Feedforward Cancellation Research Articles

A Feed-Forward Power-Supply Noise Cancellation Technique for Single-Ended Class-D Audio Amplifiers

This paper presents a feed-forward power-supply noise cancellation technique to achieve high power-supply rejection ratio (PSRR) in single-ended class-D audio amplifiers. To show the effectiveness of the technique, it is implemented on a first-order single-ended pulse-width modulation (PWM) class-D amplifier. The implemented technique improves the PSRR from 20 Hz to 20 kHz independently of the close-loop compensator's filter-order. The design methodology, implementation, and tradeoffs for the proposed technique are provided. The fabricated class-D audio amplifier achieves a PSRR of 83 dB at 217 Hz, THD+N of 0.0149%, and a maximum efficiency of 94.6% from a 1.8-V power supply. Experimental results show a PSRR improvement of 33 dB from 20 Hz to 20 kHz compared to a similar amplifier designed without the technique. The prototype was implemented using 0.18- μm CMOS standard technology, and occupies a total area of 0.121 mm2. The total quiescent power consumption was 356 μW. The feed-forward power-supply noise cancellation technique enhances single-ended structures to achieve a PSRR performance comparable to differential architecture, and at the same time it consumes small quiescent power with a reduced active silicon area overhead.

A PSRR Enhancing Method for GRO TDC Based Clock Generation Systems

This paper discusses a supply noise sensitivity problem of the gated ring oscillator (GRO) based time-to-digital converter (TDC) in all-digital phase-locked loops (ADPLLs) and presents a power supply rejection ratio (PSRR) enhancing method. A replica supply noise monitoring circuit is designed to track supply noise and enable feed-forward error cancellation for high PSRR TDC design. A prototype ADPLL with the proposed self-monitored TDC is implemented in 65 nm CMOS to evaluate the supply noise sensitivity of the TDC in the frequency domain. Intermodulation spur generation problem due to noise coupling is also addressed and demonstrated in hardware. The experimental results show that the proposed method effectively suppresses supply noise induced spurs at the output of the ADPLL, achieving the PSRR of 27 dB and 38 dB with 1 MHz supply noise and 5 MHz intermodulation noise respectively.

A process-tolerant out-of-band blocker rejection technique for SAW-less receivers

In this paper, an active filtering technique is presented which is capable of filtering the out-of-band blockers in wireless receivers. The concept is based on the feedforward cancellation technique where a blocker replica is subtracted at the output of the low-noise amplifier (LNA). In contrast to the previously reported feedforward cancellation methods, exact gain and phase matching are easily obtained in the proposed architecture to produce a highly selective narrowband frequency response at the output of the LNA with wide rejection bandwidth. For the proof of concept, the system is implemented in a 65nm CMOS technology. It occupies a total area of 0.8mm2 and the current consumption is 24mA from a 1.2V supply. The system post-layout simulations showed a blocker rejection of more than 33dB for blocker signals 100MHz away from the desired signal when the feedforward path is activated. The noise figure (NF) of the entire system is 3.8dB that degrades to 5.8dB when the feedforward path is activated.

A study of equivalence between adaptive learning and loop shaping methods for disturbance compensation

AbstractThis paper introduces a theoretical analysis of the disturbance compensation methods in positioning systems. Thereare two major methods used to compensate for disturbances. The first one is based on a loop shaping method andthe second one is based on an adaptive learning method. We make a comparison between a resonant filter used asthe loop shaping method and an enhanced adaptive feed-forward cancellation (AFC) method used as the adaptivelearning method. To compensate disturbances, the resonant filter decreases the gain of the sensitivity function atthe disturbance frequency by using the vector locus. The adaptive learning method adjusts the coefficients of theenhanced AFC to compensate for a disturbance. We found that the LTI model of an enhanced AFC is the sameas that for a resonant filter when we compared their characteristics. A simulation of the disturbance compensationin a hard disk drive showed that these time responses and frequency responses coincided. Moreover, the resultsshowed advantages of each of the control methods with the exception of the performance. A resonant filter realizeslow cost implementation with compare to an enhanced AFC. That is, a resonant filter easier to implement than anenhanced AFC. An enhanced AFC has the utility to realize a high quality function control system simultaneouslyable to compensate and estimate for disturbances. The results of the evaluation in this study will provide designengineers with guidelines for selecting an optimum control strategy in actual applications.Key words : Disturbance compensation, Periodic disturbance, Non-periodic disturbance, Adaptive feed-forward

Robustness analysis of enhanced adaptive feed-forward cancellation

This paper presents a robustness analysis of an enhanced adaptive feed-forward cancellation (AFC) function for a control system. The AFC is known as an adaptive control method, and the adaptive algorithm can estimate a periodic disturbance. In a previous study, an enhanced AFC was developed to compensate for non-periodic disturbances. The effectiveness of the enhanced AFC there was shown with only simulation results. In this study, the stable robustness of the enhanced AFC is analyzed for a one degree of freedom system. When the enhanced AFC is implemented to around a resonant frequency, the variations in the mechanical characteristics may cause instabilities in the control system, because the performance of the enhanced AFC depends on the phase condition of the mechanical characteristics. The experimental results show that variations in the resonant frequency may cause oscillation when the enhanced AFC design does not consider this kind of variation. The study confirms that the enhanced AFC must be designed considering variations in the resonant frequency.

Rolling bearing-suspended spindle run-out control using repetitive control and adaptive feedforward cancellation

The wettability, friction, adhesion, and optical characteristics of a surface are affected by its micro-topography. In turn, the characteristics of a surface micro-topography can be determined by controlling the trajectory of a cutting tool mounted on a spindle. However, this method is constrained by the tool’s cutting accuracy, which is limited by the run-out error and thermal behavior of the spindle. In this work, an electromagnetic actuator (EMA) is installed at the end of the spindle to compensate for the spindle run-out error and the thermal displacement in real time. The spindle system model includes a cross-coupled stiffness and damping term for the ball bearings. Repetitive controller (RC) reduces the repeatable run-out (RRO) while adaptive feedforward cancellation (AFC) reduces the non-repeatable run-out (NRRO). The control system uses a zero phase error tracking controller (ZPETC) to compensate for its total phase delay. Experimental results show a 70% reduction in run-out error at rotation speeds of 6,000 rpm and 12,000 rpm. The thermal displacement in the radial direction is regulated within a range of 1 µm for more than 3 hours.

Adaptive Control of Positioning Systems With Hysteresis Based on Magnetic Shape Memory Alloys

This paper considers a control strategy for systems affected by time-varying hysteretic phenomena, such as those observed in magnetic shape memory alloys subject to temperature variations. The proposed controller is based on a scheme that combines feedforward cancellation of the hysteresis using a modified Prandtl-Ishlinskii inverse model with a closed-loop control law designed to address the cancellation errors. Both the inverse hysteresis model and the closed-loop law feature adjustable parameters that are adapted online by means of learning laws based on Lyapunov design tools. The effectiveness of the proposed approach is confirmed by experiments on a prototypical micrometric positioning system containing a bar of MSMA as main actuating element.

A CMOS Transmitter Leakage Canceller for WCDMA Applications

A transmitter (TX) leakage canceller is proposed for improving the dynamic range of the receiver (RX) for wideband code division multiple access applications. A TX leakage canceller circuit in this paper is simple in implementation and has low noise figure (NF) contribution. It is a feed-forward canceller that samples a reference signal from the TX output and injects the amplitude-adjusted and phase-rotated signal to the RX chain. The canceller circuit is integrated with a low-noise amplifier and implemented in a 0.18-μm CMOS technology. A cancellation of 23 dB is achieved with only 10-mA current consumption increase and low NF increase.

Hybrid adaptive feedforward cancellation against time‐varying discrete systems with non‐stationary random periodic disturbance

This study presents a novel hybrid adaptive feedforward cancellation (AFC) methodology in particular for time-varying discrete systems with stochastic periodic disturbance. The proposed hybrid AFC framework is composed of conventional AFC modules and auxiliary PID control variables. The former is traditionally constructed with sinusoidal functions and parameters of the AFC system, and the latter is added for compensating perturbation because of non-stationary random disturbance in practice. The authors derive an estimation algorithm of parameters in the hybrid AFC system by using a gradient descent based optimisation method. In addition, a theoretical investigation is conducted for verifying convergence property of the parameter estimation by means of a well-known Lyapunov stability theory. Lastly, the authors achieve numerical simulation to prove reliability and superiority of the proposed AFC algorithm by comparing to a conventional AFC approach.

C-1-3 Adaptive feed-forward cancellationに基づくセルフセンシング・モデルフリー振動制御(情報・精密機器のサーポ・スマート制御,口頭発表)

C-1-3 Adaptive feed-forward cancellationに基づくセルフセンシング・モデルフリー振動制御(情報・精密機器のサーポ・スマート制御,口頭発表)

Improvement of Convergence for Adaptive Feed-Forward Cancellation Using Variable Gains in a Head Positioning System of Hard Disk Drives

AbstractWe present an enhanced adaptive feed-forward cancellation (AFC) with variable gainsto be used in the head positioning control system of a hard disk drive (HDD). Thevariable gains can help to improve the convergence characteristic of the enhanced AFCafter the track seeking control. Therefore, the proposed enhanced AFC can improvethe transient response of the head positioning after the track seeking control. Thetrack seeking simulation results from HDDs showed that the proposed control methodcompensated for the disturbances caused by the repeatable run-out (RRO) and airflow-induced vibration immediately after the track seeking control.Key words 1. Introduction The rapid growth in demand for a larger data capacity requires an increase in the arealdensity of hard disk drives (HDDs). The head positioning control system of an HDD mustcompensate for any disturbances, because increasing the track density requires improvingthe head positioning accuracy in the head positioning control system of an HDD

Development of Optimized Adaptive Feed-Forward Cancellation with Damping Function for Head Positioning System in Hard Disk Drives

This paper presents an adaptive feed-forward cancellation (AFC) technique with a damping function based on optimized AFC. The proposed AFC includes a mechanical resonance characteristic as an internal model that is realized by using the damping function and that achieves the best performance in the frequency domain. This makes it possible to apply the proposed AFC to suppress not only repeatable run-out (RRO) but also non-repeatable run-out (NRRO) of the head positioning system in hard disk drives. Simulation results showed that the proposed AFC can suppress NRRO such as disk flutter vibration and that the stability of the feedback loop was improved by the damping function.

Guidelines for the design and implementation of the ARPCC control applied to grid-connected converters

This paper presents implementation details of the adaptive robust predictive current control (ARPCC) applied to a grid-connected converter, such as feed-forward cancellation protocol, the selection of the observer gain and adaptive parameters or the sampling options, needed to get the best performance of this control. The feed-forward term cancellation permits to achieve a very low harmonic distortion in current waveforms when the voltage sensing circuits are well calibrated. A detailed gain adjustment protocol of the voltage sensing circuits is presented in this paper. Moreover, a control design procedure based on the observer gain Lo boundaries and the adaptive parameters has been presented and experimentally tested. Finally, different sampling options in the analog-to-digital conversion process are presented, offering programming solutions to achieve the higher stability margins or a compromise between stability margins and time available for other DSP operations.

Fractional Order Adaptive Feed‐Forward Cancellation for Periodic Disturbances

AbstractIn this paper, a fractional order adaptive feed‐forward cancellation (FO‐AFC) scheme is proposed to cancel periodic disturbances. This FO‐AFC offers one more tuning knob, the fractional order, for the performance improvement of the periodic disturbance cancellation, according to the interests of the users. The equivalence of the fractional order internal model principle (FO‐IMP) scheme is derived for FO‐AFC. So, the FO‐IMP equivalence can be used to analyze the performance of the cancellation for the target periodic disturbance and the suppression for the harmonics and noise. Two FO‐AFC cases, fractional order α ∈ (0, 1) and α ∈ (1, 2), are discussed for the performance analysis. FO‐AFC with additional tuning knob α ∈ (0, 2) has many advantages, and it is much more flexible than the integer order adaptive feed‐forward cancellation (IO‐AFC) with only α = 1. Experimental results are presented to validate the performance analysis of FO‐AFC compared with IO‐AFC.

Optimization of adaptive feedforward repeatable run-out cancellation for positioning control system of hard disk drives

To increase the recording density of hard disk drives, suppression of the disturbances is essential. In this paper, we focus on the suppression of repeatable run-out. This paper presents the design method of an adaptive feedforward cancellation (AFC) which can suppress a periodic disturbance. AFC is adaptive filter. The algorithm can be converted into a linear time-invariant (LTI) model. The LTI model is considered to be a peak filter for a closed loop system. Therefore, parameters of AFC should be designed in consideration of a closed loop characteristics. The proposed method can design the parameters that can achieve a vector locus to recede from the critical point [− 1, 0] on the Nyquist diagram. As a result, convergence performances and stability performances of AFC are optimized in frequency domain. The effectiveness of the proposed method is verified by the simulations and experiment of the hard disk drive.

Robust Analog Canceller for High-Dynamic-Range Radio Frequency Measurement

An automated analog canceller is presented that uses feedforward cancellation in a bridge configuration. A minimum of 70 dB of analog cancellation is obtained. The canceller is used to construct an intermodulation distortion measurement system achieving up to 120 dBc of intermodulation dynamic range in two-port transmission testing and 140 dBc of intermodulation dynamic range in one-port reflection testing for frequency separations of at least 1 kHz. At a two-tone frequency separation of 1 Hz, the respective dynamic ranges are at least 94 and 111 dBc. The relationship of cancellation performance and dynamic range is examined in terms of application-specific definitions of dynamic range. The system is then used to measure passive intermodulation distortion using a two-tone test with a tone frequency separation from 1 Hz to 100 MHz.

Design Method Considering Phase Condition for Adaptive Feedforward Cancellation

Design Method Considering Phase Condition for Adaptive Feedforward Cancellation

High Frequency Harmonic Cancellation in Ball-screw Drives

In many machining processes cutting forces are of harmonic nature. The frequency content of these forces may extend far beyond the closed-loop bandwidth of the commonly used feed drive controllers. In ball screw drives, high–frequency disturbances may also originate from repetitive errors synchronized with the rotation of the ball screw. To improve the track following and disturbance rejection performance of the controller at selected frequencies, the use of Adaptive Feedforward Cancellation (AFC) method has been proposed in this paper. Tuning of AFC parameters for achieving a good performance and robustness is discussed, and experimental results from high-speed tracking and metal cutting tests are provided to demonstrate the effectiveness of the proposed method in cancelling out the effect of harmonic disturbances.

A robust adaptive feedforward control in repetitive control design for linear systems

This paper proposes a new adaptive feedforward cancellation (AFC) control that achieves periodic tracking and/or periodic disturbance rejection. The new control design is a direct scheme in the sense that it adaptively updates the desired control without estimating the unknown disturbance. The proposed new control has several advantages. First, its adaptation gain can be arbitrarily chosen without upsetting the system stability if given the exact system model. Second, it can be applied to not only minimum-phase systems, but also non-minimum phase systems. Third, the new control law is independent of where the disturbance enters the system. Finally, a robustness analysis is made to show that the proposed control is robust with respect to un-modelled dynamics.

A new adaptive control for periodic tracking/disturbance rejection

This paper proposes a new adaptive feedforward cancellation (AFC) control that achieves periodic tracking and/or periodic disturbance rejection. The new control design is a direct scheme in the sense that it adaptively updates the desired control without estimating the unknown disturbance. The proposed new control has several advantages. First, its adaptation gain can be arbitrarily chosen without upsetting the system stability. Second, it can be applied to not only minimum-phase systems, but also non-minimum phase systems. Finally, it is shown that the proposed AFC control is independent of where the disturbance enters the system. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society