Browsing by Subject "Hall-effect sensor"
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Item Control and Optimization of a Compact 6-Degree-of-Freedom Precision Positioner Using Combined Digital Filtering Techniques(2012-02-14) Silva Rivas, Jose ChristianThis thesis presents the multivariable controller design and implementation for a high-precision 6-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. The positioner is a triangular single-moving part that carries three 3-phase permanent-magnet linear-levitation-motor armatures. The three planar levitation motors not only generate the vertical force to levitate the triangular platen but control the platen's position in the horizontal plane. All 6-DOF motions are controlled by magnetic forces only. The positioner moves over a Halbach magnet matrix using three sets of two-axis Hall-effect sensors to measure the planar motion and three Nanogage laser distance sensors for the vertical motion. However, the Hall-effect sensors and the Nanogage laser distance sensors can only provide measurements of the displacement of all 6-axis. Since we do not have full-state feedback, I designed two Linear Quadratic Gaussian (LQG) multivariable controllers using a recursive discrete-time observer. A discrete hybrid H2/H(infinity) filter is implemented to obtain optimal estimates of position and orientation, as well as additional estimates of velocity and angular velocity for all 6 axes. In addition, an analysis was done on the signals measured by the Hall-effect sensors, and from there several digital filters were tested to optimize the readings of the sensors and obtain the best estimates possible. One of the multivariable controllers was designed to close the control loop for the three-planar-DOF motion, and the other to close the loop for the vertical motion, all at a sampling frequency of 800 Hz. Experimental results show a position resolution of 1.5 micrometers with position noise of 0.545 micrometers rms in the x-and y-directions and a resolution of less than 110 nm with position noise of 49.3 nm rms in z.Item Design and Control of a Compact 6-Degree-of-Freedom Precision Positioner with Linux- Based Real-Time Control(2010-01-14) Yu, HoThis dissertation presents the design, control, and implementation of a compact highprecision multidimensional positioner. This precision-positioning system consists of a novel concentrated-field magnet matrix and a triangular single-moving part that carries three 3-phase permanent-magnet planar-levitation-motor armatures. Since only a single levitated moving part, namely the platen, generates all required fine and coarse motions, this positioning system is reliable and potentially cost-effective. The three planar levitation motors based on the Lorentz-force law not only produce the vertical force to levitate the triangular platen but also control the platen's position and orientation in the horizontal plane. Three laser distance sensors are used to measure vertical, x-, and yrotation motions. Three 2-axis Hall-effect sensors are used to determine lateral motions and rotation motion about the z-axis by measuring the magnetic flux density generated by the magnet matrix. This positioning system has a total mass of 1.52 kg, which is the minimized mass to produce better dynamic performance. In order to reduce the mass of the moving platen, it is made of Delrin with a mass density of 1.54 g/cm3 by Computer Numerical Controlled (CNC) machining. The platen can be regarded a pure mass, and the spring and damping effects are neglected except for the vertical dynamic. Single-input single-output (SISO) digital lead-lag controllers and a multivariable Linear Quadratic Gaussian (LQG) controller were designed and implemented. Real-time control was performed with the Linux-Ubuntu operating system OS. Real Time Application Interface (RTAI) for Linux works with Comedi and Comedi libraries and enables closed-loop real-time control. One of the key advantages of this positioning stage with Hall-effect sensors is the extended travel range and rotation angle in the horizontal mode. The maximum travel ranges of 220 mm in x and 200 mm in y were achieved experimentally. Since the magnet matrix generates periodical sinusoidal flux densities in the x-y plane, the travel range can be extended by increasing the number of magnet pitches. The rotation angle of 12 degrees was achieved in rotation around z. The angular velocities of 0.2094 rad/s and 4.74 rad/s were produced by a 200-mm-diameter circular motion and a 30-mm-diameter spiral motion, respectively. The maximum velocity of 16.25 mm/s was acquired from over one pitch motion. The maximum velocity of 17.5 mm/s in a 8-mm scanning motion was achieved with the acceleration of 72.4 m/s2. Step responses demonstrated a 10-um resolution and 6-um rms position noise in the translational mode. For the vertical mode, step responses of 5 um in z, 0.001 degrees in roation around x, and 0.001 degrees in rotation around y were achieved. This compact single-moving-part positioner has potential applications for precisionpositioning systems in semiconductor- manufacturing.Item Multi-DOF precision positioning methodology using two-axis Hall-effect sensors(Texas A&M University, 2006-08-16) Kawato, YusukeA novel sensing methodology using two-axis Hall-effect sensors is proposed, where the absolute positioning of a device atop any magnet matrix is possible. This methodology has the capability of micrometer-order positioning resolution as well as unrestricted translational and rotational range in planar 3-DOF (degree-of-freedom) motions, with potential capability of measuring all 6-DOF motions. This research presents the methodology and preliminary experimental results of 3-DOF planar motion measurements atop a Halbach magnet matrix using two sets of two-axis Hall-effect sensors. Analysis of the Halbach magnet matrix is presented to understand the generated magnetic field. The algorithm uses the Gaussian least squares differential correction (GLSDC) algorithm to estimate the relative position and orientation from the Hall-effect sensor measurements. A recursive discrete-time Kalman filter (DKF) is used in combination with the GLSDC to obtain optimal estimates of position and orientation, as well as additional estimates of velocity and angular velocity, which we can use to design a multivariable controller. The sensor and its algorithm is implemented to a magnetic levitation (maglev) stage positioned atop a Halbach magnet matrix. Preliminary experimental results show its position resolution capability of less than 10 ??m and capable of sensing large rotations. Controllers were designed to close the control loop for the three planar degrees of freedom motion using the GLSDC outputs at a sampling frequency of 800 Hz on a Pentek 4284 digital signal processor (DSP). Calibration was done by comparing the laser interferometers?? and the GLSDC??s outputs to improve the positioning accuracy.