Showing papers on "Feedback loop published in 1984"

Instantaneous Feedback Controlled PWM Inverter with Adaptive Hysteresis

Abstract: A new control strategy for a PWM inverter controlled through adaptive hysteresis in an instantaneous feedback loop is theoretically analyzed and verified through simulations and a low-power experimental circuit. This control gives excellent performance under various load conditions, and it is especially effective in reducing load injected harmonics.

What is a biological oscillator

Abstract: Biological oscillators are amenable to qualitative analysis even before they have been described exhaustively in quantitative terms. Qualitative analysis can identify the elements essential for generating the oscillations and can enhance our understanding of underlying oscillator mechanisms. Two essential elements of a biological oscillator are 1) an inhibitory feedback loop, which includes one or more oscillating variables, and 2) a source of delay in this feedback loop, which allows an oscillating variable to overshoot a steady-state value before the feedback inhibition is fully effective. The analysis of the patterns of interactions and delays observed in biological oscillators is simplified by the translation of variables, interactions, and delays into schematic representations. To illustrate how such translations can be implemented, three biological oscillators are described schematically: 1) the glycolytic oscillator, 2) the bursting of the molluscan neuron, R15, and 3) the oscillations underlying smooth muscle contractions.

A frequency domain method for automatic tuning of simple feedback loops

Abstract: This paper presents a new method for automatic tuning of simple regulators. It is based on the idea of using relay feedback to determine points on the open loop Nyquist curve and a design method which approximately positions the closed loop poles. The method has been shown to work well in a number of industrial applications.

Extensions of the Discrete-Average Models for Converter Power Stages

Abstract: An improved power converter model is developed by combining the average and discrete modeling techniques. The parameter determination of the proposed discrete-average model is shown to be dependent on the type of duty cycle control law and the nature of the error processor used in the feedback loop. Furthermore, the paper pinpoints deficiencies of the conventional loop gain measurement technique which is widely used in industries.

Stability theorems for the relaxation of the strictly positive real condition in hyperstable adaptive schemes

Abstract: The hyperstability theorems of Popov have played an important role in establishing the convergence of adaptive schemes, notably adaptive output error identification and adaptive control. The error system of these schemes has the form of a feedback loop with a time-invariant forward path and a passive time-varying feedback path. The strict positive realness of the forward path suffices to establish asymptotic stability of the feedback loop and therefore establishes convergence of the adaptive scheme. In this paper we study conditions which preserve the asymptotic stability but permit relaxation of the strict positive real condition at high frequencies, subject to restrictions on algorithm gain parameters and frequency content of the input signal. These theorems are important for the design of robust adaptive methods.

A generalized bandwidth estimation theory for feedback amplifiers

Abstract: A procedure for quickly determining the 3-dB bandwidth of active low-pass networks is derived and exemplified. The procedure is useful for realistic assessment of topological adequacy in advance of extensive computer-based studies. Unlike other methods of bandwidth estimation, the method presented in this paper explicitly accounts for the effects of finite transmission zeros and the critical parameter of an embedded feedback loop.

Extremely accurate automatic frequency control circuit and method therefor

Abstract: An automatic frequency control circuit having the ability to resolve the frequency of an incoming signal to an extreme level of accuracy and to tolerate amplitude and pulse modulation on the incoming signal is disclosed. Two negative feedback loops are utilized. A coarse adjustment feedback loop resolves the frequency of the incoming signal to within the authority of a fine adjustment feedback loop. A computer is a common element of both loops and makes decisions regarding whether to resolve incoming a signal frequency using the coarse or the fine adjustment loops. Phase differences between a signal derived from the incoming signal and a reference signal are sampled at controllable time intervals apart to determine frequency adjustments within the fine adjustment loop.

Method of real time operating point identification and pole adjustment for an induction motor drive system

Abstract: A microcomputer based method for adjusting feedback loop gains ensures a fast, predetermined response of an induction motor drive system. A pre-computed look-up table contains gain values to be loaded into feedback regulators, the gain values corresponding to each operating point of the induction motor having the values necessary to keep the poles of the closed loop system substantially constant.

Electro-optic circuit with source control feedback

Abstract: A circuit for the conversion of an electrical input signal into an optical output signal is disclosed. A portion of the main beam from a laser diode that provides the optical output is reflected to a PIN diode with a glass pane. Linearization of the electro-optical conversion process over a wide frequency range is achieved through a feedback loop. For operation at frequencies higher than that of the feedback loop bandwidth, the various conversion factors for low and high frequencies can be additionally adapted.

Predictive code conversion method capable of forcibly putting a feedback loop in an inactive state

Abstract: In a predictive encoder for encoding an encoder input signal into an encoder output signal and having in a feedback loop an adaptive predictive filter which comprises a plurality of taps assigned with adaptive prediction coefficients and produces a predictive signal predictive of the encoder input signal, an encoder control circuit monitors products between the coefficients and tap signals derived from the taps so as to force each product to zero when an absolute value of each product is not greater than a predetermined value. The feedback loop is temporarily placed in an inactive state when the predictive signal becomes zero as a result of all zeros of the products. A predictive decoder is also operated by the use of a decoder control circuit similar to the encoder control circuit and cooperating with an adaptive predictive filter of the decoder. Each adaptive predictive filter may be either of an FIR type or of an IIR type.

Robustness issues in the control of high performance robots

Abstract: A methodology is presented to achieve effective on-line tracking control of robot manipulators in the presence of model uncertainty and torque limitations. A suction controller is used in the main feedback loop, allowing to combine robust tracking with simple controller design. Pointwise optimization techniques are incorporated into a 'slow' feedback loop in order to exploit joint coupling and generate feasible desired trajectories optimally close to the original (perhaps unfeasible) desired trajectories. The algorithm is computationally cheap and can easily be implemented on-line. Further, the scheme facilitates higher-level programming by only requiring reduced information about the robot model and the task structure.

Current mode control of switching regulators

Abstract: By adapting the forward converter range of switching regulators to include an additional current-controlled feedback loop, derived from either the secondary or primary power circuit, an improvement in the closed-loop performance of the switching regulator can be obtained. The basic analysis work examines the simple single-ended forward converter, with d.c. plus a.c. current control, derived from the secondary power circuit. An additional fixed voltage ramp is also included in the control loop to provide `feedforward? compensation for input voltage disturbances, and also to extend the maximum duty cycle from 50% up to 100%. Using this circuit configuration a simple small signal equivalent circuit for the current-controlled switching regulator can be obtained, enabling the performance of practical designs to be predicted. Practical implementation of the current mode control technique using a standard large-scale integrated circuit together with a number of applications is also given.

A New Approach to the Problem of Pole Assignment through Output Feedback

Abstract: The problem of pole assignment through output feedback is examined by investigating the effect of small changes in the feedback matrix on the closed loop pole locations. The main outcome is a feasible directions search procedure for finding a feedback matrix which places the poles at specified locations. The algori thm and variations of it are described, convergence conditions are given, comparisons with other methods are made, and a numerical example is presented.

Quartz oscillator for very high frequencies

Abstract: RESPECT THE INVENTION QUARTZ OSCILLATOR FOR VERY HIGH FREQUENCY. LOOP FEEDBACK OSCILLATOR COMPENSATION INCLUDES A NETWORK OF R QUARTZ QA FREQUENCY OSCILLATOR AND A LOW PASS FILTER F ELIMINATING THE FREQUENCY OF LESS THAN F OSCILLATOR. A DA POWER SPLITTER ALLOWS TWO BRANCHES SEND ISSU SIGNAL FEEDBACK LOOP ONE HAND AT THE ENTRANCE OF THE AMPLIFIER OSCILLATOR AND OTHER HAND TO AMP OUTPUT A. quadrupole QAQ ALLOW TO ADAPT TO iMPEDANCES INTO AND OUT OF THE AMPLIFIER, oSCILLATOR, THE fEEDBACK LOOP AND BOOSTER OUTPUT.

Compensating device of interference wave

Abstract: PURPOSE:To reduce the interferring radio wave returned to a receiving antenna from a transmission antenna via space by transmitting a pilot signal from the receiving antenna CONSTITUTION:A signal received on the receiving antenna 1 is a synthesis wave between a signal by a normal incoming radio wave and an interference signal gone round the space after the irradiation from the transmission antenna 2 Since the input signal of a relay amplifier 3 is added with a feedback signal via a feedback loop 4, the interference wave is reduced by cancelling the interference signal and the feedback signal That is, when the pilot signal of a single frequency is transmitted from the receiving antenna 1, it is extracted by a pilot signal detecting filter 11a, and the amplitude and phase of the feedback loop signal are controlled by detecting the cancelling residual component of the feedback loop signal and the interference signal, allowing to form automatically the optimum compensating condition

A Study of Pole Placement in Linear Control Design

Abstract: The design of linear control by pole placement in continuous time domain formulation has been investigated by many researchers. Numerous techniques have been proposed for the design of a proportional feedback law so that closed loop poles can be specified a priori. However, because many industrial processes are large dimensional systems with many states but very few measurements and controls, the number of poles that can be specified is severely limited. In practice, exact placement of the poles is not important but that all the poles must be placed to the left of the complex plane. This paper desribes a simple technique which generates a series of feedback laws that progressively shift the closed loop poles into 'faster response' region of the complex plane. The designer simply chooses one of these laws based on other considerations. It is demonstrated that the method is simple and effective in arriving at a suitable feedback control of a distillation column.

Diagnosing system of position feedback loop function

Abstract: PURPOSE:To decide a fault of a feedback loop when the contents of an error register are not set at zero after a dummy pulse is applied to the error register from a numerical controller to actuate a servo mechanism and then the contents of the error register are checked. CONSTITUTION:When a power supply is applied to a numerical controller, a prescribed number of dummy pulses are supplied to an error register 3 via an adder 2. The output of the register 3 undergoes a D/A conversion through a servo unit 4 and is amplified. Thus a motor 5 is revolved to set the contents of the register 3 at 0. The controller 1 reads the contents of the register 3 after a fixed time elapses. When the contents show 0, it is decided that a position feedback loop is nondefective. While a fault is decided with the feedback loop when the contents of the register 3 are not 0. Thus the power supply of the motor 5 is turned off, and an alarm is delivered. This check is possible at an optional time point with operation of a keyboard 8. Thus an assured diagnosis is possible to the position feedback loop, and the runaway is prevented with a servo system.

D-class amplifying circuit

Abstract: PURPOSE:To prevent the generation of distortions due to the interference of a side band wave to attain the negative feedback of a large quantity and to eliminate satisfactorily both carrier bands and noises, by separating a pulse modulator from a negative feedback summing point and at the same time inserting an LPF of a high order to a feedback line. CONSTITUTION:The audio signal applied to an input terminal IN is supplied to an analog amplifier 4 via an LPF10, and the output of the amplifier 4 is applied to a pulse width modulator 30-1 via an HPF20. The output of the modulator 30-1 is supplied to a power switching circuit 30-2, and the output of the circuit 30-2 is supplied to a load 3 via an LPF40. At the same time, the output of the circuit 30-2 is negatively fed back to the amplifier 4 via an LPF50 and a feedback circuit 5. Then a feedback loop formed by the LPF50 and the circuit 5 is separated from the LPF40 which eliminates carriers. The feedback quantity and the elimination factor of carrier band are set independently of each other. Then an HPF 20 which is smaller than the LPF40 by an order number is put into the feedback loop. This attains a large quantity of negative feedback.

Stabilization of elastic systems using sampled data feedback

Abstract: There is substantial interest in use of feedback control techniques to achieve active stabilization of elastic systems. Most previous research has focused on use of analog feedback techniques for achieving such stabilization. Use of sampled data output feed-back to achieve stabilization of an elastic system is examined in this work. The basic formulations are stated in terms of second order vector recursions. The suggested controller form consists of an output estimator and estimated output feedback. Sufficient conditions for closed loop stability are developed. A detailed development is given for the special case of an undamped finite dimensional elastic system. Two cases where the feedback depends only on velocity measurement data and only on displacement measurement data are considered. In each case explicit conditions on the gains are given for which the closed loop is guaranteed to be stable.

Digital speed control system with integral-proportional control

Abstract: A microprocessor based speed control system for a dc motor drive is described. The motor is fed by a three phase fully controlled bridge the delay angle of which is set directly by the microprocessor. To control the speed of the drive a PI control algorithm is implemented first and the experimental results are obtained for changes in the load torque and the reference speed. The proportional term of tae PI controller is then moved from the forward loop to the feedback loop, resulting in an I-P control algorithm. Experimental results are obtained and compared with the previous ones. It is seen that the I-P controller results in a better dynamic performance.

The relation between open loop and closed loop properties of multivariable feedback systems: A practical example

Abstract: In this paper previous results of the authors are used to analyze a design example.

Control system of feedback loop control system

Abstract: PURPOSE:To improve the response of a feedback loop by holding a minor feedback at zero when the controlled variable of a controlled system is smaller than a specific value. CONSTITUTION:When a detector 35 detects the differential value of a current being larger than a specific reference value, the detector 35 turns on a switch 34. Consequently, a current variation rate control loop is constituted, and the variation rate of the current is brought under feedback control under a current variation command Vrr. In this case, a limiter operates, so the absolute value of a current variation rate command becomes constant, so only the current variation rate control loop operates. The variation rate of the current decreases below the specific reference value by following up a command Vcr, and then the feedback signal of the current variation rate control loop goes down to zero through the turning-off operation of the switch 34, so that only the current control loop is left. The current variation rate loop is turned off to increase the gain of the current control loop.

LED linearisation for video bandwidth transmission employing a monolithically integrated PIN-PD

Abstract: Nonlinear distortion and frequency response for light-emitting diodes in analogue video transmission are greatly improved by using a wideband optoelectronic feedback loop employing monolithically integrated PIN photodiodes. Large monitoring efficiency of more than 2% makes it easy to realise this wideband and high-gain feedback loop.

Sampling measuring apparatus

Abstract: PURPOSE:To improve an operation speed, by a method wherein two integrators are prepared and changed over corresponding to ON-OFF state of a sampling pulse while a feedback loop corresponding to an ON-OFF state is fabricated in time-sharing to rapidly stabilize the integrators. CONSTITUTION:Sampling gate output is amplified by an amplifier 109 and receives offset in a circuit 110 to form a signal S3' is inputted to two integrator circuits 303, 304 by an analogue gate 301. The selection of the two integrator circuits, that is, ON-OFF of the circuit 301 is performed in synchronous relation to ON-OFF state of a signal S2. The difference of the output voltages of the integrator circuits 303, 304 are detected by a differential detector 305 to form a signal S4. When the signal S2 repeats ON-OFF at a cycle T and input is stepwise generated at time to, the response of the integrator circuits 303, 304 is changed only at a selection time but, as a whole, converged to a steady value by the time constant gamma of the integrator circuits. Therefore, the cycle of the modulation signal S2 can be selected without being restrained by the time constant of the feedback loop from sampling gate output voltage to a bias current.

Limitations on Feedback Properties Imposed by Unstable Open Loop Poles

Abstract: This paper expresses limitations upon feedback properties due to unstable open loop poles. These poles impose a tradeoff between desirable properties, such as sensor noise rejection, in different frequency ranges.

Graphical design of multistage feedback amplifiers

Abstract: This paper presents a semi-analytical graphical technique for stabilizing an initial unstable feedback amplifier by the addition of passive circuit components. The stabilized amplifier can be chosen to have a Butterworth, Bessel, or critically damped transfer function, as desired. Its bandwidth is restricted to somewhat less than the transistor f_{T} 's so that the transistors can be adequately represented by a hybrid- \pi or other rational model. The technique is applied to the design of a low-noise fiber-optic receiver front end capable of driving a 50-\Omega load, with the main feedback loop around the whole amplifier.

Call current supplying circuit

Abstract: PURPOSE:To supply stably a call current even in case of an area in which a call current is small, and to make a device small-sized by a conversion to an IC, by turning on and off a feedback loop for comparing a constant-current and a detecting current, by a control signal. CONSTITUTION:A pair of detecting circuits 16, 17 convert each voltage between connecting terminals 12, 13 to a subscriber's circuit and a DC power source 22 to a current by resistances 23, 24 and current mirror circuits 25, 26 and the converted current is supplied to an adding circuit 18, further an output current of the adding circuit 18 and a current of a constant-current source 19 are supplied to a feedback circuit 20 having a feedback loop, and this feedback loop is turned on and off by a control signal from a controlling circuit 29. When the feedback loop is turned off, a constant resistance feed by which a feed resistance of DC feeding circuits 14, 15 becomes constant is obtained, and in case the feedback loop is turned on, in an area in which a call current is small, a constant voltage feed by which voltage between the terminals 12, 13 becomes constant is obtained.

Influence of a time delayed speed feedback on an inverter-fed squirrel cage drive

Abstract: Drives with inverter fed squirrel cage motors, which demand high dynamic behaviour, normally use a direct feedback of rotor speed or rotor position. By inserting a unit with phase locked loop characteristic into the speed feedback loop, the torque will be reduced at fast acceleration on the motor. This effect can be used to improve the behaviour at slip/sliding of wheels in a traction drive. Inserting a phase locked loop in the speed feedback of a 1.4 MW traction drive we confirmed this principle of self-acting reduction of surplus torque. The reaction of the drive in the case of wheel-sliding is advantageous with regard to the reduction of torque achivable by a control loop with measurement of the acceleration rate.

Precision controller for rotating choppers

Abstract: A dc motor electronic controller, driving a rotating chopper, is presented. The controller uses an integral feedback technique, consisting of charging a storage capacitor by means of width modulated pulses. These pulses are obtained by comparing the revolution time of the chopper with a fixed time. It is shown that the steady‐state angular speed is independent both of the friction coefficient and the feedback loop gain. The stability condition of the feedback loop gain is also derived.