Hierarchical estimation of uncertainties in multi-rotors:A yaw-motion study using test bench

For dynamic systems with actuator faults, sensor faults, input disturbances, and measurement noises, a novel high-gain estimation technique is presented in this paper to estimate system states, actuator faults, and sensor faults simultaneously. The key idea is to represent faults as auxiliary system states so that a descriptor system representation can be formulated. By using the estimated state and fault signals, a fault-tolerant controller design approach is developed, where the closed-loop dynamic system can still be guaranteed to operate normally when actuator and sensor faults occur. It has been shown that in the proposed design framework, the actuator fault, sensor fault, input disturbance, and measurement noise can appear simultaneously and can be allowed to be in different bounded forms. Finally, the proposed algorithm is applied to the simulation study of a three-shaft gas turbine system and desired results have been obtained.

Background: In the field of biomechanical analysis of pedaling motion, researchers studied the relationship between cost energy and cycling technique for optimal use of the force applied to the pedals, to improve cycling velocity for minimal energy cost or to compute the joint powers according to the resistive load. For that, numerous measuring devices have been developed and investigated to evaluate resultant torque and/or power output. Recently, new pedal sensors I-Crankset (ICS) are sold to measure the forces applied to the pedals and to calculate the torque and/or power output produced during cycling. These pedals’ sensors were calibrated and certificated, but it was essential to check if these devices still measured accurately after their integration on an ergometer. Purpose: The aim of this study was to compare dynamically this new device for measuring crankset’s resultant torque, mechanical power and work outputs.  Methods: A subject (Male, 75 kg, 1.82 m, trained rider) took part to this study conducted ethically according to international standards. The rider adjusted the cycle ergometer according to its personal settings. Figure 1 described the test bench. It was composed of: a chainring (A) was used to connect the ergocycle to the bench through a chain and a flywheel (D) associated with a mechanical braking device (E) composed of a tray with additional masses. The evaluation protocol was implemented to achieve three pedaling conditions and so to cover the usual torque and power ranges (Table 1). For each condition, the subject produced a pedaling torque to overcome that resistive load during one trial of 90 seconds. Feedback of cadence was displayed on the Control SRM bicycle computer. The torque reference sensor (model 1641/1648, Lebow) named RTSL (C) was installed on the axis (B). The scientific version SRM sensor was mounted on the crankset of the ergocycle. The ICS sensors were fixed at each pedal. The relative pedal to crank and the crank to ergometer angles were measured using encoders.  Analyzed parameters: As all the signals are acquired at 200 Hz and synchronized, for each cycle and for each acquisition system, we had the same number of acquisitions samples. According to the sample rate and protocol used, more than 12 000 instantaneous measures will be available for the comparison of several devices. Three power outputs were computed through these equations: (1)  with , k is the reduction coefficient between SRM and bench chainrings, ratio of the two diameters. (2) SRM:,  is the average angular velocity of the crankset over the cycle. (3) ICS: ,  is instantaneous angular velocity of the crankset computed from encoders measures. The mechanical work outputs  were given by integration over the time of the power outputs. By design, the SRM only measures an average angular velocity, so we computed mechanical work firstly considering this constant angular velocity () and secondly considering instantaneous angular velocity provided by ICS encoders (). Statistical analysis: For each condition, the same analysis was performed on torque, power and work outputs obtained from the different sensors. These instantaneous parameters, once pedaling cycles normalized, were compared using a coefficient of multiple correlation inter-protocol (CMC ip ) to appreciate the similarity of the instantaneous measures waveforms given by various sensors in a single acquisition of the same parameter. For each condition (n=30 cycles) and for all conditions (n=90 cycles), the averaged torque and power output were computed over each cycle and then these values were compared pairwise of sensors (A Bland-Altman analysis). A global normalized averaged torque evolution over cycles was also computed for condition 1 and for each sensor using.  Results: Mechanical power output comparisons: Table 2 reports all the data for the comparison of the averaged power output measured by the three sensors, for the each condition and all conditions. Especially for condition 3, we note an increase for the power output of the mean bias and error range between SRM and RTSL against those computed for the torque [mean bias: -4.4 ±2.3% for the power vs -1.20 ±0.53% for the torque; error range: 29 W (9.2%) for the power and 0.79 Nm (1.9%) for the torque]. This is not the case for ICS. The figure 3 confirms these results with a 95% limits of agreement larger for the SRM than ICS [respectively -1.81; 7.37 W and -20.70; 9.48 W for ICS and SRM]. Mechanical work output comparisons: Table 3 shows the difference of cumulative output work over thirty cycles between ICS and RTSL then SRM and RTSL for each condition. The differences are also expressed as the percentage of the total cumulated work. To analyze the influence of the angular velocity, we integrated power output over time to compute the work output in using i) the torque and angular velocity measured by SRM (W SRM ) and ii) the SRM torque multiplied by ICS angular velocity (W SRM* ). These results are presented at the last lines of table 4. The relative error is under 2% whatever the conditions, excepted for condition 3 between SRM and RTSL (5.26%). This error can be reduced by using I‰ ICS provided by ICS to compute the W SRM* (1.44 %).  Discussion: Power output discussion. For the power output, we note high values of  between ICS and RTSL (Table 3). For the steady state condition (C1: 210 W), ICS power mean relative error (0.1 ±0.5%) is better than [1] when comparing Velotron cycle ergometer (-0.8% for constant 250 W trial) with a test bench. For condition 2 (150 – 250 W, 80 rpm), ICS results (1.8 ±0.5%, Table 2) are closed to power mean relative error reported by [4] when comparing Powertap (-1.5 ±0.6% for 50-1000 W at 100 rpm trial) with a test bench. As SRM is considered as a gold standard [5], we will try to position ICS against SRM. Before that, we check that SRM results are consistent with literature. The mean relative errors reported by [1] (0.18%) and [4] (0.1 ±1.1%) are lower than errors of the present study (respectively 0.8 ±1.2% for condition 1 and -0.8 ±2.1% for condition 2). These differences can be related to the possibility of the test bench used by [6] to maintain a constant pace along all the cycle unlike the protocol of this study (mean cadence: 8.3 ±0.2 rad/s for conditions 1 and 2). Indeed, it’s difficult for a rider to produce a constant crankset angular velocity like the motorised test bench used by [1] and [3]. [1] shows that a rapidly increasing angular velocity results in a more inaccurate power measurement (mean relative error: -3.3 %; CI = -8.1 to 1.5 %). This is closer to the results for condition 3 (-4.4 %; CI = -9 to 0.2 %). This condition accentuates the inability of the SRM to record, by design, instantaneous crankset angular velocity. For a similar pedaling cadence and power output, the relative mean error (1.2 %) between Powertap ergometer and SRM reported by [2] is comparable with the relative error between ICS and SRM computed for condition 1 (0.9%, Table 3). However, ICS seems to be more accurate than SRM when looking at the individual results obtained for SRM (-2.4%) and ICS (1.2%) against RTSL for all conditions. Consequently, as for the torque, ICS can be considered sufficiently accurate. Work output discussion: Table 3 show the requirement to precisely measure the instantaneous values of crankset angular velocity to calculate the work as part of an energy study of the pedaling motion. Thus, when pedaling with constant angular velocity, the power output computed by SRM () is enough accurate to calculate the work output (). For the conditions 1 and 2, the error respectively equal to 0.98% and 1.16% is acceptable. But when the angular velocity is variable, the error becomes equal to 5.26% for the SRM while it is still under 2% for ICS. This result confirms those obtained by [1] which indicates that a rapidly increasing angular velocity causes an inaccuracy in calculating the SRM power. This error is reduced to 1.44% when the torque measured by SRM () is multiplied by the instantaneous angular velocity measured by ICS (). So, ICS should be preferred for power and work outputs investigations.  Conclusions: The study showed that ICS sensor was an accurate powermeter comparable to a standard reference sensor and to SRM regardless the pedaling cadence (56 to 90 rpm) and the resistive load (18 to 42 Nm). However, ICS was more efficient than SRM for evaluating the work particularly when the pedaling angular velocity various significantly. This study showed that it was therefore essential to measure both instantaneous torque and angular velocity in order to conduct an energy analysis of the pedaling motion.

<div class="section abstract"><div class="htmlview paragraph">In the quest for reduced cost and shorter development times for fuel cell systems in industrial applications, two major issues arise. First, the electrochemical behavior of fuel cell systems is inherently difficult to predict. Second, testing fuel cell systems is resource intensive. These issues compound: Setting up an accurate model of a fuel cell system incurs long testing periods for model validation. Further, it does not guarantee acceptable results outside the tested range or for other membrane electrode assembly compositions.</div><div class="htmlview paragraph">To mitigate these two major issues an X in the Loop concept is proposed. Essentially, this is the direct integration of the test sample, here a single fuel cell, into the modelling environment of the whole system. In practice, two strategies with different levels of integration are defined.</div><div class="htmlview paragraph">The first strategy consists of initially deducing the operating parameters of the sample cell from the fuel cell system model. Then, setting them to the sample cell in the test bench. The response of the test sample is finally used to validate the designed system or update the parameters of the fuel cell model.</div><div class="htmlview paragraph">The second strategy is a step further towards the integration of the test sample into the model. Here, the core model of the fuel cell inside the fuel cell system model is completely replaced with the test sample, reducing the need for an accurate electrochemical model while improving the prediction of the behavior of the fuel cell system.</div><div class="htmlview paragraph">Compared to previously proposed testing concepts, here the balance of plants is directly integrated through a digital emulator, leading to a closer representation of the complete system. Furthermore, the test bench results are looped back to the model at run-time leading to a closer match between testing conditions and the real world as well a reduced impact of inaccuracies in the modelling of the fuel cell.</div><div class="htmlview paragraph">On the way to realizing this goal, an experimental test bench capable of showcasing working prototypes of the proposed operating strategies has been built.</div></div>

This paper presents a strategy to emulate a reduced scale of sucker rod pump using laboratory test bench. The strategy is based on combination of software and hardware system. Torque reference is generated using the proposed strategy based on real time model of sucker rod pump that runs in LabVIEW. The output of encoder and torque sensor are integrated through NI PCI- 6221 data acquisition card to the real time platform. The performance of the experimental test bench is evaluated using current, voltage, speed, and torque measurements and power calculations. The experimental results are compared to simulation results. The results indicate the capability of this test bench to serve as a platform for conducting experimental studies on sucker rod pump.

Biological pollution creates significant obstacles in the operation of power plants' technical water supply cooling systems (SCS). To minimize biological pollution, methods of corrective treatment with biocides are implemented. While these biocides effectively prevent fouling of the cooling system, they can also adversely affect the environment and structural materials. By evaluating structural materials' corrosion resistance and biocides' environmental safety for the cooling water during biocide treatment, any potential issues can be identified and addressed before they become a safety or operational concern. The paper presents the results of bench tests of the corrosion resistance of structural materials SCS, corrosion aggressiveness of the biocides: sodium hypochlorite NaClO and 2, 2-dibromo-3-nitriloropionamide (DBNPA), and the results of measurements of the concentration of biocides and their decomposition products to assess compliance with environmental standards when discharging return water when applying from biocides treatment. The cooling water SCS of the Rivne NPP (Nuclear Power Plant) was chosen as the research object. Bench corrosion tests were carried out using samples of corrosion indicators from materials: steels Ст20, 08Х18Н10Т; copper alloy МНЖ-5-1 and aluminum, which are defined as analogs of structural materials of the technical water supply system of the Rivne NPP. The conditions of operation of the technical water SCS of the Rivne NPP were simulated on the test bench, and corrosion rate measurement was carried out by the gravimetric method.

In this study, we simultaneously evaluate the multiple‐fault diagnosis problem of a class of Lipschitz nonlinear systems with actuator and sensor faults and unknown input disturbances. A nonsingular system transformation is used to transform the original system into two subsystems for multiple‐fault diagnosis: subsystems 1 and 2. At the system level, two robust sliding‐mode observers (RSMOs) are proposed. An RSMO is designed for subsystem 1 to detect actuator faults subjected to unknown input disturbances, and another RSMO is designed for subsystem 2 to detect sensor faults subjected to actuator faults. At the component level, a bank of RSMOs is proposed to detect and isolate actuators (sensors) with faults using a dedicated observer scheme. The reachability of RSMOs is comprehensively investigated in the estimation error space. Accordingly, the proposed observer parameters are designed as an optimization problem and solved using the linear matrix inequality (LMI) optimization technique. The effectiveness of the proposed multiple‐fault diagnosis scheme was validated through simulations of a modified seventh‐order aircraft system.

In this paper, two controllers with a compound disturbance observer are proposed for a two-wheeled inverted robot (TWIR) with model uncertainty and unknown input disturbance. First, an equivalent linear model of the TWIR with uncertainty and input disturbance is proposed using the Taylor series expansion for the nonlinear model of the TWIR at an equilibrium point, in which the nonlinear part of the Taylor series and the model uncertainty are combined with unknown input disturbance as compound input disturbance. Then, the compound input disturbance is estimated by using the Newton method and reference model. As the estimated compound disturbance is used to compensate for the compound disturbance, the equivalent linear system becomes closely definite without compound input disturbance. Finally, two controllers are proposed using the equivalent linear system. Stability analysis of the proposed control methods is also given. To illustrate the proposed methods, some simulations for the TWIR are performed and compared with the existing methods. The main contribution of this work includes the following: (i) simple controllers based on compound input disturbance observer for trajectory tracking and balancing of TWIRs with unknown input disturbance and model uncertainty are proposed; (ii) the stability of proposed closed-loop control systems is proved; (iii) our proposed methods are simulated and compared with the existing methods.

The main annulus hot gas ingress into turbine wheel-spaces is still one of the most challenging problem designers face. During the decades, several experimental test benches were developed worldwide to improve the knowledge associated to the rim seal flow physics. Even if in some cases quite complex and advanced rig configurations were proposed, limitations in the operating conditions and in the reproduction of the real engine geometries/characteristics into the rig are present. In this paper, validated CFD computations are used to explore the impact of some experimental rigs design choices/limitations on the sealing effectiveness prediction and their ability to mimic the real engine configuration behaviour. Attention is paid on several test rig related aspects such as operating conditions, flow path configuration (blade and vane count) and accuracy in the real engine rim seal geometry reconstruction applied to the rig. From the computations it emerges that a scaled geometry operated at lab conditions is able to mimic pretty well the real engine sealing performance when rig and engine experience the same flow path ΔCp. The ability of the rig to match the engine data is not affected by the differences in main annulus Mach number between test bench and engine. A further result that emerges from the computation regards the fact that the Φ0 - ΔCp0.5 curve is not linear, proving that the linear extrapolation of rim sealing performance from test bench to real engine when rig and engine are characterized by different ΔCp0.5 values is not of general application and an alternative approach is given. Finally, it is found that the impact of vane count on the rim sealing effectiveness is significant, making the extrapolation of data from rig to engine difficult.

Subject of study. Technology for quantum key distribution in fiber-optic communication lines under the influence of electromagnetic fields generated by atmospheric discharges is studied. Aim of study. A test bench for testing experimental techniques to be used in studying the effect of atmospheric discharges on transmission of a quantum key via fiber-optic communication lines is developed. Method. The characteristics of a quantum communication channel upon exposure of a coil containing an optical fiber to a magnetic field from a pulsed current are experimentally studied. Main results. An experimental test bench has been created and methods have been developed to evaluate the influence of magnetic fields arising from atmospheric discharges (lightning) on the transmission speed of a quantum key in fiber-optic communication lines. It was shown that quantum key distribution blocks using the BB84 phase-encoding protocol continue to show operational stability when the optical cable is exposed to alternating magnetic fields of up to 1.2 mT. However, the very fact of exposure to magnetic fields above 0.8 mT can be detected by a systematic decrease in the quantum key transmission rate and an increase in the quantum bit error rate (QBER) by 0.5%–1%. Practical significance. The laboratory test bench and methods developed herein support magnetic-field testing of various optical cables used for transmission of qubits. Fiber-optic networks through which qubits are transmitted can serve as a distributed lightning sensor; an increase in the level of quantum errors and a decrease in quantum key generation rate will be observed in any segment of an optical network where a lightning discharge generates strong magnetic fields.

A tyre-rim interaction digital twin for biaxial loading conditions

This article investigates the finite-time fault-estimation problem for a class of Lipschitz nonlinear systems with actuator faults and unknown input disturbances. Specifically, the original system is preliminarily decoupled into two reduced-order subsystems using a linear nonsingular transformation. A novel finite-time observer is proposed to estimate actuator faults in finite time. Subsequently, the proposed finite-time observer is extended to nonlinear systems with unknown input disturbances to investigate the robust fault-estimation problem. The actuator fault and unknown input disturbance are estimated simultaneously using two finite-time observations. Furthermore, a fault-estimation scheme is designed based on finite-time observers. The finite-time stability of the observers is then analysed using the Moreno–Lyapunov function method. The analytical proofs presented herein demonstrate that estimation errors can converge to a region of zero in finite time. Finally, the effectiveness of the developed finite-time observers and fault-estimation scheme was validated through simulations of a sample single-link flexible-joint robot.

Experimental analysis of user forces by test bench and manual hammer drill experiments with regard to vibrations and productivity

This article presents the implementation of a 3.5 kW resistive load bank applied to a four-stroke single-cylinder diesel engine test bench that operates with an alternator. With this experimental test bench, it is possible to perform mechanical, thermodynamic, and polluting emissions studies in compression-ignited or induced internal combustion engines. Applying the quantitative research methodology, the design of the electric charging system is carried out. Power control circuits and safety elements are designed for the load back. CAD software is used to design the structure and casing considering anthropometric measurements. Also, finite element analysis (FEA) is incorporated to verify the structural and thermal design criteria. he implementation of an electrical and instrumentation acceleration system for sensing power and torque in low-displacement engines showed a measurement error of less than 1%. Similarly, the FEA allowed to quantify the maximum efforts and guarantee a safety factor above 5. With the characterization of the implemented sensors, a correlation coefficient of up to 99.97% was achieved. The power measurement displayed an error lower than 3%, which leads to a high characterization capacity of any thermal machine with equal power or less than the designed one.

Integrated insulation clay hollow blocks is an interesting constructive system in the context of Near Zero Energy Buildings and building energy efficiency. Their simple modification into supply air wall can increase their thermal performance without great effort. This paper deals with the creation of an original supply air wall or window test bench and with the numerical and experimental study of a supply air wall (or ventilated wall) based on modified modern integrated insulation clay hollow blocks where large cavities (about 4 cm) are filled by mineral wool. In some cavities, mineral wool is removed to create a flow pattern, which aims to recover heat losses from inside and solar energy from outside. At first, a 3D CFD numerical model is presented to assess the energy performance of a 1 m2 sample of ventilated wall. Then, an experimental test bench, based on a modified guarded hot box simulating solar effects and airflows between the two chambers, is carried out to assess the real performances. A comparison between these two studies allows validating the results which show a good correlation in terms of temperature difference gains between outdoor temperature and pre-heated temperature going up to a maximum of 14 K for only 1 m2 of wall and for a volume flow rate of 4 m3/h (4,5 K for 32 m3/h).

Development of a low-cost PV system using an improved INC algorithm and a PV panel Proteus model