Scaled bilateral teleoperation using discrete-time sliding mode controller

In this paper, the design of a discrete-time slidingmode controller based on Lyapunov theory is presented along with a robust disturbance observer and is applied to a piezostage for high-precision motion. A linear model of a piezostage was used with nominal parameters to compensate the disturbance acting on the system in order to achieve nanometer accuracy. The effectiveness of the controller and disturbance observer is validated in terms of closed-loop position performance for nanometer references. The control structure has been applied to a scaled bilateral structure for the custom-built telemicromanipulation setup. A piezoresistive atomic force microscope cantilever with a built-in Wheatstone bridge is utilized to achieve the nanonewtonlevel interaction forces between the piezoresistive probe tip and the environment. Experimental results are provided for the nanonewton-range force sensing, and good agreement between the experimental data and the theoretical estimates has been demonstrated. Force/position tracking and transparency between the master and the slave has been clearly demonstrated after necessary scalin

Design and Development of an in-house Scanning Tunneling Microscope System

ABSTRACT The invention of Scanning Tunneling Microscope (STM) by Binnig and Rohrer in 1982 eliminated the use of optical lenses and replaced the conventional optical microscopes with a new class of microscopes called the Scanning Probe Microscopes (SPM). Because of their unique characteristics such as higher resolution and acquisition of nano level images without affecting the physical properties of the sample, they have found wide applications in a variety of scientific disciplines such as biology, material science and electrochemistry. After considerable advancements in instrumentation, the STM has evolved as a nanomanipulation and nanofabrication tool. It operates in two modes: constant current mode and constant height mode. In constant current mode, the feedback parameter is the tunneling current based on which the voltage applied to the piezoelectric actuator is varied. Hence, the tip height is varied in accordance with this tunneling current. In the constant height mode, however, the height is maintained at a constant value and hence the voltage applied to the piezoelectric actuator is adjusted (PZT). Unlike constant current mode, it is the tunneling current which changes according to the surface profile and the local electronic structure of the tip and the sample. The present research is an effort in designing and fabricating an in-house STM to be operated in the constant current mode by interfacing various subsystems. The various subsystems constituting the experimental setup mainly include a micro positioner, a nano stager, STM Electronics, and STM head. The fabrication process involved testing and verification of a suitable preamplifier for providing the feedback signal, design of the STM head and development of a computer automated system in order to facilitate the acquisition of signals related to a micro positioner which acts as the coarse positioner. The software control consists of ControlDesk¨ as the front end and Simulink¨ as the backend. An optical subsystem in the form of a high resolution camera that has been interfaced facilitates visual monitoring and development of dual stage control of the fine as well as coarse positioners. The ability of the STM to acquire images at the nano level is attributed to the tip to sample interaction based on quantum mechanical tunneling. To better understand the aspects of STM, the present work also traces the development of theoretical modeling of the tip-sample interaction and the conceptual design of other classes of microscopes belonging to the SPM family. Certain hardware limitations associated with the data acquisition board need to be addressed in order to acquire nanolevel images. The future scope of the research would include development and testing of various types of controllers on the STM test bed

Micromanipulation-force feedback pushing

In micromanipulation applications, it is often desirable to position and orient polygonal micro-objects lying on a planar surface. Pushing micro-objects using point contact provides more flexibility and less complexity compared to pick and place operation. Due to the fact that in micro-world surface forces are much more dominant than inertial forces and these forces are distributed unevenly, pushing through the center of mass of the micro-object will not yield a pure translational motion. In order to translate a micro-object, the line of pushing should pass through the center of friction. Moreover, due to unexpected nature of the frictional forces between the micro-object and substrate, the maximum force applied to the micro-object needs to be limited to prevent any damage either to the probe or micro-object. In this dissertation, a semi-autonomous manipulation scheme is proposed to push microobjects with human assistance using a custom built tele-micromanipulation setup to achieve pure translational motion. The pushing operation can be divided into two concurrent processes: In one process human operator who acts as an impedance controller to switch between force-position controllers and alters the velocity of the pusher while in contact with the micro-object through scaled bilateral teleoperation with force feedback. In the other process, the desired line of pushing for the micro-object is determined continuously so that it always passes through the varying center of friction. Visual feedback procedures are adopted to align the resultant velocity vector at the contact point to pass through the center of friction in order to achieve pure translational motion of the micro-object. Experimental results are demonstrated to prove the effectiveness of the proposed controller along with nanometer scale position control, nano-Newton range force sensing, scaled bilateral teleoperation with force feedback

A force feedback haptic interface for atomic force microscopy

Integrating a force feedback haptic device with atomic force microscopy (AFM) improves the capability to investigate and manipulate the objects on a micro- and nanoscale surface. The haptic device provides the researcher with a sense of touch and movement by changing the position of the stylus or amount of force on it. The developed system\u27s concept is to provide the user a sense and feel and control of the AFM probe at the nanoscale. By positing the haptic stylus, the user generates reference to commands to the AFM probe. In turn, forces experienced by the probe are communicated to the haptic and transferred to the user. In order to ensure that the forces that act on the haptic and the probe are accurate, it is important to calibrate the normal and lateral forces that act on the tip of the probe. These forces are generated due to using a contact mode interaction between the probe tip and the sample surface. The haptic-probe coupled motion is tested to reach the desired results. Also, a low pass filter is used to remove the undesirable high frequency content from the input force to the haptic since it affects the interaction between the probe s tip and the sample s surface. To close, the sensitivities of haptic to the probe position, and displacement of the probe to the force on the haptic are discussed --Abstract, page iii

Spacelab mission 1 experiment descriptions, third edition

Experiments and facilities selected for flight on the first Spacelab mission are described. Chosen from responses to the Announcement of Opportunity for the Spacelab 1 mission, the experiments cover five broad areas of investigation: atmospheric physics and Earth observations; space plasma physics; astronomy and solar physics; material sciences and technology; and life sciences. The name of the principal investigator and country is listed for each experiment

Dynamics and Controls of Fluidic Pressure-Fed Mechanism (FPFM) of Nanopositioning System

Flexure or compliant mechanisms are employed in many precisions engineered devices due to their compactness, linearity, resolution, etc. Yet, critical issues remain in motion errors, thermal instability, limited bandwidth, and vibration of dynamic systems. Those issues cannot be negligible to maintain high precision and accuracy for precision engineering applications. In this thesis, a novel fluidic pressure-fed mechanism (FPFM) is proposed and investigated. The proposed method is designing internal fluidic channels inside the spring structure of the flexure mechanism using the additive manufacturing (AM) process to overcome addressed challenges. By applying pneumatic/hydraulic pressure and filling media into fluidic channels, dynamic characteristics of each spring structure of the flexure mechanism can be altered or adjusted to correct motion errors, increase operating speed, and suppress vibration. Additionally, FPFM can enhance thermal stability by flowing fluids without affecting the motion quality of the dynamic system. Lastly, the motion of the nanopositioning system driven by FPFM can provide sub-nanometer resolution motion, and this enables the nanopositioning system to have two linear motion in a monolithic structure. The main objective of this thesis is to propose and validate the feasibility of FPFM that can ultimately be used for a monolithic FPFM dual-mode stage for providing high positioning performance without motion errors while reducing vibration and increasing thermal stability and bandwidth

Study and Performance Enhancement of Fast Tool Servo Diamond Turning of Micro-structured Surfaces

Ph.DDOCTOR OF PHILOSOPH

Large space telescope, phase A. Volume 3: Optical telescope assembly

The development and characteristics of the optical telescope assembly for the Large Space Telescope are discussed. The systems considerations are based on mission-related parameters and optical equipment requirements. Information is included on: (1) structural design and analysis, (2) thermal design, (3) stabilization and control, (4) alignment, focus, and figure control, (5) electronic subsystem, and (6) scientific instrument design