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Control Systems, IEEE

Issue 3 • Date June 1999

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Displaying Results 1 - 13 of 13
  • CDC98 at Tampa Bay

    Page(s): 83 - 87
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    Freely Available from IEEE
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  • Board of Governors meeting report

    Page(s): 92 - 99
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  • Robust computer control of an inverted pendulum

    Page(s): 58 - 67
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    This article illustrates the design of a robust digital controller using a blend of state space and frequency response methods. The specific application is that of balancing an inverted pendulum on a moving cart while controlling the cart position. This work investigates issues regarding robust stability and disturbance attenuation. Furthermore, the effectiveness of a simple nonlinear compensation scheme for counteracting the Coulomb friction is studied. The controller design is based on an approximate discrete-time linear model of the pendulum-cart system. Design calculations and analysis are carried out using Matlab/toolboxes and M-files developed by the author View full abstract»

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  • From Wiener to hidden Markov models

    Page(s): 41 - 51
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    The authors investigate common properties of 3 types of filters obtained by considering various stochastic models; Wiener filters, Kalman filters and hidden Markov model (HMM) filters. Unifying features which particularly stand out are the forgetting of old data and of initial conditions, and protection from round-off error effects' overpowering the calculations. They differentiate the concept of fixed-lag smoothing from filtering, and expose the comparative advantages and disadvantages. Once again, there are common properties which allow a unified viewpoint. We focus especially on characterizations of a maximally effective smoothing lag, and identification of the SNR circumstances under which smoothing is especially beneficial. The motivation is the processing of data from an array of acoustic sensors towed by a submarine View full abstract»

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  • Enhancing classical controls education via interactive GUI design

    Page(s): 77 - 82
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    This column presents a graphical and somewhat automated tool for performing the iteration when using classical control design methods. The graphical user interface is an easy way for students to see the effect of the gain and the compensator pole-zero locations on the closed loop step response. Thus, the tool presented extends the capabilities of classical control design methods as they are currently presented in textbooks. Three examples are given that demonstrate the use and effectiveness of this tool. Furthermore, the Bode plot and the root locus windows are tied together in such a way that students can see how changes to the root locus affect the open loop Bode plot and vice versa View full abstract»

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  • QMotor 2.0-a real-time PC based control environment

    Page(s): 68 - 76
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    This paper describes QMotor 2.0, a QNX based single-processor software environment that allows the implementation of real-time control programs on standard Intel processor based personal computers (PCs). The control program, as well as the development tools and graphical user interface, can all execute simultaneously on the PC due to the deterministic response of the operating system. This architecture replaces the traditional multiprocessor Host/DSP board architecture used in control applications. Advantages of a single-processor system include reduced cost and complexity, as well as increased flexibility and upgradability. Since its development, QMotor 2.0 has been used successfully in all of the control experiments, including motor and robot control, active magnetic bearing experiments, web handling, and vibration control in flexible structures View full abstract»

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  • Vision-based control of an air hockey playing robot

    Page(s): 23 - 32
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    We demonstrate an integrated sensing and control design for high-speed ballistic manipulation in two dimensions. We show the effectiveness of a vision-based switched control scheme for precision impulsive manipulation. Vision-based hybrid control is a promising avenue of research for fully autonomous interaction between robots and complicated environments. Much work remains to be done in both computer vision and hybrid systems. In the context of robot air hockey, important future areas to investigate include the problems of modeling and identification of the environment dynamics, in particular, the table friction and puck spin. We show how the puck spin significantly influences its trajectory and subsequently our ability to perform accurate trajectory estimation and prediction View full abstract»

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  • The no free lunch theorem and the human-machine interface

    Page(s): 8 - 10
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    The no free lunch (NFL) theorem tells us that without any structural assumptions on an optimization problem, no algorithm can perform better on average than blind search. Although for most such impossibility theorems, the proofs are lengthy, difficult, and often not at all intuitive, we can get a feel for the NFL theorem by considering the proverbial needle in a haystack problem. Clearly, in this instance, no algorithm has any better chance of finding the optimum than blind search. The title also refers to the human-machine interface (HMI). Traditionally, this term has had the narrow meaning of facilitating communication between humans and computing machines, such as via the graphical user interface or head-up displays. But as technology advances, this communication interface will also evolve. Certainly, in the future we can see voice, fuzzy, and natural language inputs and outputs. Here, however, we are using the term in an even broader sense: to demarcate the dividing line between what humans do and what machines do in problem solving or optimization. The twin purposes of the article are to explore the implications of NFL and to address the proper allocation of natural and computational intelligence in optimization problem solving View full abstract»

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  • Technique for enhancing the performance of discretized controllers

    Page(s): 52 - 57
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    This paper introduces a method to partially compensate for the zero order hold effects of a closed-loop digital control system. By multiplying a given discretized controller in the Z-domain by a pole-zero pair, a significant closed-loop performance improvement has been achieved in many design examples View full abstract»

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  • The optimal use of the solar powered automobile

    Page(s): 12 - 22
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    Once a solar car has been built and tested, the question arises as to how to race with it. Since most teams are extremely energy limited for a race, strategy becomes critical if one is to win. In Sunrayce '97, most of the terrain, as well as the data on stop signs and stop lights, was known by the Illinois team many months before the race. We needed to determine at what speed we should be traveling during all parts of the race in order to use energy most efficiently and finish the race in the least amount of time. In what way should one optimally accelerate from a stop? Should we cruise at a constant speed, at a constant power, or in some other way? How should one climb and descend hills? Also, given a weather prediction for tomorrow, how much energy should one aim to consume today? These are some of the questions we answer through our analysis. In the next section, some of the prior work is described, followed by derivations of the equations modeling the car. The following section formulates the optimal control problem when the weather conditions are known, followed by solutions for various scenarios of interest. The next two sections first compare the results with different rule of thumb strategies and then obtain the optimal strategy given probabilistic weather predictions using stochastic dynamic programming. A post-race analysis is then provided View full abstract»

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  • Terrain navigation using Bayesian statistics

    Page(s): 33 - 40
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    The performance of terrain-aided navigation of aircraft depends on the size of the terrain gradient in the area. The point-mass filter (PMF) described in this work yields an approximate Bayesian solution that is well suited for the unstructured nonlinear estimation problem in terrain navigation. It recursively propagates a density function of the aircraft position. The shape of the point-mass density reflects the estimate quality; this information is crucial in navigation applications, where estimates from different sources often are fused in a central filter. Monte Carlo simulations show that the approximation can reach the optimal performance, and realistic simulations show that the navigation performance is very high compared with other algorithms and that the point-mass filter solves the recursive estimation problem for all the types of terrain covered in the test. The main advantages of the PMF is that it works for many kinds of nonlinearities and many kinds of noise and prior distributions. The mesh support and resolution are automatically adjusted and controlled using a few intuitive design parameters. The main disadvantage is that it cannot solve estimation problems of very high dimension since the computational complexity of the algorithm increases drastically with the dimension of the state space. The implementation used in this work shows real-time performance for 2D and in some cases 3D models, but higher state dimensions are usually intractable View full abstract»

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Richard D. Braatz
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