Electromagnetic Position Sensing and Force Feedback for a Magnetic Stylus with an Interactive Display

This letter describes the design, implementation, validation, and demonstration of an electromagnetic system that can be incorporated into a graphical display to provide computer-controlled planar feedback forces on the tip of a stylus or fingertip-mounted magnet held near the display surface, according to the magnet position and virtual fixtures implemented in software. An array of magnetometer sensors is used to detect the position of the magnet, while a pair of box-shaped coils behind the display produces feedback forces on the stylus parallel to the plane of the display. Electromagnetic analysis for the system design is presented and system implementation is described. Validation results are given for force generation within a 100 mm × 100 mm area and force interaction with a virtual obstacle is demonstrated

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

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

Electromagnetic Position Sensing and Force Feedback for a Magnetic Stylus with an Interactive Display

This letter describes the design, implementation, validation, and demonstration of an electromagnetic system that can be incorporated into a graphical display to provide computer-controlled planar feedback forces on the tip of a stylus or fingertip-mounted magnet held near the display surface, according to the magnet position and virtual fixtures implemented in software. An array of magnetometer sensors is used to detect the position of the magnet, while a pair of box-shaped coils behind the display produces feedback forces on the stylus parallel to the plane of the display. Electromagnetic analysis for the system design is presented and system implementation is described. Validation results are given for force generation within a 100 mm × 100 mm area and force interaction with a virtual obstacle is demonstrated

Design and construction of a portable force-reflecting manual controller for teleoperation systems

A man-machine system called teleoperator system has been developed to work in hazardous environments such as nuclear reactor plants. Force reflection is a type of force feedback in which forces experienced by the remote manipulator are fed back to the manual controller. In a force-reflecting teleoperation system, the operator uses the manual controller to direct the remote manipulator and receives visual information from a video image and/or graphical animation on the computer screen. This thesis presents the design of a portable Force-Reflecting Manual Controller (FRMC) for the teleoperation of tasks such as hazardous material handling, waste cleanup, and space-related operations. The work consists of the design and construction of a prototype 1-Degree-of-Freedom (DOF) FRMC, the development of the Graphical User Interface (GUI), and system integration. Two control strategies - PID and fuzzy logic controllers are developed and experimentally tested. The system response of each is analyzed and evaluated. In addition, the concept of a telesensation system is introduced, and a variety of design alternatives of a 3-DOF FRMC are proposed for future development

Design, Development, and Evaluation of a Teleoperated Master-Slave Surgical System for Breast Biopsy under Continuous MRI Guidance

The goal of this project is to design and develop a teleoperated master-slave surgical system that can potentially assist the physician in performing breast biopsy with a magnetic resonance imaging (MRI) compatible robotic system. MRI provides superior soft-tissue contrast compared to other imaging modalities such as computed tomography or ultrasound and is used for both diagnostic and therapeutic procedures. The strong magnetic field and the limited space inside the MRI bore, however, restrict direct means of breast biopsy while performing real-time imaging. Therefore, current breast biopsy procedures employ a blind targeting approach based on magnetic resonance (MR) images obtained a priori. Due to possible patient involuntary motion or inaccurate insertion through the registration grid, such approach could lead to tool tip positioning errors thereby affecting diagnostic accuracy and leading to a long and painful process, if repeated procedures are required. Hence, it is desired to develop the aforementioned teleoperation system to take advantages of real-time MR imaging and avoid multiple biopsy needle insertions, improving the procedure accuracy as well as reducing the sampling errors. The design, implementation, and evaluation of the teleoperation system is presented in this dissertation. A MRI-compatible slave robot is implemented, which consists of a 1 degree of freedom (DOF) needle driver, a 3-DOF parallel mechanism, and a 2-DOF X-Y stage. This slave robot is actuated with pneumatic cylinders through long transmission lines except the 1-DOF needle driver is actuated with a piezo motor. Pneumatic actuation through long transmission lines is then investigated using proportional pressure valves and controllers based on sliding mode control are presented. A dedicated master robot is also developed, and the kinematic map between the master and the slave robot is established. The two robots are integrated into a teleoperation system and a graphical user interface is developed to provide visual feedback to the physician. MRI experiment shows that the slave robot is MRI-compatible, and the ex vivo test shows over 85%success rate in targeting with the MRI-compatible robotic system. The success in performing in vivo animal experiments further confirm the potential of further developing the proposed robotic system for clinical applications

Haptic communication for remote mobile and manipulator robot operations in hazardous environments

Nuclear decommissioning involves the use of remotely deployed mobile vehicles and manipulators controlled via teleoperation systems. Manipulators are used for tooling and sorting tasks, and mobile vehicles are used to locate a manipulator near to the area that it is to be operated upon and also to carry a camera into a remote area for monitoring and assessment purposes. Teleoperations in hazardous environments are often hampered by a lack of visual information. Direct line of sight is often only available through small, thick windows, which often become discoloured and less transparent over time. Ideal camera locations are generally not possible, which can lead to areas of the cell not being visible, or at least difficult to see. Damage to the mobile, manipulator, tool or environment can be very expensive and dangerous. Despite the advances in the recent years of autonomous systems, the nuclear industry prefers generally to ensure that there is a human in the loop. This is due to the safety critical nature of the industry. Haptic interfaces provide a means of allowing an operator to control aspects of a task that would be difficult or impossible to control with impoverished visual feedback alone. Manipulator endeffector force control and mobile vehicle collision avoidance are examples of such tasks. Haptic communication has been integrated with both a Schilling Titan II manipulator teleoperation system and Cybermotion K2A mobile vehicle teleoperation system. The manipulator research was carried out using a real manipulator whereas the mobile research was carried out in simulation. Novel haptic communication generation algorithms have been developed. Experiments have been conducted using both the mobile and the manipulator to assess the performance gains offered by haptic communication. The results of the mobile vehicle experiments show that haptic feedback offered performance improvements in systems where the operator is solely responsible for control of the vehicle. However in systems where the operator is assisted by semi autonomous behaviour that can perform obstacle avoidance, the advantages of haptic feedback were more subtle. The results from the manipulator experiments served to support the results from the mobile vehicle experiments since they also show that haptic feedback does not always improve operator performance. Instead, performance gains rely heavily on the nature of the task, other system feedback channels and operator assistance features. The tasks performed with the manipulator were peg insertion, grinding and drilling.EThOS - Electronic Theses Online ServiceGBUnited Kingdo