Extended-POD based acoustic analysis of separated aerofoils via simultaneous time-resolved PIV and force measurements

We present a cross-correlation based analysis of the acoustic field generated in the wake of NACA 0012 and NACA 65410 aerofoils at a chord-based Reynolds number Rec = 75000 as obtained from pressure fields reconstructed from a series of planar time-resolved Particle Image Velocimetry (PIV) experiments. The experiments are performed in a water channel facility located at the University of Southampton with an overhead carriage system to allow precise control of the angle of attack α of the aerofoils as well as to mount them to a six-axis force/torque transducer to allow for simultaneous load measurements. Angles of attack in the range 4◦ < α < 17◦ are explored corresponding to a range of conditions from zero flow separation to fully stalled.

Diagnosis of the Misaligned Faults of the Vertical Test Instrument of High-Precision Industrial Robot Reducer

High-precision reducer is the core component of industrial robots. In order to achieve the comprehensive performance testing of precision reducers, an instrument with a vertical layout and a cylindrical structure is designed. As a rotating machine, the inevitable coupling misalignment of the instrument can lead to vibration faults which lead to errors in the test. So it is pretty necessary to diagnose and monitor the coupling misalignment while the instrument is working. The causes of the coupling misaligned fault of the instrument and the relationship between the misalignment fault and torque ripple are analyzed in this paper. A method of using the torque transducer in the measurement chain of the instrument to diagnose the coupling misalignment is proposed in this paper. Many experiments have been done to test the capability of detecting the coupling misalignment using this method. Experimental results show that the amplitude of torque ripple of the shaft is linearly related to the coupling misalignment and is quadratically related to the rotation speed of the shaft when the misalignment exists in the shaft. The combination of components at the rotation frequency (fr) and the additional components can be used to diagnose faults due to coupling misalignment.

A Vibrissa-Inspired Highly Flexible Tactile Sensor: Scanning 3D Object Surfaces Providing Tactile Images

Just as the sense of touch complements vision in various species, several robots could benefit from advanced tactile sensors, in particular when operating under poor visibility. A prominent tactile sense organ, frequently serving as a natural paragon for developing tactile sensors, is the vibrissae of, e.g., rats. Within this study, we present a vibrissa-inspired sensor concept for 3D object scanning and reconstruction to be exemplarily used in mobile robots. The setup consists of a highly flexible rod attached to a 3D force-torque transducer (measuring device). The scanning process is realized by translationally shifting the base of the rod relative to the object. Consequently, the rod sweeps over the object’s surface, undergoing large bending deflections. Then, the support reactions at the base of the rod are evaluated for contact localization. Presenting a method of theoretically generating these support reactions, we provide an important basis for future parameter studies. During scanning, lateral slip of the rod is not actively prevented, in contrast to literature. In this way, we demonstrate the suitability of the sensor for passively dragging it on a mobile robot. Experimental scanning sweeps using an artificial vibrissa (steel wire) of length 50 mm and a glass sphere as a test object with a diameter of 60 mm verify the theoretical results and serve as a proof of concept.

The investigation of effects of humidity and temperature on torque transducers calibration

Torque transducer is mechanical device that converts an energy form to another energy form. Torque transducers are calibrated by using machines such as dead weight calibration machines and reference torque transducer systems. Torque transducers are at risk of being affected by various environmental conditions such as temperature and humidity, and deviating from expected measurement results due to strain gauges on them. These factors should be kept under control, if this is not possible, contribution of ambient temperature and air humidity effects on measurement results should be taken into consideration. In this study, measurements were made according to DIN 51309 directive, and effect of other parameter changes on measurement uncertainty, while temperature and humidity kept constant in turn, was investigated. In this study, the goal was to reduce measurement uncertainty of calibration by determining the optimum temperature and humidity values in test environment. As a result of this study, the optimum values are obtained. The lowest measurement uncertainty was found at 21 °C and 50 % RH in this experimental study. In a test environment where optimum environmental conditions are obtained as a result of this study, the torque transducers will have the opportunity to work with maximum precision.

Visuo-Haptic Mixed Reality Simulation Using Unbound Handheld Tools

Visuo-haptic mixed reality (VHMR) adds virtual objects to a real scene and enables users to see and also touch them via a see-through display and a haptic device. Most studies with kinesthetic feedback use general-purpose haptic devices, which require the user to continuously hold an attached stylus. This approach constrains users to the mechanical limits of the device even when it is not needed. In this paper, we propose a novel VHMR concept with an encountered-type haptic display (ETHD), which consists of a precision hexapod positioner and a six-axis force/torque transducer. The main contribution is that the users work with unbound real-life tools with tracking markers. ETHD’s end-effector remains inside the virtual object and follows the tooltip to engage only during an interaction. We have developed a simulation setup and experimentally evaluated the relative accuracy and synchronization of the three major processes, namely tool tracking, haptic rendering, and visual rendering. The experiments successfully build-up to a simple simulation scenario where a tennis ball with a fixed center is deformed by the user.

Multi-Segmentation Parallel CNN Model for Estimating Assembly Torque Using Surface Electromyography Signals

The precise application of tightening torque is one of the important measures to ensure accurate bolt connection and improvement in product assembly quality. Currently, due to the limited assembly space and efficiency, a wrench without the function of torque measurement is still an extensively used assembly tool. Therefore, wrench torque monitoring is one of the urgent problems that needs to be solved. This study proposes a multi-segmentation parallel convolution neural network (MSP-CNN) model for estimating assembly torque using surface electromyography (sEMG) signals, which is a method of torque monitoring through classification methods. The MSP-CNN model contains two independent CNN models with different or offset torque granularities, and their outputs are fused to obtain a finer classification granularity, thus improving the accuracy of torque estimation. First, a bolt tightening test bench is established to collect sEMG signals and tightening torque signals generated when the operator tightens various bolts using a wrench. Second, the sEMG and torque signals are preprocessed to generate the sEMG signal graphs. The range of the torque transducer is divided into several equal subdivision ranges according to different or offset granularities, and each subdivision range is used as a torque label for each torque signal. Then, the training set, verification set, and test set are established for torque monitoring to train the MSP-CNN model. The effects of different signal preprocessing methods, torque subdivision granularities, and pooling methods on the recognition accuracy and torque monitoring accuracy of a single CNN network are compared experimentally. The results show that compared to maximum pooling, average pooling can improve the accuracy of CNN torque classification and recognition. Moreover, the MSP-CNN model can improve the accuracy of torque monitoring as well as solve the problems of non-convergence and slow convergence of independent CNN network models.

Water Ski Binding Release Characteristics in Forward Lean

To reduce the risk of injury, waterski bindings should secure the foot to the ski when the likelihood of lower leg injury is low (retention) and free the foot when the likelihood of injury is high (release). Unlike snow skiing, there are no standards dictating the release of waterski bindings. Testing was completed to determine release torques in forward lean of three commercially available waterski boot-binding systems. Each binding was mounted to a 66-inch waterski and the boot was fitted on a lower leg surrogate with a torque transducer. A forward-lean bending moment was applied quasi-statically about the transverse axis of the ski until the binding released the boot. For the three boot-binding systems, the range of release torques were 126 to 219, 50 Nm to 141, and 63 to 127 Nm.