841 research outputs found

    Numerical Method for Optimization of Semi-Passively Controlled Dynamical Systems

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    Controlled dynamical systems with different type of actuators (e.g. external powered electromotors, magnetostrictive actuators, internal unpowered (passive) spring-damper-like drives, etc.) are considered. \ua0These systems are termed semi-passively controlled. Mathematical statement of optimization problem has proposed that is suitable both for modeling of optimal motion and for optimization of structure of semi-passively controlled dynamical systems with different degree of actuation. Numerical method for solving the proposed optimization problem is described. The method was successfully used for solving optimal control problems for several semi-passively controlled dynamical systems (industrial robots, human locomotor system with intelligent lower limb prosthesis, bipedal locomotion robots, others). The results obtained have confirmed the efficiency of the proposed numerical method for solving optimization problems for semi-passively controlled dynamical systems. Analysis of the results gives insight into the study of the role of inherent dynamics in controlled motion and how much a dynamical system should be governed by external drives and how much by a system’s inherent dynamics. It has been shown that complex goal-directed and cost-efficient controlled motion of underactuated dynamical system can be design using optimal interaction between external powered drives and internal unpowered spring-damper-like drives. This constitutes the powerful ability of semi-passively controlled dynamical systems

    Modeling and design of robotic systems having spring-damper actuators

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    The role of inherent dynamics for the improvement of control strategies of robotic systems is studied. A mathematical formulation of the optimal control problem that is suitable for this investigation is proposed. In solving this problem closed-form expressions have been obtained for the optimal control strategies for n degrees-of-freedom robotic systems with passive (unpowered) drives and no restrictions upon their controlling stimuli, and with non-linear viscoelastic spring-damper actuators. The obtained results can be used in designing optimal spring-damper-like passive drives for robotic systems

    Energy-Optimal Control of Underactuated Bipedal Locomotion Systems

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    The paper deals with modeling and design of energy-optimal motion of mechatronic system having less number of actuators than degrees of freedom. Such mechatronic system is termed underactuated. We consider an underactuated mechatronic system modeled a bipedal locomotion robot with 11 degrees of freedom. The system comprises nine links and is used to represent the bipeds planar dynamics in sagittal plane. The bodies are connected by friction-free hinge joints. Its assumed that the control inputs are torque actuators acting only at hip and knee joints. The ankle and the metatarsal joints of the feet are spanned with springs al-lowing discrete switching of their stiffness parameters in accordance to varying constraints imposed on the systems motion. The algorithm has been developed for synthesizing the energy-optimal anthropomorphic motion of the bipedal locomotion system with passively controlled feet and discrete switching of their joint stiffness parameters. Algorithm uses the smoothing cubic splines for approximation of variable functions, inverse dynamics approach, extern penalty functions method, and minimization of the nonsmooth objective function in orthogonal directions. The efficiency of the developed algorithm has been confirmed by simulation of human gait like motions for considered underactuated system. Applications of the results obtained can be found in robotics, bioengineering (prosthetics, orthotics), others

    Control strategy for cooperating disparate manipulators

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    To manipulate large payloads typical of space construction, the concept of a small arm mounted on the end of a large arm is introduced. The main purposes of such a configuration are to increase the structural stiffness of the robot by bracing against or locking to a stationary frame, and to maintain a firm position constraint between the robot's base and workpieces by grasping them. Possible topologies for a combination of disparate large and small arms are discussed, and kinematics, dynamics, controls, and coordination of the two arms, especially when they brace at the tip of the small arm, are developed. The feasibility and improvement in performance are verified, not only with analytical work and simulation results but also with experiments on the existing arrangement Robotic Arm Large and Flexible and Small Articulated Manipulator

    Energy-Optimal Control of Underactuated Bipedal Locomotion Systems

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    The paper deals with modeling and design of energy-optimal motion of mechatronic system having less number of actuators than degrees of freedom. Such mechatronic system is termed underactuated. We consider an underactuated mechatronic system modeled a bipedal locomotion robot with 11 degrees of freedom. The system comprises nine links and is used to represent the bipeds planar dynamics in sagittal plane. The bodies are connected by friction-free hinge joints. Its assumed that the control inputs are torque actuators acting only at hip and knee joints. The ankle and the metatarsal joints of the feet are spanned with springs al-lowing discrete switching of their stiffness parameters in accordance to varying constraints imposed on the systems motion. The algorithm has been developed for synthesizing the energy-optimal anthropomorphic motion of the bipedal locomotion system with passively controlled feet and discrete switching of their joint stiffness parameters. Algorithm uses the smoothing cubic splines for approximation of variable functions, inverse dynamics approach, extern penalty functions method, and minimization of the nonsmooth objective function in orthogonal directions. The efficiency of the developed algorithm has been confirmed by simulation of human gait like motions for considered underactuated system. Applications of the results obtained can be found in robotics, bioengineering (prosthetics, orthotics), others

    Knee Exoskeletons Design Approaches to Boost Strength Capability: A Review

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    Exoesqueleto para incrementar la fuerza en las rodillasThere are different devices to increase the strength capacity of people with walking problems. These devices can be classified into exoskeletons, orthotics, and braces. This review aims to identify the state of the art in the design of these medical devices, based on an analysis of patents and literature. However, there are some difficulties in processing the records due to the lack of filters and standardization in the names, generating discrepancies between the search engines, among others. Concerning the patents, 74 patents were analyzed using search engines such as Google Patents, Derwent, The Lens, Patentscope, and Espacenet over the past ten years. A bibliometric analysis was performed using 63 scientific reports from Web of Science and The Lens in the same period for scientific communications. The results show a trend to use the mechanical design of exoskeletons based on articulated rigid structures and elements that provide force to move the structure. These are generally two types: (a) elastic elements and (b) electromechanical elements. The United States accounts for 32% of the technological patents reviewed. The results suggest that the use of exoskeletons or orthoses customized to the users’ needs will continue to increase over the years due to the worldwide growth in disability, particularly related to mobility difficulties and technologies related to the combined use of springs and actuators

    Modeling, Analysis and Simulation Approaches Used in Development of the National Aeronautics and Space Administration Max Launch Abort System

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    The National Aeronautics and Space Administration (NASA) Engineering and Safety Center was chartered to develop an alternate launch abort system (LAS) as risk mitigation for the Orion Project. Its successful flight test provided data for the design of future LAS vehicles. Design of the flight test vehicle (FTV) and pad abort trajectory relied heavily on modeling and simulation including computational fluid dynamics for vehicle aero modeling, 6-degree-of-freedom kinematics models for flight trajectory modeling, and 3-degree-of-freedom kinematics models for parachute force modeling. This paper highlights the simulation techniques and the interaction between the aerodynamics, flight mechanics, and aerodynamic decelerator disciplines during development of the Max Launch Abort System FTV

    Advanced flight control system study

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    The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed

    Multi-Objective Trajectory Optimization of a Hypersonic Reconnaissance Vehicle with Temperature Constraints

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    Temperature-constrained optimal trajectories for a scramjet-based hypersonic reconnaissance vehicle were generated by developing an optimal control formulation and solving it using a variable order Gauss-Radau quadrature collocation method. The vehicle was assumed to be an air-breathing reconnaissance aircraft that has specified takeoff/landing locations, airborne refueling constraints, specified no-fly zones, and specified targets for sensor data collections. The aircraft model included fight dynamics, aerodynamics, and thermal constraints. This model was incorporated into an optimal control formulation that includes constraints on both the vehicle as well as mission parameters, such as avoidance of no-fly zones and coverage of high-value targets. Optimal trajectories were be developed using several different performance costs in the optimal control formulation--minimum time, minimum time with control penalties, and maximum range. The resulting analysis demonstrated that optimal trajectories that meet specified mission parameters and constraints can be determined and used for larger-scale operational and campaign planning

    Model-based myoelectric control of robots for assistance and rehabilitation

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    The first anthropomorphic robots and exoskeletons were developed with the idea of combining man and machine into an intimate symbiotic unit that can perform as one joint system. A human-robot interface consists of processes of two different nature: (1) the physical interaction (pHRI) between the device and its user and (2) the exchange of cognitive information (cHRI) between the human and the robot. To achieve the symbiosis between the two actors, both need to be optimized. The evolution of mechanical design and the introduction of new materials pushed pHRI to new frontiers on ergonomics and assistance performance. However, cHRI still lacks on this direction because is more complicated: it requires communication from the cognitive processes occuring in the human agent to the robot, e.g. intention detection; but also from the robot to the human agent, e.g. feedback modalities such as haptic cues. A possible innovation is the inclusion of the electromyographic signal, the command signal from our brain to the musculoskeletal system for the movement, in the robot control loop. The aim of this thesis was to develop a real-time control framework for an assistive device that can generate the same force produced by the muscles. To do this, I incorporated in the robot control loop a detailed musculoskeletal model that estimates the net torque at the joint level by taking as inputs the electromyography signals and kinematic data. This module is called myoprocessor. Here I present two applications of this control approach: the first was implemented on a soft wearable arm exosuit in order to evaluate the adaptation of the controller on different motion and loads. The second one, was a generation of myoprocessor-driven force field on a planar robot manipulandum in order to study the modularity changes of the musculoskeletal system. Both applications showed that the device controlled by myoprocessor works symbiotically with the user, by reducing the muscular activity and preserving the motor performance. The ability of seamlessly combining musculoskeletal force estimators with assistive devices opens new avenues for assisting human movement both in healthy and impaired individuals
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