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Advanced Mechanics In Robotic Systems - 2011 Springer

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内容提示: Advanced Mechanics in Robotic Systems Nestor Eduardo Nava RodríguezEditorAdvanced Mechanicsin Robotic Systems123 Prof. Nestor Eduardo Nava RodríguezCarlos III UniversityAv. Universidad 3028911 Leganés, MadridSpaine-mail: nnava@arquimea.comISBN 978-0-85729-587-3DOI 10.1007/978-0-85729-588-0Springer London Dordrecht Heidelberg New Yorke-ISBN 978-0-85729-588-0British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library? Springer-Verlag London L...

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Advanced Mechanics in Robotic Systems Nestor Eduardo Nava RodríguezEditorAdvanced Mechanicsin Robotic Systems123 Prof. Nestor Eduardo Nava RodríguezCarlos III UniversityAv. Universidad 3028911 Leganés, MadridSpaine-mail: nnava@arquimea.comISBN 978-0-85729-587-3DOI 10.1007/978-0-85729-588-0Springer London Dordrecht Heidelberg New Yorke-ISBN 978-0-85729-588-0British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library? Springer-Verlag London Limited 2011Apart from any fair dealing for the purposes of research or private study, or criticism or review, aspermitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced,stored or transmitted, in any form or by any means, with the prior permission in writing of thepublishers, or in the case of reprographic reproduction in accordance with the terms of licenses issuedby the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should besent to the publishers.The use of general descriptive names, registered names, trademarks, etc. in this publication does notimply, even in the absence of a specific statement, that such names are exempt from the relevantprotective laws and regulations and therefore free for general use.The publisher makes no representation, express or implied, with regard to the accuracy of theinformation contained in this book and cannot accept any legal responsibility or liability for any errorsor omissions that may be made.Cover design: eStudio Calamar, Berlin/FigueresPrinted on acid-free paperSpringer is part of Springer Science+Business Media (www.springer.com) PrefaceThis book provides information of the stage of mechanical design for relevantapplications in robotic fields. During recent years, some new technologies havebeen developed and put into widespread use. Humans have always been fasci-nated with the concept of artificial life and the construction of machines that lookand behave like people. The robotics evolution demands even more developmentof successful systems with high-performance characteristics for practical anduseful applications. For example, humanoid robot is a system elaborated forhelping or replacing persons in dangerous or undesirable works. But, it is acomplex machine in which an effective design represents a challenge forresearchers and scientists. Therefore, mechanical designers have studied suitablemethods and procedures in order to obtain feasible results for this kind of bipedwalking machines. In rehabilitation field, the inclusion of robots is growing uprapidly since the good operation results that have been performed for theseautomated machines. Mechanical prosthesis of hand, arms or legs have improvedthe quality of life for handicap people providing them autonomy and versatility.Beside industrial robots, mobile robots can be the most frequent robot devicesfound in the market; vacuum machines or wheeled and legged robot for inspectionor security applications are examples of commercial products that can be bought ina shop or by online. Parallel manipulators have opened a place in simulatorsmarket since its high structural stiffness, high payload and high-accuracy posi-tioning in reduced workspace. Airplane simulator, automobile simulators andvideo game platforms are some examples of practical applications of these kindsof manipulators. The principal drawbacks of parallel manipulator are their limitedworkspace and losing of stiffness in singular position. The international roboticscommunity has been working for resolving these handicaps by designing novelmechanisms that allow improving the parallel robot operation. Similarly, severalinnovative solutions for mechanical design of robotic systems have been reportedfrom research centres and universities around the world. The aim of this book is toillustrate originals and ambitious mechanical designs and techniques for devel-oping new robot prototypes with successful operation skills. In particular,humanoid robots, robotics hands, mobile robots, parallel manipulators and humanv centred robots are our case of study because they represent mechatronic projectswith future growing expectation. Since for a good control strategy a goodmechanical design is required, a book chapter has been spent on description ofsuitable design methods thinking of control architecture. I would like to take thisopportunity to thank the authors of this book very much for their efforts and thetime that they have spent in order to share their accumulated information andunderstanding of robotic systems.Madrid, November 2010Nestor Eduardo Nava RodríguezviPreface ContentsHumanoid Robots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Luis Maria Cabás Ormaechea1Robotic Hands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ramiro Cabás Ormaechea19Mobile Robots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ángel Gaspar González Rodríguez and Antonio González Rodríguez41Parallel Manipulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Erika Ottaviano59Human Centered Mechatronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Alberto Jardón Huete and Santiago Martinez de la Casa75Mechanical Design Thinking of Control Architecture . . . . . . . . . . . . .Nestor Eduardo Nava Rodríguez91vii ContributorsR. Cabás Ormaechea Robotics Lab, Carlos III University, Madrid, SpainL. M. Cabás Ormaechea Robotics Lab, Carlos III University, Madrid, SpainA. González Rodríguez Applied Mechanical Department, University of Castilla-LaMancha, SpainÁ. G. González Rodríguez Electronic Engineering and Automation Department,University of Jaén, SpainÁ. Jardón Huete Robotics Lab, Universidad Carlos III de Madrid, Madrid, SpainS. Martinez de la Casa Robotics Lab, Universidad Carlos III de Madrid, Madrid,SpainN. E. Nava Rodríguez Robotics Lab, Carlos III University, Madrid, SpainE. Ottaviano DiMSAT, University of Cassino, Cassino, Italyix Humanoid RobotsLuis Maria Cabás OrmaecheaAbstract This chapter is based within the study of the humanoid robots world andfocuses specifically on the mechatronic study of them. From a scientific stand-point, will be represented mechanically this anthropomorphic robots (from now,called humanoid robots) as a final link in the evolutionary chain in robotics area.Likewise, the design of humanoid robots is based on a wide range of mechatronicdisciplines (such as material science, mechanics, and even biomechanics), and wewill try to describe them in this chapter. Therefore, the aim of this chapter is toapproach progressively the problem of the humanoid robot design, using physicaland mechanics concepts, interacting through analogies with the human body. Thechapter begins making a further description of the humanoid robots world,showing the evolutionary process that have undergone this type of robots in recentyears. With this run-through of the main important points, we try to describe ageneral procedure to find a key criteria for successful process design of humanoidrobots. This ‘‘robot-making’’ process to explain an analysis with initial theoreticalcalculations that result in the selection of the various mechanical components of ahumanoid robot (actuators, motors until structural components). Then, the objetiveof this chapter is to present the comprehensive analysis of mechanical design of ahumanoid robot that allows to know and quantify the variables you will encounteralong the design process of this type of machines.1 IntroductionThe robotics proposes an attractive point of view of the technology with respect toscience. From a purely technological point of view, there are many applicationsthrough the use of robots: military and security tasks, health sector, domesticL. M. Cabás Ormaechea (&)Robotics Lab, Carlos III University, Av. Universidad 30,28911 Leganés, Madrid, Spaine-mail: Luis.Cabas.External@military.airbus.comN. E. Nava Rodríguez (ed.), Advanced Mechanics in Robotic Systems,DOI: 10.1007/978-0-85729-588-0_1, ? Springer-Verlag London Limited 20111 services, means of access and exploration of remote or dangerous places, in theindustry (cottage, car, heavy, iron and steel) to increase the productivity and theefficiency. Therefore it is expected to generate a wide variety of applications forthe robots that will give a technological added to this type of machines, as in anyevolutionary technology process. In a scientifical point of view, understand andexplain the human intelligence behaviour and then, through this knowledge, try tocreate intelligent machines still follows one of the greatest scientific challengesand a highly topical subject even, is in this field where could best produce thesechallenges. On the other hand, one of the best theories related to human intelli-gence maintain, that the human intelligence can only be understood when it isassociated with a physical body (embody) that allows it to interact with the world.So, if we have this kind of gorgeous mechanical machines, it will allow us toadvance in modern control theories, so that the robot can not only walk even canrun and help in many tasks (dynamically controlled). Finally, the robotics allowsresearch in the design of new sensors and electronic equipment that meets needs inenergy savings (to operate in real time) and low cost required for the developmentof humanoid robots.2 Robots Coexisting with Human BeingsAll of these desires and projects listed above will influence our daily lives. It isestimated that humanoid robots will change it in a large-measure our lives in thefuture. It is expected from this kind of robots, it will assist people to performfunctions in virtually all types of activities. In fact, they are developing robots thatassist in housework (cleaning, grass cutting, etc.), security, and entertainment,educational and even robots that assist elderly people or with disabilities. In I ? Dresearches, there are more than a hundred projects related to humanoid robots inthe world. The strange thing is that we can draw a parallel of the current state ofhumanoid robot with personal computers. Just before the discovery of computers(and their high growth rate through the last 30 years), nobody thought that thisinvention would become in personal computers. Fifteen years ago no one couldsee the usefulness of phones that they could fit in their pockets. Specifically,humanoid robots offer great technological challenges that once it achieved, it willbe most fascinating. Starting with the basic tasks until they have the ability to usethe tools that man has been used throughout history and without it has to beadapted to special environments. This may seem easy, but it is very importantbecause it demonstrates the versatility of the humanoid robot in an environmentthat has been created by opening a wide range of applications (as many workenvironments).2L. M. C. Ormaechea 3 Humanoid Robots: Definition and ClassificationLike flying, one of the most sought challenges was to create a man very like him,able to communicate in their own environments and, at some point, be autonomousin its decisions: a robot. In the twenty-first century, the industrial citizen has seenthe need to learn in recent years, the meaning of new terms marked by a hightechnological content. Irrespective of technological advances and the implicationsof these developments, science-fiction element of our culture will always be amirror of our concerns, desires, and fears and hope forces for the future. Generally,robots novels and films show a little resemblance the robots that have beenmanufactured or designed in reality, however, because of their stellar participationin most, if not all, those futuristic movies have allowed us that the term and themachine be more familiar, making easier integrates it into our daily lives beforethey see the reality. After sometime was enough those we have seen as a real robot,either on a television or print news, and we put aside the myth and we accept therobot as a machine more than our environment, that sort of animated mechanicalarm with speed and precision welded vehicle body or insert electronic chips onplates. From there, the rest remained within the limits of our imagination. Roboticsas a tool of science fiction (or vice versa), takes its inspiration from reality, from alack of something or necessity in daily life and exploits it to unimagined future.This revolution not only regarding on definition of robot, but also in its practicalapplications makes that possibilities for creating will be multiplied.4 Advantages and DisadvantagesTaking into account the design of this kind of machines, the human had to lookinto the nature due to its present big part of inspiration for the designers. Howeverthe designer concluded that copying exactly the nature is not reliable and it isbecoming useless and complex. So scientists of the University of California,Berkley, have focused in one common characteristic in all of the animals thatwithout it, the robot will be useless: locomotion. After numerous studies, one ofthe most significant discoveries was that, regardless of the number of legs and howto perform the movement, each animal performs the same force to press the soilregardless of the leg in question. Therefore, the principle of motion is the same inall legs. However, bipedal animals have something we do not have as a centipede:greater stability, with respect to the first and greater maneuverability with respectto the second. The advantage of legged locomotion is that each makes the func-tions as a buffer spring and they all work as a team, led synchronously by the brainin order to do the activity that the animal wants. But paradoxically, if you look atmost of the robots that exist today, one can see that they have a common char-acteristic which is the lack of speed and smoothness of movement. The walk of therobots is very elegant and is a problem that researchers have spent decades tryingHumanoid Robots3 to solve. However, we will see a more detailed overview of benefits and differ-ences of the walk that the robots actually have:1. Mobility: Legged robots exhibit greater mobility than those who use wheelsbecause they use intrinsically omnidirectional mobility steering. This meansthey can change direction on the main axis of the body by moving only theirsupport (legs). Furthermore, they can also rotate about the axis of their bodywithout lifting their legs supported by just their joints, that means that its bodycan rotate, tilt and change position.2. Active suspension: Intrinsically, a robot with legs has a suspension for adap-tation by varying the height of his body with the position of their legs intouneven ground. In this way the movement can be softer than a wheeled robotbecause the latter will always be parallel to the ground by adopting similarpositions to the relief of the land.3. Natural ground or Land discontinuous: The wheeled robots require continuoussurface in order to move efficiently. At first the robots with legs do not require acontinuous ground and may travel along sandy, muddy, steep and smooth land.4. Landslide: A wheel can slide on a surface because of adhesion, the legs of arobot usually deposit the weight of the robot directly on the ground and thechances of slipping are lower.5. Average speed: A robot with leg can overcome small obstacles maintaining aconstant speed of its body with rectilinear uniform motion if its necessary or ifthe programmer so wishes.6. Overcoming obstacles: The robots with leg can overcome obstacles which havelow height compared to the size of the robot. On the other hand, a wheeledrobot could be stuck if the size of the obstacle is greater than the radius of thewheel.The tendency in recent years has tried to incorporate robots into daily lifewithin the home or workplace, to do this, it is very important also the design, sincethey must be able to adapt to different environments which not requiring clear andstructured extensive handling, overcome obstacles in height and also makes themlook most familiar, always eyeing the Uncanny Valley. Of course, robots with legsare not the general solution of robotic locomotion. They present a series ofproblems and disadvantages that have kept them out of the use in industrial andservice sectors. However, humanoid robots are more complex than those that usewheels with regard to electronics, Control and scroll speed (provided that thesurface is flat, of course). But the main disadvantages that we can find are thefollowing:1. Mechanics: A system for locomotion with legs is much harder to get than thosewith wheels. The wheel is an extremely simple mechanism. With a singleactuator, we can provide motion to the robot, however, one single leg requiredseveral kinematic links and joints. One leg needs at least three actuators toallow full movement.4L. M. C. Ormaechea 2. Electronics: Each robot joint is associated it with a controller and must becontrolled individually. This means that it requires many sensors as joints.A robot with wheels is always in contact with the ground, thus simplifying theelectronics.3. Control: A humanoid must coordinate the positions of all joints to make anymove even with very strict guidelines to prevent fall (ZMP Control) and it iscertainly more complex than a similar robot with wheels.4. A wheeled locomotion mechanism on land surface is much faster than a similarmechanism which use legs.5 Design MethodologyThe design process consist of transform information based on conditions, needsand requirements related to the description of a structure, in order to satisfy thisstructure. Thus, we could say that the person, who designs, is a processor ofinformation. Not only he starts with necessity to get something, but also withknowledge that the designer have acquired, this in order to get this imaginedsolution become true confirming all the characteristics for those who have beencreated. Today we speak of design as a science and it recognizes the interaction ofa large set of features within its definition, problem solving, decision making,development, learning, knowledge, optimization, organization, satisfaction ofneeds; all of them are necessary but not sufficient by themselves. In this chapter, inthe main topic of this article, we are going to describe the mechatronic designmethodology of the natural size of humanoid robot, through a methodology for thedesign of it, made through the knowledge gained during the design and manu-facture of prototypes RH and RH-0-1.Definition of the Priority TasksIt is pretended that this developed robot has to look like human beings so that theirpresence have to be friendly. That means, in general, the prototype. The RH-0 willhave a bipedal locomotion in order to move and will have a hinged clip on the endsof their arms to manipulate small objects and a head equipped with sensors,through which the robot could be orient and move in their environment work.Moreover, as one of the tasks of the robot is the attention to disabled people, it hasbeen designed with specific measures for a person sitting in a wheelchair caninteract with the humanoid robot (which is a specific constraint objective that weare looking for) but really the applications that can be allocated to a robot of thiskind today are many and various, including the following:Humanoid Robots5 1. Human Assistance, for which it must be able to live with people and work wellin their environment. Examples of such applications: assistance to elderly ordisabled persons, personal assistants in offices, hospitals, schools, hotels and allkinds of public services that can be imagined.2. Performing physical labor, transportation of goods both individually and col-lectively with other robots or with humans when it comes to large pieces. In thisregard, it is noted the importance of this kind of robots when it comes totransportation in buildings where it is necessary to go up and down stairs,walking through narrow corridors, etc.3. Periodic maintenance, with this application is intended that the robot performthose maintenance tasks that results dangerous for integrity of the operator, ase.g., electric transport airlines, and inspection of bridges in the reactor corenuclear, etc.4. Surveillance and rescue work, security and surveillance applications forbuildings and people, as well as applications in rescue work in developingnatural stress, collapse of buildings, etc.5. Entertainment and education, the robot must be capable of fulfilling leisureactivities such as sports, play. In the case of education, the applications areintended to be guides in museums, explain lessons to students.With these applications, it is understood that the environments where the robotperforms its functions should be unstructured and need to do so in a broadspectrum of possibilities, from an industry to a house, past shops and hospitals,therefore, the robot should be able to walk both flat or sloping surfaces as well assave point, from up and down stairs, up a hill or mountain. Despite the functionaldiversity that may lead to having this kind of machines, to believe in a multitudeof different solutions (in fact, hardly a human being performs the same activity inthe same way twice) can be counterproductive to the goal of project, largelybecause of our imagination. However, we must never cease to be realistic whenyou assign sizing or assign a PT. This concept of flexibility should be consideredas another fundamental requirement to be considered early in the design of thehumanoid.Finally, the basic design of this first prototype, the RH-0, and what we think thatwill be the ‘‘Priority Takes’’ are the following:1. Assist human.2. Walk straight.3. Walking in circles.4. Up/down stairs.5. Incorporate the functionality of human arms when walking.6. Carry objects weighing up to 750 gr.7. Gesturing with his arms (pointing, waving).6L. M. C. Ormaechea Conceptual DesignThese types of mechanical devices have two major subsystems, divided on kine-matic chains defined as lower body and upper body. The lower string is formed bythe legs and its primary function is to provide the entire robot locomotion throughthe environment of action and the upper chain is formed by the arms, hands andhead. The union of these two parts form the hip. Like humans beings, the upper ismade up by the arms, which can be interpreted well as two robotic manipulatorsthat give you the versatility to help achieve the objective. Furthermore, we findhere the torso and back that would be the trunk of the robot whose function due tothe lacking mobility, is host of onboard electronics. This part is also responsiblefor helping maintain the balance of the whole mechanism to shift the center ofgravity to the proper position, thanks to the large amount of mass that we havehosted here.Mechanical SynthesisAnthropomorphism is a set of beliefs or doctrines which attribute to the divinefigure, or qualities of man. One of the most important features of humanoid robotsis the spirit in which they are designed. From this point of view it will be taken intoaccount the following basic features:1. Head: It is very important that all humanoid robots have to need a head in orderto present it to the environment. The robot will be devoted primarily to theinteraction with the human population. Hence the importance of them look ashuman as possible, reflected mainly in the face and increased the capacity ofgesture that allows the interaction of emotions, in turn, social inclusion. Thus,the face of the robot must be able to reflect the basic emotions (sadness, anger,fear, surprise, happiness and disgust). Besides presenting the face, must possessvision, not for personal use but for their interaction with the user, and for othersensing systems that allow it to be positioned and be oriented in the environ-ment of interaction. For this reason, it is necessary to provide the head of amechanism in order to be oriented. For this, we should put a DoF whose lines ofaction coincide at one point and in this way facilitating the kinematics of thesame. The head should contain all the necessary mechanisms for all mentionedgestures and are able to work in a future. The use of eyelids, lips and mobiledevices that give movement to the brow of the robot will be an aim in thedevelopment of humanoid robot. In the future, are also placed here the elementsfor the humanoid robot to interact through gestures with the human population.2. Arms: Ideally, we should build an architecture arm 5, 6 and 7 DoF. In mostcases, the arms have 5 or 6 DoF, have less than human arms, which is akinematic chain of 7 DoF. If we assume that the degrees of freedom necessaryto position and orient a body in space is 6 DoF human arms would then beHumanoid Robots7 redundant. The advantage provided by 7 DoF is not only the hand is located andoriented, but also the same arm. It is also preferred that the motors are coupleddirectly to the joints (Direct Drive). This helps to eliminate weight, but mostlymechanical backlash grows over use of broadcasts. This provides the facility toorient and position the arm without changing the hand position, power neces-sary to avoid obstacles, even find positions that involve less energy expenditureduring movement. This should be taken into account to develop the bestmechanical system and that will be addressed in this research.3. Legs: This component of the robot, isthe one that will give the necessary supportto the entire structure, which involves loading the weight of all engines,machinery, batteries, electronics and various materials involved. On them willswingaroundthechestandarmsbalancebylookingforcorrectpositioningofthecenter of gravity. Their engines must respond quickly and in coordination withthewholestructure,andalsoabsorballthemomentumthatcausesthemovement.Study of the Worst Case Analysis (WCA)Following the analysis of the most unfavorable positions, forget the pair and theirsubsequent engine, also have been used several hypotheses as demonstrated in hiscase. From a more practical standpoint, we calculated the most unfavorablepositions whether they be more achievable or not. This led, of course, both to verylarge results as well as those positions impossible to achieve for the humanoid. Butthe main objective of these states was a first approach to values and also managed,better adapted to the software currently used. Then, based on the theory of ZMPthey are opted to take more realistic positions considering ZMP validity andcomply with the requirements for each PT.In conclusion of this stage, we can say1. In the sagittal plane, we obtained very convincing pairs based on technicallyfeasible positions. Pseudo-state was considered a real for each case.2. As a prerequisite, you should always consider the ZMP is located within theeligible area.3. The joints obtained were considerably lower than those estimated in previousanalysis because the engine and the structure are subjected at more relaxedposition.Preliminary Design of the RobotWithin these considerations, we point out:1. Building materials: The materials used in building the robot should be light-weight and highly resistant. Of course the design of mechanical components8L. M. C. Ormaechea should help in this task. On the other hand, one of the major problems in thedevelopment of humanoid robots is the energy efficiency because it has not yetdeveloped enough batteries and small electric motors and high capacity, so theoptimization mechanical structure is of prime importance.2. Optimal mechanical design: The performance of the humanoid robot restsessentially on the mechanical design. The pieces should have less inertiapossible without sacrificing strength and rigidity. The optimal mechanicaldesign allows to develop lighter and stronger parts, increasing responsiveness.The assembly of mechanical system should produce a stable, solid and robustsystem. Without doubt, one of the main characteristics that define the robot isthat it includes DoF. Talk of DoF is the same as talking about the number andtype of movements that the robot can perform. On the other hand, watching themovements of the robot, it is possible to determinate the number of DoF that ispresents.3. Mechanical actuators: We must use effective actuators and strong. However, weare not leaving aside the possibility of investigating other types of actuators,including hydraulic or pneumatic. It is important to develop mechanisms forsmall actuators that can be housed in very small spaces in the arm and hand.The joints may be powered by mechanical energy conversion devices of anelectrical, hydraulic or pneumatic.4. Balance: For many authors, to achieve a right balance is the most importantconsideration when designing a mechanical humanoid robot. The primaryobjective of all design in the biped locomotion is to ensure that when the robotwalks it will achieve a dynamic equilibrium. Control methods are used toachieve dynamic balance, however the mechanical design must be chosenso that the robot can respond quickly to the required movements. One methodto achieve this goal, is to distribute the dough through the robot in such waythat any movement (sudden or not) must to be small. Thus, these movementscan be made quickly without generating large moments that usually destabilizethe robot. To achieve this, the CoM should be placed as low as possible, tostabilize the inertia of the robot but also fairly high, in order to move only smallamounts of mass to correct unwanted behavior. The correct placement for thetrunk CoM would be slightly lower, similar to humans. This provides stabilityand allows the trunk to be moved; changing from place to CoM for accelera-tions that counter exist unwanted accelerations.In addition to these considerations, we studied the range of motion of joints inthe human being, to keep them as reference in the respective RH-0. So with theseconcepts we divide the study into two parts:1. Structure and distribution of the DoF in the arms.2. Structure and distribution of the DoF in the legs.So for the arms we required movements that simply are imitating the humanwalking, extension of the frontal and lateral plane, transport and carry with light-weight things. Based on these concepts, we selected an arm with sagittal mobilityHumanoid Robots9 and front in the shoulder, sagittal mobility in the elbow and transversal mobility inthe wrist; additionally we will place a clamp to manipulate objects. As a summary,4 DoF in the arm. For the trunk, we recommend one DoF in the transverse plane toenlarge the angle of arm movement around this axis. We prefer this DoF at the topof the column. The result of this study leads us to select the structure of 6 DoF,which guarantees enough mobility for a stable ride similar to human beings. In thistype of structure selected, with certain variations, related to mobility in the hip, anarea critical to a stable path and in turn keep the stability of the robot, as well asassume the primary role of supporting the upper weight of the robot (torso, arms,batteries, electronic components, etc.). We then have the conventional structuresimilar to a simple portico, whose bending strength is mainly concentrated in thecenter of it. This is used by Asimo and most humanoids, due that its good per-formance has been proved. On the other hand, the novel cantilever structure, thatwas introduced by the HRP-2, this type of structure allows to distribute the bendingstresses in the hip due to higher weight in the robot body.Calculation of the Mechanical RequirementsThe purpose of the dynamics is to establish the relationship between the forces andmoments acting on a body, and the movement in which it originates. This rela-tionship in the case of a robot is given by the mentioned dynamic model, whichmathematically relates:1. The location of the robot due to the joint variables defined by its coordinates orfor the locations of its end, and their derivatives: velocity and acceleration.2. The forces and torques applied to the joints.3. The dimensional parameters of the robot, such as length, mass and inertia of itselements.To obtain these kind of mechanisms that have a high number of degrees offreedom, the difficulty increases significantly. This makes that this dynamic modelcould not be done always in a closed manner, i.e., expressed by a set of normalequations of differential type of 2nd order, whose integration allows knowing themovement when applying forces you have to do it for a particular movement.The dynamic model must be solved iteratively using a numerical procedure. Theprob...

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