Trajectory Tracking Control Design of a Mass-Damping-Spring System with Uncertainty using the Bond Graph Approach

This paper deals with the simulation, and design of a trajectory-tracking control law for a physical system under parameter uncertainty modeled by a bond graph. This control strategy is based on the inversion of the system through their causal Input/Output (I/O) path using the principle of bicausality to track the desired trajectory. The proposed control strategy is validated with the use of a simple mechanical mass-spring-damper system. The results show that the bond graph is a very helpful methodology for the design of control laws in the presence of uncertainties. This proposed control can be applied in several applications and can be improved to ensure robust control.

Tuned Sloshing Dampers With Large Rectangular Core Penetrations

Space restrictions at the top of tall buildings may necessitate using tuned sloshing dampers (TSD) tanks with large rectangular penetrations to accommodate the structural core of the tower. A finite element model is employed to predict the natural sloshing frequencies and mode shapes of liquid sloshing in a rectangular tank with a rectangular core. Equivalent mechanical properties are determined to predict the sloshing response. Frequency response predictions of wave heights, sloshing forces, and energy-dissipation per cycle agree with results from shake table testing conducted on a rectangular tank with a rectangular core. Energy dissipation due to flow around the core adds considerable damping to the liquid and is proportional to the response velocity-squared. Nonlinear coupling among sloshing modes results in multiple peaks in the frequency response plots near the fundamental resonant frequency. An interior core with a broad dimension in one direction substantially reduces the fundamental sloshing frequency and equivalent mechanical mass in the perpendicular direction; however, the fundamental sloshing frequency and equivalent mechanical mass in the parallel direction are only influenced marginally. Large rectangular cores reduce the proportion of the total water mass that is effective in controlling tower motion. A TSD with a rectangular penetrating core may enable a TSD option to be considered for the control of a tall building in cases where a traditional rectangular TSD is infeasible.

Modal and Forced Response Analysis of Vehicle Systems With Latent Vibration Modes Due to Hydraulic Mounts

Hydraulic mounts used in vehicles for better isolation of vibrations were often approximated by lumped or mechanical mass-damper-spring (m-c-k) models, although deficiency in such modeling was pointed out and “hydraulic” modeling was proposed as an alternative. In this paper, a brief review on the mechanical m-c-k modeling and “hydraulic” modeling of the hydraulic mounts is presented. A simplest system consisting of a single mass and a hydraulic mount is used to illustrate both equivalence and difference in a closed form between the two modeling approaches. Then, modal analyses are done on an apparently three degrees-of-freedom (DOF) quarter car with a hydraulic mount, where the key idea is to use an internal variable for the movement of fluid mass which is responsible for a “latent” vibration mode. Equations of motion for the apparently 3DOF system, 4DOF system in fact, by the two modeling are formulated. Modal parameters by the proposed “hydraulic” modeling of the hydraulic mount are compared with those by the m-c-k modeling. Forced responses to transient base excitations are also compared between the two modeling approaches to illustrate how much errors can arise in the frequency and time domain analysis. To be more realistic, the modal and forced response analysis on a full car of an apparently 10DOF (3DOF for powertrain, 3DOF for car body, and 4DOF for knuckles and tires) with two more DOF internally for two hydraulic mounts between the powertrain and car body is presented.

Sex differences in thigh muscles characteristics: a systematic review

Objective: To determine differences between male and female subjects in the thigh muscles characteristics, separated into architectural (pennation, thickness, and/or fascicle length), mechanical (mass, strength, power, and/or stiffness), neuromuscular (activity) and fatigue aspects, in order to better understand the sex-related differences in the risk of muscle injuries. Methods: A systematic literature search on Pubmed was performed with different keywords: skeletal muscle AND sex characteristics AND muscle contraction, with the following limits: humans and adults (19–44 years old). Studies dealing with hamstring and quadriceps muscles, in physiological condition, and comparison between male and female healthy adult subjects were included. Studies dealing with other skeletal muscles, injuries or physiopathology situation were excluded. Thigh muscular architectural, mechanical, neuromuscular and fatigue characteristics have been analysed to determine differences between male and female subjects. Results: Seventeen studies were included, reporting significant sex-related differences for thigh muscles architecture and mechanical characteristics and muscle fatigue, and especially quadriceps, while for thigh muscles neuromuscular characteristics the results were not consensual, and few information was available regarding hamstring muscles. Conclusions: Sex-related differences in thigh muscles characteristics, and especially quadriceps, have been reported for mechanical characteristics and muscle fatigue, while for neuromuscular characteristics sex-related differences were found to be moderate. Although several macroscopic muscle characteristics have been reported to be different between male and female healthy adult subjects, it is difficult to conclude on its exact relationship with higher muscle injury rates reported in male athletes during international athletics championships.

Design and Simulation of Electro-Mechanical Mass Flow Sensor (EMMFS)

The main objective of this chapter is FEA simulation of resonating tube with different size and material configuration for evaluation of resonant frequency. Resonating tube is an important component of Electro-Mechanical Mass Flow Sensor (EMMFS) used for measuring direct mass flow. Omega and U-shaped resonating tube type EMMFS have been investigated for 200mm, 300 mm and 400mm height with three different materials Copper, Aluminium and Mild Steel. EMMFS analysis is highly nonlinear study having fluid structure interaction. To simplify the solution large deformations in resonating tube countered to be absent. Sensing points are located symmetrically at limbs of resonating tube to sense the phase shift for measuring mass flow rate. FEA simulation of EMMFS has been done using Ansys. Solid Edge and Pro-E has been used for modeling of omega and U-shaped resonating tube.