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Control Systems, IEEE

Issue 5 • Date Oct. 1994

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Displaying Results 1 - 7 of 7
  • Stiffness control of a coupled tendon-driven robot hand

    Publication Year: 1994 , Page(s): 10 - 19
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (866 KB)  

    This paper presents the methods of design and control for a coupled tendon-driven robot hand with stiffness control capability. By using the tendon as a force transmission mechanism, compact design of the robot hand is achieved with the developed controller. Problems specific to the tendon characteristics are considered, such as the slacking problem of tendons when the joint is disturbed, and the tendon elongation problem when the collocated position sensing method is used for compact design. To cope with these problems, two fundamental algorithms are developed and implemented on a laboratory apparatus, the POSTECH Hand II. First, a position estimation algorithm is developed to evaluate the accurate position of the hand, leading to an antagonistic tendon controller. Secondly, an active stiffness control algorithm is developed to control the fingertip force. It is shown that the finger produces excellent linear stiffness characteristics which justifies the effectiveness of the proposed algorithm. The object stiffness control is also implemented to exert desired force to the environment when the hand grasps an object, and is evaluated via experiments.<> View full abstract»

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  • Acceleration assisted tracking control

    Publication Year: 1994 , Page(s): 20 - 27
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (812 KB)  

    This paper discusses the use of acceleration measurements to improve the performance and robustness of controllers for mechanical systems. To use acceleration signals there are at least two approaches: direct use in a feedback loop to improve the tracking error, and indirect use by an observer to improve the estimates of position and speed. Several proposals for the use of the acceleration in a feedback loop, resulting in slightly different controllers, are discussed. The design of the controllers for the experimental system, a flexible multiple degrees-of-freedom XY-table, uses a simplified two degrees-of-freedom model. The observer is of the predictive type to compensate for the time delay in the implementation, and its design is based in part on Kalman filter theory. Simulations and experiments show that both acceleration feedback and an acceleration assisted observer can improve the performance of the control system, but the robustness does not change significantly. A combination of both approaches did not give any improvement in the experiments, but some in the simulations. Disturbances in the acceleration signal (especially motor torque ripple), phase lag introduced by the signal processing equipment, time delay caused by the sampled data implementation of the controller and observer, and the non-colocated position and acceleration sensors are believed to be limitations for the usefulness of the acceleration signal. A performance improvement up to a factor of 1.5 was possible in the author's application, so to consider the use of acceleration measurements in tracking control is recommended.<> View full abstract»

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  • Expert control of vacuum pan crystallization

    Publication Year: 1994 , Page(s): 28 - 34
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (689 KB)  

    Vacuum pan crystallization is a process that is very difficult to control by classical means. This paper presents a method of using a rule-based expert system for the control of such a process. The structure of the expert controller for adjusting the characteristic conductivity is shown to consist of a diagnostic expert system and a discrete dynamic model that is used for conversion of semantic results into numeric output values. The expert controller was implemented in the sugar factory in Lovosice in 1993.<> View full abstract»

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  • Recent advances in cross machine profile control

    Publication Year: 1994 , Page(s): 35 - 46
    Cited by:  Papers (26)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1165 KB)  

    In the last 10-15 years, control of paper variation in the cross machine direction has become a necessary requirement to meet increasing quality demands. Traditional approaches to the control of weight, moisture and caliper have realized good reductions in paper profile variability using relatively simple control technology. Recent advances in computer technology have provided the platform to implement the next generation of cross-machine controls using modern estimation, modelling and control technology. This paper describes the development of an advanced cross-machine control system using state estimation, system identification, multivariable modelling and control and summarizes the results of implementing the profile control system on a modern newsprint machine.<> View full abstract»

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  • On control system design: a comparative study

    Publication Year: 1994 , Page(s): 47 - 51
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB)  

    The linear algebraic method for designing control systems was introduced in the Magazine (Cen,1987, and Chen and Seo, 1990). In this article, the method is compared with designs using Q-parameterization and then compared with designs using pole-placement and model (pole-and-zero) matching. It is shown by an example that the method may also yield a better result than the quadratic optimal and the H/sub /spl infin// methods if the design specifications are given in terms of rise time, overshoot and the constraint on the actuating signal.<> View full abstract»

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  • An expert system for frequency response analysis

    Publication Year: 1994 , Page(s): 52 - 57
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (627 KB)  

    Frequency response analysis is a classical method for obtaining models of linear, time-invariant systems. However, the quality of the results strongly depends on the experiment design and choice of parameters. Likewise, different problems may demand a fault diagnosis. This article presents a knowledge-based system that guides the user through the planning and execution of a frequency response experiment, and it also performs a fault diagnosis and suggests remedies for possible problems.<> View full abstract»

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  • Motivation-by challenge for teaching control systems

    Publication Year: 1994 , Page(s): 64 - 68
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    An unconventional, motivation-by challenge approach is reported for teaching entry-level control courses. This approach recognizes the difference between passive learning and active learning, and therefore emphasizes motivating entry-level students with a pilot design project that is woven into lectures from beginning to end.<> View full abstract»

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