Development of a two-dimensional dynamic model of the foot-ankle system exposed to vibration

Workers in mining, mills, construction and some types of manufacturing are exposed to vibration that enters the body through the feet. Exposure to foot-transmitted vibration (FTV) is associated with an increased risk of developing vibration-induced white foot (VIWFt). VIWFt is a vascular and neurological condition of the lower limb, leading to blanching in the toes and numbness and tingling in the feet, which can be disabling for the worker. This paper presents a two-dimensional dynamic model describing the response of the foot-ankle system to vibration using four segments and eight Kelvin-Voigt models. The parameters of the model have been obtained by minimizing the quadratic reconstruction error between the experimental and numerical curves of the transmissibility and the apparent mass of participants standing in a neutral position. The average transmissibility at five locations on the foot has been optimized by minimizing the difference between experimental data and the model prediction between 10 and 100 Hz. The same procedure has been repeated to fit the apparent mass measured at the driving point in a frequency range between 2 and 20 Hz. Monte Carlo simulations were used to assess how the variability of the mass, stiffness and damping matrices affect the overall data dispersion. Results showed that the 7 degree-of-freedom model correctly described the transmissibility: the average transmissibility modulus error was 0.1. The error increased when fitting the transmissibility and apparent mass curves: the average modulus error was 0.3. However, the obtained values were reasonable with respect to the average inter-participant variability experimentally estimated at 0.52 for the modulus. Study results can contribute to the development of materials and equipment to attenuate FTV and, consequently, lower the risk of developing VIWFt.INAI

Trajectory Identification of a Reciprocating Drill for Geological Inspections

This work analyses the feasibility of a new kind of instrument for geological exploration based on the reciprocating drilling technology. The instrument design is particularly challenging, given the harsh environmental conditions typical of this field. After the analysis of the state of the art in the field of reciprocating drilling we focused on the measurement system for the computation of the drill trajectory. The Monte Carlo method is first used to compare the robustness of three different algorithms for the identification of the trajectory. On the basis of this simulation the measurement system has been designed and its principal components, underwent a metrological calibration procedure in order to evaluate the basic performances at high temperatures

Design and Testing of a 3-DOF Robot for Studying the Human Response to Vibration

This work describes the design and validation of an electro-mechanical excitation system for characterization of the response of the human body to multiaxial vibrations. The presented system is based on the linear delta configuration and is designed to expose standing subjects to vibration along three perpendicular axes, with an excitation bandwidth of at least 30 Hz and a maximum vibration amplitude of±30 mm along the vertical direction and±20 mm along the horizontal directions. The shaker characteristic dimensions are the result of numerical optimization of the inverse manipulability index; the motors and transmissions have been selected using a multibody dynamic simulation. Finite element simulations were performed to ensure that the structural resonances were outside the excitation bandwidth. Once the shaker had been manufactured, experiments were performed to verify the capability of the system in real testing conditions. The mean quadratic error between the modulus of the imposed acceleration and the measured one is between 5.7× 10− 3 and 1.4× 10− 2 m/s 2 in the frequency range between 1 and 50 Hz, proving the good outcome of the design process

Comparison of Farm Structures, Success Factors, Obstacles, Clients’ Expectations and Policy Wishes of Urban Farming’s Main Business Models in North Rhine-Westphalia, Germany

Low-cost specialization, differentiation, and diversification are common business models of urban farms in developed countries. Similarities and differences between them as well as detailed insights into specific farm characteristics are widely absent in scientific discourses. This paper compares farm structures, success factors, obstacles, clients’ expectations, and policy wishes between specialized, differentiated, and diversified farms as well as diversifiers into agriculture. A standardized questionnaire was used for 21 personal in-depth farm interviews located in metropolitan areas of North Rhine-Westphalia, Germany. Being located in a metropolitan area is the most often named Unique Selling Proposition (USP). This is also mentioned as most important success factor followed by sociability and personal contact to clients, which both underpin the importance of direct producer-consumer linkages in urban settings. Additionally, it is assumed that a single food criterion is not sufficient to be successful, but several have to be merged to meet clients’ expectations. In terms of marketing, differentiated and diversified farmers prefer a multi-channel approach, while specialized farmers and diversifiers into agriculture focus mainly on one specific channel. While both specialized farmers and diversifiers into agriculture cultivate smaller areas of farmland, the latter one offers the greatest number of jobs including those outside agricultural production. The findings obtained are expected to support farms and agricultural advisory services in individual decision making of future business development strategies and increase knowledge of urban farming’s main business models

Validation of smart insoles for the measurement of vibration exposure of workers and athletes

Wearable sensors are becoming increasingly common in daily life for medical care, athletic training, or even daily activity monitoring [1]-[3]. As these systems advance, so do their potential application, but their use for monitoring vibration exposure is limited or absent, despite the adverse effects of vibration on health being well known among the scientific community. To address this deficit, we propose a system of sensorized smart insoles capable of measuring triaxial vibration exposure according to ISO 2631-1. Each insole allows measurement of the vibration exposure and contact pressure at the forefoot and rearfoot, as well as the temperature inside the shoe. We used the insoles to measure the vibration exposure of five male subjects in three different testing conditions: 1) indoor condition (Politecnico di Milano laboratory, atop a triaxial shaker; 2) outdoor condition riding a mountain bike; and 3) skiing. The vibration exposure along the three mutually perpendicular axes was compared with that measured using instrumentation compliant with the current standards (ISO 8041). Results show that the proposed system allows direct monitoring of vibration exposure at the feet, also accounting for the vibration reduction provided by the shoe sole

Vibration transmissibility and apparent mass changes from vertical whole-body vibration exposure during stationary and propelled walking

International audienceWhole-Body Vibration (WBV) is an occupational hazard affecting employees working with transportation,construction or heavy machinery. To minimize vibration-induced pathologies, ISO identified WBV exposurelimits based on vibration transmissibility and apparent mass studies. The ISO guidelines do not account forvariations in posture or movement. In our study, we measured the transmissibility and apparent mass at themouth, lower back, and leg of participants during stationary and propelled walking. Stationary walking trans­missibility was significantly higher at the lumbar spine and bite bar at 5 and 10 Hz compared to all higherfrequencies while the distal tibia was lower at 5 Hz compared to 10 and 15 Hz. Propelled walking transmissibilitywas significantly higher at the bite bar and knee at 2 Hz than all higher frequencies. These results vary frompreviously published transmissibility values for static participants, showing that ISO standards should beadjusted for active workers