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Control Systems, IEEE

Issue 4 • Date Aug. 1994

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Displaying Results 1 - 7 of 7
  • Adaptive control of temperature in arc welding

    Publication Year: 1994 , Page(s): 4 - 12
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (841 KB)  

    We have outlined our approach for developing an integrated system for controlling centerline bead temperature in arc welding. An optical thermography system, based on an inexpensive and readily available video camera, was presented. Temperature measurements obtained with this system are within 10% of those measured by a calibrated two-color optical pyrometer. A low-order model describing the centerline temperature dynamics was developed. Two strategies for tuning a simple PI temperature controller were given. We first used off-line sensitivity-based tuning to optimize the controller gains. This method is adequate for systems whose dynamics are time invariant. For GMAW, however, the plant parameters can vary widely due to changes in plate thickness as well as other operating parameters. For this reason we applied a sensitivity-based pseudogradient adaptive algorithm for self-tuning the PI controller. The self-tuning controller is robust to changes in the operating conditions and is therefore more useful than a PI controller with fixed gains. It is also insensitive to the noise present in the GMAW system. The control design presented in this paper makes no attempt to counter the delay between the arc current command and centerline temperature output. Instead, the sample time was deliberately increased so that this delay could be ignored. To increase the bandwidth of the closed-loop system it is necessary to incorporate a Smith predictor or similar mechanism to increase the response time of the closed-loop system. We are currently investigating the design of a predictive controller.<> View full abstract»

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  • Multiplexed and distributed control of automated welding

    Publication Year: 1994 , Page(s): 13 - 24
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1143 KB)  

    Although modern sensor technology and control algorithms have enabled in-process regulation of arc welding, classical single-torch actuation methods provide only a few welding conditions that can be modulated in real time to control multiple weld geometry characteristics. To decouple the process dynamics and simultaneously control thermal characteristics of the weld, multiple virtual heat inputs are implemented by rapid periodic reciprocation (timesharing) of the single torch on the weld surface. Dynamic analytical, numerical and linearized experimental process models are developed for the design of adaptive MIMO control systems of both geometrical and thermal characteristics, and their performance is tested in rejecting disturbances and following setpoint changes. To maximize the range of achievable weld features, a continuous heat distribution and temperature monitoring on the entire weld surface is finally adopted. The necessary vector-scanning trajectories of the torch are regulated in real time by a distributed-parameter control strategy, integrated to the weld design software for flexibility in production.<> View full abstract»

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  • High-performance induction motor control via input-output linearization

    Publication Year: 1994 , Page(s): 25 - 33
    Cited by:  Papers (102)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (711 KB)  

    We have shown that a current-command input-output linearization controller can achieve high-performance motion control, that is, the precise tracking of a fast point-to-point position reference. Specifically, this controller was shown to provide the means of decoupling the speed and flux dynamics in an induction motor. This decoupling of speed and flux was exploited to simultaneously track the position/speed reference and an optimal flux reference. This flux reference was used to obtain the optimal (max/min) motor torque at any given speed without violating voltage and current limits. Experimental results were presented to demonstrate the effectiveness of this scheme.<> View full abstract»

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  • Controlling plate vibrations using piezoelectric actuators

    Publication Year: 1994 , Page(s): 34 - 41
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (913 KB)  

    Launch vehicles often experience severe vibration problems during the ascent phase due to intense acoustic fields and mechanically transmitted disturbances. These disturbances are characterized by a large number of resonances over a wide-band frequency spectrum. The payloads inside the launch vehicle must be designed strong enough to withstand these structural vibrations. Passive isolators are used to isolate the payloads from the vibrating structure but this type of isolation has no effect on the acoustic excitations. This study focuses on methods for achieving active damping on plate structures by means of piezoelectric actuators (PZTs). An experiment was conducted using PZT actuators and accelerometers mounted on a rectangular plate with an active damping controller implemented on a 486 computer. Two control design methods were evaluated for this application: the H/sub /spl infin method and rate feedback.<> View full abstract»

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  • Optimal gain scheduling controller for a diesel engine

    Publication Year: 1994 , Page(s): 42 - 48
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (757 KB)  

    A generalized gain scheduling control mechanism based on off-line optimization techniques has been developed for a 2-cylinder, water cooled diesel engine. First, a set of linearized models is obtained for the engine operating at three different speeds and a total of 15 load conditions. From the experimental data analysis, it is concluded that the behavior of the engine can best be characterized by a set of fifth order difference equations with appropriate time delays. Optimal controllers with a PID structure are then synthesized by off-line numerical optimization using these mathematical models to minimize the integral squared error of the engine speed deviation subject to a step speed change command. The designed control system has been implemented and tested on a Petter diesel engine (Model PH2W). Experimental results indicated that the designed optimal control strategy has greatly improved the performance of the original engine in terms of both speed regulation and disturbance rejection. Attempts have also been made to evaluate the fuel efficiency of the engine with respect to controller parameter variations. It is concluded that there exists a strong correlation between controller parameter settings and the engine fuel consumption rate.<> View full abstract»

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  • Industrial application of an H-infinity design method for flexible structures H/sub /spl infin

    Publication Year: 1994 , Page(s): 49 - 54
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (554 KB)  

    An industrial application has been developed by Sfim Industries Ets d'Asnieres for helicopter sight system stabilization. H/sub /spl infin synthesis of robust control for flexible structures is presented. Penalizing the closed loop regulation function G(1+GK)/sup -1/ avoids pole cancellations while damping some flexible modes without increasing the regulator order. This approach is reminiscent of the positivity idea. The stability margin is ensured by the H/sub /spl infin standard W/sub 3/ weighting function which also handles the roll-off behavior. Experimental results obtained on the flexible sight system structure confirm the efficiency of this approach.<> View full abstract»

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  • Fuzzy logic control for lateral vehicle guidance

    Publication Year: 1994 , Page(s): 55 - 63
    Cited by:  Papers (28)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    A fuzzy logic controller (FLC) is designed and implemented in real time on a Toyota Celica test vehicle to achieve control of the lateral motion of the vehicle. The structure of FLC is modularized as feedback, preview, and gain scheduling rule bases. The parameters of FLC are tuned manually using information from the characteristics of human driving operation and existing controllers. Three feedback FLCs with different feedback variables are designed. A fuzzy preview rule base is developed to utilize preview information regarding the upcoming radii of curvature. Also, a gain scheduling rule base is designed to choose the appropriate controller based on the velocity of the vehicle. These fuzzy logic control strategies are implemented on the test vehicle which follows automatically a multiple curved track using discrete magnetic markers on the roadway and magnetometers on the vehicle as a lateral error reference/sensing system. The experimental test results of the FLCs, which are designed based on an implicit model of the vehicle, are shown, and a comparison is made to similar tests conducted using the frequency shaped LQ controller as well as PID controller, both are designed based on an explicit model of the vehicle.<> View full abstract»

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