73 research outputs found
Design, Implementation and Control of a Magnetic Levitation Device
Magnetic levitation technology has shown a great deal of promise for micromanipulation
tasks. Due to the lack of mechanical contact, magnetic levitation systems are free of problems caused by friction, wear, sealing and lubrication. These advantages have made magnetic levitation systems a great candidate for clean room applications. In this thesis, a new large gap magnetic levitation system is designed, developed and successfully tested. The system is capable of levitating a 6.5(gr) permanent magnet in 3D space with an air gap of approximately 50(cm) with the traveling range of 20x20x30 cubic millimeters. The overall positioning accuracy of the system is 60 micro meters. With the aid of finite elements method, an optimal geometry for the magnetic stator is proposed. Also, an energy optimization approach is utilized in the design of the electromagnets.
In order to facilitate the design of various controllers for the system, a mathematical model of the magnetic force experienced by the levitated object is obtained. The dynamic magnetic force model is determined experimentally using frequency response system identification. The response of the system components including the power amplifiers, and position measurement system are also considered in the development of the force model.
The force model is then employed in the controller design for the magnetic levitation device. Through a modular approach, the controller design for the 3D positioning system is started with the controller design for the vertical direction, i.e. z, and then followed by the controller design in the horizontal directions, i.e. x and y.
For the vertical direction, several controllers such as PID, feed forward and feedback linearization are designed and their performances are compared. Also a control command conditioning method is introduced as a solution to increase the control performance and the results of the proposed controller are compared with the other designs.
Experimental results showed that for the magnetic levitation system, the feedback linearization controller has the shortest settling time and is capable of reducing the positioning error to RMS value of 11.56μm. The force model was also utilized in the design of a model reference adaptive feedback linearization (MRAFL) controller for the z direction. For this case, the levitated object is a small microrobot equipped with a remote controlled gripper weighting approximately 28(gr). Experimental results showed that the MRAFL controller enables the micro-robot to pick up and transport a payload as heavy as 30% of its own weight without a considerable effect on its positioning accuracy. In the presence of the payload, the MRAFL controller resulted in a RMS positioning error of 8μm compared with 27.9μm of the regular feedback linearization controller.
For the horizontal position control of the system, a mathematical formula for distributing the electric currents to the multiple electromagnets of the system was proposed and a PID control approach was implemented to control the position of the levitated object in the xy-plane. The control system was experimentally tested in tracking circular and spiral trajectories with overall positioning accuracy of 60μm.
Also, a new mathematical approach is presented for the prediction of magnetic field distribution in the horizontal direction. The proposed approach is named the pivot point method and is capable of predicting the two dimensional position of the levitated object in a given vertical plane for an arbitrary current distribution in the electromagnets of the levitation system. Experimental results showed that the proposed method is capable of predicting the location of the levitated object with less than 10% error
Bilateral Macro-Micro Teleoperation Using A Magnetic Actuation Mechanism
In recent years, there has been increasing interest in the advancement of microrobotic systems in micro-engineering, micro-fabrication, biological research and biomedical applications. Untethered magnetic-based microrobotic systems are one of the most widely developing groups of microrobotic systems that have been extensively explored for biological and biomedical micro-manipulations. These systems show promise in resolving problems related to on-board power supply limitations as well as mechanical contact sealing and lubrication. In this thesis, a high precision magnetic untethered microrobotic system is demonstrated for micro-handling tasks. A key aspect of the proposed platform concerns the integration of magnetic levitation technology and bilateral macro-micro teleoperation for human intervention to avoid imperceptible failures in poorly observed micro-domain environments.
The developed platform has three basic subsystems: a magnetic untethered microrobotic system (MUMS), a haptic device, and a scaled bilateral teleoperation system. The MUMS produces and regulates a magnetic field for non-contact propelling of a microrobot. In order to achieve a controlled motion of the magnetically levitated microrobot, a mathematical force model of the magnetic propulsion mechanism is developed and used to design various control systems. In the workspace of 30 × 32 × 32 mm 3, both PID and LQG\LTR controllers perform similarly the position accuracy of 10 µ m in a vertical direction and 2 µ m in a horizontal motion.
The MUMS is equipped with an eddy-current damper to enhance its inherent damping factor in the microrobot's horizontal motions. This paper deals with the modeling and analysis of an eddy-current damper that is formed by a conductive plate placed below the levitated microrobot to overcome inherent dynamical vibrations and improve motion precision. The modeling of eddy-current distribution in the conductive plate is investigated by solving the diffusion equation for vector magnetic potential, and an analytical expression for the horizontal damping force is presented and experimentally validated. It is demonstrated that eddy-current damping is a crucial technique for increasing the damping coefficient in a non-contact way and for improving levitation performance. The damping can be widely used in applications of magnetic actuation systems in micro-manipulation and micro-fabrication.
To determine the position of the microrobot in a workspace, the MUMS uses high-accuracy laser sensors. However, laser positioning techniques can only be used in highly transparent environments. A novel technique based on real-time magnetic flux measurement has been proposed for the position estimation of the microrobot in case of laser beam blockage, whereby a combination of Hall-effect sensors is employed to find the microrobot's position in free motion by using the produced magnetic flux. In free motion, the microrobot tends to move toward the horizontally zero magnetic field gradient, Bmax location. As another key feature of the magnetic flux measurement, it was realized that the applied force from the environment to the microrobot can be estimated as linearly proportional to the distance of the microrobot from the Bmax location. The developed micro-domain force estimation method is verified experimentally with an accuracy of 1.27 µ N.
A bilateral macro-micro teleoperation technique is employed in the MUMS for the telepresence of a human operator in the task environment. A gain-switching position-position teleoperation scheme is employed and a human operator controls the motion of the microrobot via a master manipulator for dexterous micro-manipulation tasks. The operator can sense a strong force during micro-domain tasks if the microrobot encounters a stiff environment, and the effect of hard contact is fed back to the operator's hand. The position-position method works for both free motion and hard contact. However, to enhance the feeling of a micro-domain environment in the human operator, the scaled force must be transferred to a human, thereby realizing a direct-force-reflection bilateral teleoperation. Additionally, a human-assisted virtual reality interface is developed to improve a human operator's skills in using the haptic-enabled platform, before carrying out an actual dexterous task.1 yea
NASA space station automation: AI-based technology review
Research and Development projects in automation for the Space Station are discussed. Artificial Intelligence (AI) based automation technologies are planned to enhance crew safety through reduced need for EVA, increase crew productivity through the reduction of routine operations, increase space station autonomy, and augment space station capability through the use of teleoperation and robotics. AI technology will also be developed for the servicing of satellites at the Space Station, system monitoring and diagnosis, space manufacturing, and the assembly of large space structures
Third International Symposium on Artificial Intelligence, Robotics, and Automation for Space 1994
The Third International Symposium on Artificial Intelligence, Robotics, and Automation for Space (i-SAIRAS 94), held October 18-20, 1994, in Pasadena, California, was jointly sponsored by NASA, ESA, and Japan's National Space Development Agency, and was hosted by the Jet Propulsion Laboratory (JPL) of the California Institute of Technology. i-SAIRAS 94 featured presentations covering a variety of technical and programmatic topics, ranging from underlying basic technology to specific applications of artificial intelligence and robotics to space missions. i-SAIRAS 94 featured a special workshop on planning and scheduling and provided scientists, engineers, and managers with the opportunity to exchange theoretical ideas, practical results, and program plans in such areas as space mission control, space vehicle processing, data analysis, autonomous spacecraft, space robots and rovers, satellite servicing, and intelligent instruments
Magnetic Levitation of Polymeric Photo-thermal Microgrippers
Precise manipulation of micro objects became great interest in engineering and science with the advancements in microengineering and microfabrication. In this thesis, a magnetically levitated microgripper is presented for microhandling tasks. The use of
magnetic levitation for positioning reveals the problems associated with modeling of complex surface forces and the use of jointed parts or wires. The power required for the levitation of the microgripper is generated by an external drive unit that makes further minimization of the gripper possible. The gripper is made of a biocompatible material and can be activated remotely. These key features make the microgripper a great candidate for manipulation of micro components and biomanipulation.
In order to achieve magnetic levitation of microrobots, the magnetic field generated by the magnetic levitation setup is simulated. The magnetic flux density in the air gap region is improved by the integration of permanent magnets and an additional electromagnet to the magnetic loop assembly. The levitation performance is evaluated
with millimeter size permanent magnets. An eddy current damping method is implemented and the levitation accuracy is doubled by
reducing the positioning error to 20.3 µm.
For a MEMS-compatible microrobot design, the electrodeposition of Co-Ni-Mn-P magnetic thin films is demonstrated. Magnetic films are deposited on silicon substrate to form the magnetic portion of the microrobot. The electrodeposited films are extensively
characterized. The relationship between the deposition parameters and structural properties is discussed leading to an understanding of the effect of deposition parameters on the magnetic properties.
It is shown that both in-plane and out-of-plane magnetized films can be obtained using electrodeposition with slightly differentiated deposition parameters. The levitation of the electrodeposited
magnetic samples shows a great promise toward the fabrication of levitating MEMS devices.
The end-effector tool of the levitating microrobot is selected as a microgripper that can achieve various manipulation operations such as pulling, pushing, tapping, grasping and repositioning. The
microgripper is designed based on a bent-beam actuation technique. The motion of the gripper fingers is achieved by thermal expansion through laser heat absorption. This technique provided non-contact
actuation for the levitating microgripper. The analytical model of the displacement of the bent-beam actuator is developed. Different designs of microgripper are fabricated and thoroughly characterized
experimentally and numerically. The two microgripper designs that lead to the maximum gripper deflection are adapted for the levitating microrobot.
The experimental results show that the levitating microrobot can be positioned in a volume of 3 x 3 x 2 cm^3. The positioning error is measured as 34.3 µm and 13.2 µm when
electrodeposited magnets and commercial permanent magnets are used, respectively. The gripper fingers are successfully operated
on-the-fly by aligning a visible wavelength laser beam on the gripper. Micromanipulation of 100 µm diameter electrical wire,
125 µm diameter optical fiber and 1 mm diameter cable strip is demonstrated. The microgripper is also positioned in a closed
chamber without sacrificing the positioning accuracy
Modeling and Control of a Magnetically Levitated Microrobotic System
Magnetically levitated microrobotic systems have shown a great deal of promise for micromanipulation tasks. A new large-gap magnetic suspension system has recently been developed at the University of Waterloo in order to develop microrobotic systems for various applications. In order to achieve motion with the system, a model is needed in order to facilitate the design of various aspects of the system, such as the microrobot and the controller. In order to derive equations of motion for the system attempts were made to characterize the force produced by the magnetic drive unit in terms of a simple analytical equation. The force produced by the magnetic drive unit was estimated with the aid of a finite element model. The derived equations were able to predict the general trend of the force curves, and with sufficient parameter tweaking the error between the force estimated by the finite element model and the force estimated by the analytical equation could be minimized. System models describing the motion of the system in the horizontal and vertical directions are identified and compared to the actual system response. The vertical position response is identified through a least squares parameter estimate of the closed loop response combined with a partial reconstruction of the root locus diagram, with the model structure based on the known dynamics of a simplified form of magnetic levitation. This model was able to provide a reasonable prediction of the system response for a variety of PID controllers under a variety of input conditions. The horizontal models are identified using a least-squares parameter estimate of the open loop characteristics of the system. The horizontal models are able to provide a reasonable prediction of the system response under PD and PID control. Full spatial motion of a microrobot prototype is demonstrated over a working range of 20x22x30 mm3, with PID controller parameters and reference trajectories adjusted to minimize disturbances. The RMS error at steady state is on the order of 0. 020 mm for vertical positioning and 0. 008 mm for horizontal positioning. A linear quadratic regulator implemented for vertical position control was able to reduce the vertical position RMS error to 0. 014 mm
FLUX-PINNED DYNAMICAL SYSTEMS WITH APPLICATION TO SPACEFLIGHT
Technology enables space exploration and scientific discovery. At this amazing intersection of time, new software and hardware capabilities give rise to daring robotic exploration and autonomy. Close-proximity operations for spacecraft is a particularly critical portion of any robotic mission that enables many types of maneuvers, such as docking and capture, formation flying, and on-orbit assembly. These dynamic maneuvers then enable different missions, like sample return, spacecraft construction larger than a single rocket faring, and deep-space operations. Commonly, spacecraft dynamic control uses thrusters for position and attitude control, which rely on active sensing and consumable propellant. The development of other dynamic control techniques opens new capabilities and system advantages, and further offers a more diverse technological trade space for system optimization. This research comprehensively investigates the utilization of flux-pinning physics to manipulate spacecraft dynamics. Flux-pinned interfaces differ from conventional dynamic control through its passive and compliant behavior. These unique characteristics are extremely attractive for certain applications, but flux-pinned technology must mature considerably before adoption for spaceflight missions. A dynamic capture and docking maneuver in an upcoming mission concept, Mars Sample Return, motivates the technology design. This body of work as much as possible follows a progression from cradle to grave. A flux-pinning theoretical dynamics model and a system architecture are presented to specify general capabilities of such a spacecraft system. Different analyses on stability, state sensitivity, backwards reachability result from a physics-based dynamics model. An extensive literature review and basic science experiments inform a theoretical dynamics model about the incorporation of physical parameters when simulating realistic dynamics. A series of testbeds enable experimentation and precise investigation of flux-pinned interface capabilities in the context of docking and capture. The testbeds ranged from the simplest expression of dynamics, in a single degree of freedom, to a flight traceable expression, in all six degrees of freedom. Experiments from these testbeds define and characterize system level capabilities specific to flux-pinned capture. Data collected from these experiments then supports development of a predictive dynamics model of the hardware system. Various system identification methods aid in creating a dynamics model that accurately predicts the dynamics observed during experiments. Several objective metrics are considered to evaluate the model fidelity. The types of system identification methods are separated into analytical methods and numerical methods. The analytical method involves parameter estimation in a physics-based model. Numerical methods involve Taylor expansion, bag of functions, symbolic regression, and neural networks. Theoretical extensions towards verification further develops neural network approximation methods, driving at safe, real-time system identification
Haptics: Science, Technology, Applications
This open access book constitutes the proceedings of the 12th International Conference on Human Haptic Sensing and Touch Enabled Computer Applications, EuroHaptics 2020, held in Leiden, The Netherlands, in September 2020. The 60 papers presented in this volume were carefully reviewed and selected from 111 submissions. The were organized in topical sections on haptic science, haptic technology, and haptic applications. This year's focus is on accessibility
Scientific and technical papers presented or published by JSC authors in 1986
A compilation of Lyndon B. Johnson Space Center contributions to the scientific and technical literature in aerospace and life sciences made during calender year 1985 is presented. Citations include NASA formal series reports, journal articles, conference and symposium presentations, papers published in proceedings or other collective works, and seminar and workshop results
Aerospace medicine and biology: A continuing bibliography with indexes (supplement 369)
This bibliography lists 209 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during Nov. 1992. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance
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