Variable Inertia Research Articles

Comparative Validation Study on Bioinspired Morphology-Adaptation Flight Performance of a Morphing Quad-Rotor

Inspired by the advantages from natural birds' shape-morphing adapted flight performance, this work investigates how the bioinspired adaptative morph induced inertia variation affects the flight performance of a morphing quad-rotor. Extensive numerical and experimental evaluations on a custom-built morphing quad-rotor that is steered along a predefined path and hovers in the presence of constant wind disturbance were performed and analyzed. Simulation results demonstrate that the smaller quad-rotor exhibits better agility performance due to the compact volume/size and lower weight, while the bigger one appears more flight robustness in a disturbed environment such as windy testing area. Experimental studies further prove that by adaptatively altering its volume/size, our quad-rotor with the bioinspired in-flight morphing behavior can well execute path following tasks in a constrained space without deviating the trajectory when encountering obstacles, as well it can withstand external wind torque through morphing up its volume to therewith increase relevant moment-of-inertia for improving the flight robustness. Compared to the regular scaled aerial vehicles whose volumes' change follows a weight change proportionally, our results also indicate that our in-flight morphing aerial vehicle mechanism (i.e. the quad-rotor morphs the volume but without changing weight/mass) shows more advantages in power efficiency and morphologically adaptative flight capability.

RETRACTED: Improvement of transient and small signal stability in micro grid by hybrid technique with virtual synchronous generator control scheme

In this article, a hybrid technique is proposed for improving the transient and small signal response in micro grid using virtual inertia. The proposed hybrid technique is the combined execution of both the emperor penguin optimizer (EPO) and butterfly optimization algorithm (BOA), and hence it is called EPOBOA technique. The major objective of the EPOBOA technique is to “optimize the control parameters to regulate the changes occurred in the grid parameter such as voltage and frequency based on the variations of inertia”. Here, the EPO is executed to modify the parameters of virtual synchronous generator units to achieve the objective function. The searching behaviour of the EPO is adapted by using the hunting behaviour of BOA. The proposed technique is executed in MATLAB/Simulink work site, and the experimental results are analyzed under three test cases: normal condition, irradiation change condition, and load change condition. The performance of the proposed technique is compared with different existing techniques and the calculated frequency deviation index of the proposed technique in all the cases is 0.0051, 0.0045, and 0.0047 and found to be very optimal compared with existing methods. Overall, the experimental outcomes show that the proposed EPOBOA method is more efficient and confirm its ability to solve the issues.

Implementation of Variable Blade Inertia in OpenFAST to Integrate a Flywheel System in the Rotor of a Wind Turbine

In this paper, the integration of the dynamic behavior of the flywheel system into the load simulation tool OpenFAST is presented. The flywheel system enables a wind turbine to vary the inertia of its rotor blades to control the power production and, most importantly, to affect the vibratory behavior of wind turbine components. Consequently, in order to simulate the behavior of a wind turbine with a flywheel system in its rotor, the variable blade characteristics need to be considered in the load simulation tool. Currently, computer-aided engineering tools for simulating the mechanical loads of wind turbines are not designed to simulate variable blade inertia. Hence, the goal of this paper is to explain how variable inertias of rotor blades are implanted in such load simulation tools as OpenFAST. OpenFAST is used because of it is free, publicly available, and well documentation. Moreover, OpenFAST is open source, which allows modifications in its source code. This add-on in the load simulation is applied to correct rotor mass imbalance. It can also be applied in many cases related to the change in the inertia of wind turbine rotor blades during its operation as, for example, atmospheric ice accretion on the blades, smart blades, etc.

Forced Convection Heat Transfer In a Cylindrical Porous Media exposed to Constant Wall Heat Flux.(Dept.M)

Forced convection heat flow in a cylindrical packed bed is examined numerically. The bed is filled with saturated spherical beads porous media and is exposed to a constant wall heat flux. Besides the energy equation, the generalized from. of the momentum equation including the non-Darcian effects such as the variable porosity, flow inertia, and viscous friction is considered, and the finite difference method is used. The results have been obtained numerically for sphere beads (3≤ d ≤8 mm diameter), ratio of the particle diameter to the pipe radius 0.05 ≤ D ≤0.5, and nondimensional pressure gradient B up to 108. The non-Darcian effects have a significant influence on the behavior of the temperature, thermal entry length. and Nusselt number across and at the channel wall. The channeling phenomenon near the walls enhanced the thermal communication between the fluid/solid matrix. composite and the walls. This fact yielded an overall 21 percent increase in the value of the Nu in the fully developed region, compared to the value predicted when the Darcy model was used. The results gives complete information about the flow structure and heat transfer for the expressed ranges of parameters. Also, useful correlations reporting the dependence of the thermal entry length on the problem parameters (d, D, B) were reported. A direct dependence of the thermal entry length on Re exists and gives the same correlation that obtained for the pure fluid flow case: XE = 0.1 Re To verifY the numerical results a comparison have been done with the numerical results obtained by Poulikakos and Renken [11], Kays and Crawford [26] and Petukhov [27]. The comparison shows a very good agreement for the presented results and proves the validity of the model.

Design optimization analysis of an anti-backlash geared servo system using a mechanical resonance simulation and experiment

Abstract. In many mechatronic systems, gear transmission chains are often used to transmit motion and power between motors and loads, especially for light, small but large torque output systems. Gear transmission chains will inevitably bring backlash as well as elasticity of shafts and meshing teeth. All of these nonlinear factors will affect the performance of mechatronic systems. Anti-backlash gear systems can reduce the transmission error, but elasticity has to be considered too. The aim of this paper is to find the key parameters affecting the resonance and anti-resonance frequencies of anti-backlash gear systems and then to give the design optimization methods of improving performance, both from element parameters and mechanical designing. The anti-backlash geared servo system is modeled using a two-inertia approximate model; a method of computing the equivalent stiffness of anti-backlash gear train is proposed, which comprehensively considers the total backlash of transmission chain, gear mesh stiffness, gear shaft stiffness and torsional spring stiffness. With the s-domain block diagram model of the anti-backlash geared servo system, the influences of four main factors on the resonance and anti-resonance frequencies of system are analyzed by simulation according to the frequency response, and the simulation analysis results dependent on torsional spring stiffness of anti-backlash gear pair and load moment of inertia variation are verified by the experiment. The errors between simulation and experimental results are less than 10 Hz. With these simulation and experiment results, the design optimization methods of improving the resonance and anti-resonance frequencies such as designing the center distance adjusting mechanism to reduce the initial total backlash, increasing the stiffness of torsional spring and lightweight design of load are proposed in engineering applications.

Robust spacecraft rendezvous using a variable speed control moment gyro and thruster

Robust, co-ordinate free, thrust-vector tracking controls are designed for a single Variable Speed Control Moment Gyro (VSCMG). The proposed controls, based on an adaptive active disturbance rejection control and higher-order sliding mode control are presented and compared. These controls guarantee the closed-loop pointing error converges to and remain within a bounded region of the zero error even in the presence of the variable inertia induced by the VSCMG, thruster off-set and uncertain disturbance torques. Secondly, the pointing control law is developed to address the problem of spacecraft rendezvous using only a single thruster and a single VSCMG. Here a pointing guidance law is developed that weights the desired thrust of the rendezvous using a scaling function of the pointing error. This guidance law is shown to significantly improve the performance of the rendezvous maneuver with respect to a guidance law that does not utilize the scaling function. Simulations of a rendezvous maneuver with a 12 U CubeSat are undertaken to demonstrate the applicability of the developed control laws.

Modelling and control of a semi-active dual-chamber hydro-pneumatic inerter-based suspension system

This study develops a new type of semi-active dual-chamber hydro-pneumatic inerter-based suspension (SADHPIS) based on the ‘inerter–spring–damping’ vibration isolation system and semi-active control. The mathematical model of SADHPIS is linearised to match the nonlinear SADHPIS system with a linear control strategy, and the equivalent parameters are calculated. A linear–quadratic–Gaussian (LQG) controller that matches the nonlinear characteristics of the SADHPIS system is designed. Furthermore, the performance of a quarter-vehicle model with SADHPIS is analysed and compared with that with normal semi-active hydro-pneumatic suspension (SAHPS). Simulation results show that the performance of SADHPIS is better than that of SAHPS, indicating that ride comfort and handle stability are improved greatly in SADHPIS. A prototype is also developed, and a comparative bench test is conducted to verify the accuracy of the simulations. SADHPIS can realise adjustable inertia with a small space and low energy consumption. This work provides new insights for research on variable inertia, promotes the matching of inerters and hydro-pneumatic suspension systems and further proves the practical application value of hydro-pneumatic inerter-based suspension.

The Role Played by Mass, Friction, and Inertia on the Driving Torques of Lower-Limb Gait Training Exoskeletons

Lower-limb gait training exoskeletons are extraordinary tools used to reduce the burden of locomotor impairments in patients with neurological diseases. However, the transparent operation and backdrivability of such systems still needs to be improved. Moreover, it is not completely understood how the mechanical design of the robot can interfere with the user’s gait pattern. Aiming to address these shortcomings, we investigate the required driving torques and mechanical power to move the legs under a wide range of actuator’s mass, inertia and friction and thigh/shank lengths. We used the ExoRoboWalker, a six-degree-of-freedom lower-limb exoskeleton, to build a framework model based on the double-pendulum approach integrated with the actuators’ mechanical impedance. Decoupled joint apparent inertia and the Rayleigh’s dissipation function were introduced to the robot’s Lagrangian to consider the effects of gearhead ratio and joint friction in the model. Firstly, it is presented the isolated effect of such variables on the required driving torques of the system. The oscillation frequency for the minimum joint torque was severely affected by variations of inertia, friction, and links length. Secondly, the combined effect of the actuator’s mass, inertia and friction reveled that a heavier exoskeleton with low-ratio transmission required less torque and mechanical power than a lighter one with greater reduction ratio depending on the oscillation frequency, which is remarkable. These findings have important implications for new designs of lower-limb gait training systems.

The Effect of Wing Spar Cross-Sectional Profile Variation on the Unmanned Aerial Vehicle (UAV) Natural Frequency

Natural frequency is a critical dynamic parameter in designing the unmanned aerial vehicle (UAV) wing structure. The low-value natural frequency causes the aircraft wing to deflect easily while flying. Furthermore, the low-value natural frequency can causes resonance when this natural frequency is closest to the wind frequency. An increase in the UAV natural frequency can be conducted by increasing the wing structural stiffness. However, increased stiffness by enlarging dimensions is often followed by an increase in mass that is avoided in the design of aircraft structures. One technique that can be used to increase UAV natural frequency is by increasing the cross-sectional moment of inertia of the wing spar. In this study, an analysis of the effect of the wing spar cross-sectional inertia variations on the UAV natural frequency is conducted. Several wings spar cross-sectional profiles with different cross-sectional inertia are evaluated, such as U profile, circular, T profile, square, L profile, I profile, and Z profile. The results of the investigation showed that the wing spar using T profile is better than other profiles in increasing the wing structure natural frequency. This profile could increase the 1st elastic natural frequency by 22.9%, with only a 3.4 % increase in mass.

Trajectory planning and optimization of the bionic mantis robot front leg

In this paper, a manipulator of the bionic mantis robot is designed inspired by the anatomical structure of the mantis front leg. A geometrical method is utilized to calculate the forward kinemics. Then, by analyzing the mantis motion video frame by frame, each of the front leg joints angles is measured in crawling and preying motion, which are used as interpolation conditions to solve the planned trajectory for manipulator by cubic spline interpolation. In some circumstance, the planned joint angles may exceed its limitation. By undermining the interpolation conditions, the problem is transformed from solving a cubic spline function to optimization. Finally, particle swarm optimization with variable inertia weight is introduced to optimize the planned trajectory. The result indicates that the trajectory, smoother after optimization could effectively imitate the motion of mantis front leg within the joint rotation range, which lays the basis for further research on the motion control.

Application of optimization algorithms to adaptive motion control for repetitive process

The application of optimization algorithms to adaptive motion control is proposed in this paper. In order to provide optimal system response, optimization algorithm is used as adjustment mechanism of controller coefficients. Most of optimization algorithms are not able to work in continuous optimization mode and with non-constant search space (i.e. dataset). For this reason, the introduction of a novel approach, Adaptive Procedure for Optimization Algorithms (APOA), that allows to apply most of optimization algorithms to adaptation process seems to be necessary. Such an algorithm is innovative, due to its universality in terms of applied optimization algorithm. Its application allows to obtain optimal motion control in modern electric drives. The proposed APOA is presented together with the novel desired-response adaptive system (DRAS) approach for repetitive processes. This solution provides unchanged system response regardless of plant parameters variation or external disturbances. The developed adaptive approach based on optimization algorithm is implemented in permanent magnet synchronous motor (PMSM) drive to adapt state feedback speed controller during moment of inertia variations. Since the proposed DRAS is model-free approach, the adaptation procedure is immune to issues related to plant parameters mismatch. The obtained results prove that proposed adaptive speed controller for PMSM assures desired system response regardless of the moment of inertia variation.

Vibration control of vehicle suspension with magneto-rheological variable damping and inertia

To avoid the limitation of conventional vehicle magnetorheological (MR) suspension, a variable damping and inertia device is applied in the vehicle suspension with MR technology. A semi-active adaptive MR inerter (AMRI) is discussed. A quarter car suspension model with an AMRI installed in parallel with a double-ended MR damper (D-MRD) is considered. First, the vehicle suspension with variable damping and inertia is analyzed. The prototype of D-MRD and MR variable inertia flywheel (MRVIF) are fabricated and tested respectively. Then, the control model of D-MRD and MRVIF is developed on the basis of test data. An improved Fuzzy PID controller for the semi-active suspension with D-MRD and AMRI is formulated. Numerical simulation is investigated to validate the proposed variable damping and inertia device. The results demonstrate that the performance of the semi-active suspension with D-MRD and AMRI can achieve much better ride comfort than the semi-active suspension with only D-MRD or AMRI.

Using LSTM Neural Network Based on Improved PSO and Attention Mechanism for Predicting the Effluent COD in a Wastewater Treatment Plant

Enhancing the monitoring capabilities of wastewater treatment plant (WWTP) key features can accomplish accurate prediction to help WWTPs develop a plan, which is of great significance to control regional water environmental pollution. Chemical oxygen demand (COD) is one of the key features of wastewater treatment. Traditional monitoring methods are time consuming and have high costs making it difficult to meet the needs of rapid monitoring in practical applications. To address this issue, a method for optimizing a long short term memory (LSTM) neural network model based on adaptive hybrid mutation particle swarm optimization (AHMPSO) and an attention mechanism (AM) is proposed. As the hyperparameters of the LSTM are difficult to select, AHMPSO is used to optimize the LSTM. A nonlinear variable inertia weight with random factors is introduced to balance the global search ability and the local search ability and to improve the convergence speed of the PSO algorithm. In addition, the hybrid mutation strategy is added in the search process to reduce the risk of particles falling into local optimal solutions. Finally, an AM is added to the LSTM model to mine local water quality features to improve the effluent COD prediction accuracy. Compared with other models (LSTM, LSTM-AM, and PSO-LSTM-AM), the RMSE(the root mean square error) of the optimized model decreased by 7.803%-19.499%, the MAE(the mean absolute error) of the optimized model decreased by 9.669%-27.551%, the MAPE(the mean absolute error) of the optimized model decreased by 8.993%-25.996%, and the R2 (the coefficient of determination) value of the optimized model increased by 3.313%-11.229%. The experimental results show that the optimized model has better performance and achieves a more accurate prediction of the effluent COD.

Oscillator with Hyperbolically Variable Inertia

Oscillator with Hyperbolically Variable Inertia

A wavelet‐based approach for describing the mechanical behaviour of cellular beams

AbstractThis paper describes how a wavelet model comprised of a linear combination of sine terms is capable of representing the cross‐section inertia variation along the length of cellular beams. This allows the efficient computation of deflections of cellular beams when these are deployed as a part of steel‐concrete composite flooring systems. This method does not involve purely statistical approaches or piece‐wise integration of moment‐curvature relationships that lead to cumbersome matrix approaches and complicate the assessment of deflections. Despite its simplicity, the proposed approach is found to be reliable as it successfully predicts displacements obtained through finite element model representations of more than 260 cases with errors smaller than ±5 %. Furthermore, the proposed analytical description of cross‐section inertia along the beam length is defined by only three parameters that can be inferred through linear expressions considering the geometrical characteristics of a perforated beam, namely, the ratio of flange to web thickness, the second moment of inertia of the steel beam and the ratio between beam length and depth, making it easy for widespread application by practitioners.

Tunable Wave Energy Converter Using Variable Inertia Flywheel

Axisymmetric heaving point absorbers are popular wave energy converters because of their easy deployment and insensitivity to incident wave directions. These devices are designed ideally to resonate with the incident wave to achieve high power output. However, as the device resonant frequency deviates from the dominant frequency of ever-changing irregular waves, the performance drops drastically. To solve this problem and as a complement to existing measures, we propose a mechanism, named variable inertia flywheel, to directly manipulate the equivalent mass of the point absorber, thus altering the system resonance frequency and power absorption bandwidth. We use a flywheel with symmetrically placed mass spring dampers in a ballscrew-based power take-off system. With its variable inertia and mass amplification effect, we can economically and dynamically adapt the system equivalent mass and corresponding parameters with small mass spring dampers. Apart from the passive configuration, we also propose the semi-active and active configurations to further enhance the performance and broaden the functionality scope of the proposed power take-off system. Numerical studies have revealed the dynamics of variable inertia flywheel, and have validated its adaptivity to varying wave conditions and its potential for increasing power output of point absorbers in both regular and irregular waves.

Refinement of the Rotational Deformation of the Viscoelastic Earth

Using a modal approach, this work determined the deformations caused by the pole tide for the axisymmetric model of a deformable Earth with a viscoelastic layer. We compared centrifugal moments of inertia variations with generally accepted expressions. The main properties of the theoretical pole tide are considered in comparison with those observed on the basis of processing high-precision measurements of the gravity acceleration.

Handling Qualities Analysis of an Unmanned Aircraft Vehicle for Agricultural Spraying

The use of unmanned aircraft vehicles (UAVs) for the most diverse aeronautic missions is a reality. Then, with the rise of precision agriculture (PA), the viability of the incorporation of this technology in the countryside on both big and small proprieties is under study. This work aims to analyze the handling qualities of an UAV with a mission of pest control chemical spraying. With this objective, aircraft data was used to analyze the eigenvalues of the aircraft modes. Then, the impact of mass and inertia variation during its mission was studied. Also, the longitudinal and latero-directional dynamics were evaluated based on the Cooper–Harper scale. The results found indicate that all aircraft modes are stable for both full hopper and empty hopper conditions. Moreover, the determined handling quality grades of the UAV in the Cooper–Harper scale indicate the need for some correction applied by the pilot during flight.

Research on the Damping Device with Adjustable Inertia and Damping

In this paper, a new type of composite structure is proposed based on the original semi-active suspension of magnetorheological shock absorber and automobile suspension with inertia container, and the structure is analysed theoretically. The proposed new composite device is composed of a hydraulic cylinder, a magnetorheological damper and a hydraulic motor. The magnetorheological damper is compounded in the hydraulic cylinder and connected to the hydraulic motor through a hydraulic pipeline. The magnetorheological damper has the function of adjusting the damping, and the hydraulic motor achieves the purpose of adjusting the inertia by changing the mass. In order to analyse the device, the mechanical characteristics of magnetorheological valve and hydraulic motor are modelled and analysed. A quarter-vehicle suspension simulation analysis was performed on the overall operating characteristics of the system. The analysis results showed that the compound device has good variable damping inertia capacity characteristics, which is of great significance for improving the semi-active control suspension system.

Design and Analysis of a Variable Inertia Spatial Robotic Tail for Dynamic Stabilization.

This paper presents the design of a four degree-of-freedom (DoF) spatial tail and demonstrates the dynamic stabilization of a bipedal robotic platform through a hardware-in-loop simulation. The proposed tail design features three active revolute joints with an active prismatic joint, the latter of which provides a variable moment of inertia. Real-time experimental results validate the derived mathematical model when compared to simulated reactive moment results, both obtained while executing a pre-determined trajectory. A 4-DoF tail prototype was constructed and the tail dynamics, in terms of reactive force and moments, were validated using a 6-axis load cell. The paper also presents a case study where a zero moment point (ZMP) placement-based trajectory planner, along with a model-based controller, was developed in order for the tail to stabilize a simulated unstable biped robot. The case study also demonstrates the capability of the motion planner and controller in reducing the system’s kinetic energy during periods of instability by maintaining ZMP within the support polygon of the host biped robot. Both experimental and simulation results show an improvement in the tail-generated reactive moments for robot stabilization through the inclusion of prismatic motion while executing complex trajectories.