Internal Reaction Forces Research Articles

Leader/Follower Force Control of Aerial Manipulators

This article focuses on the modeling and controlling of Unmanned Aerial Manipulators (UAMs) in a leader/follower configuration performing a cooperative manipulation task. Each UAM consists of an Unmanned Aerial Vehicle (UAV) with an attached serial-link robotic manipulator. The Recursive Newton-Euler dynamics formulation is employed to account for the interaction between the UAV and its manipulator. The overall system consists of a couple UAMs with a carrying load. The coupling between these systems is due to the exerted forces by their manipulators through the object characterized by its stiffness matrix. A leader/follower control scheme is employed with a stability-analysis tailored to the UAM-pair. The leader UAM defines the trajectory of the moving object while the follower acts so as to reduce the system’s internal reaction forces. Simulation studies are employed to validate the controller’s performance while comparing the system’s response against that derived from a classical nonlinear tracking controller.

Correction: On the internal reaction forces, energy absorption, and fracture in the hip during simulated sideways fall impact.

[This corrects the article DOI: 10.1371/journal.pone.0200952.].

On the internal reaction forces, energy absorption, and fracture in the hip during simulated sideways fall impact.

The majority of hip fractures have been reported to occur as a result of a fall with impact to the greater trochanter of the femur. Recently, we developed a novel cadaveric pendulum-based hip impact model and tested two cadaveric femur-pelvis constructs, embedded in a soft tissue surrogate. The outcome was a femoral neck fracture in a male specimen while a female specimen had no fracture. The aim of the present study was, first, to develop a methodology for constructing and assessing the accuracy of explicit Finite Element Models (FEMs) for simulation of sideways falls to the hip based on the experimental model. Second, to use the FEMs for quantifying the internal reaction forces and energy absorption in the hip during impact. Third, to assess the potential of the FEMs in terms of separating a femoral fracture endpoint from a non-fracture endpoint. Using a non-linear, strain rate dependent, and heterogeneous material mapping strategy for bone tissue in these models, we found the FEM-derived results to closely match the experimental test results in terms of impact forces and displacements of pelvic video markers up to the time of peak impact force with errors below 10%. We found the internal reaction forces in the femoral neck on the impact side to be approximately 35% lower than the impact force measured between soft tissue and ground for both specimens. In addition, we found the soft tissue to be the component that absorbed the largest part of the energy of the tissue types in the hip region. Finally, we found surface strain patterns derived from FEM results to match the fracture location and extent based on post testing x-rays of the specimens. This is the first study with quantitative data on the energy absorption in the pelvic region during a sideways fall.

Calibration procedure of measuring system for vehicle wheel load estimation

The calibration procedure of wheel load measuring system is presented. Designed method allows estimation of selected wheel load components while the vehicle is in motion. Mentioned system is developed to determine friction forces between tire and road surface, basing on measured internal reaction forces in wheel suspension mechanism. Three strain gauge bridges and three-component piezoelectric load cell are responsible for internal force measurement in suspension components, two wire sensors are measuring displacements. External load is calculated via kinematic model of suspension mechanism implemented in Matlab environment. In the described calibration procedure, internal reactions are measured on a test stand while the system is loaded by a force of known direction and value.

Modeling of articular cartilage replacement materials

The development of replacement material for human articular cartilage exhibiting similar mechanical properties as the native tissue is a problem of high actuality in biomedicine. In the present work a new condensed collagen material is investigated. The study aims at developing a mechanical model especially adapted to this particular collagen material. For this purpose, a viscoelastic-diffusion (VED) model is proposed, accounting for two different diffusion evolutions assumed. Moreover, the need for a gradient material description is discussed in order to cover fabrication influences leading to a variable Young’s modulus for the material. On this background, a phe-nomenological law is presented to predict deformation-dependent diffusion behavior and internal reaction forces. Furthermore, the present approach allows a practible identification of diffusion parameters. The theoretical model is implemented into a fi-nite element code and parameters are identified by tension tests. The simulation results are validated experimentally.

Three-dimensional contact dynamic model of the human knee joint during walking

It is well known that the geometry of the articular surface has a major role in determining the position of articular contact and the lines of action for the contact forces. The contact force calculation of the knee joint under the effect of sliding and rolling is one of the most challenging issues in this field. We present a 3-D human knee joint model including sliding and rolling motions and major ligaments to calculate the lateral and medial condyle contact forces from the recovered total internal reaction force using inverse dynamic contact modeling and the Least-Square method. As results, it is believed that the patella, muscles and tendon affect a lot for the internal reaction forces at the initial heel contact stage. With increasing flexion angles during gait, the decreasing contact area is progressively shifted to the posterior direction on the tibia plateau. In addition, the medial side contact force is larger than the lateral side contact force in the knee joint during normal human walking. The total internal forces of the knee joint are reasonabe compared to previous studies.

A computational model for estimating the mechanics of horizontal flapping flight in bats: model description and validation.

We combine three-dimensional descriptions of the movement patterns of the shoulder, elbow, carpus, third metacarpophalangeal joint and wingtip with a constant-circulation estimation of aerodynamic force to model the wing mechanics of the grey-headed flying fox (Pteropus poliocephalus) in level flight. Once rigorously validated, this computer model can be used to study diverse aspects of flight. In the model, we partitioned the wing into a series of chordwise segments and calculated the magnitude of segmental aerodynamic forces assuming an elliptical, spanwise distribution of circulation at the middle of the downstroke. The lift component of the aerodynamic force is typically an order of magnitude greater than the thrust component. The largest source of drag is induced drag, which is approximately an order of magnitude greater than body form and skin friction drag. Using this model and standard engineering beam theory, we calculate internal reaction forces, moments and stresses at the humeral and radial midshaft during flight. To assess the validity of our model, we compare the model-derived stresses with our previous in vivo empirical measurements of bone strain from P. poliocephalus in free flapping flight. Agreement between bone stresses from the simulation and those calculated from empirical strain measurements is excellent and suggests that the computer model captures a significant portion of the mechanics and aerodynamics of flight in this species.

Hemodynamics as a possible internal mechanical disturbance to balance.

The postural control system is assessed by observing body sway while the subject involved aims at maintaining a specified up-right posture. Internal masses generate internal reaction forces that constitute an internal mechanical stimulus that may contribute to cause segmental displacements, i.e. body sway. Thus, gaining knowledge about the amplitude and direction of these reaction forces would contribute to gain insights into the mechanisms that influence the maintenance of balance and into its control. The 3-D force vector that acts on the body centre of mass (COM) and is associated with the transient blood movement at each cardiac cycle was assessed in a population sample of 20 young adults during the maintenance of a quiet up-right posture. Typical patterns of the three components of this force vector were identified. Relevant parameters were selected and submitted to sample statistics. For a number of them, linear correlation with subject-specific parameters was found. The antero-posterior force component was characterised by a triphasic major wave, the peaks of which had values up to 0.40 N. The vertical component showed a repeatable triphasic wave with peak-to-peak values in the range 1.3-3.0 N. The medio-lateral component showed relatively low peak-to-peak values (in the range 0.05-0.10 N). The resultant vector had an amplitude that underwent several oscillations during the cardiac cycle and reached its maximal value in the range 0.6-1.7 N.

Computer-aided design of an artillery system

This paper discusses the design approaches of an artillery system and the developments of a computer-aided design analysis that automates the laborious and complicated design calculations for a complete howitzer artillery system. From the initial input of a gun configuration at zero elevation and traversing angle, the analysis is capable of re-calculating the change in active dimensions, positions and internal reaction forces of all the major sub-assemblies at any given new elevation and traversing angle. This greatly reduces the time taken to re-analyse the gun design for various gun configurations, with any design modifications. The analysis also provides a better understanding of the design and characteristics of the gun as a whole because with these analysis tools the designer is able to examine the effects of any modified components on other parts of the gun assembly with minimum time and effort.

Modelling the Stochastic Nature of Trunk Muscle Forces

In an effort to understand the mechanism of low back disorders, researchers have developed EMG driven biomechanical models which estimate the magnitude of the internal reaction forces of the spine (compression and shear), by using information about the activity of the muscles of the trunk. But, because the trunk ls multi-dimensional in nature, there is variability in the relative contribution of the various muscles, which implies variability in the reaction forces of the spine. Therefore, it may be more appropriate to discuss the range of spine reaction forces during a lift as opposed to the mean spine reaction force. The present research was an attempt to model the muscle forces stochastically and to develop a simulation model which predicts trunk muscle EMG that could occur during a lift. The simulated EMGs which resulted were then input into an EMG driven biomechanical model so the variability in spine reaction forces could be quantified. Under simple sagittally symmetric isometric conditions, compression which occurred at three standard deviations above the mean was 12% higher than that of the mean. The results for anterior shear (24% higher) and lateral shear (50% higher) showed even larger Increases.

14—THE GEOMETRY AND MECHANICS OF THE PLAIN-WEAVE STRUCTURE: A COMPARISON OF THE GENERAL ENERGY METHOD OF ANALYSIS AND PREVIOUS MODELS

Woven-fabric parameters obtained from the general energy analysis of fabric mechanics developed by de Jong and Postle are compared with those predicted by older geometrical and mechanistic models. When the energy model is modified to include constraints on the yarn curvature for a plain-weave fabric subject to internal reaction forces only, the parameters obtained agree with the Peirce mechanistic model for low values of crimp but approach those predicted by the Peirce geometrical model as jamming conditions are approached. Results are also presented for a plain-weave fabric subject to external biaxial tension, and these are compared with experimental results reported by Ellis and Munden for initial-loomstate fabrics.

A Method for Analysis of a Prototype Articulated Multiline Marine Production Riser System

This paper describes a newly developed nonlinear computer program that predicts internal reaction forces and motions of a multiline marine production riser exposed to wave and current forces. The paper also presents an analytical method that accounts for large geometric displacements and nonlinear wave forces. A simulation of the response of a prototype articulated multiline marine production riser during a mild tropical storm illustrates the program’s capability.