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  • 1
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    The experimental results of a self tuning adaptive controller using online frequency identification (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A fourth-order laboratory dynamic system featuring very low structural damping and a noncolocated actuator-sensor pair has been used to test a novel real-time adaptive controller, implemented in a minicomputer, which consists of a state estimator, a set of state feedback gains, and a frequency-locked loop for real-time parameter identification. The adaptation algorithm employed can correct controller error and stabilize the system for more than 50 percent variation in the plant's natural frequency, compared with a 10 percent stability margin in frequency variation for a fixed gain controller having the same performance as the nominal plant condition. The very rapid convergence achievable by this adaptive system is demonstrated experimentally, and proven with simple, root-locus methods.
    Keywords: CYBERNETICS
    Type: Journal of the Astronautical Sciences (ISSN 0021-9142); 33; 71-83
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Performance improvement of robots using a learning control scheme (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Many applications of robots require that the same task be repeated a number of times. In such applications, the errors associated with one cycle are also repeated every cycle of the operation. An off-line learning control scheme is used here to modify the command function which would result in smaller errors in the next operation. The learning scheme is based on a knowledge of the errors and error rates associated with each cycle. Necessary conditions for the iterative scheme to converge to zero errors are derived analytically considering a second order servosystem model. Computer simulations show that the errors are reduced at a faster rate if the error rate is included in the iteration scheme. The results also indicate that the scheme may increase the magnitude of errors if the rate information is not included in the iteration scheme. Modification of the command input using a phase and gain adjustment is also proposed to reduce the errors with one attempt. The scheme is then applied to a computer model of a robot system similar to PUMA 560. Improved performance of the robot is shown by considering various cases of trajectory tracing. The scheme can be successfully used to improve the performance of actual robots within the limitations of the repeatability and noise characteristics of the robot.
    Keywords: CYBERNETICS
    Type: NASA, Goddard Space Flight Center, Proceedings of 1987 Goddard Conference on Space Applications of Artificial Intelligence (AI) and Robotics; 20 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    An automated computerized vision technique for determination of three-dimensional object geometry (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It is very important to determine three dimensional geometry of objects quickly in various military, space, construction, and industrial applications. An automatic scheme to obtain three dimensional geometry of objects by employing only one camera is presented. At present, this technique is applicable to a limited category of objects, satisfying the following constraints: they are flat-surfaces, and all the vertex points have to be recognized as corner points of the two dimensional image. The scheme consists of corner detection, data communication, camera calibration techniques and point searching and matching, edge cancelation, and creation procedures. An L shaped model is chosen as a test object. Experimental results demonstrated the reconstruction of this object geometry within 5 mm discrepancy. This scheme is quite convenient, efficient to use and can be applied to a wide range of problems in the real world.
    Keywords: CYBERNETICS
    Type: NASA, Goddard Space Flight Center, The 1988 Goddard Conference on Space Applications of Artificial Intelligence; p 243-257
    Format: text
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    NASA TECHNICAL REPORTS
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