A Caging Inspired Gripper using Flexible Fingers and a Movable Palm

This paper proposes the design of a robotic gripper motivated by the bin-picking problem, where a variety of objects need to be picked from cluttered bins. The presented gripper design focuses on an enveloping cage-like approach, which surrounds the object with three hooked fingers, and then presses into the object with a movable palm. The fingers are flexible and imbue grasps with some elasticity, helping to conform to objects and, crucially, adding friction to cases where an object cannot be caged. This approach proved effective on a set of basic shapes, such as cuboids and cylinders, in which every object could be grasped. In particular, flat bottom parts could be grasped in a very stable manner, as demonstrated by testing grasps with multiple 5N and 10N disturbances. A set of supermarket items were also tested, highlighting promising features such as effective grasping of fruits and vegetables, as well as some limitations in the current embodiment, which is not always able to slip the fingers underneath objects

Psychophysical Evaluation of A Mechanotactile Haptic Feedback Device

Sensory feedback enhances the intuitive operation of upper limb prostheses. However, most modern commercial prosthetic devices lack sensory feedback mechanisms due to the difficulty of integration and added complexity. Mechanotactile haptic feedback provides a non-invasive and low-cost alternative to traditional electromechanical haptic feedback modalities. While mechanotactile haptic feedback systems have been studied for their mechanical behaviour, their practical integration in prosthetic devices and associated human factors still remain to be investigated. Therefore, in this paper, we perform a psychophysics study to investigate the perceptual thresholds associated with a mechanotactile feedback system. We use a mechanotactile sensory system and feedback device to provide force feedback on the forearm of healthy volunteers. We systematically assess the optimal placement of the feedback devices and the minimum perceptible forces at each position. We found that the minimum perceptible force that a user can perceive range lies in the range of 0.39 N to 1.36 N at various points on the forearm. The distal forearm was found to have higher perception sensitivity compared to the proximal forearm. Our results shed light on the perception thresholds achievable with mechanotactile haptic elements. Results also indicate that proper placement and site selection of the mechanotactile feedback elements are crucial to enhance force perception accuracy

Evaluation of Pseudo-Haptic Interactions with Soft Objects in Virtual Environments

This paper proposes a pseudo-haptic feedback method conveying simulated soft surface stiffness information through a visual interface. The method exploits a combination of two feedback techniques, namely visual feedback of soft surface deformation and control of the indenter avatar speed, to convey stiffness information of a simulated surface of a soft object in virtual environments. The proposed method was effective in distinguishing different sizes of virtual hard nodules integrated into the simulated soft bodies. To further improve the interactive experience, the approach was extended creating a multi-point pseudo-haptic feedback system. A comparison with regards to (a) nodule detection sensitivity and (b) elapsed time as performance indicators in hard nodule detection experiments to a tablet computer incorporating vibration feedback was conducted. The multi-point pseudo-haptic interaction is shown to be more time-efficient than the single-point pseudo-haptic interaction. It is noted that multi-point pseudo-haptic feedback performs similarly well when compared to a vibration-based feedback method based on both performance measures elapsed time and nodule detection sensitivity. This proves that the proposed method can be used to convey detailed haptic information for virtual environmental tasks, even subtle ones, using either a computer mouse or a pressure sensitive device as an input device. This pseudo-haptic feedback method provides an opportunity for low-cost simulation of objects with soft surfaces and hard inclusions, as, for example, occurring in ever more realistic video games with increasing emphasis on interaction with the physical environment and minimally invasive surgery in the form of soft tissue organs with embedded cancer nodules. Hence, the method can be used in many low-budget applications where haptic sensation is required, such as surgeon training or video games, either using desktop computers or portable devices, showing reasonably high fidelity in conveying stiffness perception to the user

Accurate Bolt Tightening Using Model-Free Fuzzy Control for Wind Turbine Hub Bearing Assembly

"In the modern wind turbine industry, one of the core processes is the assembly of the bolt-nut connections of the hub, which requires tightening bolts and nuts to obtain well-distributed clamping force all over the hub. This force deals with nonlinear uncertainties due to the mechanical properties and it depends on the final torque and relative angular position of the bolt/nut connection. \ud This paper handles the control problem of automated bolt tightening processes. To develop a controller, the process is divided into four stages, according to the mechanical characteristics of the bolt/nut connection: a Fuzzy Logic Controller (FLC) with expert knowledge of tightening process and error detection capability is proposed. For each one of the four stages, an individual FLC is designed to address the highly non-linearity of the system and the error scenarios related to that stage, to promptly prevent and avoid mechanical damage.\ud The FLC is implemented and real time executed on an industrial PC and finally validated. Experimental results show the performance of the controller to reach precise torque and angle levels as well as desired clamping force. The capability of error detection is also validated.\ud

Validation of the Fracture Mobility Score against the Parker Mobility Score in hip fracture patients

IntroductionThe Parker Mobility Score has proven to be a valid and reliable measurement of hip fracture patient mobility. For hip fracture registries the Fracture Mobility Score is advised and used, although this score has never been validated. This study aims to validate the Fracture Mobility Score against the Parker Mobility Score. MethodsThe Dutch Hip Fracture Audit uses the Fracture Mobility Score (categorical scale). For the purpose of this study, five hospitals registered both the Fracture Mobility Score and the Parker Mobility Score (0 – 9 scale) for every admitted hip fracture patient in 2018. The Spearman correlation between the two scores was calculated. To test whether the correlation coefficient remained stable among different patient subgroups, analyses were stratified according to baseline patient characteristics. ResultsIn total 1,201 hip fracture patients were included. The Spearman correlation between the Fracture Mobility Score and the Parker Mobility Score was strong: 0.73 (p = Conclusion The Fracture Mobility Score is overall strongly correlated with the Parker Mobility Score and can be considered as a valid score to measure hip fracture patient mobility. This may encourage other hip fracture audits to also use the Fracture Mobility Score, which would increase the uniformity of mobility score results among national hip fracture audits and decrease the overall registration load. Trauma Surger

Reconfigurable Assembly Approach for Wind Turbines Using Multiple Intelligent Agents

This paper investigates the use of an agent based assembly strategy for a wind turbine hub. The manual assembly procedure for a wind turbine is presented. The hub parts are constantly optimised and therefore a fully automated assembly line requires continously reprogramming. Thus, a new reconfigurable assembly system is introduced which is flexible and self-adaptive. The methodology of implementing an intelligent agent for designing the assembly strategy for the wind generator hub and the algorithm for the optimal task sequence are described. This reconfigurable automation runs a Partial Order Planning algorithm in real-time using Beckhoff TwinCAT® 3. © Springer-Verlag 2012

Magnetic Resonance-Compatible Tactile Force Sensor Using Fiber Optics and Vision Sensor

This paper presents a fiber optic based tactile array sensor that can be employed in magnetic resonance environments. In contrast to conventional sensing approaches, such as resistive or capacitive-based sensing methods, which strongly rely on the generation and transmission of electronics signals, here electromagnetically isolated optical fibers were utilized to develop the tactile array sensor. The individual sensing elements of the proposed sensor detect normal forces; fusing the information from the individual elements allows the perception of the shape of probed objects. Applied forces deform a micro-flexure inside each sensor tactel, displacing a miniature mirror which, in turn, modulates the light intensity introduced by a transmitting fiber connected to a light source at its proximal end. For each tactel, the light intensity is read by a receiving fiber connected directly to a 2-D vision sensor. Computer software, such as MATLAB, is used to process the images received by the vision sensor. The calibration process was conducted by relating the applied forces to the number of activated pixels for each image received from a receiving fiber. The proposed approach allows the concurrent acquisition of data from multiple tactile sensor elements using a vision sensor such as a standard video camera. Test results of force responses and shape detection have proven the viability of this sensing concept.</p