Adaptive Gain Control Research Articles

Variable Upper Bounding Approach for Adaptive-Robust Control in Robot Control

This paper presents a new adaptive-robust control law for robot manipulators with parametric uncertainty. Stability of the uncertain system has been guaranteed using the Lyapunov theory and the control law is derived by means of analytical approach. In this scheme, the manipulator parameters are determined with an estimation law, and both adaptive gain and additional control input are also updated as a function of the estimated value. The proposed adaptive control input includes a parameter estimation law as an adaptive controller and an additional control input vector as a robust controller. The developed approach has the advantages of both adaptive and robust control laws, and besides it eliminates the disadvantages of them.

Saccadic adaptation in the horizontal and vertical directions in normal subjects

We studied the properties of adaptive gain control in the saccadic system and examined whether the adaptations in the horizontal direction transferred to those in the vertical direction, and vice versa, in 16 normal subjects. Eye movements were measured using search coil system. In the adaptive session, a target moved randomly in amplitude steps of 20° or 30°, with half of the subjects performing in the horizontal direction and the others in the vertical direction. The target eccentricity was changed by a constant percentage (70%) during each saccade aimed at the target. Gains were gradually decreased during the course of 120 repetitions, and then approached approximately 70%. Comparison was made of the accuracy (saccadic amplitude/first target step amplitude) of horizontal and vertical vectors of oblique saccades before and after the adaptation. After the horizontal adaptation, the accuracy of horizontal vectors decreased in the horizontal direction ( P<0.05) but not in the vertical direction. After the vertical adaptation, however, the accuracy of horizontal and vertical vectors did not decrease. Our data show that adaptive gain control in the horizontal direction might not transfer to that in the vertical direction, nor vice versa.

Hamiltonian modelling and nonlinear disturbance attenuation control of TCSC for improving power system stability

To tackle the obstacle of applying passivity-based control (PBC) into power systems, an affine non-linear system widely existing in power systems is formulated as a standard Hamiltonian system using a pre-feedback method. The port controlled Hamiltonian with dissipation (PCHD) model of TCSC is then established corresponding with a revised Hamiltonian function. Furthermore, employing the modified Hamiltonian function directly as the storage function, a non-linear adaptive L2 gain control method is proposed to solve the problem of L2 gain disturbance attenuation for this Hamiltonian system with parametric perturbations. Finally, simulation results are presented to verify the validity of the proposed controller.

オブザーバを用いた適応ゲインコントローラによる未知パラメータを含む線形システムに対するロバスト制御

オブザーバを用いた適応ゲインコントローラによる未知パラメータを含む線形システムに対するロバスト制御

Physiological and pharmacological properties of GABA-ergic gain modulation of canine ventral respiratory group (VRG) neurons

In vivo local application of the selective GABAA receptor antagonist bicuculline methochloride (BIC) to respiratory neurons in the caudal VRG of dogs produces a profound increase in their discharge frequency (Fn) pattern. The resulting Fn pattern is an amplified replica on the underlying control Fn pattern even when the pattern is reflexly altered, for example by lung inflation, or enhanced by changes in chemodrive [1]. These results suggested the presence of a tonic GABAergic gain modulation (GM) that normally attenuates the pattern to typically less than 50% of the Fn unblocked pattern. This multiplicative process can be modeled as: Fout = (1-α)*Fin, where Fout and Fin are the instantaneous Fns in the presence and absence of GABAergic inhibition, respectively, and α is the relative magnitude of tonic inhibition. The pharmacology of this mechanism is unusual in that picrotoxin, a noncompetitive GABAA receptor antagonist, does not produce GM, but is able to block the silent phase inhibition [2]. Also, recent in vitro studies have shown that the methyl derivatives of bicuculline block spike afterhyperpolarizations (AHPs) mediated by small conductance Ca2+ activated K+ channels (SK) [3]. The main objective of this study was to compare the in vivo effects of BIC with those of the SK channel blocker apamin on endogenously- (spontaneous) and exogenously-induced neuronal activities to discern the mechanism for BIC effects. Multibarrel micropipettes were used to record single unit activity from cVRG neurons in decerebrate dogs before and during picoejection of agonists and antagonists. Cycle-triggered histograms were used to quantify the Fn patterns and to determine the drug-induced changes in the gain and offset of the spontaneous Fn patterns. For the exogenous aspect of the study, the net increase in Fn due to repeated short duration picoejections of the glutamate receptor agonist, α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), was quantified before and during locally induced antagonism of 1) GABAA receptors by BIC or 2) SK channels by apamin. BICm and apamin produced similar marked increases in gain, but different offsets. During maximum SK channel block with apamin, BICm produced an additional 112 ± 22% increase in peak Fn. Conversely, apamin produced an additional 176 ± 74% increase in peak Fn during the maximum BICm-induced response. The net AMPA-induced increases in Fn were not significantly altered by BIC, but were amplified in accordance with the gain increase produced by apamin block of AHPs. These results suggest that the BIC-sensitive GM of canine cVRG neurons is not due to a nonspecific block of AHPs, but is due to a GABAergic mechanism that modulates endogenously-, but not exogenously-induced activity. GABAergic GM, acting possibly via a shunting inhibition, may be functionally isolated from the soma/spike initiation zone to allow multiple nonrespiratory behaviors to be expressed by the same neurons, while providing adaptive respiratory gain control.

Dropout compensation in magnetic tape channels by adaptive equalization and coding

A simple adaptive extended partial response IV (EPR4) equalizer with an adaptive gain controller driven by a threshold detector with relaxed thresholds can be applied effectively on fading tape channels. The equalizer closely approximates the performance of the optimal EPR4 equalizer. Other EPR4 equalizers with certain advantageous features (the EPR4 equalizer with decision feedback and the PW/sub 50/-based EPR4 equalizer) are also studied. The parallel concatenated parity check (PCPC) code with iterative decoding is quite effective in mitigating the dropout effect. The complexity/performance tradeoffs of the PCPC code seem favorable compared to the low-density parity check code or to the turbo code.

Implementation of the Takagi-Sugeno model-based fuzzy control using an adaptive gain controller

A fuzzy controller of the type of the Takagi–Sugeno model is investigated. The proposed adaptive gain controller for Takagi–Sugeno fuzzy control, which results from the direct adaptive approach, is employed to directly adapt the appended gain parameters in the THEN-part of the Takagi–Sugeno model. Then, the constructed Takagi–Sugeno fuzzy controller can be best approximated to a given optimal control. Generally speaking, a complicated design procedure is necessary to determine the parameters in the Takagi–Sugeno fuzzy controller, but the number of parameters in THEN-part is proportional to the number of rules and states. However, in this study, the THEN-part of each rule with only an injected parameter could be adapted to determine the control action of each rule. The best merits of the proposed method are that the number of regulated parameters depends on the number of rules, and the design algorithm is implemented more easily than existing approaches. In addition, a maximum control is established to guarantee the system robust stability. The derivation shows that the proposed controller is stable in the sense of Lyapunov. Finally, a nonlinear system simulation example is applied to verify the effectiveness and ability of the proposed controller.

A control strategy for general-purpose active filters based on voltage detection

A new control strategy to realize general-purpose active filters based on voltage detection is proposed as an economical solution to harmonic compensation in distribution lines. The proposed control method is based on real-time digital simulation of an LC filter accomplished by a digital signal processor. The adaptive gain control to realize the automatic online adjustment of the compensating characteristics is introduced. This achieves the optimum operation according to the condition of the AC lines. Thus, the proposed active filter can be used as a general-purpose active filter. In this paper, the compensation characteristics of plural units of the proposed active filters connected to a distribution line are investigated. The theoretical investigation of the compensation characteristics is presented. Furthermore, to confirm the effectiveness of the proposed control strategy, some experimental results employing a test system are included.

Adaptive sampling control of high-gain stabilizable systems

It is well known that proportional output feedback control can stabilize any relative-degree one, minimum-phase system if the sign of the feedback is correct and the proportional gain is high enough. Moreover, there exist simple adaptation laws for tuning the proportional gain (so-called high-gain adaptive controllers) which do not need to know the system and do not attempt to identify system parameters. The authors consider sampled versions of the high gain adaptive controller. The motivation for sampling arises from the possibility that the output of a system may not be available continuously, but only at sampled times. The main point of interest is the need to develop techniques for adapting the sampling rate, since the stiffness of the system increases as the proportional gain is increased. Our main result shows that adaptive sampling stabilization is possible if the product hk of the decreasing sampling interval h and the increasing proportional gain k decreases at a rate proportional to 1/log k.

Performance of a fast frequency-hopped noncoherent MFSK receiver with nonideal adaptive gain control

An error probability analysis is performed for an orthogonal noncoherent M-ary frequency-shift keying (MFSK) communication system employing fast frequency-hopped (FFH) spread spectrum with diversity. The signal is assumed to be transmitted through a frequency-nonselective slowly fading channel with partial-band noise interference. The partial-band interference is modeled as a Gaussian process. Both the information signal and the partial-band noise interference signal are assumed to be affected by channel fading; it is assumed that the two fading processes are independent and that channel fading need not necessarily affect the information signal and the interference signal in the same way. Each diversity reception is assumed to fade independently according to a Rician process. Adaptive gain control is employed to minimize partial-band interference effects, and the effect of inaccurate noise measurement on the ability of the adaptive gain control receiver to reject partial-band interference is examined. The effect of thermal noise is included in the analysis.

High-performance CMOS buffered gate modulation input (BGMI) readout circuits for IR FPA

A new CMOS current readout structure for the infrared (IR) focal-plane-array (FPA), called the buffered gate modulation input (BGMI) circuit, is proposed in this paper. Using the technique of unbalanced current mirror, the new BGMI circuit can achieve high charge sensitivity with adaptive current gain control and good immunity from threshold-voltage variations. Moreover, the readout dynamic range can be significantly increased by using the threshold-voltage-independent current-mode background suppression technique. To further improve the readout performance, switch current integration techniques, shared-buffer biasing technique, and dynamic charging output stage with the correlated double sampling circuit are also incorporated into the BGMI circuit. An experimental 128/spl times/128 BGMI readout chip has been designed and fabricated in 0.8 /spl mu/m double-poly-double-metal (DPDM) n-well CMOS technology. The measurement results of the fabricated readout chip under 77 K and 5 V supply voltage have successfully verified both readout function and performance improvement. The fabricated chip has the maximum charge capacity of 9.5/spl times/10/sup 7/ electrons, the transimpedance of 2.5/spl times/10/sup 9/ /spl Omega/ at 10 nA background current, and the arrive power dissipation of 40 mW. The uniformity of background suppression currents can be as high as 99%. Thus, high injection efficiency, high charge sensitivity, large dynamic range, large storage capacity, and low noise can be achieved In the BGMI circuit with the pixel size of 50/spl times/50 /spl mu/m/sup 2/. These advantageous characteristics make the BCMI circuit suitable for various IR FPA readout applications with a wide range of background currents.

Maximum-likelihood diversity combining in partial-band noise

Maximum-likelihood diversity combining is investigated for an FFH/MFSK spread spectrum system in partial-band noise (PBN). The structure of maximum-likelihood diversity reception in PBN plus white Gaussian noise is derived. It is shown that signal-to-noise ratio and the noise variance at each hop have to be known to implement this optimum diversity combiner. Several suboptimum diversity combining schemes are also considered. The performance of the optimum combining scheme is evaluated. It is shown that adaptive gain control diversity combining actually achieves the optimum performance when interference is not very weak.

Adaptive Stabilization of Minimum Phase Plants with Relative Degree n or n+1

This paper proposes a robust high gain adaptive stabilization of minimum phase plants with its relative degree n or n+1. The proposed method uses the fact that any minimum phase plant with its relative degree zero or one can be stabilized by a high gain adaptive control and extends this result by using backstepping. The σ-modification is applied in order to avoid an unnecessarily high gain feedback.

Adaptive Stabilization of any Minimum Phase Plant with Relative Degree N or N + 1

This paper proposes a robust high gain adaptive stabilization of any minimum phase plant with its relative degree n or n + 1. The proposing method uses the fact that any minimum phase plant with its relative degree zero or one can be stabilized by a high gain adaptive control and extends this result by using backstepping. The σ-modification is applied in order to avoid an unnecessarily high gain feedback.

Neural mechanisms of adaptive gain control in a joint control loop: muscle force and motoneuronal activity

An adaptive gain control system of a proprioceptive feedback system, the femur&shy;tibia control loop, is investigated. It enables the joint control loop to work with a high gain but it prevents instability oscillations. In the inactive stick insect, the realisation of specific changes in gain is described for tibial torque, for extensor tibiae muscle force and for motoneuronal activity. In open-loop experiments, sinusoidal stimuli are applied to the femoral chordotonal organ (fCO). Changes in gain that depend on fCO stimulus parameters (such as amplitude, frequency and repetition rate), are investigated. Furthermore, spontaneous and touch-induced changes in gain that resemble the behavioural state of the animal are described. Changes in gain in motoneurones are always realised as changes in the amplitude of modulation of their discharge frequency. Nevertheless, depending on the stimulus situation, two different mechanisms underlie gain changes in motoneurones. (i) Changes in gain can be based on changes in the strength of the sensorimotor pathways that transmit stimulus-modulated information from the fCO to the motoneurones. (ii) Changes in gain can be based on changes in the mean activity of a motoneurone by means of its spike threshold: when, during the modulation, the discharge of a motoneurone is inhibited for part of the stimulus cycle, then a change in mean activity subsequently causes a change in modulation amplitude and gain. A new neuronal mechanism is described that helps to compensate the low-pass filter characteristics of the muscles by an increased activation, especially by a sharper distribution of spikes in the stimulus cycle at high fCO stimulus frequencies.

Activity-dependent regulation of neural networks: the role of inhibitory synaptic plasticity in adaptive gain control in the siphon withdrawal reflex of Aplysia.

Activity-dependent regulation of neural networks: the role of inhibitory synaptic plasticity in adaptive gain control in the siphon withdrawal reflex of Aplysia.

An adaptive gain control with a variable step size for use in high-speed data communication systems

A high-precision adaptive gain control is an important function in high-speed data communication systems. The nonsymmetric statistics of the received signal results in a biased value of gain, particularly if 2B1Q line code is used, which contains a periodically repeated synchronization word, i.e., a Barker sequence. A bias-free gain is obtained using a step size that depends on the statistics of the received signal. The additional computations may be successfully approximated by shift-add operations.

Directional ear device with adaptive bandwidth and gain control

An ear device protects a user from damaging sound levels while permitting the user to hear and understand conversation in a noisy environment. The device includes an enclosure system for at least partially isolating the user's ear drums from ambient sounds, at least on directional microphone, an adaptive band pass filter and a speaker. The adaptive band pass filter further includes adaptive high pass and adaptive low pass filters which adaptively and independently control the range of the pass band depending upon the characteristics of the noise in the user's environment. A speaker transmits the processed signal to the user. The adaptive filter also includes a detector connected to receive the processed signal which controls the gain of the system to prevent overcompression of the audio signal. The adaptive filter further includes an adaptive compression circuit utilizing multiple time constants to control the response time of the adaptive filter under various conditions.

Saturation revealed by clamping the gain of the retinal light response.

The saturation nonlinearity of the retinal light response in human was measured by a psychophysical technique in which the adaptive gain control mechanism was clamped by the presence of a fixed surround in a small (7') foveal test field. Gain clamping was established by showing that the normal variation in temporal summation properties with test intensity was abolished in the gain clamping paradigm. The static saturation function constructed from the increment/decrement asymmetries around a range of base intensities was shown to conform more closely to the Naka-Rushton hyperbolic saturation equation than to three other candidate nonlinearities.

Kinematic analysis of eyelid movements in patients recovering from unilateral facial nerve palsy.

We assessed eyelid function by subjective clinical examination and quantitative means in patients recovering from facial nerve palsy. Electromagnetic search coil techniques were used to record the concurrent movements of the two eyelids to study alterations in blink main sequence (peak velocity versus amplitude) relationships and interocular differences in eyelid kinematics. After onset of unilateral palsy, the paresis of eyelid closure showed varying degrees of recovery. Adaptive increases in blink main sequence slope contributed to maximizing closure of the paretic eyelid. However, blink adaptation mechanisms must operate bilaterally, as there also was evidence of altered main sequence slope in the nonparetic eyelid. In general, main sequence slope was inversely related to the level of eyelid paresis. The highest indices of blink adaptation were in those patients with moderate paresis, and main sequence slope was decreased in those patients with increasing degrees of recovery. The assessment of eyelid function with search coil techniques provides a sensitive means of monitoring disease and treatment course. Data also aid understanding of adaptive gain control in the neural control of blink in health and disease.