Patents by Inventor Homayoun Seraji

Homayoun Seraji 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).

  • Patent number: 5737500
    Abstract: The present invention is a mobile redundant dexterous manipulator with a seven-degree-of-freedom robot arm mounted on a 1 degree-of-freedom mobile platform with a six-degree-of freedom end effector including a real-time control system with multiple modes of operation. The manipulator-plus-platform system has two degrees-of-redundancy for the task of hand placement and orientation. The redundancy resolution is achieved by accomplishing two additional tasks using a configuration control technique. This mobile manipulator with control system allows a choice of arm angle control or collision avoidance for the seventh task, and platform placement or elbow angle control for the eighth task. In addition, joint limit avoidance task is automatically invoked when any of the joints approach their limits. The robot is controlled by a processor employing a 6-by-7 Jacobian matrix for defining location and orientation of the end effector.
    Type: Grant
    Filed: April 28, 1995
    Date of Patent: April 7, 1998
    Assignee: California Institute of Technology
    Inventors: Homayoun Seraji, David Lim, Thomas S. Lee
  • Patent number: 5550953
    Abstract: A simple and computationally efficient approach is disclosed for on-line coordinated control of mobile robots consisting of a manipulator arm mounted on a mobile base. The effect of base mobility on the end-effector manipulability index is discussed. The base mobility and arm manipulation degrees-of-freedom are treated equally as the joints of a kinematically redundant composite robot. The redundancy introduced by the mobile base is exploited to satisfy a set of user-defined additional tasks during the end-effector motion. A simple on-line control scheme is proposed which allows the user to assign weighting factors to individual degrees-of-mobility and degrees-of-manipulation, as well as to each task specification. The computational efficiency of the control algorithm makes it particularly suitable for real-time implementations. Four case studies are discussed in detail to demonstrate the application of the coordinated control scheme to various mobile robots.
    Type: Grant
    Filed: April 20, 1994
    Date of Patent: August 27, 1996
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventor: Homayoun Seraji
  • Patent number: 5430643
    Abstract: A seven-degree-of-freedom robot arm with a six-degree-of-freedom end effector is controlled by a processor employing a 6-by-7 Jacobian matrix for defining location and orientation of the end effector in terms of the rotation angles of the joints, a 1 (or more)-by-7 Jacobian matrix for defining 1 (or more) user-specified kinematic functions constraining location or movement of selected portions of the arm in terms of the joint angles, the processor combining the two Jacobian matrices to produce an augmented 7 (or more)-by-7 Jacobian matrix, the processor effecting control by computing in accordance with forward kinematics from the augmented 7-by-7 Jacobian matrix and from the seven joint angles of the arm a set of seven desired joint angles for transmittal to the joint servo loops of the arms. One of the kinematic functions constrains the orientation of the elbow plane of the arm. Another one of the kinematic functions minimizing a sum of gravitational torques on the joints.
    Type: Grant
    Filed: March 11, 1992
    Date of Patent: July 4, 1995
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventor: Homayoun Seraji
  • Patent number: 5414799
    Abstract: The described and improved multi-arm invention of this application presents three strategies for adaptive control of cooperative multi-arm robots which coordinate control over a common load. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through a load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions; while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load.
    Type: Grant
    Filed: June 16, 1993
    Date of Patent: May 9, 1995
    Assignee: California Institute of Technology
    Inventor: Homayoun Seraji
  • Patent number: 5294873
    Abstract: The invention fulfills new goals for redundancy resolution based on manipulator dynamics and end-effector characteristics. These goals are accomplished by employing the recently developed configuration control approach. Redundancy resolution is achieved by controlling the joint inertia matrix or the end-effector mass matrix that affect the inertial torques, or by reducing the joint torques due to gravity loading and payload. The manipulator mechanical-advantage and velocity-ratio are also used as performance measures to be improved by proper utilization of redundancy. Furthermore, end-effector compliance, sensitivity, and impulsive force at impact are introduced as redundancy resolution criteria. The new goals for redundancy resolution allow a more efficient utilization of the redundant joints based on the desired task requirements.
    Type: Grant
    Filed: October 27, 1992
    Date of Patent: March 15, 1994
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventor: Homayoun Seraji
  • Patent number: 5150026
    Abstract: A redundant robot control scheme is provided for avoiding obstacles in a workspace during motion of an end effector along a preselected trajectory by stopping motion of the critical point on the robot closest to the obstacle when the distance therebetween is reduced to a predetermined sphere of influence surrounding the obstacle. Algorithms are provided for conveniently determining the critical point and critical distance.
    Type: Grant
    Filed: November 19, 1990
    Date of Patent: September 22, 1992
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: Homayoun Seraji, Richard D. Colbaugh, Kristin L. Glass
  • Patent number: 5049796
    Abstract: Model-based and performance-based control techniques are combined for an electrical robotic control system. Thus, two distinct and separate design philosophies have been merged into a single control system having a control law formulation including two distinct and separate components, each of which yields a respective signal component that is combined into a total command signal for the system. Those two separate system components include a feedforward controller and a feedback controller. The feedforward controller is model-based and contains any known part of the manipulator dynamics that can be used for on-line control to produce a nominal feedforward component of the system's control signal. The feedback controller is performance-based and consists of a simple adaptive PID controller which generates an adaptive control signal to complement the nominal feedforward signal.
    Type: Grant
    Filed: May 17, 1989
    Date of Patent: September 17, 1991
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventor: Homayoun Seraji
  • Patent number: 5023808
    Abstract: The described and improved multi-arm invention of this application presents three strategies for adaptive control of cooperative multi-arm robots which coordinate control over a common load. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through a load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions; while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load.
    Type: Grant
    Filed: September 30, 1988
    Date of Patent: June 11, 1991
    Assignee: California Institute of Technology
    Inventor: Homayoun Seraji
  • Patent number: 4999553
    Abstract: A method and apparatus to control a robot or manipulator configuration over the entire motion based on augmentation of the manipulator forward kinematics. A set of kinematic functions is defined in Cartesian or joint space to reflect the desirable configuration that will be achieved in addition to the specified end-effector motion. The user-defined kinematic functions and the end-effector Cartesian coordinates are combined to form a set of task-related configuration variables as generalized coordinates for the manipulator. A task-based adaptive scheme is then utilized to directly control the configuration variables so as to achieve tracking of some desired reference trajectories throughout the robot motion. This accomplishes the basic task of desired end-effector motion, while utilizing the redundancy to achieve any additional task through the desired time variation of the kinematic functions.
    Type: Grant
    Filed: December 28, 1989
    Date of Patent: March 12, 1991
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventor: Homayoun Seraji
  • Patent number: 4860215
    Abstract: The present invention discloses systematic methods and apparatus for the design of real time controllers. Real-time control employs adaptive force/position by use of feedforward and feedback controllers, with the feedforward controller being the inverse of the linearized model of robot dynamics and containing only proportional-double-derivative terms is disclosed. The feedback controller, of the proportional-integral-derivative type, ensures that manipulator joints follow reference trajectories and the feedback controller achieves robust tracking of step-plus-exponential trajectories, all in real time.The adaptive controller includes adaptive force and position control within a hybrid control architecture. The adaptive controller, for force control, achieves tracking of desired force setpoints, and the adaptive position controller accomplishes tracking of desired position trajectories. Circuits in the adaptive feedback and feedforward controllers are varied by adaptation laws.
    Type: Grant
    Filed: April 6, 1987
    Date of Patent: August 22, 1989
    Assignee: California Institute of Technology
    Inventor: Homayoun Seraji