Set Of Actuators Research Articles

State-restricted adaptive control of a multilevel rotating electromagnetic mechanical flexible device using electromagnetic actuators

This work presents the development of a multilevel electromagnetic actuation system that controls the shape of a flexible rotatory robotic structure. An array of electromagnets is used as the set of actuators that regulate the position of permanent magnets within the flexible device. The primary outcome of this study is the design and experimental validation of the multilevel rotating device. In addition, the theoretical description of the system motion under electromagnetic actuation is formulated using Euler–Lagrange and electromagnetic theories. Given the developed model, a theoretical study leads to designing an adaptive control that considers motion restrictions in the flexible device. The controller aims to modify the current applied to the electromagnets, which changes the interaction forces between the electromagnet and the permanent magnets in the robotic flexible structure. A set of numerical simulations confirms the proposed controller’s effectiveness compared to the traditional state feedback approach that does not consider the state restrictions, which is implemented in devices that also operate under an electromagnetic approach. Furthermore, an experimental version of the flexible device allows for testing of the developed controller. The experimental results show the suitability of the proposed control to generate non-oscillatory controlled motion during the regulation of the flexible mechanic device shape.

Feasibility region analysis of active systems: investigating the lateral performance envelope of sports cars

Active systems are gaining significant importance because of their ability of enhancing handling performance, stability, and driver engagement, especially in sports cars. The upfront study of the achievable handling characteristics with a specific actuator set is crucial, given the involved development costs and time. In this context, although several recent studies have compared the cornering response associated with different chassis actuations, none of them has analysed in detail the resulting performance envelope, i.e. the feasibility region, based on the operating limit of the available hardware. This study targets the identified gap and presents a methodology for obtaining the feasibility region of chassis actuation systems, defined as the locus of the achievable understeer characteristics. The analysis considers front and rear active camber (FAC and RAC), rear-wheel-steering (RWS) and variable roll moment distribution (RMD). Simplified vehicle models with reduced number of degrees of freedom (DoFs) and other features to accurately obtain the feasibility region and the relevant dynamic response indicators in the early design stages of the vehicle are compared with a high-fidelity model based on VI-CarRealTime. The results highlight the favourable trade-off between complexity and accuracy of a 3-DoF nonlinear model accounting for suspension kinematics and compliances.

Effect of moisture on the sensing capabilities of piezoelectric actuator/sensor pairs on flax fibre reinforced composite laminates

The sensitivity of the piezoelectric actuators’ response to the moisture uptake has been investigated on flax fibre reinforced composite laminates. Non-woven flax fabric was impregnated with epoxy and composite laminates were fabricated using hand lay-up and cured in a compression moulding machine. The laminates were initially impacted with a drop-weight impact machine at a low energy level, with the aim to generate an artificial surface crack that will allow the moisture to enter the fibre-matrix interface more effectively. A set of piezoelectric actuators and sensors were adhered on the surfaces of the composite panels in a specific rectangular arrangement to allow for wave capturing at various directions. The wave characteristics of the samples were extracted in pristine stage and then the samples were impacted and immersed in distilled water until saturation. At regular intervals after the water immersion, the panels’ weight was measured using a laboratory scale and the wave propagation characteristics of the materials ware measured in order to investigate the gradual effect of moisture on the capabilities of the actuators and sensors. The propagation of stress waves in the dry and wet samples was investigated and the effect of moisture absorption was examined experimentally using piezoelectric wafers until the saturation was reached. Finally, a continuum damage mechanics layerwise time domain spectral finite element model, both for the composite laminate and the rich resin layers, was also developed to simulate the materials’ performance under impact and evaluate the wave propagation within the material at the dry state.

The Use of Spatially Multi-Component Plasma Structures and Combined Energy Deposition for High-Speed Flow Control: A Selective Review

This review examines studies aimed at the organization of energy (non-mechanical) control of high-speed flow/flight using spatially multi-component plasma structures and combined energy deposition. The review covers selected works on the experimental acquisition and numerical modeling of multi-component plasma structures and the use of sets of actuators based on plasma of such a spatial type for the purposes of control of shock wave/bow shock wave–energy source interaction, as well as control of shock wave–boundary layer interaction. A series of works on repetitive multiple laser pulse plasma structures is also analyzed from the point of view of examining shock wave/bow shock wave–boundary layer interaction. Self-sustained theoretical models for laser dual-pulse, multi-mode laser pulses, and self-sustained glow discharge are also considered. Separate sections are devoted to high-speed flow control using combined physical phenomena and numerical prediction of flow control possibilities using thermal longitudinally layered plasma structures. The wide possibilities for organization and applying spatially multi-component structured plasma for the purposes of high-speed flow control are demonstrated.

Actuator and sensor fault isolation in a class of nonlinear dynamical systems

Fault isolation in dynamical systems is a challenging task due to modeling uncertainty and measurement noise, interactive effects of multiple faults and fault propagation. This paper proposes a unified approach for isolation of multiple actuator or sensor faults in a class of nonlinear uncertain dynamical systems. Actuator and sensor fault isolation are accomplished in two independent modules, that monitor the system and are able to isolate the potential faulty actuator(s) or sensor(s). For the sensor fault isolation (SFI) case, a module is designed which monitors the system and utilizes an adaptive isolation threshold on the output residuals computed via a nonlinear estimation scheme that allows the isolation of single/multiple faulty sensor(s). For the actuator fault isolation (AFI) case, a second module is designed, which utilizes a learning-based scheme for adaptive approximation of faulty actuator(s) and, based on a reasoning decision logic and suitably designed AFI thresholds, the faulty actuator(s) set can be determined. The effectiveness of the proposed fault isolation approach developed in this paper is demonstrated through a simulation example.

Learning-based actuator selection for increased attack resilience of uncertain systems

In this paper, we consider a security-aware and learning-based actuator selection formulation for cyber–physical systems. A set of actuators is chosen to be used by the system so that a metric of controllability and actuation attack resilience is maximized, given only partial knowledge of the physics of the system. Such a metric is related to the trace of a game theoretic Gramian, which is obtained by solving a zero-sum game between a defender who acts as a minimizer and wants to regulate the system, and an attacker who acts as a maximizer with an eventual goal to disrupt the regulation. To account for the lack of full knowledge of the system dynamics, we design an estimator that can learn the trace of the proposed game theoretic Gramian online, by utilizing data obtained across the system’s trajectories. Subsequently, we propose a scheduling algorithm that utilizes the estimator to select actuators for the system in an online manner. In fact, we prove that the set of actuators that optimize the game-based metric will be learnt and scheduled permanently in finite time. Finally, we show that the learning-based actuator placement procedure can be utilized, in its steady state, to detect a large class of actuation attacks in a partially model-free manner. We carry out a simulation on an aircraft model to show the efficacy of our framework.

Observer-Based Fault Estimation Applied to a Point Absorber Wave Energy Converter

The economic viability of wave energy conversion systems is one of the open points among the research community. To lower the energy cost, the devices in charge of extracting the wave power, called wave energy converters (WEC), are often controlled by means of optimal control (OC) strategies. Such OC systems, which have proven their effectiveness in wave energy applications, often rely on a mathematical model of the device (and, in some cases, on the wave excitation force) to optimize the control action provided to the system. Nevertheless, the marine environment results hostile for general device safe operations, potentially triggering a variety of faults in the WEC system. Such condition (for example, a sensor failure or additional friction inside a gearing) directly affects the system dynamics. If this deviation is not considered by the control algorithm, the energy production performance can degrade considerably, or the control action itself can cause a more serious fault. A possible solution is that of designing an algorithm capable of compensating for eventual faults in the system, while still respecting the initial design performance or, when not possible, preserving the main device functionalities. Such a control strategies belong to the family of Fault Tolerant Control (FTC) techniques, which can be divided into two macro-categories: Passive (PFTC) and active (AFTC) algorithms. While PFTC systems are designed offline and can account only for a predefined set of system faults, AFTC algorithms are more suitable to tackle significant system deviations from the nominal model. For this purpose, such algorithms may require some routine to detect, isolate and eventually estimate the specific fault. This task is accomplished by Fault Detection and Identification (FDI) routines. According to the AFTC algorithm, the FDI module must accomplish different tasks. Furthermore, the FDI module accuracy plays a crucial role in some AFTC strategies, since the poor estimation of a faulty signal can induce the controller to behave incorrectly. This paper presents an FDI algorithm applied to a point-absorber wave energy converter (WEC). The proposed structure consists of an observer-based strategy in charge of detecting, isolating, and tracking effectively faulty signals occurring in numerical simulations. The results demonstrate the proposed observer effectiveness for a predefined set of actuator and sensor faults, both in the case of independent, and simultaneous fault occurrence.

Piezoelectric Actuators Placement Using Genetic Algorithm and Active Vibration Control of Smart Plane Frame Structure

A Genetic Algorithm-based optimisation scheme is presented to find the optimum actuator elements infinite element analysis for active vibration control applications. The dynamic strain data is used to reduce the size of search domain for the actuators placement problem. A modal velocity, feedback control is employed to estimate the active damping of piezoelectric actuators. The structural damping index is taken as a fitness function; which directly reflects the status of active damping effect for a given piezoelectric actuator set. Modal preference is attempted by assigning a different weighting factor in the fitness function for desired modes to have better controllability. As an illustration, a 20-member smart plane frame is modeled with d3I based extension-bending piezoelectric actuators using 2-D piezoelectric Timoshenko beam element. It is shown that the vibration of first four elastic modes is actively controlled with optimally, selected four piezoelectric actuators.

Integrated Conceptual Design and Parametric Control Assessment for a Hybrid Mobility Lunar Hopper

The lunar lava tubes are envisioned as possible hosting structures for a human base in the Moon’s equatorial regions, providing shelter from radiations, micrometeoroids, and temperature excursion. A first robotic mission is set to scout the habitability of these underground architectures in the near future. The communication inside these underground tunnels is heavily constrained; hence, the scouting system should rely on a high degree of autonomy. At the same time, the exploration system may encounter different types of terrain, requiring an adaptable mobility subsystem able to travel fast on basaltic terrain while avoiding considerable obstacles. This paper presents a cave explorer’s mission study and preliminary sizing targeting the lunar lava tubes. The study proposes using a hybrid mobility system with wheels and thrusters to navigate smoothly inside the lava tubes. The peculiar mobility system of the cave explorer requires an accurate study of the adaptability of its control capabilities with the change of mass for a given set of sensors and actuators. The combination of conceptual design techniques and control assessment gives the engineer a clear indication of the feasible design box for the studied system during the initial formulation phases of a mission. This first part of the study focuses on framing the stakeholders’ needs and identifying the required capabilities of the cave explorer. Furthermore, the study focuses on assessing a design box in terms of mass and power consumption for the cave explorer. Following different mission-level assessments, a more detailed design of the cave explorer is discussed, providing an initial design in terms of mass and power consumption. Finally, the objective shifts toward studying the performances of the guidance, navigation, and control (GNC) algorithms varying the mass of the cave explorer. The GNC significantly impacts the design box of the surface planetary system. Hence, investigating its limitations can indicate the feasibility of mass growth to accommodate, for example, more payload.

Post-occupancy evaluation for enhancing building performance and automation deployment

Building automation systems are building control and management systems that control/operate different systems in a building such as HVAC, lighting, safety systems, security and access control, surveillance, indoor air quality, and waste management. These systems manage, control, and integrate other building systems to enhance living experience and optimise energy use through a set of sensors and actuators that are deployed in the building to collect data and execute commands that are sent through a gateway. These management systems generate real-time commands and act or reacts to stochastic occupant behaviours. Buildings in Oman used to be built with burned clay mixed with date palm leaves, and wadi stones and date palm trunks are used for building structure. This architecture keeps the indoor environment warm in winter and cold in summer. However, with advancing technology there has been a shift in building towards using concrete and steel that have high thermal conductivity and pose some challenges for energy use. This paper will show that the main concern of occupants in Oman is indoor temperature control, especially during summer months. This has raised concerns for building performance in Oman and shows a need to review building materials, recommend sustainable alternatives, and more widely, implement sustainable building techniques. This paper seeks to develop recommendations to overcome these issues by exploring post-occupancy satisfaction measures and potential use of BAS and sustainable building materials to enhance building performance in Oman. Following on from this, this paper explores the motivations behind people's decision in Oman to deploy home automation and explore techniques to enhance building performance.

Lamé Resonator Integrated With Chevron-Shaped Thermal Actuators to Improve Motional Resistance and Temperature Stability

This paper presents a capacitive bulk mode resonator operating in Lamé mode, where the motional resistance and temperature stability are enhanced by implementing a set of chevron-shaped thermal actuators to reduce the transducer air gaps. The chevrons are heated using micro-heaters that are integrated on the actuator. The device is fabricated in the PiezoMUMPS standard microfabrication process by MEMSCAP. The measured resonant frequency for the fabricated device was observed to be 17.9 MHz. It has been experimentally shown that the transducer air gap can be reduced from 2.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu m$</tex-math> </inline-formula> to 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu m$</tex-math> </inline-formula> by applying a heater voltage of 2.7 V at atmospheric pressure. In the proposed resonator, the transmission loss can be reduced by 8.54 dB when the actuators are biased at 1.8 V in vacuum, as opposed to when the actuator is off. Under these conditions, the thermal actuators each consume 39 mA. In addition, the implemented thermal actuators can function as integrated heaters that increase the temperature of the suspended square structure to compensate for ambient temperature variations. As such, applying a voltage of 1.8 V in vacuum reduces the resonant frequency from 17.95 MHz to 17.91 MHz, while applying a voltage of 2.6 V at atmospheric pressure reduces the resonant frequency from 17.97 MHz to 17.86 MHz.2022-0188

IoT-based smart monitoring and management system for fish farming

Fish farming is still controlled and managed in the traditional way where water quality and fish feeding are manually controlled. There is a need to use computer and communication technology in fish farms for remote monitoring and control. This paper deals with the design and implementation of an internet of things (IoT) based system for real-time monitoring, control and management of fish farming. The design of such a system is based on measuring different types of variables and using the information to control fish growth and increase productivity. Each fish pond is a node in a wireless sensor network. The node contains an embedded microcontroller connected to a set of sensors and actuators and a wireless communication module. Two fuzzy controllers are designed to control the water quality in the ponds as well as the environment using five sensors in each pond plus three environmental sensors. Practical results indicate the accuracy of the measurement system compared to the results obtained from commercial devices used on the farm. These results also showed that the proposed approach achieves the best performance of the real-time monitoring and control system in fish ponds.

Actuator Selection for Dynamical Networks with Multiplicative Noise

We propose a greedy algorithm for actuator selection considering multiplicative noise in the dynamics and actuator architecture of a discrete-time, linear system network model. We show that the resultant architecture achieves mean-square stability with lower control costs and for smaller actuator sets than the deterministic model, even in the case of modeling uncertainties. Networks with multiplicative noise may fail to be mean-square stabilizable by any small actuator set, leading to a failure of a cost-based greedy algorithm. To account for this, we propose a multi-metric greedy algorithm that allows actuator sets to be evaluated effectively even when none of them stabilize the system. We illustrate our results on networks with multiplicative noise in the open-loop dynamics and the actuator inputs, and we analyze control costs for random graphs of different network sizes and generation parameters.

Global stabilizability to trajectories for the Schlögl equation in a Sobolev norm

The stabilizability to trajectories of the Schlögl model is investigated in the norm of the natural state space for strong solutions, which is strictly contained in the standard pivot space of square integrable functions. As actuators a finite number of indicator functions are used and the control input is subject to a bound constraint. A stabilizing saturated explicit feedback control is proposed, where the set of actuators and the input bound are independent of the targeted trajectory. Further, the existence of open-loop optimal stabilizing constrained controls and related first-order optimality conditions are investigated. These conditions are then used to compute stabilizing receding horizon based controls. Results of numerical simulations are presented comparing their stabilizing performance with that of saturated explicit feedback controls.

A novel piezoelectric motor design and its controller

The paper aims to develop a novel piezoelectric motor and its controller; here the motor shaft needs to be rotated fully by 360° using two sets of Parallelly Prestressed Actuators (PPA) and one set of lock release actuators (LR). The first set of PPA drives the driving element and produces a displacement of 39 µm for an applied input voltage of 150 V & rotates by an angle of 0.145°, thus taking 2483 steps to complete one complete rotation. The second set of PPA is deployed to transfer the rotation caused by the first set of PPA to the output shaft. The lock release actuator will arrest the rotation that occurred and avoids the shaft from moving back to its original position till the next cycle begins. The above set of operations is continued to obtain continuous rotation of the piezoelectric motor shaft. There is a FAP used to hold the shaft during the power-off condition. The mathematical controller is developed to obtain both forward and reverse rotation of the shaft by applying an input voltage, further the developed model is simulated using MATLAB Simulink software to illustrate the working of a piezoelectric motor.

Rapidly Exploring Random Trees for Autonomous Navigation in Observable and Uncertain Environments

This paper proposes the use of a small differential robot with two DC motors, controlled by an ESP32 microcon-troller, that implements the Rapidly Exploring Random Trees algorithm to navigate from an origin point to a destination point in an unknown but observable environment. The motivation behind this research is to explore the use of a low-cost, versatile and efficient robotic platform for autonomous navigation in complex environments. This work presents a practical and cost-effective solution that can be easily replicated and implemented in various scenarios such as search and rescue, surveillance, and industrial automation. The proposed robotic platform is equipped with a set of sensors and actuators that allow it to observe the environment, estimate its position, and move through it. The Rapidly Exploring Random Trees algorithm is implemented to generate a path from an origin to a destination point, avoiding obstacles and adjusting the robot’s motion accordingly. The implementation of this algorithm enables the robot to navigate through complex environments with high efficiency and reliability, making it a suitable solution for a wide range of applications. The results obtained through simulations and experiments show that the proposed robotic platform and algorithm achieve high performance and accuracy in autonomous navigation, even in complex environments.

A Constrained Control Allocation and Tuning Scheme for Hybrid Actuators in Spacecraft Attitude Control

Agile rotational maneuvers of spacecraft requires careful execution since its actuators may not be able to produce the demanded torques, causing the state trajectories to deviate and a desired attitude would not be guaranteed. We investigate the control allocation problem for a redundant set of hybrid actuators that include reaction wheels, magnetorquers, and continuous-force thrusters. The main objective of the magnetorquers is to dump momentum from the reaction wheels, whereas the wheels are the primary actuators in attitude control, and more agile maneuvers or faster unloading of momentum can be handled by the thrusters. A modified mixed optimization scheme for control allocation is presented where the equality constraints account for satisfying the high-level (virtual) control inputs for both attitude control and momentum dumping. Variants of dynamic weights in the optimization are developed such that magnetorquers and thrusters may contribute with a relative degree of importance in the attitude control problem. The control allocation scheme is solved using quadratic programming where simulation results are shown for fast and slow rotational maneuvers together with fast and slow momentum dumping.

Implementation of structurally pre-stressed piezo actuator based active vibration isolation system for micro milling

This paper presents the implementation of a structurally pre-stressed piezo actuator based active vibration isolation system incorporated with tool based micromachining setup for analyzing and comparing the milled pocket depth surface before and after isolation. A carbide micro end mill tool with 1 mm diameter and 4 flutes has been used for carrying out pocket milling experiments with and without vibrations on copper work pieces having 3 mm thickness. The machining parameters selected were spindle speed of 16,000 rev/min with 64 mm/min feed rate and 50 μm depth of cut. Two sets of pocket milling experiments were carried out using the proposed vibration isolation setup one with vibration and the other without vibration. In the first set of experiment, the source actuator was actuated for generating vibrations during pocket milling whereas in the second set of experiment, both source and isolator actuators were actuated for nullifying the vibrations generated during pocket milling. The macroscopic lens output images of the pocket depth surfaces before and after isolation were then compared corresponding to various actuation voltages at different frequencies using the proposed vibration isolation setup. Based on the macroscopic lens output images it was observed that the milled pocket depth surface obtained by actuating only source actuator showed distinct rings wherein the ring count matched with frequency and feed rate that has been provided during machining. However, the milled pocket obtained by actuating both source and isolator actuators resulted in surface characteristics with less pronounced rings similar to that of regular machining. Also the rings that has been formed showed more defined edges with the increase in actuator voltage indicating that these distinct patterns were caused due to the vibrations generated by the source actuator alone and not other factors.

A Developed IoT Platform-Based Data Repository for Smart Farming Applications

Generally, it is possible to increase agricultural output while decreasing the time required for human oversight by automating routine tasks. In this work, the Internet of things (IoT) played a vital role in designing a platform to monitor a farm wirelessly, reducing human involvement, allowing remote observing, and remote control of the design using a public IP address based cross-platform, Apache, MySQL, PHP and Perl (XAMPP) Apache package. A cloud is appealing when a wireless sensor network generates a lot of data. Cloud-based wireless communication systems are being tested to monitor and manage a set of sensors and actuators to estimate paddy (rice) water requirements in a particular location. The proposed design shows robust interaction between two microcontrollers to deal with different sensors and simultaneously act as a WiFi unit. The row data obtained from the sensors is uploaded to the cloud through specific Hypertext Preprocessor (PHP) files to store and fetch the data from the database. Through the programming method, the system focuses on tracking the paddy growing value and the amount of water available in the soil, which should be around (10 Kpa) for an optimum paddy environment. The results emphasized that 80% of water is retained when a maximal 10 Kpa of soil moisture is achieved.

Identifiability of diffusively coupled linear networks with partial instrumentation*

This paper presents identifiability conditions for identifying the complete dynamics of diffusively coupled linear networks. These conditions are derived by exploiting the uniqueness of the nonmonic polynomial network description, given the locations of the actuators and sensors. The analysis is performed under a more relaxed instrumentation setup than the typical restriction to a full set of sensors (full measurement) or a full set of actuators (full excitation). This leads to more general identifiability conditions, including more flexible instrumentation requirements.