Ramp Signal Research Articles

Control for transformation of afour wheeled to two wheeled mobile robot

This paper proposes a study on the linearization of a four wheeled mobile robot with wheel arms, its behavior with a variable structure control for both linearized system and nonlinear system when it transform to two wheeled inverted pendulum state from four wheeled state. It also proposes a control technique to stabilize the system in inverted pendulum mode after the system transforms. Since the system have to reach the target stable state from initial state a nonlinear sliding mode controller is used for transformation mean while taking the velocity of the system into consideration and sub-optimal methods are used to minimize switching-function chattering. To stabilize the system in the inverted pendulum mode, an LQR controller has been implemented. Also the position tracking and behavior of the system using a ramp signal is studied. The transformation and movement of the robot could be achieved by two DC motors on each side of the robot.

FMCW SAR System for Near-Distance Imaging Applications—Practical Considerations and Calibrations

A combination of frequency-modulated continuous-wave (FMCW) technology with a synthetic aperture radar (SAR) technique is a highly sought after method, which leads to a compact and cost-effective imaging system, for near-distance target imaging. One of the limiting factors of FMCW radars is that the ramp signal modulates the received signal, which limits the minimum achievable range resolution. In addition, the voltage-controlled oscillator (VCO) adds a certain degree of phase noise and nonlinearity to the transmitted signal that degrades the signal-to-noise ratio, range accuracy, and image resolution. This paper presents a signal processing procedure with system calibration methods to mitigate the effect of deramp, phase noise, and nonlinearity of the VCO on the beat spectrum. Additionally, the effect of phase noise of the received signal on the SAR image resolution in both range and cross-range directions is comprehensively studied. To improve the range accuracy, different calibration methods are proposed. An $S$ -band homodyne FMCW radar system, using off-the-shelf components, is designed for near-distance target imaging using linear and circular SAR techniques. The reconstructed images show the improvement of image quality and accuracy in target position.

A design of single-switch two-stage DC-DC converters with PWM and PFM for off-grid solar power system

In this paper, a single-switch two-stage DC-DC conversion circuit is proposed for an off-grid solar power application. A photovoltaic(PV) panel powers the load and a storage unit(battery) via the proposed circuit. The battery is designed to balance the supply and the demand of power under different irradiation situations. Based on conventional cascaded DC-DC converters, the proposed design is developed with the single switch technique reducing size, cost and power loss. The control scheme in this design is pulse width modulation(PWM) with pulse frequency modulation(PFM). The PWM module is similar to conventional design except its ramp signal with a variable frequency is provided by a resettable integrator. As a result, the PWM and PFM modules regulate the two stages of the proposed circuit separately with the same switching control signal. In this paper, the modes of operation of the circuit are discussed as well as the control schemes. The design process is described along with the circuit analysis and comparisons with conventional design are made as well. A prototype has been built to verify the proposed circuit with simulation and experimental results.

A Low-cost Dithering Method for Improving ADC Linearity Test Applied in uSMILE Algorithm

Analog-to-digital converters (ADCs) are an important component in electronics design. One of the difficulties being faced is to be able to accurately and cost-effectively test the continually higher performance of ADCs under budget constraints. Test time for static linearity is a major portion of the total test cost. Our group proposed an ultrafast segmented model identification of linearity error (uSMILE) algorithm for estimating linearity, which reduces test time dramatically compared to the conventional method. However, this algorithm produces large estimation errors in low resolution ADCs (10-12 bits) when the input is a ramp signal, for which the quantization noise of ADC becomes a dominant part in the total noise. In this study, we propose three types of distribution dithering methods added to the ramp input signal to reduce the estimation error when uSMILE was applied to low resolution ADCs. Fixed pattern was proved to be the most efficient and cost-effective method by comparing with the Gaussian, uniform, and fixed-pattern distributions. The simulation results indicate that the estimation error can be significantly reduced in a 12-bit SAR ADC with effective dithering. Furthermore, a hardware evaluation board with commercial ADC products was used to validate the effectiveness of the fixed-pattern dithering methods, and our measurement shows the INL estimation error can be reduced to less than 0.1 LSB. Such dithering method relaxes the input requirement of uSMILE algorithm which dramatically reduces the test setup cost.

Influence of Design Reference on Tracking Performance of Feedback Control

In this paper, we present an investigation on the tracking performances of feedback control as a function of reference signals. We use multi-objective optimal designs of feedback controls as a fair basis for comparing different control designs, and examine step, ramp, and periodic signals at various frequencies. Through comparing the tracking performances of controls designed with different reference signals, we find that the controls designed with ramp signals perform better in tracking step and ramp references than those designed with step signals. To track periodic signals, we find that the controls designed with periodic signals at the same frequency generally provide the best performance, and those designed with step and ramp signals perform comparably.

Effect of ADC Resolution on Low-Frequency Electrical Time-Domain Impedance Spectroscopy

AbstractIn this paper, the effect of the resolution of an analogue-to-digital converter (ADC) on the accuracy of timedomain low-frequency electrical impedance spectroscopy is examined. For the first time, we demonstrated that different wideband stimuli signals used for impedance spectroscopy have different sensitivities to the resolution of ADC used in impedance spectroscopy systems. We also proposed Ramp and Half-Gaussian signals as new wideband stimulating signals for EIS. The effect of ADC resolution was studied for Sinc, Gaussian, Half-Gaussian, and Ramp excitation signals using both simulation and experiments. We found that Ramp and Half-Gaussian signals have the best performance, especially at low frequencies. Based on the results, a wideband electrical impedance spectroscopy circuit was implemented with a high accuracy at frequencies bellow 10 Hz.

10-1 高精細CMOSイメージセンサ用カラムA/D変換器のための小面積低消費電力カラム分散型ランプ信号生成回路(第10部門情報センシング1)

10-1 高精細CMOSイメージセンサ用カラムA/D変換器のための小面積低消費電力カラム分散型ランプ信号生成回路(第10部門情報センシング1)

An 802.11a/b/g/n Digital Fractional- $N$ PLL With Automatic TDC Linearity Calibration for Spur Cancellation

A fractional-N digital phase-locked loop (PLL) architecture with low fractional spur is presented in this paper. A 2-D Vernier time-to-digital convertor (TDC) is implemented to achieve wide detection range with fine resolution. The TDC is calibrated automatically utilizing the ramp signal generated from the fractional-N accumulator for optimal linearity. A digi-phase spur cancellation technique with automatic TDC gain tracking is also implemented to further suppress the fractional spurs. The chip also includes an improved multimodulus divider (MMD) structure that overcomes the glitch problem during division ratio toggling associated with the prior art MMDs, enabling carrier synthesis across wide frequency range continuously. As part of an 802.11a/b/g/n transceiver, the DPLL can provide coverage for both 2.4/5 G WiFi bands. The proposed fractional-N DPLL is implemented in a 55-nm CMOS technology. The DPLL achieves a largest fractional spur level of −55 dBc without using a sigma–delta modulator and an in-band phase noise of −107 dBc/Hz (0.55 ps integrated jitter) while consuming 9.9 mW.

Inertia Identification and PI Parameter Tuning of PMSM Servo Drives

The goal of this paper is to improve the performance of permanent magnet synchronous motor(PMSM) servo system by identification of the inertia parameter and auto-tuning of PI parameters. The method relies on the speed acceleration and deceleration response produced by speed ramp signals applied to a speed-controlled servo. The proposed method relies on simple numerical calculations, thus make the proposed scheme more practical. After the knowledge of the inertia parameter, the tuning of the speed control loop can be performed. The experimental results verified that the proposed identification scheme can estimate inertia parameters accurately and effectively and the control system tuned can achieve good dynamic performance.

Ultracompact 160-GHz FMCW Radar MMIC With Fully Integrated Offset Synthesizer

The dynamic range of frequency modulated continuous wave (FMCW) radar sensors is often limited by the phase noise of the ramp signal. Especially at millimeter wave (mm-wave) frequencies, a low phase noise signal is very difficult to obtain. In this paper, a new system architecture, which is implemented in a low-cost, ultracompact FMCW radar monolithic microwave integrated circuit (MMIC) at 160 GHz, is proposed to address this topic. The approach is based on a frequency offset synthesizer, whose upconverting mixer is driven by a stabilized low phase noise local oscillator (LO) signal. This LO is generated by a fixed-frequency phase locked loop with a $2^{N}$ divider. The upconversion of the ramp signal with the stabilized LO signal leads to an excellent mm-wave phase noise of −89 dBc/Hz at a frequency offset of 1 MHz. By integrating the antennas on the MMIC, interconnects at mm-wave frequencies to package or printed circuit board are avoided and a simple assembly and interconnection technology is feasible. The ultracompact MMIC is realized on an area of only 2 mm2, including the integrated antennas. A precision below 5 $\mu \text{m}$ for range measurements is demonstrated with the radar sensor. Additionally, the radar performance is evaluated with two different voltage-controlled oscillators for the generation of the ramp signal.

Leader‐following consensus with connectivity preservation of uncertain Euler–Lagrange multi‐agent systems

SummaryThe leader‐following consensus problem for multiple Euler–Lagrange systems has been extensively studied for various scenarios. Under the assumption that the communication graph is jointly connected, one of our recent papers gave the solution for the case where the leader system can generate a combination of arbitrary step signal, arbitrary ramp signal, and arbitrary sinusoidal signals. In practice, it is desirable to enable the control law the capability of maintaining the connectivity of the communication graph, thus achieving the leader‐following consensus without assuming the connectivity of the communication graph. We call such a problem as leader‐following consensus with connectivity preservation. By combining the adaptive control technique and potential function technique, we will show that such a problem is solvable. By employing different potential functions, our approach may also lead to the solution of such problems as rendezvous, flocking and swarming. Copyright © 2017 John Wiley & Sons, Ltd.

A Simple Fuzzy PI Control of Dual-Motor Driving Servo System

Aiming at the control problem of dual-motor driving servo system, in order to avoid the complicated numerical calculation of complicated control algorithm, we presented a simple fuzzy PI controller for the first time. Firstly, we explained system control principle. In view of the shortcomings of current-error negative feedback, we used speed-error negative feedback synchronous driving control strategy. Then we theoretically analyzed dual-motor synchronous driving system in detail. We proposed the conditions of dual-motor driving servo system synchronous operation for step signal and ramp signal, respectively. Finally, we presented a simple fuzzy PI controller, by combining fuzzy controller with PI controller. We analyzed the fuzzy PI control system and found it was stable. We considered two cases in simulation tests comparing fuzzy PI control with PI control. Simulation results show that fuzzy PI control has better adaptability than conventional PI control, validating the effectiveness and efficiency of the proposed control strategy.

The influence of the type of the test signal on the result of numerical optimization of regulators

This paper studies the effect of the choice of the test signal on the result of optimization of the regulator by the example of PID and PI2D structures. It is shown that if the quality response to ramp signals is necessary, optimization of the system only by the simple signals is ineffective. In this case, the resulting system is characterized by excessively large overshoot when the step is supplied to the system input. The paper proposes a method for designing an effective system consisting in numerical optimization for two parallel operating control systems. Its effectiveness has been proved by simulation.

The effect of quality control on the function of magnetic resonance imaging (MRI), using American College of Radiology (ACR) phantom

ObjectiveTo study image quality of MRI scanner using the American College of Radiology (ACR) phantom. Material and methodsImage quality of 1.5T MRI scanner was tested using ACR phantom. A standard head coil with standard restraints was used to fix the phantom head position. The phantom included seven modules for measuring MRI scanner image quality. MRI images for each module were analyzed. ResultsFor the Geometric accuracy test the inside length of the phantom was 146mm and the inside diameter was 189.4mm. For the High-contrast spatial resolution, individual small bright spots on the image were three pairs of hole arrays and were distinguishable. For the slice thickness test, the top signal ramp length was 54.4mm and bottom signal ramp length was 54.8mm so the slice thickness was 5.46mm. For the slice position accuracy, the bar length differences of intensity uniformity a value, called percent integral uniformity (PIU), was 96.15%. For the percent-signal ghosting, ghosting ratio was 0.0002. For the low contrast object detectability, the sum of numbers of complete spokes scored was 30 spokes. ConclusionsImage quality tests were very important in acceptance of any MRI scanner after installation and during maintenance. Using ACR phantom, these tests approve that the image parameters are acceptable.

Coordinated control with multiple dynamic leaders for uncertain Lagrangian systems via self‐tuning adaptive distributed observer

SummaryThis paper studies coordinated control of multiple Lagrangian systems with parametric uncertainties subject to external disturbances by proposing a fully distributed continuous control law based on the improved self‐tuning adaptive observer inspired by non‐identifier‐based high‐gain adaptive control technique. Under this distributed continuous control law, a group of Lagrangian systems are driven to the convex hull spanned by multiple heterogenous dynamic leaders, which can be any combination of step signals of arbitrary unknown magnitudes, ramp signals of arbitrary unknown slopes, and sinusoidal signals of arbitrary unknown amplitudes, initial phases, and any unknown frequencies. It is also worth to mention that this control law we propose, depending neither on any information of leader systems for uninformed followers, nor on external disturbances, even independent of neighbors' velocity, can achieve asymptotic tracking of multiple leaders without any additional condition instead of ensuring the ultimate boundedness of the containment error as in the literature. Copyright © 2016 John Wiley & Sons, Ltd.

A 40–170 MHz PLL-Based PWM Driver Using 2-/3-/5-Level Class-D PA in 130 nm CMOS

A high-speed driver that provides a pulsewidth modulated output while using a class-D Power Amplifier (PA) is described. A PLL-based architecture is employed, which eliminates the requirement for a precise ramp or triangular signal generator, and a high-speed comparator, which are typically used in pulsewidth modulation (PWM) generation. Multilevel signaling is proposed to enhance back-off as well as peak efficiency, which is critical for signals with high peak-to-average power ratios (PAPRs). A differential folded PWM scheme is introduced to achieve highly linear operation. 3-level operation is achieved without the requirement for additional supply source or sink paths, while 5-level operation is achieved with an additional supply source/sink path compared with the 2-level operation. The PWM driver has been implemented in a 130 nm CMOS process and can operate with a switching frequency of 40–170 MHz. For the 2-/3-/5-level PA operation, with a 500 kHz sinusoidal input and 60 MHz switching frequency, the measured THD is −61/−62/−53 dB and the corresponding efficiency is 71%/83%/86% with 175/200/220 mW output power level, respectively. Performance has also been verified for 2-/3-level PA with a high PAPR signal with 500 kHz bandwidth. While intended as a general-purpose amplifier, the approach is well-suited for applications such as power-line communications.

Co-excitation of normal modes and burst ion signal in an ion-beam–plasma system

The co-excitation of plasma normal modes and a pseudo-mode (burst-ion signal) in a beam–plasma system containing a stationary ion beam is experimentally investigated in a double-plasma device. The ion waves are excited by applying a ramp voltage to an excitation grid (rather than separation grid) immersed in the beam–plasma system. By studying the dependence of the phase velocities of the excited signals on the characteristics of the ramp signal and on the ion-beam velocity, four kinds of coexisting waves can be identified, i.e., a fast and a slow ion-beam modes, an ion-acoustic mode, and the burst-ion signal, respectively.

An Area-Efficient and Low-Power 12-b SAR/Single-Slope ADC Without Calibration Method for CMOS Image Sensors

This paper presents an area-efficient and low-power 12-b successive approximation register/single-slope analog-to-digital converter (SAR/SS ADC) for CMOS image sensor (CIS) applications. The number of unit capacitors of the proposed SAR/SS ADC is reduced to 1/64th of that of a conventional 12-b SAR ADC using only a 6-b capacitor digital-to-analog converter (DAC) and the power consumption is reduced by sharing analog circuits between the SAR ADC and the SS ADC. In addition, the proposed ADC properly operates without using any calibration method as it is designed to be robust to inaccuracies in analog circuits by connecting the ramp signal to the bottom plate of the unit capacitor in the capacitor DAC. A $1936 \,\, \times \,\, 840$ pixel 60 frames/s CIS with the proposed SAR/SS ADCs was fabricated using a 90-nm CMOS process, and each readout channel with the proposed SAR/SS ADC occupies an area of $2.24~\mu \text{m} \,\, \times \,\, 998~\mu \text{m}$ and consumes a power of $30~\mu \text{W}$ . The measurement results show that the SAR/SS ADC has a differential nonlinearity of −0.45/+0.84 LSB and an integral nonlinearity of −1.5/+0.74 LSB. In addition, the developed CIS has a temporal noise of 2.7 LSB $_{\mathrm {\mathrm {rms}}}$ and a column fixed pattern noise of 0.07 LSB.

Position control of nonlinear hydraulic system using an improved PSO based PID controller

This paper addresses the position control of valve-controlled cylinder system employed in hydraulic excavator. Nonlinearities such as dead zone, saturation, discharge coefficient and friction existed in the system are highlighted during the mathematical modeling. On this basis, simulation model is established and then validated against experiments. Aim for achieving excellent position control performances, an improved particle swarm optimization (PSO) algorithm is presented to search for the optimal proportional-integral-derivative (PID) controller gains for the nonlinear hydraulic system. The proposed algorithm is a hybrid based on the standard PSO algorithm but with the addition of selection and crossover operators from genetic algorithm in order to enhance the searching efficiency. Furthermore, a nonlinear decreasing scheme for the inertia weight of the improved PSO algorithm is adopted to balance global exploration and local exploration abilities of particles. Then a co-simulation platform combining the simulation model with the improved PSO tuning based PID controller is developed. Comparisons of the improved PSO, standard PSO and Phase Margin (PM) tuning methods are carried out with three position references as step signal, ramp signal and sinusoidal wave using the co-simulation platform. The results demonstrated that the improved PSO algorithm can perform well in PID control for positioning of nonlinear hydraulic system.

Integrated Chip Current Mode DC-DC Buck Converter for Wireless Power Receiver

In this paper, we propose integrated chip DC-DC buck converter for wireless power receiver. The control of DC-DC buck converter is designed by current-mode technique. The DC-DC converter is an essential power management circuit that adjusts the output voltage based on portable electronic device applications. In addition, it reduces the energy loss due to thermal degradation and noise generated at power transmission. Therefore, DC-DC converter that operates at high efficiency is a major design constraint for wide input voltage variation. The proposed DC-DC converter is implemented andfabricated using 0.18μm BCD process. The DC-DC converter comprises of OTA, compensator, current sensing circuit, clock and ramp signal generator and a comparator. It is designed for 85% peak efficiency with a 1MHz switching frequency, 5.5V to 10V input voltage and 400mA maximum load current. The maximum accuracy for sensing current reaches 99%.