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Control Systems Technology, IEEE Transactions on

Issue 4 • Date Jul 1996

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Displaying Results 1 - 18 of 18
  • Design of robust vehicle launch control system

    Page(s): 326 - 335
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (932 KB)  

    This paper presents a robust algorithm for vehicle start-up from a stop (commonly referred to as “vehicle launch”) using a microprocessor controlled friction clutch. The design applies an “M-exclusion” concept for achieving guaranteed robust tracking and stability using quantitative feedback theory (QFT). The analytical design technique is carried out in the complex plane and improves on the conventional graphical QFT design. An inner control loop achieves a second-order response within specified tolerances for the driveline and clutch. An outer loop develops a reference signal for the inner loop to achieve smooth lockup. A feedforward signal derived from engine acceleration prevents both over-speed and speed droop in the engine. The control algorithm was programmed into a microprocessor and tested in a heavy duty truck. The truck was driven by experienced drivers, who rated the smoothness and responsiveness of the launch better than achievable with a manual clutch View full abstract»

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  • Stochastic modeling of fatigue crack dynamics for on-line failure prognostics

    Page(s): 443 - 451
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    This paper presents a nonlinear stochastic model of fatigue crack dynamics for real-time computation of the time-dependent damage rate and accumulation in mechanical structures. The model configuration allows construction of a filter for estimation of the current damage state and prediction of the remaining service life based on the underlying principle of extended Kalman filtering instead of solving the Kolmogorov forward equation. This approach is suitable for online damage sensing, failure prognosis, life prediction, reliability analysis, decision-making for condition-based maintenance and operation planning, and life extending control in complex dynamical systems. The model results have been verified by comparison with experimentally generated statistical data of time-dependent fatigue cracks in specimens made of 2024-T3 aluminum alloy View full abstract»

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  • Output feedback control of current-fed induction motors with unknown rotor resistance

    Page(s): 336 - 347
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    On the basis of a third-order reduced model of an induction motor (current-fed) the authors design an output feedback control (from rotor speed measurements) which guarantees global exponential tracking of speed and rotor flux modulus reference signals. An adaptive version is designed when load torque is constant and unknown. The rotor resistance, which is a crucial parameter for the control, is updated by a seventh-order dynamic estimator designed on the basis of speed, current, and voltage signals. The estimator provides exponentially convergent estimates in physical operating conditions. A good performance of the adaptive control algorithm using a sampling time of 0.5 ms is documented by experimental tests. Experiments show that the main advantage of the proposed control with respect to the classical field oriented control algorithm is the decoupling of speed and flux tracking; in addition, efficiency is improved in presence of rotor resistance variations View full abstract»

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  • Fuzzy control of a class of hydraulically actuated industrial robots

    Page(s): 419 - 426
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    Application of a fuzzy logic controller to a class of hydraulically actuated industrial robots is investigated. A simple set of membership functions and rules are described which meets certain control requirements. An off-line routine based on the simplex method is outlined to tune the controller gains for an optimum response. The fuzzy control gains are tuned by minimizing the summation of absolute position errors over step input responses. The fuzzy logic controller is first examined through simulation of a two-link hydraulic robot of the same hydraulic configuration as many industrial manipulators. The controller has positive aspects which cannot be easily achieved by conventional control techniques. These include a fast rise-time and a well maintained damped response. The fuzzy controller is applied to an instrumented Unimate MK-II industrial hydraulic robot. The experimental results are encouraging in that the best performing control gains are found for different links with a reasonable number of trials and produce step responses with fast response and few oscillations at the set point. The controller demonstrates robustness View full abstract»

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  • Adaptive rejection of the preponderant harmonic of a pulsed flow

    Page(s): 452 - 458
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    Pulsed flows, characterized by periodic fluctuations in flow rate, are noise-productive, but an oscillating valve positioned in the exhaust duct can attenuate the main harmonic of pulsed flow. We define a valve adaptive control in the frequency domain implemented by a digital signal processor for experimental purposes. Results show noise reduction at ground level and tracking of process unstationarity View full abstract»

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  • Uncertainty decomposition-based robust control of robot manipulators

    Page(s): 384 - 393
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    In this paper, a new robust control approach is proposed for robot manipulators based on a decomposition of model uncertainty. Parameterized uncertainty is distinguished from unparameterized uncertainty. A compensator is designed for each uncertainty group, and the combination of both compensators yields the robust controller. The effect of parameterized uncertainty is completely compensated by an integral compensator, and the unparameterized uncertainty is compensated with a saturation-based robust compensator. As a result, since the magnitude of the unparameterized uncertainty is usually much lower than the global uncertainty, the typical demand of robust controllers for high feedback gains is dramatically reduced. In the proposed control law, double boundary layers are used to achieve both good transient response and accurate steady-state tracking. Uniform ultimate boundedness of the tracking error is obtained, and it is shown that the ultimate error bound is not affected by the parameterized uncertainty. The proposed method has been experimentally tested on a direct-drive robot arm and the results are presented in this paper. The effectiveness of the new method has been confirmed by both simulation and experiments View full abstract»

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  • A new approach to feedback-linearizing control of variable reluctance motors for direct-drive applications

    Page(s): 348 - 362
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1308 KB)  

    Considers feedback-linearizing control of VR (variable reluctance) motors which have been increasingly used in high performance direct-drive applications. The authors characterize all torque controllers that can make the total torque of a VR motor linear to torque command but without torque ripple. The torque controllers maximize the range of torque commands which are admissible under the physical limitation in stator currents. The whole class of all such torque controllers is parameterized in the explicit form which contains a function to be chosen freely. This free function can be used to achieve other control objectives as well as linear dynamic characteristics. As the examples for optimal choices of the free function, are actually determine two optimal free functions, one for minimal rate of change in current commands and the other for minimal power loss due to stator resistance. To illuminate further the practical use of their torque controllers, the authors present some experimental results for the case of a commercially available VR motor View full abstract»

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  • A control system for a microgravity isolation mount

    Page(s): 313 - 325
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1720 KB)  

    This paper describes the development of a control system and associated technology for a microgravity isolation mount (MGIM)-a device to isolate sensitive scientific payloads on orbiting spacecraft from ambient vibration. The construction of the MGIM, and the specifications which it must satisfy, are briefly described; the control system which achieves this is described in more detail. A model for the MGIM is derived which includes the effect of asymmetric distribution of the payload mass. It is shown that this induces angular motion of the payload and violation of the tolerable microgravity level, unless counteracting control forces are produced. The technology required to support the concept is also described and the results of vibration tests conducted on a full-scale laboratory version of the MGIM are presented View full abstract»

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  • A new control scheme for improving disturbance rejection in speed control of permanent magnet synchronous motors

    Page(s): 437 - 442
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    The major hurdle encountered in achieving high performance in servo speed control is the occurrence of large relative errors at low speeds due to torque variations. In this paper, it is shown that this problem can be tackled in the case of synchronous motors, by keeping the stator current and the rotor flux nonorthogonal and including an inner position control loop to improve the transient behavior of the system. Such a scheme substantially improves disturbance rejection at the cost of accentuating the nonlinearities of the system and increasing the copper losses. In view of the pronounced nonlinearities encountered here, adaptive control using neural networks is resorted to View full abstract»

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  • Interval model identification and robustness analysis for uncertain flexible structures

    Page(s): 411 - 418
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    System identification and robustness verification techniques are implemented for vibration control of flexible structures. This control methodology allows engineers to develop models which account for parametric uncertainties in a system. The test bed is a 10-bay aluminum truss-like structure. A reaction mass actuator (RMA) is used as the force actuator device for controlling the structure. A local velocity feedback controller is utilized to suppress structural vibration. Added masses to structural nodes represent parametric uncertainties. Interval control system analysis was applied to show the limits of performance of the uncertain experimental system View full abstract»

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  • Performance and gain and phase margins of well-known PID tuning formulas

    Page(s): 473 - 477
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    The performance and robustness of well-known PID formulas for process with deadtime to time constant ratio between 0.1 and 1 are discussed in this paper. The Ziegler-Nichols, Cohen-Coon, and tuning formulas that optimize for load disturbance response (integral absolute error, integral squared error, and integral time-weighted absolute error) give gain margins of about 1.5. The phase margins increase from about 30 to 60° as the process deadtime to time constant ratio increases from 0.1 to 1. Tuning formulas that optimize setpoint response give gain margins of about two and phase margins of about 65°. These formulas mostly make use of the proportional-integral derivative (PID) controller zeros to cancel the process poles. Approximate analytical formulas to compute gain and phase margins of PID control systems are also derived in this paper to facilitate online computation which would be particularly useful for implementing adaptive control View full abstract»

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  • Application of the l1-optimal regulation strategy to a hard disk servo system

    Page(s): 467 - 472
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    This paper examines the use of the l1-optimal regulation strategy on a hard disk servo system. The l1-optimal regulation algorithm seeks to minimize the maximum position error signal (PES), which is the deviation of the read/write head from the center of the track. Comparison studies were made against the linear quadratic Gaussian (LQG) optimal control strategy. Experimental results show that the LQG control algorithm helps to reduce the energy of the PES, but does not help to reduce the maximum error signal. On the other hand, the l1-optimal control scheme reduces the maximum error signal. The energy of the error signal, however, is larger View full abstract»

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  • Frequency-weighted state estimation with application to estimation in the presence of sensor bias

    Page(s): 427 - 436
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    This paper introduces a general state-estimation methodology, frequency-weighted linear quadratic Gaussian estimation (FWLQGE) that enables a control designer to modify a standard LQG estimator to account for sensor imperfections. Using FWLQGE, a designer can account explicitly for colored sensor noise (i.e., the noise spectrum varies as a function of frequency). Alternatively, the designer can use the frequency dependent degree of freedom as a mechanism to specify the relative confidence in a sensor's output. Presented is a technique for solving the FWLQGE problem with existing software tools by simply augmenting the system matrices. Also presented is an example demonstrating how the procedure can be used to account for sensor biases. Here, FWLQGE is compared with two classic methods: state augmentation and post-sensor filtering, It is shown that while all methods can be made to yield equivalent estimators, FWLQGE incorporates a design degree of freedom that is intuitively appealing allowing an explicit trade off between bias rejection and estimator performance. Simulation and experimental results are presented View full abstract»

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  • Suboptimal intelligent control: agile aircraft application

    Page(s): 363 - 368
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Near-optimal control of an aircraft using artificial neural networks is discussed with the optimal control problem solved off-line for numerous initial and final conditions using standard techniques. The obtained trajectories are then used to train a neural network controller. The concept is applied to minimum-time control and quadratic-performance optimal control of the longitudinal motion of a super-agile aircraft. Full nonlinear dynamics with control (magnitude and rate) constraints as well as state constraints are considered. Suboptimal feedback synthesized by a neural network is tested on a simulated rapid manoeuvre with extremely large changes in pitch angle and angle of attack View full abstract»

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  • Setpoint PI controllers for systems with large normalized dead time

    Page(s): 459 - 466
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    This paper derives proportional-integral (PI) control algorithms for first-order plants with time lag. First, the effects of proportional control on overshoot and rise time are analyzed. Then these results are applied to aid in the design of PI controllers that utilize a pole-zero cancellation. New PI tuning methods are proposed for design criteria typical of those found in metal rolling mill applications with large normalized dead time View full abstract»

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  • Reducing automotive engine speed fluctuation at idle

    Page(s): 404 - 410
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    This paper concerns an automotive idle speed control problem. Specifically, a problem of reducing engine idle speed fluctuations is considered. The authors develop an engine model for the instantaneous engine speed containing quasi-AC component. When there are different torque variations in the cylinders of the engine, the periodic variation of the engine speed fluctuates, which causes more vibration of the vehicle. The authors develop a control strategy to reduce this fluctuation with only engine speed as the measured variable by using four spark advances as control inputs View full abstract»

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  • Adaptive control of full penetration gas tungsten arc welding

    Page(s): 394 - 403
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    This application paper addresses the control of a nonminimum-phase plant with variable large orders and delays. The process concerned is full penetration gas tungsten arc welding. Based on an analysis of accepted adaptive algorithms, the generalized predictive control algorithm presented by Clarke et al., is selected as the principal control strategy. An adaptive generalized predictive decoupling control scheme is constructed. To decouple the authors' nonminimum-phase multivariable plant, a predictive decoupling algorithm is also proposed. Simulations are performed to determine the default parameters of the algorithms. The performance has been tested by both simulations and experiments View full abstract»

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  • Robust control of a 360° flexible arm using the combined pole placement/sensitivity function shaping method

    Page(s): 369 - 383
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1264 KB)  

    The control of a 360° flexible arm is investigated both from a theoretical and practical point of view. Based on identified discrete time models of the arm, a robust linear digital controller is designed using the combined pole placement/sensitivity functions shaping method. The particularities of the flexible arm and of the sensor used for the measure of the tip position are taken in account for the design and implementation of the control system. Extensive experimental results are given View full abstract»

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