Patents by Inventor Woo Sok Chang

Woo Sok Chang has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20080286441
    Abstract: An apparatus for the rotational coating of a surface of a substrate with a fluid, in particular the surface of a wafer with a polymer liquid, especially with a photoresist includes a rotary plate (2) for receiving the substrate (11), a drive device (3) for rotating the rotary plate (2), a dispensing nozzle (4) for the application of a predeterminable quantity of fluid onto the surface of the substrate (11) for the purpose of forming a layer (12) and also a pump (5) for conveying the fluid, the pump being connectable, on the one hand, to a source (20) for the fluid and, on the other hand, to the dispensing nozzle (4). A viscosimeter (6) is provided with which the actual viscosity of the fluid can be determined by physical measurement prior to the application of the fluid. Furthermore a corresponding method is proposed.
    Type: Application
    Filed: May 4, 2007
    Publication date: November 20, 2008
    Applicant: Levitronix LLC
    Inventors: Woo Sok Chang, Christos Monovoukas, Reto Schoeb
  • Patent number: 6755166
    Abstract: The present invention provides a means to reduce holding current and driving current of EMVD's effectively and practically and to provide soft landing of a valve. The invention incorporates a nonlinear mechanical transformer as part of an EMVD system. The nonlinear mechanical transformer is designed for the spring and the inertia in the EMVD to have desirable nonlinear characteristics. With the presently disclosed invention, the holding current and driving current are reduced and soft valve landing is achieved. The nonlinear characteristics of a nonlinear mechanical transformer can be implemented in various ways. The concept of the invention can be applied not only to EMVD's but also to general reciprocating and bi-stable servomechanical systems, where smooth acceleration, soft landing, and small power consumption are desired.
    Type: Grant
    Filed: September 17, 2002
    Date of Patent: June 29, 2004
    Assignee: Massachusetts Institute of Technology
    Inventors: Woo Sok Chang, Thomas A. Keim, John G. Kassakian
  • Publication number: 20030051688
    Abstract: The present invention provides a means to reduce holding current and driving current of EMVD's effectively and practically and to provide soft landing of a valve. The invention incorporates a nonlinear mechanical transformer as part of an EMVD system. The nonlinear mechanical transformer is designed for the spring and the inertia in the EMVD to have desirable nonlinear characteristics. With the presently disclosed invention, the holding current and driving current are reduced and soft valve landing is achieved. The nonlinear characteristics of a nonlinear mechanical transformer can be implemented in various ways. The concept of the invention can be applied not only to EMVD's but also to general reciprocating and bi-stable servomechanical systems, where smooth acceleration, soft landing, and small power consumption are desired.
    Type: Application
    Filed: September 17, 2002
    Publication date: March 20, 2003
    Inventors: Woo Sok Chang, Thomas A. Keim, John G. Kassakian
  • Patent number: 6457864
    Abstract: A high precision friction drive positioning stage system is described. The friction drive positioning stage system uses three special actuation systems, each having a tip in contact with the stage and being capable of generating directional elliptical motion which allows the stage to move in any direction in the plane of the stage and in rotation. In one embodiment, each actuation system includes a plurality of piezoelectric elements in contact with a hat-shaped element at which the tip of the actuation system is located.
    Type: Grant
    Filed: May 11, 1999
    Date of Patent: October 1, 2002
    Assignee: Massachusetts Institute of Technology
    Inventors: Woo Sok Chang, Kamal Youcef-Toumi
  • Patent number: 5598304
    Abstract: A fuzzy controller controls a track seeking operation and a track following operation for an actuator in accordance with a position error between a present position value and a reference value. When the actuator is in track seeking operation, the actuator is accelerated or decelerated based on a velocity error value between an actual velocity value of the actuator and a target velocity value determined from a velocity profile according to the position error. In a deceleration control of the actuator, a fuzzy inference value generated based on the velocity error value and its differentiated velocity error value is used for a control of the actuator, thereby reducing an occurrence of overshooting at a target track.
    Type: Grant
    Filed: February 2, 1995
    Date of Patent: January 28, 1997
    Assignee: Daewoo Electronics Co., Ltd.
    Inventors: Hyun-Taek Choi, Il hong Suh, Woo Sok Chang, Janghee Lee, Goonjin Kim