About the dynamic error of strain gauge torque measuring devices

The dynamic error of devices belongs to the number of errors that are difficult to estimate. The mechanism for forming this error on the example of torsional torque dynamometersis briefly considered as the most common in the practice of research on the energy of agricultural machines. The limiting ratios of frequencies of external influences and natural vibrations of strain-measuring devices are given. Recommendations are made to reduce dynamic error in torque strain analysis. The present review and the accumulated experience of strain gauge research allows us to recommend some directions for reducing dynamic errors in torque measurements. In order for a strain gauge to keep up with changes in torque in its inertial characteristics, it must have the smallest torque inertia. In order to reduce the probability of high-frequency harmonics from the elastic vibrations of the strain gauge, it must be sufficiently rigid. From this point of view, strain rods, strain sprockets, etc., having a moment of inertia greater than that of the same gear parts, are irrational. Based on modern micromodules and power supplies, the system can have a small mass and have no significant effect on the inertial characteristic of the strain gauge.

Modular 3D printable orthodontic measuring apparatus for force and torque measurements of thermoplastic/removable appliances

The magnitude of forces and moments applied on teeth during orthodontic treatment is crucial to achieve the desired tooth movement. The aim of this study is to introduce a modular 3D printable orthodontic measurement apparatus (M3DOMA), which can be used for measurements of forces and moments acting on teeth during treatment with aligners. The measurement device was characterized regarding signal to noise ratio (SNR) of the sensors, repeatability of measurements, influence of thermoforming, as well as reliability. Forces and moments were evaluated for an activation range of 0.1–0.4 mm, comparing them among different activation patterns with two aligner thicknesses. The sensors exhibited a SNR from 13–33 dB. Repeatability with repeated measurements showed standard deviations ≤0.015 N and 0.769 Nmm. The influence of thermoforming represented by standard deviation of forces ranges from 0.019–0.147 N. The device showed a range of intra class correlation (ICC) for repeated measurements for all sensors from 0.932 to 0.999. Hence the reliability of the device has been proven to be excellent.

Ferromagnetism out of charge fluctuation of strongly correlated electrons in κ-(BEDT-TTF)2Hg(SCN)2Br

We perform magnetic susceptibility and magnetic torque measurements on the organic κ-(BEDT-TTF)2Hg(SCN)2Br, which is recently suggested to host an exotic quantum dipole-liquid in its low-temperature insulating phase. Below the metal-insulator (MI) transition temperature, the magnetic susceptibility follows a Curie–Weiss law with a positive Curie–Weiss temperature, and a particular $$M\propto \sqrt{H}$$ M ∝ H curve is observed. The emergent ferromagnetically interacting spins amount to about 1/6 of the full spin moment of localized charges. Taking account of the possible inhomogeneous quasi-charge-order that forms a dipole-liquid, we construct a model of antiferromagnetically interacting spin chains in two adjacent charge-ordered domains, which are coupled via fluctuating charges on a Mott-dimer at the boundary. We find that the charge fluctuations can draw a weak ferromagnetic moment out of the spin singlet domains.

Rotational Rheology of Wood Flour Composites Based on Recycled Polyethylene

In this paper, we study the effect of the addition of wood flour as a filler in a recycled polyethylene (r-PE) in view of its potential applications in 3D printing. The composites, prepared by melt mixing, are characterized with torque measurements performed during the compounding, dynamic rotational rheology, and infrared spectroscopy. Data show that the introduction of wood results in increased viscosity and in sensible viscous heating during the compounding. The r-PE appear to be stable at temperatures up to 180 °C while at higher temperatures the material shows a rheological response characterized by time-increasing viscoelastic moduli that suggests a thermal degradation governed by crosslinking reactions. The compounds (with wood loading up to 50% in wt.) also shows thermal stability at temperatures up to 180 °C. The viscoelastic behavior and the infrared spectra of the r-PE matrix suggests the presence of branches in the macromolecular structure due to the process. Although the addition of wood particles determines increased viscoelastic moduli, a solid-like viscoelastic response is not shown even for the highest wood concentrations. This behavior, due to a poor compatibility and weak interfacial adhesion between the two phases, is however promising in view of common processing technologies as extrusion or injection molding.

Estimation of Wind Turbine Gearbox Loads for Online Fatigue Monitoring Using Inverse Methods

In this article a novel approach for the estimation of wind turbine gearbox loads with the purpose of online fatigue damage monitoring is presented. The proposed method employs a Digital Twin framework and aims at continuous estimation of the dynamic states based on CMS vibration data and generator torque measurements from SCADA data. With knowledge of the dynamic states local loads at gearbox bearings are easily determined and fatigue models are be applied to track the accumulation of fatigue damage. A case study using simulation measurements from a high-fidelity gearbox model is conducted to evaluate the proposed method. Estimated loads at the considered IMS and HSS bearings show moderate to high correlation (R = 0.50–0.96) to measurements, as lower frequency internal dynamics are not fully captured. The estimated fatigue damage differs by 5–15 % from measurements.

Detumbling a Non-Cooperative Space Target With Unknown Inertial Parameters Using a Space Manipulator Subjected to End-Effector Force/Torque Limits

This study addresses the problem of detumbling a non-cooperative space target, such as a malfunctioning satellite, using a space robot for the purpose of performing on-orbit servicing. The space robot is denoted as the servicer and consists of a satellite base equipped with a robotic manipulator. The formulation of a detumbling control strategy must respect limits on the grasping force and torque at the servicer’s end-effector without knowledge of the target’s inertial parameters (mass, inertia tensor, location of center of mass). In the literature, prior studies have formulated detumbling strategies under the assumption of accurate knowledge of the target’s inertial parameters. However, obtaining accurate estimates of the target’s inertial parameters is difficult, and parameter uncertainty may lead to instability and violation of the end-effector force/torque limits. This study will address the problem of detumbling a noncooperative target with unknown but bounded inertial parameters subjected to force/torque limits at the servicer’s end-effector. In this study, two detumbling control strategies are presented. The first detumbling strategy is presented under the assumption that force/torque measurements at the end-effector are available. Detumbling of the target is achieved by applying a reference force/torque to the target that is designed to bring the target’s tumbling motion to rest subjected to force/torque limits. To ensure stable detumbling of the target, a robust compensator is designed based on bounds of the target’s unknown inertial parameters. Furthermore, once the detumbling process starts, in order to reduce the robust control gains, bounds on the target’s unknown inertial parameters are estimated in real-time. The resultant detumbling controller enables the servicer to detumble the target while complying with the target’s unknown residual tumbling motion. The second detumbling control strategy is developed without the need of end-effector’s force/torque measurements and takes into account magnitude constraints on servicer’s control inputs in the detumbling controller’s design. Detumbling is achieved by tracking a desired detumbling trajectory that is delineated subjected to end-effector force/torque limits and requires bounds on the target’s inertial parameters. The hyperbolic tangent function is utilized to model the magnitude constraints on the servicer’s control inputs, resulting in a system that is non-affine in its control inputs. As a result, an augmented model of the servicer is presented to allow the formulation of the detumbling controller. Using bounds on the target’s inertial parameters, robust adaptive control approach is utilized to design the detumbling controller with the backstepping technique in order to track the desired detumbling trajectory and to reject the gained target’s momentum. Numerical simulation studies were conducted for both detumbling control strategies utilizing a servicer equipped with a 7-degree-of-freedom (DOF) manipulator. The results demonstrate that both control strategies are capable of detumbling a non-cooperative target with unknown inertial parameters subjected to force/torque limits. Experiments conducted with a 3-DOF manipulator demonstrate that the design procedure utilized to delineate the desired detumbling trajectory in the second detumbling strategy respects force/torque limits at the end effector. The study is concluded with a discussion comparing the two proposed detumbling strategies by highlighting their advantages and disadvantages.