Showing papers on "Control theory published in 1980"

Resolved-acceleration control of mechanical manipulators

Abstract: Position control of a manipulator involves the practical problem of solving for the correct input torques to apply to the joints for a set of specified positions, velocities, and accelerations. Since the manipulator is a nonlinear system whose joints are highly coupled, it is very difficult to control. This paper presents a technique which adopts the idea of "inverse problem" and extends the results of "resolved-motion-rate" controls. The method deals directly with the position and orientation of the hand. It differs from others in that accelerations are specified and that all the feedback control is done at the hand level. The control algorithm is shown to be asymptotically convergent. A PDP 11/45 computer is used as part of a controller which computes the input torques/forces at each sampling period for the control system using the Newton-Euler formulation of equations of motion. The program is written in floating point assembly language, and has an average execution time of less than 11.5 ms for a Stanford manipulator. This makes a sampling frequency of 87 Hz possible. The controller is verified by an example which includes a simulated manipulator.

Stable adaptive controller design, part II: Proof of stability

Abstract: The paper presents a proof of stability of model reference adaptive control systems using direct control. The structure of the adaptive system is similar to that considered by Monopoli [1] and Narendra and Valavani [2] but contains an additional feedback term which ensures that the time derivative of the parameter error vector belongs to the L2space. The output of the plant is shown to be bounded by expressing the plant feedback loop as an exponentially stable system with a time-varying gain \dot{\phi}(\cdot)\in L^{2} in the feedback path.

Frequency-shaped cost functionals - Extension of linear-quadratic-Gaussian design methods

Abstract: The linear-quadratic-Gaussian method for feedback control design is extended to include frequency-shaped weighting matrices in the quadratic cost functional. This extension provides a means to meet classical design requirements with automated computational procedures of modern control theory. A design algorithm to optimize frequency-shaped cost functional requires definition of new states and the solution of a modified linearquadratic-Gaussian problem. Four examples are presented to demonstrate frequency shaping methodology: 1) aircraft in lateral wind, 2) an industrial crane, 3) vibration control in helicopters, and 4) a system with truncated modes.

Kinesthetic coupling between operator and remote manipulator

Abstract: A universal force-reflecting hand controller has been developed which allows the establishment of a kinesthetic coupling between the operator and a remote manipulator. The six-degree-of-freedom controller was designed to generate forces and torques on its three positional and three rotational axes in order to permit the operator to accurately feel the forces encountered by the manipulator and be as transparent to operate as possible. The universal controller has been used in an application involving a six-degree-of-freedom mechanical arm equipped with a six-dimensional force-torque sensor at its base. In this application, the hand controller acts as a position control input device to the arm, while forces and torques sensed at the base of the mechanical hand back drive the hand controller. The positional control relation and the back driving of the controller according to inputs experienced by the force-torque sensor are established through complex mathematical transformations performed by a minicomputer. The hand controller is intended as a development tool for investigating force-reflecting master-slave manipulator control technology.

The design of controllers for the multivariable robust servomechanism problem using parameter optimization methods

Abstract: The problem of designing realistic multivariable controllers to solve the servomechanism problem is considered in this paper. Specifically it is desired to find a controller for a plant to solve the robust servomechanism problem, so that closed loop stability and asymptotic regulation occur, and also so that other desirable properties of the controlled system, such as fast response, low-interaction, integrity, tolerance to plant variations, etc. occur. The method of design is based on using state space methods via a two-state process: (1) using theory, determine the existence of a solution and control structure required to solve the problem, (2) using nonlinear progranming methods, determine the unknown controller parameters so as to minimize a performance index for the system subject to certain constraint requirements. Numerous examples, varying from a single-input/single-output to a four-input/four-output system, are given to illustrate the design method, and the results obtained are compared with the results obtained by using other alternate design methods. In all cases, the controllers obtained have been highly competitive (i.e. always superior) with controllers obtained by alternate design methods.

Application of vector performance optimization to a robust control loop design for a fighter aircraft.

Abstract: For a McDonnell-Douglas F-4C aircraft a robust, fixed gain controller is designed, which provides satisfying handling qualities of the longitudinal motion or the aircraft over the complete flight range without gain scheduling. Robustness is achieved in the sense of covering largo paramoter variations and providing good gain and phase margins, Only low control rates and low feedback gains are involved, The results are obtained by application of a performance vector optimization design method which accounts for a great many different design objectives simultaneously in a highly systematic fashion. Two different designs are presented placing emphasis on pitch rate control (pointing) and normal acceleration control (manoeuvring) respectively.

State feedback integral control with ‘ intelligent’ integrators

Abstract: Integral controllers designed for various state determined systems, which are subject to constant disturbances and large initial conditions, very often turn out to be unsatisfactory, The overshoot becomes large and the speed of response may not be fast enough even when optimum (in some sense) feedback gains are employed. One euro for such problems is the use of ‘ intelligent’ integral controllers. A scheme for synthesizing an ‘ intelligent ’ controller is given, and then it is applied to the case of a simple system, by which the superiority of the ‘ intelligent’ integral control becomes clear.

Process control system with improved system security features

Abstract: A process control system includes two digital controllers each capable of exercising direct digital control over the process. One of the controllers is selected to be on-control, the other serving as a backup. A separate data buffer memory connected to both controllers stores the most recent static and dynamic data base of the on-control controller which is transferred to the backup controller. In the event of failure or other loss of service, the backup automatically acquires control with an up-to-date data base resulting in a smooth transition. Provisions are also included to have the backup controller examine the health of the on-control unit before deciding whether or not to accept the data buffer contents thereby reducing the likelihood of corrupted data being fed to the backup.

Attitude Control of a Flexible Spacecraft

Abstract: An algorithm is presented for designing optimal low order compensators for high order systems and it is applied to the title problem where many vibration modes are excited by the control torque. These low order compensators are compared with the full order optimal compensator and found to be less sensitive to modeling errors and to provide near optimal attitude regulation.

Modal cost analysis for linear matrix-second-order systems

Abstract: Reduced models and reduced controllers for systems governed by matrix-second-order differential equations are obtained by retaining those modes which make the largest contributions to quadratic control objectives. Such contributions, expressed in terms of modal data, used as mode truncation criteria, allow the statement of the specific control objectives to influence the early model reduction from very high order models which are available, for example, from finite element methods. The relative importance of damping, frequency, and eigenvector in the mode truncation decisions are made explicit for each of these control objectives: attitude control, vibration suppression and figure control. The paper also shows that using modal cost analysis (MCA) on the closed loop modes of the optimally controlled system allows the construction of reduced control policies which feedback only those closed loop modal coordinates which are most critical to the quadratic control performance criterion. In this way, the modes which should be controlled (and hence the modes which must be observable by choice of measurements), are deduced from truncations of the optimal controller.

Design for active and passive flutter suppression and gust alleviation

Abstract: Analytical design techniques for active and passive control of aeroelastic systems are based on a rational approximation of the unsteady aerodynamic loads in the entire Laplace domain, which yields matrix equations of motion with constant coefficients. Some existing schemes are reviewed, the matrix Pade approximant is modified, and a technique which yields a minimal number of augmented states for a desired accuracy is presented. The state-space aeroelastic model is used to design an active control system for simultaneous flutter suppression and gust alleviation. The design target is for a continuous controller which transfers some measurements taken on the vehicle to a control command applied to a control surface. Structural modifications are formulated in a way which enables the treatment of passive flutter suppression system with the same procedures by which active control systems are designed.

Control system analysis and synthesis for a six degree-of-freedom universal force-reflecting hand controller

Abstract: A six degree-of-freedom joystick with feedback motors, called the Force-Reflecting Hand Controller (FRHC) is used as control input for the human operator in a teleoperator system. The geometric and dynamic properties of the FRHC are entirely different from those of the manipulator being controlled. The paper discusses the analysis and synthesis of the control loop between the FRHC and the robot arm and examines the necessary position and force transformations. The controller is implemented through a dedicated minicomputer.

Microcomputer control for heat pump system

Abstract: A method of controlling energy usage of a multi-state heat pump system in which the system includes a preprogrammed microprocessor-based controller which places and maintains the system in the most energy efficient mode of operation consistent with achieving a desired room temperature level within a reasonable period of time. The controller responds to actual room temperature and a user-inserted temperature setting to place the heat pump system into an operating state indicated by a predetermined set of operating state criteria which establishes the required operating state and the timing of state changes. Changing to higher (less energy efficient) operating states is enabled only when periodic checks of the rate of change of room temperature indicate the desired temperature will not be achieved in a selected time period. The user-inserted temperature setting is modified as a function of outside temperature extremes to modify the target temperature to which the heat pump system operates to further improve energy efficiency of the system.

Controllability and Observability for Flexible Spacecraft

Abstract: Current interest in extended sensing and actuation for the control of flexible spacecraft has led to the use of modern multivariable control theory and the associated concepts of controllability and observability. This paper shows how to evaluate these properties on a mode-by-mode basis for flexible spacecraft control analysis. Relatively simple criteria are derived which indicate the degree of controllability (observability) of each mode in simple literal terms. These criteria provide physical insight and practical guidance on the type, number, and positioning of sensors and actuators. The results are interpreted for force and torque actuators, and for attitude and deformation measurements. To illustrate these ideas, sample controllability and observability 'surfaces' are presented for the Purdue generic flexible spacecraft model.

Systematic control design by optimizing a vector performance index

Abstract: An iterative procedure for control design is presented. By optimizing a vector performance index, the components of which rate different design specifications, free controller coefficients in a given control structure are determined in such a way that a systematic improvement of the result in each iteration step is guaranteed, even if a great many of design specifications have to be considered. Opposite to previous works, handling design specifications as constraints within the meaning of nonlinear programming the described procedure excels by high systematic policy for choosing free design parameters and by requiring only unconstrained minimization which can be realized comparatively simple.

A Microprocessor-Controlled Fast-Response Speed Regulator with Dual Mode Current Loop for DCM Drives

Abstract: A new control method is described in which a microprocessor is used to regulate the speed of a dc motor driven by antiparallel-connected three-phase dual thyristor converters. A distinct feature of this speed regulating system is that speed response is improved by using a fast-response current controller for the internal loop. A fast-response current controller is obtained by employing a nonlinear compensation subloop and a proportional plus integral compensation subloop. The nonlinear compensation subloop is used to linearize the nonlinear load characteristics of the thyristor converter, which are encountered under discontinuous conduction states of current. The proportional plus integral compensation subloop reduces the deviation of detected current from the current reference. With these two current-control subloops a fast motor speed response is achieved under discontinuous as well as continuous conduction states; hence the steady-state accuracy of speed is improved. A speed regulator using a microprocessor was trial manufactured and tested with a 20-kW dc motor. It was found that an extremely fast controlled current response can be obtained even with a relatively long sampling period. Further, normal action was confirmed in four-quadrant operation.

Extensions of Linear-Quadratic Control Theory

Abstract: Review of linear dynamic systems.- Canonical forms, pole assignment and state observers.- Lyapunov stability theory.- Linear-quadratic optimal control.- to kalman filtering.- The maximum principle and the Hamilton-Jacobi-Bellman equation.- The non-convex case.- Controllability subject to controller constraints.- Linear-quadratic problems with conical control set.- Special non-linear-quadratic formulations.- Hybrid criteria and parameter sensitivity.- Conditional definiteness of quadratic functionals.- Exponential performance criteria and state-dependent noise.- Differential games.- Optimal control of partial differential equations.

Microprocessor Control for Color-TV Receivers

Abstract: A microprocessor control that makes available sophisticated and desirable features not feasible with current standard or custom IC's is described. The TV controller features modular design, which permits essential functions to be implemented on a priority basis while events of secondary importance are held until processing time is available. Physical modularity also permits features to be added in the form of software changes, thus saving manufacturers the expense in time and money of hardware redesign.

Electronic controller and portable programmer system for a pneumatically-powered point-to-point robot

Abstract: An electronic controller and portable programmer system for a pneumatically-powered point-to-point robot is disclosed. The microprocessor-based controller includes a read-only memory for storing the main control program, a non-volatile memory (EAROM) for storing a sequence of robot functions forming a user program, an output interface for transmitting control signals to the robot solenoid values, and an input interface for receiving feedback pressure signals to indicate that the various robot functions have been completed. The portable programmer provides a teach control unit, which is used to enter, edit, and test the user program. The teach control unit includes a matrix keyboard, a display, circuit means for decoding the keyboard and driving the display, and an interface for providing serial communication with the controller.

Automatic control apparatus for a heat pump system

Abstract: A microprocessor based heat pump control apparatus having a user-operated system console and a system function controller is provided in which normal operating target temperature settings are automatically converted to an expanded operating temperature range (standby operating mode), having preset upper and lower target temperature settings, in response to predetermined operating conditions within the system. The system function controller is preprogrammed to respond to a predetermined number of invalid data signal communications emanating from the user-operated console to switch into the standby operating mode. Provision is made for the user to insert a standby mode instruction at the user-operated console. Provision is also made for the system controller to enter standby during a power-up sequence when invalid user-inserted volatile data is sensed from storage means used to retain the volatile data during the power-off time period.

The Measurement of the Air Traffic Controller

Abstract: Measures of the air traffic controller are reviewed and critically assessed. There are many reasons for measuring the controller, and no measure can yet be treated as either indispensable or useles...

Memory controller with queue control apparatus

Abstract: A memory controller couples to a bus and controls a number of memory module units or memory modules. The controller includes a number of queue circuits for processing a variety of different types of memory requests received from a number of command generating units coupled to the bus requiring the controller to operate in a corresponding number of different modes. The controller includes queue timing and control apparatus which couples to the modules and to the queue circuits for minimizing conflicts between the types of requests and the internal operations required to be performed by the controller.

Hierarchical-structure plant control system

Abstract: Sub-loop controllers arranged around a microprocessor are assigned to operation terminals to be controlled, and connected to a master controller and a host computer through a system bus to be supplied with a control command therefrom. Analog memories for manual control of the operation terminals are connected to the host computer through a special, common wiring. If one of the sub-loop controllers breaks down, the host computer directly controls the operation terminal by use of this analog memory thereby to back up the sub-loop controller.

On the steering of automated vehicles—A velocity-adaptive controller

Abstract: A velocity-adaptive lateral controller is designed to meet requirements pertaining to lateral-position tracking accuracy, ride comfort, and an insensitivity to both changes in critical vehicle parameters and disturbance forces. This controller was tested under full-scale conditions wherein a wire-follower configuration and a dual-mode test vehicle were employed. The latter was automatically steered on straight sections of roadway at speeds up to 35.8 m/s, lane-changing maneuvers were performed up to this speed, and small-radius (100 m) curves were traversed at speeds up to 17.9 m/s. Excellent lateral control, close tracking, good insensitivity to disturbance forces, and a comfortable ride resulted; thus, a relatively simple controller can be effectively employed for nonemergency situations.

Suboptimal control strategies for multilocomotive powered trains

Abstract: This paper introduces two different controllers for the handling of very long multipowered trains, including braking operations. The purpose of the controller is to minimize coupler forces and velocity deviations from reference values due to grade changes and other disturbances. The controller is superimposed on a throttling and braking schedule which is assumed to be known beforehand. Due to the constraints on the inputs (especially the braking inputs) and the coupler forces that cannot be neglected, a linear control cannot be applied straightforward. Therefore, a switching policy is chosen such that a piecewise linear system results. The linear suboptimal controllers acting between the switching moments are derived from two different small scale train models using standard optimal control design. One model represents a reduced order model of the long train, the other one uses a short train configuration consisting of fewer cars than the given train, where the cars however preserve the original characteristics. From the obtained weighting patterns, a control law for the large scale system is derived. Since not all the states are assumed to be measurable, a simple observer-like structure is used for the estimation of the important missing states needed for the control. Simulation results are presented for a train consisting of three locomotives and sixty cars operating over various grade profiles.

Automatic speed control for heavy vehicles

Abstract: An automatic speed control for a heavy duty vehicle includes a controller which regulates communication between a compressed air source and an air actuated throttle mechanism. The controller generates a control signal which is a function of a speed error signal and the position of the air actuated throttle to regulate the compressed air source. The speed error signal is calculated as the difference between a commanded speed signal and an actual speed signal. To generate the control signal, the error signal and throttle position signal are operated on by different lead-lag transfer functions. These lead-lag terms are thereafter combined with a proportional speed error term to yield the desired control signal. The system further includes a throttle control feature for powering auxiliary equipment when the actual speed signal is zero. Another feature of the control limits the commanded speed signal to a set value when it exceeds a predetermined limit.