Unidirectional Input Research Articles

Hysteresis Compensation-Based Intelligent Control for Pneumatic Artificial Muscle-Driven Humanoid Robot Manipulators With Experiments Verification

Pneumatic artificial muscles (PAMs), as a kind of soft actuators, can overcome compliance limitations of traditional rigid actuators to improve the adaptability of robots. However, some inherent strong nonlinearities and time-varying properties of PAMs, e.g., complex hysteresis and creep, may lead to a lot of control problems. In addition, PAM-driven systems are also faced with input constraints (e.g., deadzones, saturations, and unidirectional inputs), unknown/unmodeled dynamics and external disturbances, which badly degrade the control performance and even cause accidents. Therefore, this paper proposes a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">new</i> hysteresis compensation-based immersion and invariance (I&I) adaptive fuzzy control method for PAM-driven humanoid robot manipulators, which can approximate the unknown functions and estimate the unknown parameters. To our knowledge, this is the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first</i> method for PAM-driven systems that compensates for system nonlinearities ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">not only</i> complex hysteresis, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">but also</i> input deadzones) by utilizing the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">prior</i> information in inverse hysteresis models, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">simultaneously</i> estimates the unknown functions and parameters by designing a fuzzy update law and a parameter update law based on I&I methodology, respectively, which increases the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">control frequency</i> of systems and improves tracking performance during high-speed motions. Finally, we apply the proposed approach on a self-built PAM-driven humanoid robot manipulator to validate its effectiveness and robustness. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Faced with the practical requirements of robots that interact closely with humans, improving the adaptability and compliance of robots by utilizing soft actuators, such as PAMs, can satisfy current demands. Moreover, PAMs also have many expective characteristics (e.g., high power density, light material, low costs, clean power, etc.), which makes PAMs occupy an important status in the field of soft robotics. However, unknown parameters/structures, strong nonlinearities, and input constraints, may badly degrade the control performance of PAMs. Based on the above characteristics, this paper proposes a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">new</i> hysteresis compensation-based adaptive fuzzy controller for PAM-driven humanoid robot manipulators, which realizes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">accurate tracking</i> control during high-speed motions by using inverse hysteresis models to compensate for strong nonlinearities in PAMs, and a fuzzy update law and a parameter update law based on I&I methodology are utilized to estimate unknown parameters/structures. In addition, the proposed controller can <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">simultaneously</i> compensate for input deadzones by utilizing the hysteresis information, which improves the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">control frequency</i> of the manipulators, and can rapidly suppress tracking errors. Experimental results are provided to validate the effectiveness of the presented method. In the future, more effective compensation methods, such as rate-dependent hysteresis models, will further be carried out to compensate for system nonlinearities.

Output Feedback Bounded Control for Unidirectional Input Constrained Hysteretic Systems With Application to Piezoelectric-Driven Micropositioning Stage

Output Feedback Bounded Control for Unidirectional Input Constrained Hysteretic Systems With Application to Piezoelectric-Driven Micropositioning Stage

Research on Viral Marketing of Global Warming Communication based on the STEPPS Model

Effective communication of global warming information is the basic process to alleviate the climate change problem closely linked to humans’ sustainable development. What’s more, climate change is not reversible and invisible. The reasons for the failure to communicate global warming-related information can be attributed to obscure language, unidirectional input, and disinformation. Therefore, catching people’s eyes in this field isn’t easy. Although the United Nations and governments implement lots of policies to reduce the emission of carbon dioxide, global warming has threatened millions of lives of creatures and their habitats. The communication strategies of global warming information or policies need to be more valid to raise people’s attention and put them into action. The application of the viral marketing model STEPPS will be the main focus of this essay. The suggestion is theoretically based on this model, combining the current communication challenges from emotions, practical value, story, and social currency. Combining the STEPPS model with scientific information communication is a creative strategy to spread the important message to the audience effectively, and there is research about the application of the viral marketing model in the global warming field. This essay will provide a new and original method to the transmitter of environmental protection organizations.

Extendable Multiport High Step-Up DC–DC Converter for Photovoltaic-Battery Systems With Reduced Voltage Stress on Switches/Diodes

In the standalone photovoltaic (PV)-battery power system, a multiport converter is more desirable than several single-input converters as it has advantages of the simpler circuit, higher efficiency, and lower cost. In this paper, a novel structure based on a non-isolated high step-up multi-port converter (MPC) is proposed. The proposed MPC has the capability of providing high voltage gain and low normalized peak inverse voltage (NPIV) across semiconductor devices. Maximum power point tracking (MPPT) algorithm can be applied for each PV input source, which is an effective method to prevent mismatches among PV modules. Different from the existing extendable MPCs, the proposed MPC can extend both unidirectional input ports and bidirectional ports to involve more types of renewable energy sources and energy storage devices. Continuous input currents and modularity are the other profits of the proposed MPC. Various operating modes, steady-state analysis, and design considerations have been discussed. Comparison results verify the above advantage of the proposed MPC. Finally, a 240W laboratory prototype is designed to validate the performance of the proposed MPC.

A battery integrated multiple input DC-DC boost converter

In this paper, the proposed single boost converter aims to harness more than one renewable energy (RE) input source and achieve a high voltage gain. The interleaved technique combined with voltage multiplier (VM) cells, reduced inductor current and attained high voltage transfer ratio. The boost converter possesses two unidirectional input ports and a bidirectional input port that is connected to a battery storage. The duty ratios of the power and interleaving switches are used to regulate the output voltage of the proposed converter. Three operation modes are identified, and steady state analyses of the converter are presented and discussed. The converter can store excess energy in the battery during periods of abundance and deliver power to the loads when the RE sources are low or unavailable. In addition, the output voltage is higher than that of the conventional boost converter. The converter delivered 278 V from 12 V and 24 V dual input sources. The converter operation is simulated and verified using MATLAB/Simulink.

New Dual-Source High-Gain ZVS DC-DC Converter for Integrating Renewable Power Source and Battery Storage

A new soft-switching high-gain two-source dc-dc boost converter is proposed here. The proposed converter provides two bidirectional and unidirectional input ports, handling the energies of a battery storage and a renewable power source, respectively, to supply a resistive load through a switched-capacitor (SC) voltage multiplier. As a result, three power switches, four power diodes, two inductors and four capacitors are used in the converter structure. The ZVS of all power switches is realized without any auxiliary circuit and in whole power ranges of the converter input sources and the output load. The converter power MOSFETs are switched in PWM manner with two individual duty ratios, allowing to regulate the output voltage and control the power coming from the input unidirectional port. Depending on the converter duty ratios, its basic operation principle is analyzed in two different operation cases. The behavior of the proposed converter is analytically investigated, and a low-power laboratory prototype is built to evaluate the converter performance in different operation conditions. The proposed converter benefits from simple and compact structure, minimum number of power switches and magnetic elements, reduced voltage stress across the power semiconductor devices, high voltage gain and high efficiency.

Multiport converters for incorporating solar photovoltaic system with battery storage: A pilot survey towards modern influences, challenges and future scenarios

The increasing significance of renewable power systems with diverse sources has produced an unexpected demand for electronic converters to integrate and simultaneously control, various energy resources, and storage devices. The voltage-current characteristics and the voltage levels of storage, as well as energy generating systems, are naturally diverse from those of loads. Hence, converters are employed to transform the energy from the renewable power plants to meet the total power demand, to enable the renewable energy system to use Maximum Power Point Tracking algorithm, to enhance the dynamic and static characteristics of the system, and to integrate the energy storage devices to resolve the issue of the irregularity of the load demand and unstable characteristics of the renewable sources. The implementation of a Multiport DC/DC converter (MDC) is a viable solution to increase the system efficiency and power density. The conventional MDC contains 1) DC unidirectional input ports to connect the renewable energy generating system; 2) two-way input ports to interface battery like storage devices; and 3) output ports to interface the load. Recently, numerous multiport converter configurations have been developed and described in the literature. Each of these reported MDCs has distinct architecture and working mechanism, which leads to a diverse level of intricacies, different component count, different performance, and reliability. This paper reviews various configurations of MDCs that have been introduced by different research communities to integrate solar energy with Battery Storage System (BSS). Different MDCs topologies such as partially-isolated, isolated, non-isolated configurations are discussed according to their physical structures and other aspects. This article can be employed as a guideline to select the appropriate configuration to match the certain condition of a system.

Fuzzy-Sliding Mode Control for Humanoid Arm Robots Actuated by Pneumatic Artificial Muscles With Unidirectional Inputs, Saturations, and Dead Zones

Recently, the pneumatic artificial muscle (PAM) that can reproduce natural muscle functionalities has become one of the core actuator mechanisms of intelligent interactive soft robots. Unfortunately, some inherent defects (e.g., unignorable nonlinearities, hysteresis, low shrinkage frequencies, etc.) have limited the application progress of humanoid PAM arm robots. Additionally, the input constraints (e.g., saturations, dead zones, unidirectional inputs, etc.), unexpected external disturbances, unidentifiable system parameters, and inevitable unmodeled dynamics are usually complicated, which cannot be easily eliminated through existing adaptive control methods. This article proposes an adaptive fuzzy-sliding mode control method for humanoid PAM arm robots <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">without</i> any information of precise model structures and system parameters, which can suppress the unexpected effects of complicated unknown functions and achieve high performance tracking control, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">simultaneously</i> . To the best of our knowledge, the proposed controller is the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first</i> method for the humanoid PAM arm robots that considers the nonlinear input constraints including unidirectional conditions, saturations, and dead zones, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">simultaneously</i> . Next, all the input constraints, system parameter uncertainties, unmodeled dynamics, and external disturbances can be estimated adaptively by utilizing the proposed fuzzy update law. Particularly, a sliding mode control law is designed to compensate possible fuzzy approximation errors, and rigorous Lyapunov-based stability analysis is provided to ensure that the state errors can converge to zero within <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">finite</i> time. Hardware experiments are carried out later tovalidate the effectiveness and robustness of the proposed method.

Model reference adaptive control of a soft bending actuator with input constraints and parametric uncertainties

In this article, model reference adaptive control of a pneumatically actuated soft robot has been studied in detail. To deal with the effects of system uncertainties, in the proposed control scheme, parametric uncertainties and input constraints are taken into account. To design such a controller, based on experimental analysis, the robot has been modeled as a second-order Linear Parameter Varying (LPV) system. Then, the dominant dynamics are presented as a Linear Time-Invariant (LTI) system, while uni-directional input constraint has been considered as a critical issue in the control scheme design. Furthermore, to compensate parametric uncertainties as well as unmodeled dynamics, adaptive laws are modified. Finally, the effectiveness is studied in different scenarios on an experimental platform to validate our claims. Moreover, to show the proposed approach capabilities and performance, the proposed controller has been compared with a PID and a recent sophisticated robust-adaptive controller, which presented a new formulation to achieve a better tracking performance with guaranteed stability in the presence of different constraints and unmodeled dynamics.

Laboratory calibration for multidirectional spectroradiometers

A method for the calibration of multidirectional spectroradiometers (MUDISs) capable of the simultaneous measurement of spectral radiance at different wavelengths is presented. The calibration of the spectroradiometer is challenging and crucial for high quality measurements of the angular dependence of the radiance. The calibration device consists of an integrating sphere (also known as Ulbrichtkugel), with a diameter of 100 cm, equipped with three 100 W lamps positioned in the lower hemisphere, with the input optics of the MUDIS directed towards the upper hemisphere. The MUDIS detects radiation from 113 different directions simultaneously in a wavelength range from 300 nm to 550 nm. Due to multiple reflections within the sphere, the radiance from the upper hemisphere is nearly homogeneous with deviations of less than 3% on average. Disregarding the 3% variability and assuming a homogeneous radiance inside the upper hemisphere of the integrating sphere, the spectral responsivities of all the MUDIS channels were determined based on the measured zenith radiance, which was detected by a pre-calibrated Network for the Detection of Atmospheric Composition Change reference spectroradiometer containing a scanning double monochromator with a unidirectional input optics. The input optics of the MUDIS contains thin fibers that should not be moved to avoid changes in the instrument’s responsivity. The proposed method is therefore suited to determine the absolute responsivity of the MUDIS for all directions.

A High Step Up Multi-Input DC/DC SEPIC-Based Converter with Coupled Inductor for Renewable Applications

To overcome low output voltage of renewable energy sources such as photovoltaic arrays and fuel cells, a high step up SEPIC-based multi-input converter with dual coupled inductor is proposed. A new structure is presented in this paper, as an improved structure. This converter is based on combination of modified quadratic buck-boost converter, Dickson switched capacitor (DSC), and voltage multiplier modules (VMM). The high voltage gain can be achieved by adjusting the duty cycle and turn ratio of coupled inductor of VMM. This structure inherits all the advantages of the SEPIC converter such as step-up/down capability without inverting the polarity of regulated output voltage and using a bidirectional input port (in which an energy storage system (ESS) can be connected), and several unidirectional input ports. The load power can be flexibly divided among various power sources. Due to the buck-boost characteristics of the presented converter, it is suitable to charge-discharge the ESS. A coupled inductor (CI) is used to couple energy from input to the output equipped with the VMM. The usage of the DSC technique also enables the converter to obtain an additional double voltage gain while reducing the voltage stress on switches. Simulation results verify the performance of the proposed converter and feasibility of the control strategy.

The study of different unidirectional input parallel output series connected DC‐DC converters for wind farm based multi‐connected DC system

The study of different unidirectional input parallel output series connected <scp>DC‐DC</scp> converters for wind farm based <scp>multi‐connected DC</scp> system

Seismic vulnerability assessment of RC curved bridges piers subjected to bidirectional earthquake

Curved beam bridge is a kind of irregular structure, which has the advantage of adapting to complex terrain, but it is more vulnerable to damage than regular bridge under earthquake. This paper investigates the vulnerability of curved continuous girder bridges under the action of bidirectional earthquake horizontal earthquake, and the difference of vulnerability between side pier and intermediate pier is analyzed. Fragility assessment is performed using an incremental dynamic analysis method subjected to a wide range of as-recorded sequences. A proper engineering demand parameter (EDP) which can result in the most probability of failure at bridges employed in this study is determined. Result indicates that only considering the unidirectional seismic input will underestimate the seismic response and potential damage of the structure, which is not accurate for the seismic performance evaluation of the bridge. Result also shows that the damage probability of the intermediate pier of the curved bridge is higher than that of the side pier, and the more serious the failure, the smaller the difference between the two piers.

Adaptive Control for Pneumatic Artificial Muscle Systems With Parametric Uncertainties and Unidirectional Input Constraints

Pneumatic artificial muscle (PAM) systems are a kind of tube-like actuators, which can act roughly like human muscles by performing contractile or extensional motions actuated by pressurized air. At present, it is still an open and challenging issue to tackle positioning and tracking control problems of PAM systems, due to inherent characteristics, e.g., unidirectional inputs, high nonlinearities, hysteresis, time-varying characteristics, etc. In this paper, a new adaptive control method is proposed for PAM systems, which achieves satisfactory tracking performance. To this end, an update law is designed to estimate unknown system parameters online. Also, some control input transforming operations are applied to address unidirectional constraints (i.e., control inputs of PAM systems should always be positive). As far as we know, compared with most of the existing control methods, this paper gives the first continuous control solution for PAM systems that can simultaneously compensate parametric uncertainties, reject external disturbances, and meet unidirectional constraints. Without linearizing the nonlinear dynamics, the closed-loop system is theoretically proven to be asymptotically stable at the equilibrium point with the stability analysis. In addition, a series of hardware experiments are implemented on a self-built hardware platform, indicating that the proposed method achieves satisfactory tracking control and exhibits robustness against parametric uncertainties and disturbances.

Implications of bidirectional interaction on nonlinear seismic response of steel piers

The seismic performance assessment of bridges by nonlinear time history analysis using unidirectional spectrum-matched accelerograms is generally adopted in Japan's specifications. However, the simultaneous action of two horizontal components is known to induce a potentially higher inelastic response in steel piers relative to that under unidirectional excitation. In this background, a rising concern within research communities is the bidirectional effect on the risk of bridge failure or damage under a given seismic intensity during the service life of a bridge. In this study, the difference in the risk of steel pier damage/failure between unidirectional ground motion and bidirectional ground motion is assessed using seismic fragility. Fragility curves are constructed by subjecting a single steel pier with various geometric designs to a large number of earthquake ground motions using the incremental dynamic analysis methodology. The study indicates that the damage state of collapse is not changed by bidirectional excitations, whereas the use of bidirectional excitations in less damaging states reduces the bridge seismic performance and induces higher fragility. The response difference is quantified by introducing an equifragility factor. This factor is calculated as the ratio of intensity of the unidirectional input to the bidirectional input, which causes the same fragility caused by the unidirectional counterpart. The constant characteristic value of the equifragility factor provides useful information for considering the bidirectional effect in seismic design.

Battery‐integrated multi‐input step‐up converter for sustainable hybrid energy supply

This paper presents a battery-integrated multi-input step-up DC–DC converter (BI-MISUC) as a unified interface for multiple energy sources in the frame of a sustainable hybrid energy supply. The proposed converter comprises one bidirectional port for a battery and several unidirectional input power ports. Battery can be charged by input sources, discharged into load or bypassed while charging/discharging durations are independent of switching duty ratios for input sources. In the presented BI-MISUC, higher voltage gains with lower duty ratios are achieved not only by increasing the number of inputs but also using the switched inductor (SI) modules. It therefore enables BI-MISUC to be used for a wide range of applications from low to high voltage/power. Furthermore, input sources can be operated individually or simultaneously to supply load energy at the desired output voltage. The converter operation is described for three scenarios (i.e. no battery, battery charging and discharging). A linear quadratic regulator (LQR) control is also used to regulate the output voltage and output power of input sources at the desired references for different scenarios. Finally, the performance of the BI-MISUC is validated by simulations and experimental results.

A Nonisolated Three-Port DC–DC Converter with Continuous Input and Output Currents Based on Cuk Topology for PV/Fuel Cell Applications

A nonisolated three-port DC–DC converter based on Cuk topology (NI-TPC) to handle the renewable sources (RS) is proposed in this paper. This converter includes two unidirectional input ports accommodating both a fuel cell (FC) and photovoltaic (PV) cell; and one output port with DC load. Due to the inductors at all the ports, it claims the advantage of continuous input and output currents. Additionally, it uses less number of switches, diodes and inductors compared with conventional ‘n-1’ separate Cuk converters. Synthesis procedure for a generalized n-port DC–DC structure is explained. The derivation law based on conventional Cuk converter, operating principle, design calculation, and analysis are presented in detail, and then the analysis is validated through simulation and a 100W prototype, verifying the performance of the proposed NI-TPC converter.

Topological design of compliant orthogonal displacement amplification mechanism under the unidirectional input force

The orthogonal displacement amplification mechanism is used to output and amplify the displacement perpendicular to the direction of the input force, and its configuration often uses a typical bridge-type. However, the bridge-type amplifier to achieve orthogonal shift conversion must enter the bidirectional symmetric input forces, otherwise the output will produce parasitic displacement. In view of this problem, the topology optimization method is used to find the new configuration of the displacement amplification mechanism, so that it can still realize the orthogonal displacement transformation under the unidirectional input force condition. Based on the solid isotropic material with penalization (SIMP) topological description method, the ratio of output and input displacements is maximized as the objective function, the ratio of parasitic displacement and output displacement as one of constraint functions, and the topological optimization mathematical model of the compliant orthogonal displacement amplifier is established under the unidirectional input force. The sensitivity information of the objective and constraint functions is deduced by the adjoint matrix method, and the optimization problem is solved by the method of moving asymptotes (MMA). The topology optimization results of orthogonal displacement amplifier are given through numerical examples, and the effect of spring stiffness on the topology optimization result is also discussed. Finally, the parasitic motions of the displacement amplification mechanism obtained from topology optimization and the bridge-type amplification mechanism are compared through the finite element analysis and experiment. Finite element simulation and experiment confirm the correctness and validity of the proposed method.

Soft-switched non-isolated high step-up multi-port DC-DC converter for hybrid energy system with minimum number of switches

This paper proposes a non-isolated high step-up multi-input DC-DC converter for utilizing in hybrid applications. This converter provides the interfaces between input power sources, energy storage devices and load. The resonant auxiliary circuit used in the proposed converter provides soft switching condition for the main switches as well as charging the storage device which has caused considerable improvement in the converter efficiency. This converter uses only three switches to control the power absorbed from a unidirectional input, the power absorbed or stored in the bidirectional port and also the power transmitted to load while provides soft switching condition of all semiconductor devices. Thus, the number of switches applied is same as conventional hard switched converters for this purpose. This converter shares only one inductor between all inputs, so the volume is reduced. Various converter operating modes are discussed and design considerations are presented. Finally, to validate the theoretical analysis, a prototype of the proposed converter is implemented for a 400 V output voltage at 200 W.

Design and analysis of a novel SEPIC‐based multi‐input DC/DC converter

A novel single-ended primary-inductor converter (SEPIC)-based multi-input DC/DC converter is presented. The structure inherits all the advantages of the SEPIC converter such as step-up/down capability without inverting the polarity of the regulated output voltage and using a series capacitor to couple energy from the input to the output. The presented converter has a bidirectional input port, in which the energy storage system (ESS) can be connected, and several unidirectional input ports. Hybridising several alternative energy sources is achievable by the proposed converter. In addition, the load power can be flexibly divided among various power sources. Due to the buck-boost characteristic of the presented converter, it is suitable to charge-discharge the ESS and to extract maximum power from the photovoltaic panels. Based on the charging state of the ESS, two operation modes are defined. Steady-state and dynamic behaviour of the proposed converter is analysed thoroughly. Experimental results are also provided to verify the analysis and feasibility of the proposed converter.