center of FEI University Center of FEI

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Plinio Thomaz Aquino Junior University Center of FEI

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Robotic Manipulators Mechanical Project For The HERA

Marina Yukari Gonbata1, Fabrizio Leonardi1 and Plinio Thomaz Aquino Junior1

Abstract— Robotics can ease peoples life, in the industrial that can ”read” the environment where it acts), ability to act and home environment. When talking about homes, robot may actuators and motors capable of producing actions, such as assist people in some domestic and tasks, done in repeat. To the displacement of the robot in the environment), robustness accomplish those tasks, a robot must have a , so it can interact with the environment physically, therefore, a robot and intelligence (ability to handle the most diverse situations, must use its arm to do the tasks that are required by its user. in order to solve and perform tasks as complex as they are) [2]. The use of robust planning and control techniques I. INTRODUCTION for the navigation and autonomous operation of is When we talk about the term robotics, we associate it known by the term ”Intelligent Robotic Control”, in which with the robot concept. A robot is a set of multifunctional this intelligent control allows the RMAs to be able to perform reprogrammable digital manipulators, sensors and devices, the most diverse and complex tasks [3]. designed to move specific materials, objects, tools or devices With all this, the field of robotics has been developing ac- through various movements programmed to perform certain tively in the last few years, the research in Human tasks. Robots can help people in a variety of ways in a Interaction (IHR) comes to take the development of robots home, for example, multiple tasks can be performed such as to a whole new level. Imagine a robot that understands your cleaning the house, being your pet, looking for lost objects, feelings and reacts not only the way pets behave, but even warning about health hazards when monitoring children and better if they know what to do to improve their mood or have the elderly. The of tasks that robots execute fun. The first topic of this work is exactly a study about this, motivates the creation of a whole new field for people to using the world-known AIBO robot dog from Sony [4], a build robots, provide maintenance, or simply share daily system was developed to analyze human speech and define tasks with robots. the emotional state of the person, for each emotional state the robot behaves differently [5]. In industry and in business, tiresome and repetitive activi- ties can be performed by machines. In the past it was thought II. SERVICE ROBOTS that robots would replace humans in almost every task. There are robots being fully created for household chores, Nowadays, it has been recognized that there has been a cost from devices for cleaning tasks such as iRobot robots, reduction in production with the automation and inclusion of [6], to robots performing RoboCup @ HOME robots, while at the same time the labor dispensed has discov- competition tasks, such as picking up objects and receiving ered that even though the need of workforce has decrease in voice commands, e.g. TIAGo robot (Take It and Go) [7]. these environments, there are still several options available. Roomba is one of the pioneers in the line of home care Typically, the industry applies static robotics solutions, i.e., robots available to the public, serving to clean homes, and machines that have well-defined, finite functionalities that can be programmed through applications for mobile phones. operate within a small area of space. IRobot owns other cleaning machines on sale. However the attention of the paradigm of robots required The TIAGo machine, which was created by PAL Robots, by the industry, based on fixed robots with robotic mechan- has a with 7 (seven) degrees of freedom and ical arms, nowadays attention has turned to mobile robots, the claw reproducing the human hand with five fingers. To able to move in the environment they are, and especially increase the volume of work, it is possible to extend its trunk, in Autonomous Mobile Robots (RMAs) and Intelligent Au- reaching from the ground up to 1.5 meters in height. Contains tonomous Vehicles [1]. The RMAs have, as fundamental cameras to recognize objects or faces of people, also has laser characteristics, the locomotion and operation capacities in for mapping and location. semi or completely autonomous mode. It should also be Other robots of PAL Robotics with this same purpose are considered that higher levels of autonomy will be achieved REEM [8] and REEM-C [9], this being humanoid. Both have only as the robot begins to integrate other aspects considered two degrees of freedom in the head, rotation and flexion, and of major importance, such as: ability to perceive (sensors seven in the manipulator. *The present work was carried out with the support of the Centro Universitario´ FEI with the Scholarship Program of Scientific Initiation. III. ROBOTS FROM OTHER ROBOCUP @ HOME 1Centro Universitario´ FEI Fundac¸ao˜ Educacional Ina- PARTICIPANTS ciana Pe. Saboia´ de Medeiros Sao˜ Bernardo do Campo, Sao˜ Paulo, Brazil [email protected], As the purpose of this project is to model the manipulator [email protected], [email protected] for the robot to meet requirements of the same nature as

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RoboCup @ HOME competition tasks, the robots of the The current manipulator has 6 (six) degrees of freedom other participants were examined. and a rigid claw with low contact area, with Robotis servo- Some of the researched teams: motors [17], RX-24F, RX-28 and RX-64 for drive as shown The REEM@LaSalle team uses a REEM robot, from in Figure 2. • PAL Robotics, affiliated with La Salle university [10]; The human arm basically has joints in the shoulder, elbow The team from Thailand SKUBA, who uses a robot and wrist. The human shoulder joint is of the spheroid type, • named Lumvai, created by them. Its mechanical manip- allowing 3 degrees of freedom, and its range of motion ulator has 6 degrees of freedom and it is made of inox covers almost 65% of a sphere, and can also axially rotate metal. The head is a composed by a Microsoft Kinect, in almost all positions [18]. The articulation of the elbow, of a Logitech C920 HD camera and a RODE microphone, the ginglimo type, is a joint in hinge, simplifying, it allows the head has 2 degrees of freedom [11]; flexion. The wrist already allows flexion and rotation, but Tech United Eindhoven has two robots, AMIGO (Au- does not allow axial rotation as the shoulder, although the • tonomous Mate for Intelligent Operations) and SERGIO twisting of the forearm allows the joint pulse and hand to (Second Edition Robot for Generic Indoor Operations). rotate axially [19]. Both have two degrees of freedom in the head con- trol, using Dynamixel servomotors and one Microsoft V. ROBOCUP@HOME COMPETITION Kinect. They also have two manipulators with seven degrees of freedom, AMIGOs manipulator is a PERA The robot participates in RoboCup @ HOME, a competi- (Philips Experimental Robotic Arms) [12]; tion focused on domestic robots, and consists of tests to be Justina Robot is from the Mexican team Pumas. It has solved by service robots. The medicated robot performance • two mechanical arms, each one with seven degrees of is based on a score judged by a jury. The following criteria freedom, each one uses ten Dynamixels servomotors. are considered in the competition: Justinas head has two degrees of freedom, also using Human-Robot Interaction; • Dynamixels servomotors [13]. Socially relevant; • Command-Oriented; IV. ROBOT HERA • Scientifically challenging; • The RoboFEI @ HOME project [14] gave rise to a home- Easy adaptive to the environment; • based robot, Home Environment Robot Assistant (HERA) Intuitive Interaction; • (Figure 1), as an initiative to include the Human-Computer Interesting for the spectators. • Interaction area in FEI robotics projects. A robot can have a structure equivalent to the elements of a human being, VI. RESEARCH COMPONENTS for example, head, arms, legs. When the robot has all the characteristics of a person, it is usually defined as humanoid, A. Servomotor because it ergonomically has an arm and a head to accom- plish tasks that occur inside homes, where their utensils are Servomotors are used when the work operation requires designed to be manipulated by people. high precision. Servos are machines with components such as electric motors, gearboxes and sensors. The motor of the A. Robotic Arm servomotors has a movable part, this being the rotor, and a fixed part, the stator. The stator of a DC servomotor consists The manipulators are separated by their structures, de- of permanent magnets that generate a magnetic field through pending on how the arm moves, counting only the type of the chain [20]. the first three joints and thus forming the working volume [15], [16].

Fig. 1. Robot HERA Fig. 2. Current Manipulator

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B. Position Sensors of the elements, to be evaluated and, if necessary, parts There are several types of position sensors, the simplest correction [25]. sensor is the potentiometer, which consists of a circular resistor connected to the output shaft of the motor via a E. 3D Printing sliding connection [21]. Because of several problems that can result in low accuracy, resulting in low cost, its use is The term additive manufacturing is used for rapid proto- limited. Since the resolvers emit two analog signals on the typing, or commonly called 3D printing [26]. 3D printing axis of the servomotor, the angle is calculated from these produces complex three-dimensional parts, ideal for man- signals. Because your resolution is low, and you need extra ufacturing prototypes to verify the dimensions and shape equipment in the joint to improve it, it is not the most of the design, simulation of the assembly, visual inspection commonly used. among others, before producing the final piece [27]. Another that can be used with position sensor is the There are three major 3D manufacturing technologies that tachometer, providing a signal concerning the speed of the will be shown below [28]: shaft.The rotary optical encoder is the most used as a Fused Deposition Modeling (FDM) or Fused Filament • feedback position sensor, the axis rotation response is based Fabrication (FFF): uses polymer filaments as feedstock, on the interruption of light by a perforated disc[22]. such as acrylonitrile butadiene styrene (ABS) and poly- lactic acid (PLA); C. 3D Modelling Stereolithography Apparatus (SLA): Uses ultraviolet • 3D modeling was possible in the 1990s, with the evolution light to convert liquid plastic to solid objects. ABS is of Computer-Aided Design (CAD) systems. Therefore, it widely used in this technology [29]; Selective Laser Sintering (SLS): Manufactures 3D ob- is possible to graphically represent engineering projects, • analyzing kinematically and structurally the geometries, as jects from granular particles of ceramics, glass, metals possible interferences and structural failures. This system and plastics. consists of a command set for drawing and manipulation operations, these form an easy-to-use interface [23]. F. G-code Language Some advantages when using CAD are: Simplicity in the use of standardized repetitive symbols, The G-code language used in RepRap 3D printers is • unlike the classic drawing board, where these symbols similar to those used in CNC machines. There are different were made by decal sheets and normograph features; programs to prepare the code for printing, some of them are Ease of error correction in the drawings and being the Slic3r and the Cure. A 3D modeling program is used • possible to save all the previous versions. In the classic for the three-dimensional drawing of the part to be printed, drawing of the clipboard the adjustment is not so this drawing is exported in a format considered standard practical and there is need to redesign the whole design in the industry, STL format. This format makes a simple to maintain old versions; representation of apart from a triangular mesh covering all Geometric constructions that spend a lot of time drawn surfaces of the three-dimensional object. • by hand (such as tangent, ellipses) are made quickly The triangles of this mesh have three vertices and a normal and simply in these systems; unit vector, which points to the outer side of the piece, that is, 3D CAD systems have the advantage of directly where there is no material. When exporting to this format, it • building three-dimensional files and, if required, two- is important the quality of these triangles, which can directly dimensional views of parts. influence the final workpiece finish, as can be seen in Figure 3. D. Finite Elements For calculations in complex geometries, you need mathe- matical processes such as the Finite Element Method (FEM). This method is used to verify and thus improves engineering designs. For this, software such as ASYS Workbench, which is dedicated to these analyzes, is used, some 3D modeling programs also have this function, such as the Inventor 3D CAD software. The MEF consists of dividing the geometry to be analyzed in small elements, these connected by knots or nodal points, simplifying the calculations, but maintaining all the original properties, the set of these elements and knots is called a mesh [24]. From this mesh, differential equations are described and solved by mathematical models, obtaining the results not totally accurate, because it depends on the size Fig. 3. STL format exportation quality example

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G. Fin-Ray Effect In 1997, Leif Kniese patented the Fin-Ray Effect, a flexible construction for transferring strength. This structure was inspired by the fish, which is two bones with elastic connection [30], [31]. When a force is placed on this shape, it is modeled around the object (Figure 4). The company Festo has designed a robotic arm with this type of claw, the Fig. 5. Servomotor Disposition MultiChoice Gripper, the claw is made of polyurethane [32]. H. Servomotor disregarding the servos for the movement of the claw itself, 3, The choice of actuators is essential for the design, as they 2 and 1 servo respectively, with the positioning of the servos are the servos that limit the speed and torque available for to obtain desired degrees of freedom according to Figure 5. the drive, as well as the rotation accuracy and quality of The XM540-W270-R and XM540-W150-R are the servos the materials (such as gear unit gear) to predict machine for the shoulder, elbow, and wrist of the manipulator. A durability. smaller servo, the XM430-W350-R, is required for gripping Through the study of the robots of the other RoboCup the clutch drive, as it requires less torque. @ HOME competition teams and comparing with the move- ment of a human arm, it was decided to develop a manipula- I. Structure tor with 7 degrees of freedom. It was found that other groups For parts of the manipulator structure, such as the forearm use the Robotis servos in the construction of the robotic arms and arm, along with joints such as elbow, shoulder and of the Competition, because they are compact and still have wrist, parts made of aluminum will be used. Since the a high torque, so it was decided to stay with the servomotors components have simple shapes, not requiring the use of of Robotis Dynamixel line [17]. the 3D printer, since for simple parts, the aluminum material By studying the Dynamixel series servomotors, it was is more resistant to the same thickness and, consequently, possible to obtain a decision matrix from Table 1, the weights weight. were distributed according to the need of the project and the From the criteria to perform tasks and the specifications scores were assigned to the average of each series. of the servos, the parts of the robotic arm structure can be As it can be seen in the decision matrix, the series developed. From the three-dimensional modeling of the parts Dynamixel X was the one that obtained the highest score, and the stress analysis of the parts (Figure 6), it was possible therefore this one that will be used as servomotor in the to choose the manufacturing method that would be the best project. for each type of part. The ideal arrangement, with references in a human arm, is to use in the joints of the shoulder, elbow and pulse, still J. Flexible Grip The grip, based on the Fin Ray structure, will be produced in the 3D printer with a flexible filament. The part made with this filament renders the piece malleable such as a rubber (Figure 7). After testing thickness changes it was possible to find out a value of 1.4 mm with a flexibility that was suitable for the required movement and stability. Then, changes were made in the dimensions of the inner bar bearings, such as increased diameter, aperture and bar thickness. Fig. 4. Bionic Toys Fin-ray grip. Source: bionic Toys When exporting the part to the STL format it is important TABLE I to check the quality / size of the elements in the export ROBOTIS SERVOMOTORS DECISION MATRIX

Weight RX AX MX X PRO Price 0,16 7 9 6 7 4 Controler 0,16 3 3 10 10 10 Size 0,12 7 8 6 9 4 Torque 0,12 6 1 7 8 10 Ease of assembly 0,08 3 3 3 9 7 Speed 0,06 7 6 4 4 3 Weight 0,12 6 7 5 8 3 Operation Angle 0,06 4 4 9 9 9 Material 0,10 4 2 5 8 9 TOTAL 1 5,3 5,0 6,4 8,2 6,6 Fig. 6. Von Mises voltage analysis of the clamping coupling

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Fig. 9. Manipulators 3D model

Fig. 7. Material flexibility implementation of control is another work necessary for the good performance of the robotic arm. options of the software, as shown in Figure 3, export quality REFERENCES is essential to maintain the integrity of the dimensions of the [1] C. R. Jung, F. S. Osrio, e C. Roberto, Computao Embarcada: Projeto e final piece to be printed. Implementao de Veculos Autnomos Inteligentes, XXV Congr. da Soc. After all these tests, it was possible to produce an efficient Bras. Comput., 2005. [2] R. A. F. Romero, E. P. Silva Junior, F. S. Osrio, e D. F. Wolf, Robtica prototype (Figure 8), so to increase the claw friction with the mvel, 2014. objects, the external areas of the claw will have a layer of [3] D. Fernando Wolf, F. S. Osrio, E. Simes, e O. Trindade Junior, Tutorial silicone. Intelligent Robotics: From Simulation to Real World Applications Captulo 1 Robtica Mvel Inteligente: Da Simulao s Aplicaes no Mundo Real. 2009. VII. CONCLUSION [4] Sony, AIBO. [Online]. Available at: http://aibo.sony.jp/. [Acessed: 10- mar-2019]. Based on the above results, the new handler will have more [5] G. Lakatos et al., Sensing sociality in dogs: What may make an degrees of freedom for the required tasks and a longer length interactive robot social?, Anim. Cogn., 2014. [6] iRobot, iRobot Vacuum Cleaning, Mopping amp; Outdoor Mainte- than the current HERA robot, therefore, a workload will be nance. [Online]. Available at: https://www.irobot.com/. [Acessed: 10- greater. The robotic arm (Figure 9) has 7 degrees of freedom, mar-2019]. with the claw one degree more than the current one and a [7] PAL Robotics, TIAGo The robot from PAL Robotics. [Online]. Available at: http://tiago.pal-robotics.com/. length of approximately 539 mm extended with a maximum [Acessed: 27-abr-2017]. load of approximately 600g. With these modifications, the [8] PAL Robotics, REEM. [Online]. Available at: http://www.pal- robot can aid in more domestic activities, pick up objects in robotics.com/en/products/reem/. [Acessed: 27-abr-2017]. [9] PAL Robotics, REEM-C. [Online]. Available at: http://www.pal- different positions and larger weights, as well as the area of robotics.com/en/products/reem-c/. [Acessed: 27-abr-2017]. contact with objects will be greater, improving the fixation [10] C. L. Zhu, R. Bold, C. de Saint Germain, S. X. Ubach, J. Alb, e S. of the object. Pfeiffer, The Reem@LaSalle 2014 Robocup@Home Team Descrip- tion, Barcelona, 2014. For future work, it is considered to perform tests in a real [11] B. Sripetchdanon et al., SKUBA 2017 Team Description, Bangkok, environment, requiring integration with other areas, such as 2017. electronics and computational, allowing the actions to have [12] J. J. M. Lunenburg, S. Van Den Dries, R. P. W. Appeldoorn, R. W. J. Wijnands, e M. J. G. Van De Molengraft, Tech United Eindhoven greater precision and feedback of operations performed. The @Home 2016 Team Description Paper, Eindhoven University of Technology. [13] Laboratory, Pumas@Home 2016 Team Description Paper. [14] Centro Universitrio FEI, RoboFEI@HOME, Pgina desenvolvida por Plinio Thomas Aquino Jr. [Online]. Available at: http://robofei.aquinno.com/athome/. [Acessed: 22-mar-2019]. [15] V. Carrara, Apostila de Robtica. [Online]. Available at: www.valcar.netwww.carrara.us. [Acessed: 02-mar-2019]. [16] O. R. Fernandes, Robs Manipuladores: Tipos e Linguagens. [Online]. Available at: https://paginas.fe.up.pt/ lpreis/robo2005 06/apres/Robos Manipuladores.pdf. [Acessed: 27-fev-2016]. [17] Robotis, Dynamixel Selection Guide. [Online]. Available at: http://en.robotis.com/index/product.php?cate code=101310. [Acessed: 27-dez-2017]. [18] A. N. Correia e others, Estudo da biomecnica do ombro, 2010. [19] K. M. GRAAFF, Van de; RHEES, R. Ward, Anat. e Fisiol. Humana. So Paulo Makron Books, 1991. [20] A. OTTOBONI, Servo-acionamentos, Mecatrnica Atual, So Paulo, no 6, p. 714, 2010. [21] M. Vukobratovic, Introduction to Robotics. Springer Berlin Heidel- berg, 1989. Fig. 8. Printed grip flexible filament [22] J. J. Craig, Robtica. 3aedio. So Paulo: Editora Pearson, 2012.

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[23] A. Silva, J. Dias, e L. Sousa, Desenho Tcnico Moderno. 4aEdio, Ed. LTC, 2006. [24] G. Mirlisenna, Mtodo dos Elementos Finitos - o que ? [Online]. Available at: https://www.esss.co/blog/metodo-dos-elementos-finitos- o-que-e/. [Acessed: 12-jan-2017]. [25] R. S. Lotti, A. W. Machado, Ł. T. Mazzieiro, e J. Landre Jnior, Aplicabilidade cientfica do mtodo dos elementos finitos, R Dent. Press Ortodon Ortop Facial, vol. 11, no 2, p. 3543, 2006. [26] I. Gibson, D. W. Rosen, B. Stucker, e others, Additive manufacturing technologies, vol. 17. Springer, 2014. [27] A. de FARIAS, Prototipagem Rpida/Manufatura Aditiva. 2017. [28] K. Marques, Manufatura aditiva: o futuro do mercado industrial de fabricao e inovao. [Online]. Available at: http://bit.ly/2Vq1rg9. [Acessed: 20-set-2017]. [29] M. P. Da Costa, Processo de Estereolitografia (SLA) no Auxlio do Design de Veculos Automotivos, 2012. [Online]. Available at: https://maua.br/files/monografias/processo-de-estereolitografia-sla- no-auxilio-do-design-de-veiculos-automotivos.pdf. [Acessed: 15-out- 2017]. [30] bionic Toys, Fin-Ray. [Online]. Available at: http://bionictoys.de/fin- ray. [Acessed: 20-dez-2017]. [31] O. Pfaff, S. Simeonov, I. Cirovic, e P. Stano, Application of FinRay Effect approach for production process automation, Ann. DAAAM Proc., p. 12471249, 2011. [32] Festo, MultiChoiceGripper. [Online]. Available at: https://www.festo.com/group/en/cms/10221.htm. [Acessed: 20- dez-2017].

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