Simultaneous controller design for linear time-invariant systems

The use of generalized sampled-data hold functions (GSHF) in the problem of simultaneous controller design for linear time-invariant plants is discussed. This problem can be stated as follows: given plants P₁, P₂, . . ., P_N , find a controller C which achieves not only simultaneous stability, but also simultaneous optimal performance in the N given systems. By this, it is meant that C must optimize an overall cost function reflecting the closed-loop performance of each plant when it is regulated by C. The problem is solved in three aspects: simultaneous stabilization, simultaneous optimal quadratic performance, and simultaneous pole assignment in combination with simultaneous intersampling performance     

Geometric structure and feedback in singular systems

The output-nulling (A, E, R(B))-invariant subspaces are defined for singular systems, rigorously justifying the name and demonstrating that special cases of these geometric objects are the familiar subspace of admissible conditions and the supremal (A, E, R(B ))-invariant subspace. A novel singular-system-structure algorithm is used to compute them by numerically efficient means. Their importance for describing the possible closed-loop geometric structure in terms of the open-loop geometric structure is shown. An approach to spectrum assignment in singular systems that is based on a generalized Lyapunov equation is introduced. The equation is used to compute feedback gains to place poles and assign various closed-loop invariant subspaces while guaranteeing closed-loop regularity     

Numerical algorithms for eigenvalue assignment by constant anddynamic output feedback

Algorithms are proposed for eigenvalue assignment (EVA) by constant as well as dynamic output feedback. The main algorithm is developed for single-input, multioutput systems and the results are then extended to multiinput, multioutput systems. In computing the feedback, use is made of the fact that the closed-loop eigenvalues can almost always be assigned arbitrarily close to the desired locations in the complex plane, provided the system satisfies the condition m+ p>n, where m, p, and n are , respectively, the number of inputs, outputs and states of the system. The EVA problem has been treated as a converse of the algebraic eigenvalue problem. The proposed algorithms are based on the implicitly shifted QR algorithm for solving the algebraic eigenvalue problem. The performance of the algorithms is illustrated by several numerical examples     

Chained aggregation of singular systems

Extends the notion of aggregation to singular systems (sE-A). Necessary and sufficient conditions for complete aggregability are given which reduce in the state-space case, E=I, to Aoki's conditions. A geometric quotient-space analysis is given which uses a new result on the pencil induced in the quotient space by a regular matrix pencil. A generalized chained aggregation algorithm is used to put the system into a Hessenberg form which provides a reduced-order model for the output dynamics. It is shown that, as in the state-space situation, chained aggregation corresponds to removal of the unobservable subspace. It is also pointed out that the usual state-space chained aggregation algorithm is very efficient and numerically unstable. Specializing the singular system chained aggregation algorithm to the state-space case yields a better and more streamlined approach     

Output feedback eigenstructure assignment using two Sylvesterequations

The eigenstructure assignment problem with output feedback is studied for systems satisfying the condition p+m> n. The main tool used is the concept of (C, A, B)-invariance and two coupled Sylvester equations, the solution of which leads to the computation of an output stabilizing feedback. A computationally efficient algorithm for the solution of these two coupled equations, which leads to the computation of a desired output feedback, is presented     

Observers for discrete singular systems

The author considers the design of observers for the discrete singular system Ex(k+1)=Ax(k)+Bu (k), y(k)=Cx(k), placing special emphasis on the problems of state reconstruction and minimal-time state reconstruction. It is shown that for a singular system, finite poles can be moved to infinity by state feedback and the state can be reconstructed by causal observers     

Linear periodic systems: eigenvalue assignment using discreteperiodic feedback

The eigenvalue assignment problem of a T-periodic linear system using discrete periodic state feedback gains is discussed. For controllable systems, an explicit formula for the feedback law is given that can be used for the arbitrary assignment of the eigenvalues of Φ_c1(T,0), the closed-loop state transition matrix from 0 to T. For the special case of periodic systems controllable over one period, this control law can be used to obtain any desired Φ_c1(T,0)     

Solutions of the equation AV+BW=VF andtheir application to eigenstructure assignment in linear systems

Two new simple, complete, analytical, and restriction-free solutions with complete and explicit freedom of the matrix equation AV+BW=VF are proposed. Here [AB] is known and is controllable, and F is in the Jordan form with arbitrary given eigenvalues. Based on the proposed solutions of this matrix equation, a complete parametric approach for eigenstructure assignment in linear systems via state feedback is proposed, and two new algorithms are presented. The proposed solutions of the matrix equation and the eigenstructure assignment result are generalizations of some previous results and are simpler and more effective     

An algorithm for the multiinput eigenvalue assignment problem

A very simple and inexpensive algorithm is presented for pole placement in the multiinput case. The algorithm consists of orthogonal reduction to a Block-Hessenberg form and a simple linear recursion. It yields a matrix F such that A+BF has any specified set of eigenvalues whenever the system is controllable. It is extremely easy to program on a computer. The algorithm is not a robust pole-placement algorithm but appears to give comparable results in most well-conditioned cases at a fraction of the cost. It is a direct (noniterative) algorithm and no eigenvalues or singular values are computed. The algorithm does not need any complex arithmetic, even when complex conjugate eigenvalues need to be assigned     

Decentralized stabilization and pole assignment for general propersystems

Considered is the problem of finding existence conditions and a controller synthesis procedure, using decentralized control, for assigning the poles of a linear time-invariant proper system described by a state-space model (C, A, B, D), where no assumption is made regarding the structure of D. This problem has direct application to the decentralized stabilization problem, decentralized robust servomechanism problem, etc., and is a nontrivial extension to the standard decentralized problem where it is assumed that the direct feedthrough terms either are absent or have a block-diagonal structure     

On the number of digital straight line segments

A closed-form expression has been reported in the literature for L_N, the number of digital line segments of length N that correspond to lines of the form y=ax+β, O⩽α, β<1. The authors prove an asymptotic estimate for L_N that might prove useful for many applications, namely, L_N=N ³/π²+O(N² log N). An application to an image registration problem is given     

Decoupling of square singular systems via proportional statefeedback

Necessary and sufficient conditions for the decoupling of a solvable square singular system Ex˙(t)=Ax(t)+Bu(t ) with output y(t)=Dx(t), through an admissible control law of the form u(t)=Kx(t)+Hr(t) where H is a square nonsingular matrix. It has been shown that for a given singular system that satisfies these conditions, a propagational state feedback exists for which the system's transfer function is a diagonal, nonsingular, and proper rational matrix. The proofs of the main results are constructive and provide a procedure for computing an appropriate proportional state feedback     

A VLSI constant geometry architecture for the fast Hartley andFourier transforms

An application-specific architecture for the parallel calculation of the decimation in time and radix 2 fast Hartley (FHT) and Fourier (FFT) transforms is presented. A real sequence with N=2ⁿ data items is considered as input. The system calculates the FHT and the FFT in n and n+1 stages. respectively. The modular and regular parallel architecture is based on a constant geometry algorithm using butterflies of four data items and the perfect unshuffle permutation. With this permutation, the mapping of the algorithm in VLSI technology is simplified and the communications among processors are minimized. Organization of the processor memory based on first-in, first-out (FIFO) queues facilitates a systolic data flow and permits the implementation in a direct way of the complex data movements and address sequences of the transforms. This is accomplished by means of simple multiplexing operations, using hardwired control. The total calculation time is (Nlog₂N)/4Q cycles for the FHT and N(1+log₂N)/4Q cycles for the FFT, where Q is the number of processors ( Q= 2^q, Q⩽N/4)     

Solution to Morgan's problem

A necessary and sufficient condition is presented for the solution of the row-by-row decoupling problem (known as Morgan's problem) in the general case, that is, without any restrictive assumption added to the system to the feedback law u=Fx+Gy (G may be noninvertible). This is a structural condition in terms of invariant lists of integers which are easily computable from a given state realization of the system. These integers are the infinite zero orders (Morse's list I₄) and the essential orders of the system, which only depend on the input-output behavior, and Morse's list I₂ of the system, which depends on the choice of a particular state realization     

Trace bounds on the covariances of continuous-time systems withmultiplicative noise

Matrix equations such as AP+PA^T+FPF^T+Ω=0 and AQ+QA^T+-QVQ+FPF^T +Ω=0, which arise in the estimation problem of systems with both additive and multiplicative noise, are treated. Trace bounds on the steady-state and error covariances P and Q are established, under complete and incomplete noise information. An example illustrates the usefulness of these bounds in determining the size of the estimation error     

Optimal flow control allocation policies in communication networkswith multiple message classes

Flow control is considered for M(⩾2) transmitting stations sending packets to a single receiver over a slotted time-multiplexed link. The optimal allocation problem is generalized to the case of nonidentical holding costs at the M transmitters. Qualitative properties of optimal discounted and time-average policies that reduce the computational complexity of the M-dimensional optimal flow control algorithm are derived. For M=2, a simple relationship between optimal allocations for states x and x +e_i (i=1,2) that leads to significant computational savings in the optimal algorithm is established     

Descent algorithms for optimal periodic output feedback control

Periodic output feedback is investigated in the context of linear-quadratic regulation for finite-dimensional time-invariant linear systems. Discrete output samples are multiplied by a periodic gain function to generate a continuous feedback control. The optimal solution is obtained in two steps by separating the continuous-time from the discrete-time structure. First, the optimal pole placement problem under periodic output feedback is solved explicitly under the assumption that the behavior at the sample times has been specified in terms of a gain matrix G. Then the minimum value, which depends on G, is substituted into the overall objective. This results in a finite-dimensional nonlinear programming problem over all admissible gain matrices G. The solution defines the optimal periodic output feedback control via the formulas of the optimal pole placement problem. A steepest descent and a direct iterative method for solving this problem are formulated and compared. Numerical examples show that the performance using periodic output feedback is almost equivalent to that using optimal continuous-state feedback     

Efficient algorithms for list ranking and for solving graphproblems on the hypercube

A hypercube algorithm to solve the list ranking problem is presented. Let n be the length of the list, and let p be the number of processors of the hypercube. The algorithm described runs in time O(n/p) when n=Ω(p ^1+ε) for any constant ε>0, and in time O(n log n/p+log³ p) otherwise. This clearly attains a linear speedup when n=Ω(p ^1+ε). Efficient balancing and routing schemes had to be used to achieve the linear speedup. The authors use these techniques to obtain efficient hypercube algorithms for many basic graph problems such as tree expression evaluation, connected and biconnected components, ear decomposition, and st-numbering. These problems are also addressed in the restricted model of one-port communication     

不确定广义系统的圆形区域极点配置

考虑不确定连续或离散广义系统的圆形区域极点配置问题, 目的是设计状态反 馈控制律, 使得闭环系统正则, 无脉冲(连续广义系统情形)或因果(离散广义系统情形), 且 闭环极点位于一给定的圆形区域内. 给出了所期望的状态反馈控制律存在的充分条件及其解 析表达式.     

On the gap between the structural controllability of time-varyingand time-invariant systems

Structural controllability of time-invariant and time-varying systems when the input control sequences have a restricted length k is compared. The dimensions of controllable space coincide in the following three special cases: the input sequences have length k=2; the input sequences have k=n, where n is the size of the system (i.e., the ultimate controllability is the same in both cases); and for every length of input sequences provided that the system has a single input only. It is proved that there may appear a gap for every input length k such that 2< k⩽n/2. The case when n/2<k<n is left open