A study of commercial vehicle brake judder transmission using multi-body dynamic analysis

YesBraking-induced forced vibration, known as brake judder in road vehicles, causes dissatisfaction to drivers and passengers and also damage and possible early failure in components and systems. In this paper, the transmission of judder vibration from the point of generation (the brake friction pair) through the vehicle structure to the driver is investigated for the particular case of a heavy commercial vehicle. The investigation uses a computer simulation multi-body dynamic model based on the automatic dynamic analysis of mechanical systems software to identify any characteristics of the vehicle suspension design that might influence the vibration transmission from the wheel to the driver. The model uses a simplified rigid chassis and cab to lump the chassis parameters, so that the investigation can focus on the front axle/suspension design, which is a beam axle leaf spring arrangement, and the rear axle/suspension assembly, which is a tandem axle bogie design. Results from the modelling indicate that brake judder vibration is transmitted to the chassis of the vehicle through a leaf spring `wind-up¿ mode and a `walking¿ mode associated with the rear tandem axle. Of particular interest is the longitudinal vibration transmitted through the chassis, since this creates a direct vibration transmission path to the cab and driver. The simulation results were compared with the previously published experimental work on the same design of commercial vehicle, and agreement between the predicted and the measured vibration characteristics and frequencies was found. It is concluded that the rear suspension design parameters could affect the transmission of brake judder vibration to the cab and driver and that a tandem rear axle offers some design opportunity to control the transmission of brake judder vibrations from the wheel to the cab and driver. Given that brake judder has so far defied all attempts to eliminate completely from vehicle brake systems, this is potentially an important opportunity

Advancements in Prosthetics and Joint Mechanisms

abstract: Robotic joints can be either powered or passive. This work will discuss the creation of a passive and a powered joint system as well as the combination system being both powered and passive along with its benefits. A novel approach of analysis and control of the combination system is presented. A passive and a powered ankle joint system is developed and fit to the field of prosthetics, specifically ankle joint replacement for able bodied gait. The general 1 DOF robotic joint designs are examined and the results from testing are discussed. Achievements in this area include the able bodied gait like behavior of passive systems for slow walking speeds. For higher walking speeds the powered ankle system is capable of adding the necessary energy to propel the user forward and remain similar to able bodied gait, effectively replacing the calf muscle. While running has not fully been achieved through past powered ankle devices the full power necessary is reached in this work for running and sprinting while achieving 4x’s power amplification through the powered ankle mechanism. A theoretical approach to robotic joints is then analyzed in order to combine the advantages of both passive and powered systems. Energy methods are shown to provide a correct behavioral analysis of any robotic joint system. Manipulation of the energy curves and mechanism coupler curves allows real time joint behavioral adjustment. Such a powered joint can be adjusted to passively achieve desired behavior for different speeds and environmental needs. The effects on joint moment and stiffness from adjusting one type of mechanism is presented.Dissertation/ThesisDoctoral Dissertation Mechanical Engineering 201

Design and Verification of a Compact Variable Stiffness Actuator With a Very Large Range of Stiffness

Current conventional robots require high stiffness joints to provide absolute positioning accuracy in free space which also causes problems when operating in constrained space. To circumvent these problems, Variable Stiffness Actuators (VSAs) can be used to vary their stiffness to suit the task being performed. A new VSA was designed to provide a very large range of stiffness in a compact size. The Arched Flexure VSA uses a cantilevered beam acting as the flexure with a variable point of contact. It allows the joint to have continuous variable stiffness, have zero stiffness for a small range of motion, and rapid stiffness change. Finite element analysis was used to evaluate flexture stiffness. The flexure geometry was optimized for two different objectives. In the first case, the flexture was optimized for maximum stiffness range. This optimization resulted in a stiffness ratio of 1200. In the second case, the flexture was optimized for both maximum stiffness range and constant relative sensitivity. This optimization resulted in a stiffness ratio of 100. A small proof-of-concept VSA actuator based on the constant relative sensitivity alternative was designed, built, and tested. The VSA provided a stiffness ratio of 55, a little more than half of that expected for the flexure alone. The VSA weighed 1.45 pounds and fits within a 4.5 inch by 2 inch by 5 inch volume. The VSA provides the anticipated free joint range for zero stiffness and provides 360 degrees of rotation. It changes from minimum to maximum stiffness in 0.12 seconds

Racing car chassis

Cílem této bakalářské práce je analýza současných konceptů podvozků závodních okruhových aut. V první části práce je zpracován historický vývoj, charakteristika kol a pneumatik s reprezentací dobře známých produktů. V druhé části je popsán systém odpružení, pružné média a tlumící členy. Systémy odpružení je zde rozdělen na nezávisle a polozávislé zavěšení kol a odpružení pevných náprav. Následující oddíl této práce je zaměřený na standardní kontrolní systémy, jako jsou ABS, ESC a TSC. Závěr přináší rychlé shrnutí této problematiky.The aim of this bachelor thesis is to analyse contemporary concepts of circuit race car chassis. In the first part of the thesis, the historical evolution is described and then wheels and tires characteristic within some well-known brand products are represented. The second important part includes the suspension systems, springing medium and damping members. The suspension systems are further divided to independent and semi-independent solutions and rigid axle suspensions. The end of this thesis deals with the standard braking control systems, such as ABS, ESC and TCS. The conclusion brings the quick summary of this subject.

Design and Analysis of Novel Actuation Mechanism with Controllable Stiffness

Actuators intended for human–machine interaction systems are usually designed to be mechanically compliant. Conventional actuators are not suitable for this purpose due to typically high stiffness. Advanced powered prosthetic and orthotic devices can vary their stiffness during a motion cycle and are power-efficient. This paper proposes a novel actuator design that modulates stiffness by means of a flexible beam. A motorized drive system varies the active length of the cantilever beam, thus achieving stiffness modulation. New large deflection formulation for cantilever beams with rolling contact constraints is used to determine the moment produced by the actuator. To validate the proposed solution method, an experiment was performed to measure large static deformations of a cantilever beam with the same boundary conditions as in the actuator design. The experiments indicate excellent agreement between measured and calculated contact forces between beam and roller, from which the actuator moment is determined

Use of scale models to determine the structural dynamic characteristics of space vehicles

Scale model designs for determining structural dynamic characteristics of future spacecraf

Development of compressor end seals stator interstage seals, and stator pivot seals in air breathing propulsion systems Semiannual report no. 1, 29 Jun. - 31 Dec. 1965

Seal concepts evaluation for compressor end seals, stator interchange seals, and stator pivot seals in air breathing propulsion syste

Advances in Mechanical Systems Dynamics 2020

The fundamentals of mechanical system dynamics were established before the beginning of the industrial era. The 18th century was a very important time for science and was characterized by the development of classical mechanics. This development progressed in the 19th century, and new, important applications related to industrialization were found and studied. The development of computers in the 20th century revolutionized mechanical system dynamics owing to the development of numerical simulation. We are now in the presence of the fourth industrial revolution. Mechanical systems are increasingly integrated with electrical, fluidic, and electronic systems, and the industrial environment has become characterized by the cyber-physical systems of industry 4.0. Within this framework, the status-of-the-art has become represented by integrated mechanical systems and supported by accurate dynamic models able to predict their dynamic behavior. Therefore, mechanical systems dynamics will play a central role in forthcoming years. This Special Issue aims to disseminate the latest research findings and ideas in the field of mechanical systems dynamics, with particular emphasis on novel trends and applications