Hybrid force/position control for a 3-DOF 1T2R parallel robot: Implementation, simulations and experiments

"This is an Author's Accepted Manuscript of an article published in Cazalilla, José, Marina Vallés, Ángel Valera, Vicente Mata, and Miguel Díaz-Rodríguez. 2016. Hybrid Force/Position Control for a 3-DOF 1T2R Parallel Robot: Implementation, Simulations and Experiments. Mechanics Based Design of Structures and Machines 44 (1 2). Informa UK Limited: 16 31. doi:10.1080/15397734.2015.1030679, available online at: https://www.tandfonline.com/doi/full/10.1080/15397734.2015.1030679."[EN] A robot interacting with the environment requires that the end effector \hboxposition is tracked and that the forces of contact are kept below certain reference values. For instance, in a rehabilitation session using a robotic device, the contact forces are limited by the allowed strength of the human limbs and their complex-joints. In these cases, a control scheme which considers both position and force control is essential to avoid damage to either the end effector or the object interacting with the robot. This paper therefore develops a real-time force/position control scheme for a three-DOF parallel robot whose end effector holds a DOF one translation (1T) and two rotations (2R). The implemented hybrid force/position control considers, as a reference, the normal force on the mobile platform, which is measured by means of a load cell installed on the platform. The position control is designed to track the orientations of the robot either in joint or task space using a model-based control scheme with identified parameters. Moreover, the force control is based on a PD action. The control scheme is developed through simulations, before being applied to an actual parallel robot. The findings show that with the implemented controller, the actual robot accomplishes the reference values for the normal force on the mobile platform, while at the same time the platform accurately follows the required angular orientation.The authors wish to thank the Plan Nacional de I+D, Comision Interministerial de Ciencia y Tecnologia (FEDER-CICYT) for the partial funding of this study under the projects DPI2011-28507-C02-01 and DPI2013-44227-R. This work was also partially supported by the Fondo Nacional de Ciencia, Tecnologia e Innovacion (FONACIT-Venezuela).Cazalilla, J.; Vallés Miquel, M.; Valera Fernández, Á.; Mata Amela, V.; Díaz-Rodríguez, M. (2016). Hybrid force/position control for a 3-DOF 1T2R parallel robot: Implementation, simulations and experiments. Mechanics Based Design of Structures and Machines. 44(1-2):16-31. https://doi.org/10.1080/15397734.2015.1030679S1631441-2Åström, K. J., & Murray, R. M. (2008). Feedback Systems. doi:10.1515/9781400828739Bellakehal, S., Andreff, N., Mezouar, Y., & Tadjine, M. (2011). Force/position control of parallel robots using exteroceptive pose measurements. Meccanica, 46(1), 195-205. doi:10.1007/s11012-010-9411-zCao, R., Gao, F., Zhang, Y., Pan, D., & Chen, W. (2014). A New Parameter Design Method of a 6-DOF Parallel Motion Simulator for a Given Workspace. Mechanics Based Design of Structures and Machines, 43(1), 1-18. doi:10.1080/15397734.2014.904234Carretero, J. A., Podhorodeski, R. P., Nahon, M. A., & Gosselin, C. M. (1999). Kinematic Analysis and Optimization of a New Three Degree-of-Freedom Spatial Parallel Manipulator. Journal of Mechanical Design, 122(1), 17-24. doi:10.1115/1.533542Clavel, R. (1988). DELTA, a fast robot with parallel geometry.Proceedings of 18th International Symposium on Industrial Robot, Lausanne, April, 91–100.Díaz-Rodríguez, M., Mata, V., Valera, Á., & Page, Á. (2010). A methodology for dynamic parameters identification of 3-DOF parallel robots in terms of relevant parameters. Mechanism and Machine Theory, 45(9), 1337-1356. doi:10.1016/j.mechmachtheory.2010.04.007Diaz-Rodriguez, M., Valera, A., Mata, V., & Valles, M. (2013). Model-Based Control of a 3-DOF Parallel Robot Based on Identified Relevant Parameters. IEEE/ASME Transactions on Mechatronics, 18(6), 1737-1744. doi:10.1109/tmech.2012.2212716Farhat, N., Mata, V., Page, Á., & Valero, F. (2008). Identification of dynamic parameters of a 3-DOF RPS parallel manipulator. Mechanism and Machine Theory, 43(1), 1-17. doi:10.1016/j.mechmachtheory.2006.12.011Garg, A., Vikram, C. S., Gupta, S., Sutar, M. K., Pathak, P. M., Mehta, N. K., … Gupta, V. K. (2014). Design and Development of In Vivo Robot for Biopsy. Mechanics Based Design of Structures and Machines, 42(3), 278-295. doi:10.1080/15397734.2014.898587Gough, V. E., Whitehall, S. G. (1962). Universal tire test machine.Proceedings of 9th International Technical Congress FISITA, pp. 117–135.García de Jalón, J., & Bayo, E. (1994). Kinematic and Dynamic Simulation of Multibody Systems. Mechanical Engineering Series. doi:10.1007/978-1-4612-2600-0Lee, K.-M., & Arjunan, S. (1991). A three-degrees-of-freedom micromotion in-parallel actuated manipulator. IEEE Transactions on Robotics and Automation, 7(5), 634-641. doi:10.1109/70.97875Li, Y., & Xu, Q. (2007). Design and Development of a Medical Parallel Robot for Cardiopulmonary Resuscitation. IEEE/ASME Transactions on Mechatronics, 12(3), 265-273. doi:10.1109/tmech.2007.897257Merlet, J.-P. (2000). Parallel Robots. Solid Mechanics and Its Applications. doi:10.1007/978-94-010-9587-7Pierrot, F., Nabat, V., Company, O., Krut, S., & Poignet, P. (2009). Optimal Design of a 4-DOF Parallel Manipulator: From Academia to Industry. 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Mechatronic development and dynamic control of a 3-DOF parallel manipulator

This is an Author's Accepted Manuscript of an article published in Mechanics Based Design of Structures and Machines: An International Journal, 40:4, 434-452 [September 2012] [copyright Taylor & Francis], available online at: http://www.tandfonline.com/10.1080/15397734.2012.687292The aim of this article is to develop, from the mechatronic point of view, a low-cost parallel manipulator (PM) with 3-degrees of freedom (DOF). The robot has to be able to generate and control one translational motion (heave) and two rotary motions (rolling and pitching). Applications for this kind of parallel manipulator can be found at least in driving-motion simulation and in the biomechanical field. An open control architecture has been developed for this manipulator, which allows implementing and testing different dynamic control schemes for a PM with 3-DOF. Thus, the robot developed can be used as a test bench where control schemes can be tested. In this article, several control schemes are proposed and the tracking control responses are compared. The schemes considered are based on passivity-based control and inverse dynamic control. The control algorithm considers point-to-point control or tracking control. When the controller considers the system dynamics, an identified model has been used. The control schemes have been tested on a virtual robot and on the actual prototype. © 2012 Taylor & Francis Group, LLC.The authors wish to express their gratitude to the Plan Nacional de I+D, Comision Interministerial de Ciencia y Tecnologia (FEDER-CICYT) for the partial financing of this study under the projects DPI2009-13830-C02-01 and DPI2010-20814-C02-(01, 02). This work was also supported in part by the CDCHT-ULA Grant I-1286-11-02-B.Vallés Miquel, M.; Díaz-Rodríguez, M.; Valera Fernández, Á.; Mata Amela, V.; Page Del Pozo, AF. (2012). Mechatronic development and dynamic control of a 3-DOF parallel manipulator. Mechanics Based Design of Structures and Machines: An International Journal. 40(4):434-452. https://doi.org/10.1080/15397734.2012.687292S434452404Awtar, S., Bernard, C., Boklund, N., Master, A., Ueda, D., & Craig, K. (2002). Mechatronic design of a ball-on-plate balancing system. Mechatronics, 12(2), 217-228. doi:10.1016/s0957-4158(01)00062-9Carretero, J. A., Podhorodeski, R. P., Nahon, M. A., & Gosselin, C. M. (1999). Kinematic Analysis and Optimization of a New Three Degree-of-Freedom Spatial Parallel Manipulator. Journal of Mechanical Design, 122(1), 17-24. doi:10.1115/1.533542Castelli, G., Ottaviano, E., & Ceccarelli, M. (2008). A Fairly General Algorithm to Evaluate Workspace Characteristics of Serial and Parallel Manipulators#. Mechanics Based Design of Structures and Machines, 36(1), 14-33. doi:10.1080/15397730701729478Chablat, D., & Wenger, P. (2003). Architecture optimization of a 3-DOF translational parallel mechanism for machining applications, the orthoglide. IEEE Transactions on Robotics and Automation, 19(3), 403-410. doi:10.1109/tra.2003.810242Clavel , R. ( 1988 ). DELTA, a fast robot with parallel geometry.Proceedings of 18th International Symposium on Industrial Robot.Switzerland: Lausanne, April, pp. 91–100 .Díaz-Rodríguez, M., Mata, V., Farhat, N., & Provenzano, S. (2008). Identifiability of the Dynamic Parameters of a Class of Parallel Robots in the Presence of Measurement Noise and Modeling Discrepancy#. Mechanics Based Design of Structures and Machines, 36(4), 478-498. doi:10.1080/15397730802446501Díaz-Rodríguez, M., Mata, V., Valera, Á., & Page, Á. (2010). A methodology for dynamic parameters identification of 3-DOF parallel robots in terms of relevant parameters. Mechanism and Machine Theory, 45(9), 1337-1356. doi:10.1016/j.mechmachtheory.2010.04.007García de Jalón, J., & Bayo, E. (1994). Kinematic and Dynamic Simulation of Multibody Systems. Mechanical Engineering Series. doi:10.1007/978-1-4612-2600-0Gough , V. 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(1989). Adaptive motion control of rigid robots: A tutorial. Automatica, 25(6), 877-888. doi:10.1016/0005-1098(89)90054-xPaccot, F., Andreff, N., & Martinet, P. (2009). A Review on the Dynamic Control of Parallel Kinematic Machines: Theory and Experiments. The International Journal of Robotics Research, 28(3), 395-416. doi:10.1177/0278364908096236Rosillo, N., Valera, A., Benimeli, F., Mata, V., & Valero, F. (2011). Real‐time solving of dynamic problem in industrial robots. Industrial Robot: An International Journal, 38(2), 119-129. doi:10.1108/01439911111106336Stewart , D. A. ( 1965 ). A platform with 6 degree of freedom.Proceedings of the Institution of Mechanical Engineers.Part 1 15:371–386 .Syrseloudis , C. E. , Emiris , I. Z. ( 2008 ). A parallel robot for ankle rehabilitation-evaluation and its design specifications.Proceeding of 8th IEEE International Conference on BioInformatics and BioEngineering, Athens, October 1–6

Mechatronic design, experimental setup, and control architecture design of a novel 4 DoF parallel manipulator

"This is an Author's Accepted Manuscript of an article published in [include the complete citation information for the final versíon of the article as published in the Mechanics Based Design of Structures and Machines 2018 [copyright Taylor & Francis], available online at: https://www.tandfonline.com/doi/10.1080/15397734.2017.1355249."[EN] Although parallel manipulators started with the introduction of architectures with six degrees of freedom, a vast number of applications require less than six degrees of freedom. Consequently, scholars have proposed architectures with three and four degrees of freedom, but relatively few four degrees of freedom parallel manipulators have become prototypes, especially of the two rotation and two translation motion types. In this article, we explain the mechatronics design, prototype, and control architecture design of a four degrees of freedom parallel manipulators with two rotation and two translation motions. We chose to design a four degrees of freedom manipulator based on the motion needed to complete the tasks of lower limb rehabilitation. To the author's best knowledge, parallel manipulators between three and six degrees of freedom for rehabilitation of lower limb have not been proposed to date. The developed architecture enhances the three minimum degrees of freedom required by adding a four degrees of freedom, which allows combinations of normal or tangential efforts in the joints, or torque acting on the knee. We put forward the inverse and forward displacement equations, describe the prototype, perform the experimental setup, and develop the hardware and control architecture. The tracking accuracy experiments from the proposed controller show that the manipulator can accomplish the required application.The authors wish to thank the Plan Nacional de I + D, Comision Interministerial de Ciencia y Tecnologia (FEDER-CICYT) for the partial funding of this study under project DPI2013-44227-R. We also want to thank the Fondo Nacional de Ciencia, Tecnologia e Innovacion (FONACIT-Venezuela) for its financial support under the project No. 2013002165.Vallés Miquel, M.; Araujo-Gómez, P.; Mata Amela, V.; Valera Fernández, Á.; Díaz-Rodríguez, M.; Page Del Pozo, AF.; Farhat, N. (2018). Mechatronic design, experimental setup, and control architecture design of a novel 4 DoF parallel manipulator. Mechanics Based Design of Structures and Machines. 46(4):425-439. https://doi.org/10.1080/15397734.2017.1355249S425439464Araujo-Gómez, P., Díaz-Rodriguez, M., Mata, V., Valera, A., & Page, A. (2016). Design of a 3-UPS-RPU Parallel Robot for Knee Diagnosis and Rehabilitation. CISM International Centre for Mechanical Sciences, 303-310. doi:10.1007/978-3-319-33714-2_34Bruyninckx, H., Soetens, P., Issaris, P., Leuven, K. (2002). The Orocos Project. http://www.orocos.org.Cao, R., Gao, F., Zhang, Y., Pan, D., & Chen, W. (2014). A New Parameter Design Method of a 6-DOF Parallel Motion Simulator for a Given Workspace. Mechanics Based Design of Structures and Machines, 43(1), 1-18. doi:10.1080/15397734.2014.904234Carretero, J. A., Podhorodeski, R. P., Nahon, M. A., & Gosselin, C. M. (1999). Kinematic Analysis and Optimization of a New Three Degree-of-Freedom Spatial Parallel Manipulator. Journal of Mechanical Design, 122(1), 17-24. doi:10.1115/1.533542Cazalilla, J., Vallés, M., Valera, Á., Mata, V., & Díaz-Rodríguez, M. (2016). Hybrid force/position control for a 3-DOF 1T2R parallel robot: Implementation, simulations and experiments. Mechanics Based Design of Structures and Machines, 44(1-2), 16-31. doi:10.1080/15397734.2015.1030679Chablat, D., & Wenger, P. (2003). Architecture optimization of a 3-DOF translational parallel mechanism for machining applications, the orthoglide. IEEE Transactions on Robotics and Automation, 19(3), 403-410. doi:10.1109/tra.2003.810242Clavel, R. (1988). A Fast Robot with Parallel Geometry. Proc. Int. Symposium on Industrial Robots, Lausanne, Switzerland, 91–100.Díaz, I., Gil, J. J., & Sánchez, E. (2011). Lower-Limb Robotic Rehabilitation: Literature Review and Challenges. Journal of Robotics, 2011, 1-11. doi:10.1155/2011/759764Díaz-Rodríguez, M., Mata, V., Valera, Á., & Page, Á. (2010). A methodology for dynamic parameters identification of 3-DOF parallel robots in terms of relevant parameters. Mechanism and Machine Theory, 45(9), 1337-1356. doi:10.1016/j.mechmachtheory.2010.04.007Escamilla, R. F., MacLeod, T. D., Wilk, K. E., Paulos, L., & Andrews, J. R. (2012). Cruciate ligament loading during common knee rehabilitation exercises. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 226(9), 670-680. doi:10.1177/0954411912451839Gan, D., Dai, J. S., Dias, J., Umer, R., & Seneviratne, L. (2015). Singularity-Free Workspace Aimed Optimal Design of a 2T2R Parallel Mechanism for Automated Fiber Placement. Journal of Mechanisms and Robotics, 7(4). doi:10.1115/1.4029957Garage, W. (2009). Robot Operating System. www.ros.org. Accessed date: August 2nd, 2017.Girone, M., Burdea, G., Bouzit, M., Popescu, V., & Deutsch, J. E. (2001). Autonomous Robots, 10(2), 203-212. doi:10.1023/a:1008938121020Gough, V., Whitehall, S. (1962). Universal Tyre Test Machine. Proceedings 9th Int. Technical Congress FISITA, London, vol. 117, 117–135.Jamwal, P. K., Hussain, S., & Xie, S. Q. (2013). Review on design and control aspects of ankle rehabilitation robots. Disability and Rehabilitation: Assistive Technology, 10(2), 93-101. doi:10.3109/17483107.2013.866986Lee, K.-M., & Arjunan, S. (1992). A Three Degrees of Freedom Micro-Motion In-Parallel Actuated Manipulator. Precision Sensors, Actuators and Systems, 345-374. doi:10.1007/978-94-011-1818-7_9Li, Y., & Xu, Q. (2007). Design and Development of a Medical Parallel Robot for Cardiopulmonary Resuscitation. IEEE/ASME Transactions on Mechatronics, 12(3), 265-273. doi:10.1109/tmech.2007.897257Mohan, S., Mohanta, J. K., Kurtenbach, S., Paris, J., Corves, B., & Huesing, M. (2017). Design, development and control of a 2PRP-2PPR planar parallel manipulator for lower limb rehabilitation therapies. Mechanism and Machine Theory, 112, 272-294. doi:10.1016/j.mechmachtheory.2017.03.001Ortega, R., & Spong, M. W. (1989). Adaptive motion control of rigid robots: A tutorial. Automatica, 25(6), 877-888. doi:10.1016/0005-1098(89)90054-xPierrot, F., Company, O. (1999). H4: A New Family of 4 DoF Parallel Robots. Proceedings of 1999 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, Georgia, USA, 508–513.Ramsay, J. O., & Silverman, B. W. (1997). Functional Data Analysis. Springer Series in Statistics. doi:10.1007/978-1-4757-7107-7Rastegarpanah, A., Saadat, M., & Borboni, A. (2016). Parallel Robot for Lower Limb Rehabilitation Exercises. Applied Bionics and Biomechanics, 2016, 1-10. doi:10.1155/2016/8584735Stewart, D. (1965). A Platform with Six Degrees of Freedom. Proceedings of the Institution of Mechanical Engineers, 180(1), 371-386. doi:10.1243/pime_proc_1965_180_029_02Vallés, M., Cazalilla, J., Valera, Á., Mata, V., Page, Á., & Díaz-Rodríguez, M. (2015). A 3-PRS parallel manipulator for ankle rehabilitation: towards a low-cost robotic rehabilitation. Robotica, 35(10), 1939-1957. doi:10.1017/s0263574715000120Vallés, M., Díaz-Rodríguez, M., Valera, Á., Mata, V., & Page, Á. (2012). Mechatronic Development and Dynamic Control of a 3-DOF Parallel Manipulator. Mechanics Based Design of Structures and Machines, 40(4), 434-452. doi:10.1080/15397734.2012.687292Xu, W. L., Pap, J.-S., & Bronlund, J. (2008). Design of a Biologically Inspired Parallel Robot for Foods Chewing. IEEE Transactions on Industrial Electronics, 55(2), 832-841. doi:10.1109/tie.2007.909067Yoon, J., Ryu, J., & Lim, K.-B. (2006). Reconfigurable ankle rehabilitation robot for various exercises. Journal of Robotic Systems, 22(S1), S15-S33. doi:10.1002/rob.20150Zarkandi, S. (2011). Kinematics and Singularity Analysis of a Parallel Manipulator with Three Rotational and One Translational DOFs. Mechanics Based Design of Structures and Machines, 39(3), 392-407. doi:10.1080/15397734.2011.55914

Kinematics and workspace analysis of a 3ppps parallel robot with u-shaped base

This paper presents the kinematic analysis of the 3-PPPS parallel robot with an equilateral mobile platform and a U-shape base. The proposed design and appropriate selection of parameters allow to formulate simpler direct and inverse kinematics for the manipulator under study. The parallel singularities associated with the manipulator depend only on the orientation of the end-effector, and thus depend only on the orientation of the end effector. The quaternion parameters are used to represent the aspects, i.e. the singularity free regions of the workspace. A cylindrical algebraic decomposition is used to characterize the workspace and joint space with a low number of cells. The dis-criminant variety is obtained to describe the boundaries of each cell. With these simplifications, the 3-PPPS parallel robot with proposed design can be claimed as the simplest 6 DOF robot, which further makes it useful for the industrial applications

Kinematics, workspace and singularity analysis of a multi-mode parallel robot

A family of reconfigurable parallel robots can change motion modes by passing through constraint singularities by locking and releasing some passive joints of the robot. This paper is about the kinematics, the workspace and singularity analysis of a 3-PRPiR parallel robot involving lockable Pi and R (revolute) joints. Here a Pi joint may act as a 1-DOF planar parallelogram if its lock-able P (prismatic) joint is locked or a 2-DOF RR serial chain if its lockable P joint is released. The operation modes of the robot include a 3T operation modes to three 2T1R operation modes with two different directions of the rotation axis of the moving platform. The inverse kinematics and forward kinematics of the robot in each operation modes are dealt with in detail. The workspace analysis of the robot allow us to know the regions of the workspace that the robot can reach in each operation mode. A prototype built at Heriot-Watt University is used to illustrate the results of this work.Comment: International Design Engineering Technical Conferences \& Computers and Information in Engineering Conference, Aug 2017, Cleveland, United States. 201

Design and motion control of a 6-UPS fully parallel robot for long bone fracture reduction : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Mechatronics at Massey University

The incidences of long bone fractures in New Zealand are approximately 1 in 10,000. Long bones such as tibia and femur have complicated anatomic structures, making the realignment of these long bone fractures reliant on the skill of the surgeon. The drawbacks of current practice result in long time exposure to radiation, slow recovery and possible morbidity. A semi-automated long bone fracture reduction system based on a 6-DOF parallel robot platform has been in development since 2004. The developed 6-DOF parallel robot platform comprises of six linear actuators with rotary incremental encoders. To implement a realignment of long bone fractures, a framework for the 6-DOF platform robot has been developed. The inverse kinematics and singularity of the 6-DOF parallel robot has been studied to obtain the actions and Jacobin matrices. In motion control a multiple axis motion controller and amplifiers were used for 6-DOF parallel robot. PID tuning algorithms were developed based on the combination of the general tuning result and the contour control principle. The PID parameters have been validated by a number of experiments. The practical realignment of bone fractures requires a "Pull-Rotate-Push" action implemented by the 6-DOF parallel robot. After calibration, the reduction trajectories were generated accurately. The actual trials on the artificial fractures have shown that the robot developed is capable of performing the required reduction motion

The Ariadne's Clew Algorithm

We present a new approach to path planning, called the "Ariadne's clew algorithm". It is designed to find paths in high-dimensional continuous spaces and applies to robots with many degrees of freedom in static, as well as dynamic environments - ones where obstacles may move. The Ariadne's clew algorithm comprises two sub-algorithms, called Search and Explore, applied in an interleaved manner. Explore builds a representation of the accessible space while Search looks for the target. Both are posed as optimization problems. We describe a real implementation of the algorithm to plan paths for a six degrees of freedom arm in a dynamic environment where another six degrees of freedom arm is used as a moving obstacle. Experimental results show that a path is found in about one second without any pre-processing

Using a 3DOF Parallel Robot and a Spherical Bat to hit a Ping-Pong Ball

Playing the game of Ping-Pong is a challenge to human abilities since it requires developing skills, such as fast reaction capabilities, precision of movement and high speed mental responses. These processes include the utilization of seven DOF of the human arm, and translational movements through the legs, torso, and other extremities of the body, which are used for developing different game strategies or simply imposing movements that affect the ball such as spinning movements. Computationally, Ping-Pong requires a huge quantity of joints and visual information to be processed and analysed, something which really represents a challenge for a robot. In addition, in order for a robot to develop the task mechanically, it requires a large and dexterous workspace, and good dynamic capacities. Although there are commercial robots that are able to play Ping-Pong, the game is still an open task, where there are problems to be solved and simplified. All robotic Ping-Pong players cited in the bibliography used at least four DOF to hit the ball. In this paper, a spherical bat mounted on a 3-DOF parallel robot is proposed. The spherical bat is used to drive the trajectory of a Ping-Pong ball.Fil: Trasloheros, Alberto. Universidad Aeronáutica de Querétaro; MéxicoFil: Sebastián, José María. Universidad Politécnica de Madrid; España. Consejo Superior de Investigaciones Científicas; EspañaFil: Torrijos, Jesús. Consejo Superior de Investigaciones Científicas; España. Universidad Politécnica de Madrid; EspañaFil: Carelli Albarracin, Ricardo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; ArgentinaFil: Roberti, Flavio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentin

On the optimal design of parallel robots taking into account their deformations and natural frequencies

This paper discusses the utility of using simple stiffness and vibrations models, based on the Jacobian matrix of a manipulator and only the rigidity of the actuators, whenever its geometry is optimised. In many works, these simplified models are used to propose optimal design of robots. However, the elasticity of the drive system is often negligible in comparison with the elasticity of the elements, especially in applications where high dynamic performances are needed. Therefore, the use of such a simplified model may lead to the creation of robots with long legs, which will be submitted to large bending and twisting deformations. This paper presents an example of manipulator for which it is preferable to use a complete stiffness or vibration model to obtain the most suitable design and shows that the use of simplified models can lead to mechanisms with poorer rigidity