Input Force Research Articles

Technical Note: A Novel Servo-Driven Dual-Roller Handrim Wheelchair Ergometer

The measurement of handrim wheelchair propulsion characteristics and performance in the field is complicated due to the non-stationary nature of wheelchair driving. In contrast, the laboratory provides a constrained and standardisable environment to conduct measurements and experiments. Apart from wheelchair treadmills, dynamometers or ergometers for handrim wheelchairs are often custom-made, one-of-a-kind, expensive, and sparsely documented in the research literature. To facilitate standardised and comparable lab-based measurements in research, as well as in clinical settings and adapted sports, a new wheelchair ergometer was developed. The ergometer with instrumented dual rollers allows for the performance analysis of individuals in their personal handrim wheelchair and facilitates capacity assessment, training and skill acquisition in rehabilitation or adapted sports. The ergometer contains two servomotors, one for each rear wheel roller, that allow for the simulation of translational inertia and resistive forces as encountered during wheelchair propulsion based on force input and a simple mechanical model of wheelchair propulsion. A load cell configuration for left and right roller enables the measurement of effective user-generated torque and force on the handrim and the concomitant timing patterns. Preliminary results are discussed.

Biomechanical analysis on human gait and posture for development of floating backpack

Floating backpack system or also known as suspended-load backpack has been known as a new type of backpack which able to reduce the effect of impact force from the loads carried in the backpack while walking or running. Particularly on the application for military or rescue team, this new backpack design claimed to improve the comfort and reduce the burden on the skeletal muscle as well as the risk of injury. In this research, we try to assess the biomechanics performance of our novel floating backpack design on reducing the impact force on the wearer by firstly analyzing the human gait cycle and posture adjustment. This analysis conducted by motion analysis method which able to track the change of position of certain points while walking and running. We tracked several points on the volunteer’s lower extremity and analyze its kinematics information throughout the walk and running cycle with a different pace and velocity. From this data, we try to get the standard gait model as a mechanical input force for the floating backpack system. Furthermore, with this 3D analysis we can also analyze the posture adjustment as the balancing mechanism of human body to compensate the different forces from the different state of walking-running cycle. A sinusoidal pattern with a frequency of 2-3 Hz are measured on the transition phase of walking and running, while the maximum amplitude was varying on throughout each cycle phase

Dynamics and stabilization of flexible spacecraft structures with magnetic coil-pair actuators

The dynamics of flexible spacecraft structures with embedded magnetic actuators are studied. Discretized equations of motion for a constrained plate model and an unconstrained two-plate/rigid bus model are derived for actuators that create in-plane forces via current-carrying coils. Taking inputs to be the magnetic forces generated between pairs of coils, the goal of vibration suppression is shown to result in a bilinear control problem. The selection of a generalized rate output variable is used to obtain a passive map from coil-pair force inputs, yielding $$\mathscr {L}_2$$ stability for strictly passive feedback laws. The implementation of one such feedback corresponds to using collocated sensing at the actuator locations, and given mild assumptions about the actuator location, is a robust stabilizer with respect to unstructured uncertainties. Simulations of the closed-loop system are completed to support findings throughout.

Evaluation of Flood Prediction Capability of the WRF-Hydro Model Based on Multiple Forcing Scenarios

The Weather Research and Forecasting (WRF)-Hydro model as a physical-based, fully-distributed, multi-parameterization modeling system easy to couple with numerical weather prediction model, has potential for operational flood forecasting in the small and medium catchments (SMCs). However, this model requires many input forcings, which makes it difficult to use it for the SMCs without adequate observed forcings. The Global Land Data Assimilation System (GLDAS), the WRF outputs and the ideal forcings generated by the WRF-Hydro model can provide all forcings required in the model for these SMCs. In this study, seven forcing scenarios were designed based on the products of GLDAS, WRF and ideal forcings, as well as the observed and merged rainfalls to assess the performance of the WRF-Hydro model for flood simulation. The model was applied to the Chenhe catchment, a typical SMC located in the Midwestern China. The flood prediction capability of the WRF-Hydro model was also compared to that of widely used Xinanjiang model. The results show that the three forcing scenarios, including the GLDAS forcings with observed rainfall, the WRF forcings with observed rainfall and GLDAS forcings with GLDAS-merged rainfall, are optimal input forcings for the WRF-Hydro model. Their mean root mean square errors (RMSE) are 0.18, 0.18 and 0.17 mm/h, respectively. The performance of the WRF-Hydro model driven by these three scenarios is generally comparable to that of the Xinanjiang model (RMSE = 0.17 mm/h).

Algebraic approach towards the exploitation of “softness”: the input–output equation for morphological computation

Recently, soft robots that consist of soft and deformable materials have received much attention for their adaptability to uncertain environments. Although these robots are difficult to control with a conventional control theory owing to their complex body dynamics, research from different perspectives attempts to actively exploit these body dynamics as an asset rather than a drawback. This approach is called morphological computation, in which the soft materials are used for computation that includes a new kind of control strategy. In this article, we propose a novel approach to analyze the computational properties of soft materials based on an algebraic method, called the input–output equation used in systems analysis, particularly in systems biology. We mainly focus on the two scenarios relevant to soft robotics, that is, analysis of the computational capabilities of soft materials and design of the input force to soft devices to generate the target behaviors. The input–output equation directly describes the relationship between inputs and outputs of a system, and hence by using this equation, important properties, such as the echo state property that guarantees reproducible responses against the same input stream, can be investigated for soft structures. Several application scenarios of our proposed method are demonstrated using typical soft robotic settings in detail, including linear/nonlinear models and hydrogels driven by chemical reactions.

State-space system identification with physically motivated residual states and throughput rank constraint

It has been observed that energy conjugate input-output pair transfer functions with strongly participating outside-band modes of mechanical systems often render identified state-space models with poor fit to data. That holds even after common practice inclusion of mass and stiffness residual states. The inclusion of a particular form of extra residual states are suggested to improve the model fit for such pairs. A pole placement strategy for the extra states is derived. Furthermore, for identification of state-space models with force input and acceleration output, the system direct throughput matrix relating the two is modelled. For flexible structures with rigid body motion, it is shown that the direct throughput matrix can be decomposed into a rigid body and flexible motion part. In test situations with more inputs and outputs than rigid body modes, the rigid body partition of the direct throughput matrix of the identified model must be rank constrained for physical consistency. The constraint is enforced using a singular value decomposition during iterations of the state-space matrices used to further improve the identified model fit. The procedures are illustrated on simulated finite element data from an industrial component with known model order. A successful application to real experimental data is also shown.

Circuit Modeling of the Mechanical-Motion Rectifier for Electrical Simulation of Ocean Wave Power Takeoff

As is the case with several other mechanical power takeoffs (PTOs), the mechanical-motion-rectifier-based PTO consists of components, such as one-way clutches, gears, a ball screw, mechanical couplings, and a generator. Equivalent circuit models have been created in this article to describe the dry frictions, viscous damping, and mechanical compliances in these components, so the nonideal efficiency and nonlinear force of the PTO can be predicted in electrical simulations by integrating these subcircuit models. The circuit model is simplified, and its parameters are categorized as dc and ac unknowns. The dc and ac tests on the PTO are performed sequentially to extract two sets of parameters through linear regression or nonlinear curve fitting. Then, the model is validated through its prediction capability over 25 test conditions on input forces, output voltages, and efficiencies, with correlation coefficients of 0.9, 0.98, and 0.981, respectively.

Shape-constrained Input Estimation for Efficient Multi-shaker Vibration Testing

Multi-shaker vibration testing is gaining interest from structural dynamics test engineers as it can provide a much more accurate match to complicated field vibration responses than traditional single-axis shaker tests. However, the force capabilities of the small modal shakers typically used in multi-shaker vibration tests has limited the achievable response levels. To date, most multi-shaker vibration tests have been performed using a variety of standard, commercially-available control systems. While these control systems are adequate for a wide range of multiple-input/multiple-output tests, their control algorithms have not been tailored for the specific problem of multi-shaker vibration tests: efficiently coordinating the various shakers to work together to achieve a desired response. Here, a new input estimation algorithm is developed and demonstrated using simulations and actual test data. This algorithm, dubbed shape-constrained input estimation, is shown to effectively coordinate multiple shakers using a set of constraint vectors based on the deflection shapes of the test structure. This is accomplished by using the singular vector shapes of the system frequency response matrix, which allows the constraint vectors to automatically change as a function of frequency. Simulation and test results indicate a significant reduction in the input forces required to achieve a desired response. The results indicate that shape-constrained input estimation is an effective method to achieve higher response levels from limited shaker forces which will enable higher level multi-shaker vibration tests to be performed.

Process Parametric Dependency of Axial Downward Force and Macro- and Microstructural Morphologies in Ultrasonically Assisted Friction Stir Welding of Al/Mg Alloys

An elementary analysis is proposed to quantify the effects of ultrasonic vibrations during friction stir welding (FSW) of AA6061-T6 to AZ31B Mg alloy. In the present context, the ultrasonic vibrations are applied in the stirred zone (SZ) via a specially designed welding tool. The influence of ultrasonic vibration has been analyzed for a wide range of welding and rotation speeds. The acoustic addition has proven beneficial to enhance joint strength. Significant diminutions in axial downward force, tool torque, and tool input power equal to ~ 38, 38.7, and 38.75 pct, respectively, have been observed during the ultrasonic addition. Melioration in interfacial bonding, enhanced material mixing, and an improvement in weldment surface quality are observed for ultrasonic joints. For conventional joints, the intermetallic phases βAl3Mg2 and γAl12Mg17 have been found in the SZ and are fragmented under the acoustic influence. The microstructural analysis of the fracture surface shows a ductile fracture mechanism at ultrasonically treated surfaces. A noteworthy grain refinement cum recrystallization is observed in the SZ as well as the immediate deformation zone. The maximum ultrasonic effects are apparent at the weld center and gradually diminish as they move ahead from it.

Exploration on the emergency support mode of hospital medical supplies under the epidemic of NCP/ 中华医院管理杂志

Since the outbreak of Novel Coronavirus Pneumonia(NCP), hospitals have taken the fight against the virus as its own responsibility, and keep standing in the front line of epidemic prevention and control. The continuous input of anti-epidemic forces in hospitals also brings challenges to the medical supplies support, including the management of protective supplies and the maintenance of medical equipment. In the face of increasing security pressure, the medical materials support team broke the game on multiple fronts. Firstly, the team implements active material procurement strategy, sets material distribution priority according to risk level, releases materials uniformly based on stock and use, and implements traceability management of donated materials to ensure material supply. Secondly, centralized allocation management of equipment, emergency installation, advanced maintenance and emergency maintenance work is effectively completed. Thirdly, disinfection strategies for items and equipment are developed safely and effectively with the aid of disinfection equipment functions. At last, personnel management and training have been strengthened. These measures have provided strong support for the orderly prevention and control of the epidemic. Key words: clinical medical engineering; New crown pneumonia; Medical material support; Medical equipment maintenance

The role of third windows on human sound transmission of forward and reverse stimulations: A lumped-parameter approach.

The vestibular and cochlear aqueducts serve as additional sound transmission paths and produce different degrees of volume velocity shunt flow in cochlear sound transmission. To investigate its effect on forward and reverse stimulations, a lumped-parameter model of the human ear, which incorporates the third windows, was developed. The model combines a transmission-line ear-canal model, a middle-ear model, and an inner-ear model, which were developed previously by different investigators. The model is verified by comparison with experiments. The intracochlear differential-pressure transfer functions, which reflect the input force to the organ of Corti, were calculated. The results show that middle-ear gain for forward sound transmission is greater than the gain for reverse sound transmission. Changes in the cochlear aqueduct impedance have little effect on forward and reverse stimulations. The vestibular aqueduct has little effect on forward stimulation, but increasing its impedance causes deterioration on reverse stimulation below 300 Hz. Decreasing its impedance increases the excitation effect during reverse stimulation over the entire frequency, especially below 1000 Hz. Moreover, compared with the case without the third windows, the presence of the third windows has little effect on forward stimulation. Whereas, it boosts the reverse stimulation's performance below 300 Hz.

Analysis of Physical Education Teaching Evaluation System

In order to realize the accurate evaluation of physical education teaching quality, a big data analysis model of physical education teaching quality evaluation is proposed, and the system analysis the evaluation of physical education teaching .Big data classification and identification of physical education quality are carried out by using K-means clustering method. According to the results of statistical feature clustering of physical education quality, the input effectiveness of physical education hardware facilities is evaluated. Establish the quantitative evaluation model of financial expenditure and PE teaching quality evaluation project performance, adopt F statistic quantity analysis method to adjust the structure of physical education teaching hardware input and teacher force input. According to the statistical analysis results of physical education teaching quality evaluation, the self-adaptive evaluation of physical education teaching quality evaluation is carried out, and the optimization of physical education teaching quality evaluation is realized by combining the big data analysis method.

Sensitivity analysis and uncertainty assessment in water budgets simulated by the variable infiltration capacity model for Canadian subarctic watersheds

AbstractIn this study, we evaluate uncertainties propagated through different climate data sets in seasonal and annual hydrological simulations over 10 subarctic watersheds of northern Manitoba, Canada, using the variable infiltration capacity (VIC) model. Further, we perform a comprehensive sensitivity and uncertainty analysis of the VIC model using a robust and state‐of‐the‐art approach. The VIC model simulations utilize the recently developed variogram analysis of response surfaces (VARS) technique that requires in this application more than 6,000 model simulations for a 30‐year (1981–2010) study period. The method seeks parameter sensitivity, identifies influential parameters, and showcases streamflow sensitivity to parameter uncertainty at seasonal and annual timescales. Results suggest that the Ensemble VIC simulations match observed streamflow closest, whereas global reanalysis products yield high flows (0.5–3.0 mm day−1) against observations and an overestimation (10–60%) in seasonal and annual water balance terms. VIC parameters exhibit seasonal importance in VARS, and the choice of input data and performance metrics substantially affect sensitivity analysis. Uncertainty propagation due to input forcing selection in each water balance term (i.e., total runoff, soil moisture, and evapotranspiration) is examined separately to show both time and space dimensionality in available forcing data at seasonal and annual timescales. Reliable input forcing, the most influential model parameters, and the uncertainty envelope in streamflow prediction are presented for the VIC model. These results, along with some specific recommendations, are expected to assist the broader VIC modelling community and other users of VARS and land surface schemes, to enhance their modelling applications.

Simulation and time-frequency analysis of the longitudinal train dynamics coupled with a nonlinear friction draft gear

AbstractTrain safety and operational efficiency can be improved by investigating the dynamics of the train under varying conditions. Longitudinal train dynamics (LTD) simulations performed for such purposes, usually by utilising a nonlinear time-domain model. This paper covers two modes of LTD results corresponding to the time domain and frequency domain analysis. Time-domain solutions are essential to evaluate the full response used for parameter optimisation and controller design studies while frequency domain solutions can provide significant but straightforward clues regarding system dynamics. An advanced draft gear model, which works under a four-stage process is constructed considering all structural components, geometric relationships, friction modelling and dynamic characteristics such as hysteresis, stiffening, state transition, locked unloading, softening. Then, this model is parametrically reduced and implemented into an LTD simulation. The simulation in the time domain is conducted assuming a locomotive connected with a nine wagon via “ode3” fixed-step solver. The transfer function among the first wagon acceleration (output) and the locomotive force (input) estimated through system identification methodology. Then, the identification results interpreted by investigating step-response characteristic and best response giving parameter set is selected. Next, the modal and spectral analysis performed to reveal the behaviour of the in-train forces and the effects of vibration. This paper discusses a reliable methodology for the longitudinal dynamic analysis of the multi-bodied train in time and frequency domain and clarifies in-train vibration behaviour under the existence of sophisticated draft gear.

Design and Development of a Novel Two-Directional Energy Harvester With Single Piezoelectric Stack

This article presents the design, fabrication, and testing of a novel piezoelectric energy harvester. Its unique feature is that a single piezoelectric stack is used for harvesting the energy from two-directional excitation in vertical directions. To accept the input forces in two directions, a flexure-based two-stage force amplifier is integrated with a conical transmission mechanism and a sliding guiding mechanism. An analytical model is established to predict the force amplification ratio of the proposed energy harvester. In order to maximize the output performance of the energy harvester, the dominant parameters of the mechanism are determined, which are optimally designed by resorting to a genetic algorithm. A prototype energy harvester is fabricated for experimental testing. Experimental results indicate that the developed harvester exhibits the advantages of high safety factor, large force amplification ratio, and compact size. It can provide the maximum average output power density of over 286.70 kW · m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> from 10-N force excitation in two directions.

The Features of the First Year Inputs of Materials, Labor force and Money in New Apple Orchard Systems

The Features of the First Year Inputs of Materials, Labor force and Money in New Apple Orchard Systems

Design and testing of a new dual-axial underfloor piezoelectric energy harvester

This paper presents the design, fabrication, and testing of a dual-axial underfloor piezoelectric energy harvester based on piezoelectric stack. Usually, an underfloor energy harvester can only scavenge the energy from vertical force excitation. In addition to vertical pressure, the floor also suffers from lateral friction force during human walking. One uniqueness of the designed underfloor energy harvester lies in that it can collect energy from both vertical and horizontal excitation forces. To amplify the input force to get a larger output power, a flexure-based two-stage force amplifier is introduced and optimally designed. In order to transmit the two-directional (2-D) input force into the single direction that can be received by the force amplifier, the conical transmission mechanisms and slider mechanisms are introduced. Position limiters are adopted to protect the proposed mechanism. A prototype has been fabricated and tested. Experimental results indicate that the fabricated dual-axial piezoelectric energy harvester can provide an average output power up to 1.25 mW with a load resistance of 12 kΩ from 5 Hz force excitation of 100 N in two directions. With a load resistance of 26 kΩ, the harvested energy per walking footstep is derived as 7.00 mJ for the underfloor energy harvester.

Regularization-Based Dual Adaptive Kalman Filter for Identification of Sudden Structural Damage Using Sparse Measurements

This paper proposes a dual adaptive Kalman filter to identify parameters of a dynamic system that may experience sudden damage by a dynamic excitation such as earthquake ground motion. While various filter techniques have been utilized to estimate system’s states, parameters, input (force), or their combinations, the filter proposed in this paper focuses on tracking parameters that may change suddenly using sparse measurements. First, an advanced state-space model of parameter estimation employing a regularization technique is developed to overcome the lack of information in sparse measurements. To avoid inaccurate or biased estimation by conventional filters that use covariance matrices representing time-invariant artificial noises, this paper proposes a dual adaptive filtering, whose slave filter corrects the covariance of the artificial measurement noises in the master filter at every time-step. Since it is generally impossible to tune the proposed dual filter due to sensitivity with respect to parameters selected to describe artificial noises, particle swarm optimization (PSO) is adopted to facilitate optimal performance. Numerical investigations confirm the validity of the proposed method through comparison with other filters and emphasize the need for a thorough tuning process.

Frequency Response Evaluation by a Scaling Method Considering the Structure Change

Under operating conditions of machine tool, the structure’s dynamic is usually evaluated by operational modal (OM) analysis that is difficult to be used to estimate the frequency response function (FRF) because of the unknown state of complex input forces. In this paper, the scaling factor of OM shape was evaluated by the proposed scaling method which was based on the structure change. Firstly, OM parameters of the selected machine tool structure were estimated at four different positions. Results indicated that the mode shapes and the damping ratios were not influenced obviously by the structural change, but the natural frequency can be affected evidently. Secondly scaling factors were calculated by the frequency changes of the machine tool and the mode shapes of the movable components such as the worktable and the stocks, using the proposed method. Thirdly, machine tool’s FRF was calculated from the scaled operational modal parameters. Besides, it has been found an interesting phenomenon that different natural frequencies were sensitive to different movable components of the machine tool.

Finite Element Based Analysis of Steering Construction System of ORCA Class Fisheries Inspection Ship

The fisheries inspection class is the ship which featured with high maneuver and speed. The rudder construction system must be strong enough to withstand the external pressure due to the maneuver of the ship. Therefore, material selection must be proper. Before selecting the material, the external pressure of steering construction must be examined and performs the Finite Element (FE) analysis. In this paper, the variable for FE analysis was focused on the slope of the rudder. It consisted of 0o, 10o, 20o, and 35o. The slope analysis was performed numerically by Computational Fluid Dynamics (CFD) software. Then, the external pressure can be generated based on the CFD analysis results, which can be used as an input force in Finite Element analysis. Finally, the results were distinguished from the von-Mises stress, deflection, and safety factor. Each component of the steering construction system was examined in which the component consisted of the rudder, rudder stock, flange, bolts, and nuts. It was found that the flange component had a more significant value of stress and a smaller value of safety factor.