Route Swarm: Wireless Network Optimization through Mobility

In this paper, we demonstrate a novel hybrid architecture for coordinating networked robots in sensing and information routing applications. The proposed INformation and Sensing driven PhysIcally REconfigurable robotic network (INSPIRE), consists of a Physical Control Plane (PCP) which commands agent position, and an Information Control Plane (ICP) which regulates information flow towards communication/sensing objectives. We describe an instantiation where a mobile robotic network is dynamically reconfigured to ensure high quality routes between static wireless nodes, which act as source/destination pairs for information flow. The ICP commands the robots towards evenly distributed inter-flow allocations, with intra-flow configurations that maximize route quality. The PCP then guides the robots via potential-based control to reconfigure according to ICP commands. This formulation, deemed Route Swarm, decouples information flow and physical control, generating a feedback between routing and sensing needs and robotic configuration. We demonstrate our propositions through simulation under a realistic wireless network regime.Comment: 9 pages, 4 figures, submitted to the IEEE International Conference on Intelligent Robots and Systems (IROS) 201

Correct-by-Construction Approach for Self-Evolvable Robots

The paper presents a new formal way of modeling and designing reconfigurable robots, in which case the robots are allowed to reconfigure not only structurally but also functionally. We call such kind of robots "self-evolvable", which have the potential to be more flexible to be used in a wider range of tasks, in a wider range of environments, and with a wider range of users. To accommodate such a concept, i.e., allowing a self-evovable robot to be configured and reconfigured, we present a series of formal constructs, e.g., structural reconfigurable grammar and functional reconfigurable grammar. Furthermore, we present a correct-by-construction strategy, which, given the description of a workspace, the formula specifying a task, and a set of available modules, is capable of constructing during the design phase a robot that is guaranteed to perform the task satisfactorily. We use a planar multi-link manipulator as an example throughout the paper to demonstrate the proposed modeling and designing procedures.Comment: The paper has 17 pages and 4 figure

Optimal Reconfiguration of a Limited Parallel Robot for Forward Singularities Avoidance

[EN] The positioning of the anchoring points of a Parallel Kinematic Manipulator has an important impact on its later performance. This paper presents an optimization problem to deal with the reconfiguration of a Parallel Kinematic manipulator with four degrees of freedom and the corresponding algorithms to address such problem, with the subsequent test on an actual robot. The cost function minimizes the forces applied by the actuators along the trajectory and considers singular positions and the feasibility of the active generalized coordinates. Results are compared among different algorithms, including evolutionary, heuristics, multi-strategy and gradient-based optimizers.This work was supported by the Spanish Ministry of Education, Culture and Sports through the Project for Research and Technological Development with Ref. DPI2017-84201-RLlopis-Albert, C.; Valero, F.; Mata, V.; Escarabajal, RJ.; Zamora-Ortiz, P.; Pulloquinga, JL. (2020). Optimal Reconfiguration of a Limited Parallel Robot for Forward Singularities Avoidance. Multidisciplinary Journal for Education, Social and Technological Sciences. 7(1):113-127. https://doi.org/10.4995/muse.2020.13352OJS11312771Arakelian, V., Briot, S., & Glazunov, V. (2008). Increase of singularity-free zones in the workspace of parallel manipulators using mechanisms of variable structure. Mechanism and Machine Theory, 43(9), 1129-1140. https://doi.org/10.1016/J.MECHMACHTHEORY.2007.09.005Araujo-Gómez, P., Díaz-Rodríguez, M., Mata, V., & González-Estrada, O. A. (2019). Kinematic analysis and dimensional optimization of a 2R2T parallel manipulator. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 41(10), 425. https://doi.org/10.1007/s40430-019-1934-1Araujo-Gómez, P., Mata, V., Díaz-Rodríguez, M., Valera, A., & Page, A. (2017). Design and kinematic analysis of a novel 3UPS/RPU parallel kinematic mechanism with 2T2R motion for knee diagnosis and rehabilitation tasks. Journal of Mechanisms and Robotics, 9(6), 061004. https://doi.org/10.1115/1.4037800Beiranvand, V., Hare, W., & Lucet, Y. (2017). Best practices for comparing optimization algorithms. Optimization and Engineering, 18(4), 815-848. https://doi.org/10.1007/s11081-017-9366-1Dash, A. K., Chen, I. M., Yeo, S. H., & Yang, G. (2005). Workspace generation and planning singularity-free path for parallel manipulators. Mechanism and Machine Theory, 40(7), 776-805. https://doi.org/10.1016/j.mechmachtheory.2005.01.001Gosselin, C., & Angeles, J. (1990). Singularity Analysis of Closed-Loop Kinematic Chains. IEEE Transactions on Robotics and Automation, 6(3), 281-290. https://doi.org/10.1109/70.56660Llopis-Albert, C., Rubio, F., & Valero, F. (2018). Optimization approaches for robot trajectory planning. Multidisciplinary Journal for Education, Social and Technological Sciences, 5(1), 1. https://doi.org/10.4995/muse.2018.9867Patel, Y. D., & George, P. M. (2012). Parallel Manipulators Applications-A Survey. Modern Mechanical Engineering, 02(03), 57-64. https://doi.org/10.4236/mme.2012.23008Rubio, F., Llopis-Albert, C., Valero, F., & Suñer, J. L. (2016). Industrial robot efficient trajectory generation without collision through the evolution of the optimal trajectory. Robotics and Autonomous Systems, 86, 106-112. https://doi.org/10.1016/j.robot.2016.09.008Rubio, F., Valero, F., & Llopis-Albert, C. (2019). A review of mobile robots: Concepts, methods, theoretical framework, and applications. International Journal of Advanced Robotic Systems, 16(2), 172988141983959. https://doi.org/10.1177/1729881419839596Tsai, L.-W. (1999). Robot Analysis and Design. John Wiley & Sons, Inc. New York, NY, USA ©1999.Valero, F., Rubio, F., & Llopis-Albert, C. (2019). Assessment of the Effect of Energy Consumption on Trajectory Improvement for a Car-like Robot. Robotica, 37(11), 1998-2009. https://doi.org/10.1017/S0263574719000407Vallés, M., Araujo-Gómez, P., Mata, V., Valera, A., Díaz-Rodríguez, M., Page, Á., & Farhat, N. M. (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/10.1080/15397734.2017.1355249Wehage, K. T., Wehage, R. A., & Ravani, B. (2015). Generalized coordinate partitioning for complex mechanisms based on kinematic substructuring. Mechanism and Machine Theory, 92, 464-483. https://doi.org/10.1016/j.mechmachtheory.2015.06.006www.esteco.com. (n.d.). Retrieved June 10, 2019, from https://www.esteco.com/Xianwen Kong, B., & Gosselin, C. M. (2002). Kinematics and singularity analysis of a novel type of 3-CRR 3-DOF translational parallel manipulator. International Journal of Robotics Research, 21(9), 791-798. https://doi.org/10.1177/02783649020210090501Yang, X. (2017). Optimization Algorithms Optimization and Metaheuristic Algorithms in Engineering. (March). https://doi.org/10.1007/978-3-642-20859-

A Distributed Model Predictive Control Framework for Road-Following Formation Control of Car-like Vehicles (Extended Version)

This work presents a novel framework for the formation control of multiple autonomous ground vehicles in an on-road environment. Unique challenges of this problem lie in 1) the design of collision avoidance strategies with obstacles and with other vehicles in a highly structured environment, 2) dynamic reconfiguration of the formation to handle different task specifications. In this paper, we design a local MPC-based tracking controller for each individual vehicle to follow a reference trajectory while satisfying various constraints (kinematics and dynamics, collision avoidance, \textit{etc.}). The reference trajectory of a vehicle is computed from its leader's trajectory, based on a pre-defined formation tree. We use logic rules to organize the collision avoidance behaviors of member vehicles. Moreover, we propose a methodology to safely reconfigure the formation on-the-fly. The proposed framework has been validated using high-fidelity simulations.Comment: Extended version of the conference paper submission on ICARCV'1

Optimal Reconfiguration of a Parallel Robot for Forward Singularities Avoidance in Rehabilitation Therapies. A Comparison via Different Optimization Methods

[EN] This paper presents an efficient algorithm for the reconfiguration of a parallel kinematic manipulator with four degrees of freedom. The reconfiguration of the parallel manipulator is posed as a nonlinear optimization problem where the design variables correspond to the anchoring points of the limbs of the robot on the fixed platform. The penalty function minimizes the forces applied by the actuators during a specific trajectory. Some constraints are imposed to avoid forward singularities and guarantee the feasibility of the active generalized coordinates for a certain trajectory. The results are compared with different optimization approaches with the aim of avoiding getting trapped into a local minimum and undergoing forward singularities. The comparison covers evolutionary algorithms, heuristics optimizers, multistrategy algorithms, and gradient-based optimizers. The proposed methodology has been successfully tested on an actual parallel robot for different trajectories.This research was funded by the Spanish Ministry of Education, Culture and Sports, grant number DPI2017-84201-R.Llopis-Albert, C.; Valero Chuliá, FJ.; Mata Amela, V.; Pulloquinga-Zapata, J.; Zamora-Ortiz, P.; Escarabajal-Sánchez, RJ. (2020). Optimal Reconfiguration of a Parallel Robot for Forward Singularities Avoidance in Rehabilitation Therapies. A Comparison via Different Optimization Methods. Sustainability. 12(14):1-18. https://doi.org/10.3390/su12145803S1181214Rubio, F., Valero, F., & Llopis-Albert, C. (2019). A review of mobile robots: Concepts, methods, theoretical framework, and applications. International Journal of Advanced Robotic Systems, 16(2), 172988141983959. doi:10.1177/1729881419839596Jamwal, P. K., Xie, S. Q., Hussain, S., & Parsons, J. G. (2014). An Adaptive Wearable Parallel Robot for the Treatment of Ankle Injuries. IEEE/ASME Transactions on Mechatronics, 19(1), 64-75. doi:10.1109/tmech.2012.2219065Niu, X., Yang, C., Tian, B., Li, X., & Han, J. (2019). Modal Decoupled Dynamics Feed-Forward Active Force Control of Spatial Multi-DOF Parallel Robotic Manipulator. Mathematical Problems in Engineering, 2019, 1-13. doi:10.1155/2019/1835308Chablat, D., Kong, X., & Zhang, C. (2018). Kinematics, Workspace, and Singularity Analysis of a Parallel Robot With Five Operation Modes. Journal of Mechanisms and Robotics, 10(3). doi:10.1115/1.4039400Gao, Z., & Zhang, D. (2011). Workspace Representation and Optimization of a Novel Parallel Mechanism with Three-Degrees-of-Freedom. Sustainability, 3(11), 2217-2228. doi:10.3390/su3112217Hu, B., Shi, D., Xie, T., Hu, B., & Ye, N. (2020). Kinematically identical manipulators derivation for the 2-RPU+UPR parallel manipulator and their constraint performance comparison. Journal of Mechanisms and Robotics, 1-13. doi:10.1115/1.4047540Schappler, M., Tappe, S., & Ortmaier, T. (2019). Modeling Parallel Robot Kinematics for 3T2R and 3T3R Tasks Using Reciprocal Sets of Euler Angles. Robotics, 8(3), 68. doi:10.3390/robotics8030068Chen, Z., Xu, L., Zhang, W., & Li, Q. (2019). Closed-form dynamic modeling and performance analysis of an over-constrained 2PUR-PSR parallel manipulator with parasitic motions. Nonlinear Dynamics, 96(1), 517-534. doi:10.1007/s11071-019-04803-2Zhang, D., & Wei, B. (2017). Interactions and Optimizations Analysis between Stiffness and Workspace of 3-UPU Robotic Mechanism. Measurement Science Review, 17(2), 83-92. doi:10.1515/msr-2017-0011Wu, G., & Zou, P. (2016). Comparison of 3-DOF asymmetrical spherical parallel manipulators with respect to motion/force transmission and stiffness. Mechanism and Machine Theory, 105, 369-387. doi:10.1016/j.mechmachtheory.2016.07.017Meng, W., Xie, S. Q., Liu, Q., Lu, C. Z., & Ai, Q. (2017). Robust Iterative Feedback Tuning Control of a Compliant Rehabilitation Robot for Repetitive Ankle Training. IEEE/ASME Transactions on Mechatronics, 22(1), 173-184. doi:10.1109/tmech.2016.2618771Yang, Z., & Zhang, D. (2019). ENERGY OPTIMAL ADAPTION AND MOTION PLANNING OF A 3-RRS BALANCED MANIPULATOR. International Journal of Robotics and Automation, 34(5). doi:10.2316/j.2019.206-0171Zhang, D., & Gao, Z. (2012). Optimal Kinematic Calibration of Parallel Manipulators With Pseudoerror Theory and Cooperative Coevolutionary Network. IEEE Transactions on Industrial Electronics, 59(8), 3221-3231. doi:10.1109/tie.2011.2166229Lou, Y., Zhang, Y., Huang, R., Chen, X., & Li, Z. (2014). Optimization Algorithms for Kinematically Optimal Design of Parallel Manipulators. IEEE Transactions on Automation Science and Engineering, 11(2), 574-584. doi:10.1109/tase.2013.2259817Dumlu, A., & Erenturk, K. (2014). Trajectory Tracking Control for a 3-DOF Parallel Manipulator Using Fractional-Order $\hbox{PI}^{\lambda}\hbox{D}^{\mu}$ Control. IEEE Transactions on Industrial Electronics, 61(7), 3417-3426. doi:10.1109/tie.2013.2278964Llopis-Albert, C., Rubio, F., & Valero, F. (2018). Optimization approaches for robot trajectory planning. Multidisciplinary Journal for Education, Social and Technological Sciences, 5(1), 1. doi:10.4995/muse.2018.9867Gosselin, C., & Angeles, J. (1990). Singularity analysis of closed-loop kinematic chains. IEEE Transactions on Robotics and Automation, 6(3), 281-290. doi:10.1109/70.56660Briot, S., Arakelian, V., Bonev, I. A., Chablat, D., & Wenger, P. (2008). Self-Motions of General 3-RPR Planar Parallel Robots. The International Journal of Robotics Research, 27(7), 855-866. doi:10.1177/0278364908092466Karimi, A., Masouleh, M. T., & Cardou, P. (2016). Avoiding the singularities of 3-RPR parallel mechanisms via dimensional synthesis and self-reconfigurability. Mechanism and Machine Theory, 99, 189-206. doi:10.1016/j.mechmachtheory.2016.01.006Patel, Y. D., & George, P. M. (2012). Parallel Manipulators Applications—A Survey. Modern Mechanical Engineering, 02(03), 57-64. doi:10.4236/mme.2012.23008Araujo-Gómez, P., Díaz-Rodríguez, M., Mata, V., & González-Estrada, O. A. (2019). Kinematic analysis and dimensional optimization of a 2R2T parallel manipulator. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 41(10). doi:10.1007/s40430-019-1934-1Araujo-Gómez, P., Mata, V., Díaz-Rodríguez, M., Valera, A., & Page, A. (2017). Design and Kinematic Analysis of a Novel 3UPS/RPU Parallel Kinematic Mechanism With 2T2R Motion for Knee Diagnosis and Rehabilitation Tasks. Journal of Mechanisms and Robotics, 9(6). doi:10.1115/1.4037800Vallés, M., Araujo-Gómez, P., Mata, V., Valera, A., Díaz-Rodríguez, M., Page, Á., & Farhat, N. M. (2017). 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. doi:10.1080/15397734.2017.1355249Koziel, S., & Yang, X.-S. (Eds.). (2011). Computational Optimization, Methods and Algorithms. Studies in Computational Intelligence. doi:10.1007/978-3-642-20859-1Beiranvand, V., Hare, W., & Lucet, Y. (2017). Best practices for comparing optimization algorithms. Optimization and Engineering, 18(4), 815-848. doi:10.1007/s11081-017-9366-1Page, A., De Rosario, H., Mata, V., Hoyos, J. V., & Porcar, R. (2006). Effect of marker cluster design on the accuracy of human movement analysis using stereophotogrammetry. Medical and Biological Engineering and Computing, 44(12), 1113-1119. doi:10.1007/s11517-006-0124-3Arora, J. S., Chahande, A. I., & Paeng, J. K. (1991). Multiplier methods for engineering optimization. International Journal for Numerical Methods in Engineering, 32(7), 1485-1525. doi:10.1002/nme.1620320706Modefrontier Toolhttps://www.esteco.com.202

A Rapidly Reconfigurable Robotics Workcell and Its Applictions for Tissue Engineering

This article describes the development of a component-based technology robot system that can be rapidly configured to perform a specific manufacturing task. The system is conceived with standard and inter-operable components including actuator modules, rigid link connectors and tools that can be assembled into robots with arbitrary geometry and degrees of freedom. The reconfigurable "plug-and-play" robot kinematic and dynamic modeling algorithms are developed. These algorithms are the basis for the control and simulation of reconfigurable robots. The concept of robot configuration optimization is introduced for the effective use of the rapidly reconfigurable robots. Control and communications of the workcell components are facilitated by a workcell-wide TCP/IP network and device level CAN-bus networks. An object-oriented simulation and visualization software for the reconfigurable robot is developed based on Windows NT. Prototypes of the robot systems configured to perform 3D contour following task and the positioning task are constructed and demonstrated. Applications of such systems for biomedical tissue scaffold fabrication are considered.Singapore-MIT Alliance (SMA

Modeling, Control and Estimation of Reconfigurable Cable Driven Parallel Robots

The motivation for this thesis was to develop a cable-driven parallel robot (CDPR) as part of a two-part robotic device for concrete 3D printing. This research addresses specific research questions in this domain, chiefly, to present advantages offered by the addition of kinematic redundancies to CDPRs. Due to the natural actuation redundancy present in a fully constrained CDPR, the addition of internal mobility offers complex challenges in modeling and control that are not often encountered in literature. This work presents a systematic analysis of modeling such kinematic redundancies through the application of reciprocal screw theory (RST) and Lie algebra while further introducing specific challenges and drawbacks presented by cable driven actuators. It further re-contextualizes well-known performance indices such as manipulability, wrench closure quality, and the available wrench set for application with reconfigurable CDPRs. The existence of both internal redundancy and static redundancy in the joint space offers a large subspace of valid solutions that can be condensed through the selection of appropriate objective priorities, constraints or cost functions. Traditional approaches to such redundancy resolution necessitate computationally expensive numerical optimization. The control of both kinematic and actuation redundancies requires cascaded control frameworks that cannot easily be applied towards real-time control. The selected cost functions for numerical optimization of rCDPRs can be globally (and sometimes locally) non-convex. In this work we present two applied examples of redundancy resolution control that are unique to rCDPRs. In the first example, we maximize the directional wrench ability at the end-effector while minimizing the joint torque requirement by utilizing the fitness of the available wrench set as a constraint over wrench feasibility. The second example focuses on directional stiffness maximization at the end-effector through a variable stiffness module (VSM) that partially decouples the tension and stiffness. The VSM introduces an additional degrees of freedom to the system in order to manipulate both reconfigurability and cable stiffness independently. The controllers in the above examples were designed with kinematic models, but most CDPRs are highly dynamic systems which can require challenging feedback control frameworks. An approach to real-time dynamic control was implemented in this thesis by incorporating a learning-based frameworks through deep reinforcement learning. Three approaches to rCDPR training were attempted utilizing model-free TD3 networks. Robustness and safety are critical features for robot development. One of the main causes of robot failure in CDPRs is due to cable breakage. This not only causes dangerous dynamic oscillations in the workspace, but also leads to total robot failure if the controllability (due to lack of cables) is lost. Fortunately, rCDPRs can be utilized towards failure tolerant control for task recovery. The kinematically redundant joints can be utilized to help recover the lost degrees of freedom due to cable failure. This work applies a Multi-Model Adaptive Estimation (MMAE) framework to enable online and automatic objective reprioritization and actuator retasking. The likelihood of cable failure(s) from the estimator informs the mixing of the control inputs from a bank of feedforward controllers. In traditional rigid body robots, safety procedures generally involve a standard emergency stop procedure such as actuator locking. Due to the flexibility of cable links, the dynamic oscillations of the end-effector due to cable failure must be actively dampened. This work incorporates a Linear Quadratic Regulator (LQR) based feedback stabilizer into the failure tolerant control framework that works to stabilize the non-linear system and dampen out these oscillations. This research contributes to a growing, but hitherto niche body of work in reconfigurable cable driven parallel manipulators. Some outcomes of the multiple engineering design, control and estimation challenges addressed in this research warrant further exploration and study that are beyond the scope of this thesis. This thesis concludes with a thorough discussion of the advantages and limitations of the presented work and avenues for further research that may be of interest to continuing scholars in the community