Mechanical Clutch Research Articles

Reducing the energy cost of human walking using an unpowered exoskeleton.

With efficiencies derived from evolution, growth and learning, humans are very well-tuned for locomotion. Metabolic energy used during walking can be partly replaced by power input from an exoskeleton, but is it possible to reduce metabolic rate without providing an additional energy source? This would require an improvement in the efficiency of the human-machine system as a whole, and would be remarkable given the apparent optimality of human gait. Here we show that the metabolic rate of human walking can be reduced by an unpowered ankle exoskeleton. We built a lightweight elastic device that acts in parallel with the user's calf muscles, off-loading muscle force and thereby reducing the metabolic energy consumed in contractions. The device uses a mechanical clutch to hold a spring as it is stretched and relaxed by ankle movements when the foot is on the ground, helping to fulfil one function of the calf muscles and Achilles tendon. Unlike muscles, however, the clutch sustains force passively. The exoskeleton consumes no chemical or electrical energy and delivers no net positive mechanical work, yet reduces the metabolic cost of walking by 7.2 ± 2.6% for healthy human users under natural conditions, comparable to savings with powered devices. Improving upon walking economy in this way is analogous to altering the structure of the body such that it is more energy-effective at walking. While strong natural pressures have already shaped human locomotion, improvements in efficiency are still possible. Much remains to be learned about this seemingly simple behaviour.

ELASTIC AND SAFETY CLUTCH WITH RADIALLY DISTRIBUTED ELASTIC DOWELS

Within mechanical transmissions, clutches fulfil the function of transmitting the rotational movement from the shaft of a driving element to the shaft of a driven element. However, clutches can fulfil other functions necessary for the good operation of the transmission. From a constructive point of view, clutches can be simple or combined. This paper presents a simple mechanical clutch that is able to fulfil the properties of a mixed one. This new type of clutch represents an optimal solution from the construc- tive and functional point of view. The design of the clutch allows the combination of the functions of elastic and safety clutches. The clutch's intermediate element between the semi-clutches is the elastic dowel. The paper presents the assembly drawing and the calculus schemes used for the analytical modeling of the torque, which the clutch can transmit. INTRODUCTION The clutches used in mechanical transmissions can fulfil differ - ent functions, which can ensure a good operation of these trans- missions. The main function of these clutches is to transmit the rotational movement and the torque from a driving shaft to a driven shaft. The clutches must ensure the proper functioning of the transmission regardless of the technological and assembling conditions of its components. In technological processes a series of disturbances occur, which negatively influence the operation of the transmission. The clutches are able to take over technological and assembling de- viations, torsional vibration and shoks, protection and fitting vi- brations of its component machine elements (1), (2). Besides fulfilling the main function of an elastic clutch and of a safety clutch, the proposed type of clutch is able to fulfil the sec- ondary functions of these two types of clutches. The clutch is a simple clutch, which can have the same functions as a combined clutch by choosing the intermediate elements between the semi- clutches and their layout. The main advantage of the proposed clutch are its reduced dimensions and low cost.

Dynamics study of the operating behavior of hydrodynamic coupling by experimental and numerical simulation

The hydrodynamic clutch is a device of coupling which works according to the principle of the hydrody-namic transmission. Fluid couplings work on the hydrody-namic principle. It consists of a pump-generally known as impeller and a turbine generally known as rotor, both en-closed suitably in a casing. It is a hydrodynamic device used to transmit rotating mechanical power. The Fluid coupling has centrifugal characteristics during starting, thus enabling no load start-up of prime mover, which is of great importance. It has been used in automobile transmis-sions as an alternative to a mechanical clutch. This study aimed at the installation of a test bench of hydrodynamic couplings or clutches, on which it was planned to, analyze the pressing problems of the coupler in its not still regime. One parallel in the experimental part, we made a theoreti-cal study of these phenomena which based itself essentially on the resolution of a system of equations of movement of the wheel-pump, the wheel-turbine and the fluid. For the numerical simulation, a special program is written in FORTRAN 90 were used, we’ll find the values of characteristic of speed and the moments, we compared the two results. They are given in the form of the curves. DOI: http://dx.doi.org/10.5755/j01.mech.20.4.6297

MODELING AND ANALYSIS OF THERMAL PROCESSES IN MECHANICAL FRICTION CLUTCH — NUMERICAL AND EXPERIMENTAL INVESTIGATIONS

Thermal processes occurring in the mechanical clutch or brake systems have a great influence on the strength of elements of these systems as well as on their dynamics. The contact problems exhibited by such systems include heat generated by dry friction contact surfaces. The contact dynamics in general depends on many system parameters, and it attracted attention of many researches focused on analysis of the mentioned phenomena in different kinds of mechanical systems like clutches, brakes, and others. In this work a mathematical model describing the processes of heat generation and its propagation in the mechanical friction clutch is presented. The presented model takes into account the unequal distribution of flux density of produced heat in the clutch, the thermal conductivity of materials of friction linings, and the heat transfer between the friction linings of clutch and its environments. The analyzed object is described by a set of algebraic linear homo- and heterogeneous equations, and it is derived using a computer numerical method. Many interesting numerical and experimental results are obtained, illustrated and discussed. Presented numerical results coincide with experimental data.

Optimal Fuzzy Control of Automated Mechanical Transmission Clutch Engagement during Start-Up Process

Engagement control of the clutch in the starting process is the core part and difficulty of the Automated Mechanical Transmission (AMT) control strategy, which was directly related to the clutch disc lifetime and riding. Engine speed, clutch speed and throttle angle are the only signals to develop clutch control strategy in the entire start-up process made by Transmission Control Unit (TCU) in a vehicle equip with AMT. The TCU even need to determine the driver's intention to select different control schemes. In this paper, fuzzy logic control was adopted in order to eliminate the impact of subtle change during driver operation, thus the start quality was optimized.

Design and Research on the Clutch Mechanism in Modern Offset Printing Machine

The clutch mechanism is the important part of printing machine. At present, cam connecting rod type mechanical clutch mechanism has been used by most of the domestic offset printing machine and its mechanical structure is very complex and its reliability is very poor. So a new type of pneumatic clutch mechanism is designed to meet its technological requirements. For the new mechanism, the motion law of the blanket cylinder can be calculated in the pressing process by complex number vector method and the finite element model has been established, natural frequency, maximum amplitude and mode of vibration of the cylinder can be calculated based on Block Lanczos method. The analysis results show that the relationship between the cylinders is flexible impact at the pressing instant, positioning is accurate, stable and reliable, which meets flexible design requirements. Thus it is important significance to improve design level and the product quality of the domestic printing machine and shorten the gap with foreign advanced printing machine.

Computer‐aided tool for teaching mechanical clutch systems design

AbstractThis paper describes an educational computer application—MecClutch—focused on teaching the design process of mechanical clutches and their operational conditions to Mechanical Engineering students. The software is divided into three sections: (1) multimedia files, pictures, and videos, produced in order to teach the working of the mechanism, (2) theoretical information related to mechanical clutches, and (3) interactive problems that allow to design a mechanical clutch and test changes in operational conditions when varying the value of critical design parameters. This software has become a very useful tool for undergraduate Mechanical Engineering students in compliment to theoretical classes or alone, as a self‐study tool. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 19: 493–500, 2011

Engine operation control for an electromagnetic coupling dual electric machine hybrid electric bus

An electromagnetic coupling dual electric machine hybrid electric bus is investigated. The flywheel and start-motor of the Internal Combustion Engine (ICE), the mechanical clutch and the manual transmission are replaced by Double-electric Machines (DM). The DM work as an electromagnetic clutch and a continuously variable transmission, simultaneously. An Improved Engine Operation Control (IEOC) is proposed to maximise the efficiency of the overall electromagnetic coupling system, in which the ICE efficiency, the DM efficiencies and the battery efficiency are all explicitly taken into account. Simulation results indicate potential fuel economy improvement relative to the traditional control.

Design of a mechanical clutch-based needle-insertion device

Insertion of trocars, needles, and catheters into unintended tissues or tissue compartments results in hundreds of thousands of complications annually. Current methods for blood vessel cannulation or epidural, chest tube, and initial trocar placement often involve the blind pass of a needle through several layers of tissue and generally rely on distinguishable anatomic landmarks and a high degree of clinical skill. To address this simply and without the use of electronics, a purely mechanical clutch system was developed for use in medical devices that access tissue and tissue compartments. This clutch utilizes the surface contact of a buckled filament inside an S-shaped tube to transmit force from the filament (catheter/guide wire) to the tube (needle). Upon encountering sufficient resistance at the tip, such as dense tissue, the catheter buckles and locks within the tube, causing the filament and needle to advance as one. When the needle reaches the target tissue or fluid-filled cavity, the filament unlocks and slides freely into the target region while the needle remains stationary. A similar locking phenomenon has long been observed in drill strings inside drill shafts used by the oil-drilling industry, and oil industry models were adapted to describe the motion of this clutch system. A predictive analytical model was generated and validated with empirical data and used to develop prototypes of a complete device then tested in vitro on muscle tissue and in vivo on a porcine laparoscopic model with promising results.

Development of a hydraulic limited slip differential system using a pressure generator

The limited slip differential (LSD) is a device that enables the driving force to be transmitted from one slipping wheel to the other by temporarily restraining the differential function when unwanted slipping occurs on muddy or icy roads. Many types of LSD have been developed, such as mechanical lock, disk clutch, viscous coupling, torsen and multiple clutch. This study designed a new type of hydraulic LSD using a pressure generator base on a trochoid gear pump and evaluated the performance of the new design.

Current Trends in the Vehicle Mechanical Transmissions Control

The article presents a brief overview of modern electromechanical actuating devices that automate the management of mechanical clutch and a mechanical transmission; automation of mechanical transmission is highly actual.

Auxiliary power system technology using a hydrodynamic clutch

A hydraulic clutch used for Auxiliary Power Unit (APU) drives provides a flexibility in adapting its characteristic to the requirements of the typical application. In comparison to a mechanical clutch, the hydrodynamic clutch is able to engage dynamically both unloaded and loaded. In particular, the dynamic engagement can be varied very easily by controlling the oil flow into the clutch. This paper describes the general function of the APU system and explains the advantages of the hydrodynamic clutch with respect to the system requirements. The clutch working principle and its design for the special application are presented. Measurement results illustrate the clutch performance in engaged and disengaged mode. The optimization of the APU starting procedure, which benefits significantly from the smooth clutch behaviour, is explained in detail.

Mechatronic strategies for torque control of electric powered screwdrivers

The paper presents the results of a study on using mechatronics to enhance the performance and reliability of small electric powered screwdrivers (SEPS). A mechatronic solution to control the final tightening torque replacing the mechanical clutch of a purely electromechanical SEPS is presented. Torque estimation methods based on motor armature current measurements are integrated with an SEPS driven by a direct current motor. Strategies for controlling the final tightening torque of the screw fastening process are developed. The control strategies are tested in accordance with the ISO 5393 standard. It is shown that the mechatronic controller gives comparable performance to a SEPS with a mechanical clutch. The mechatronic solution has the advantage of reduced cost, size and complexity. The paper demonstrates the application of low-cost mechatronics in industrial power tools.

Punch press mechanical clutch engagement noise and noise reduction

Results of an analysis of noise radiated during mechanical clutch key engagement for a 170-kN, a 230-kN, and a 300-kN punch press indicate operator noise levels, 1 second Leq, to be on the order of 90 dB(A). For all three presses, the value of ten times the logarithmic ratio of sound energy radiated to the kinetic energy of the flywheel is on the order of −55 dB re 1 joule. Experiments undertaken to reduce the noise radiated by replacement of the all steel key with a composite steel-Nylatron key indicate reductions of up to 6 dB(A) can be achieved at an operator's position.

Electro-control: am EMG-controlled A/K prosthesis

Locking of the flexion of the knee-joint in this knee prosthesis can be accomplished by means of a mechanical clutch released by a control pulse which, in turn, is derived from the myolectric activity of the patient's stump. The feature enables the amputee to use the artificial leg as a reaction point for his residual muscles. Ascending stairs and ramps using the prosthesis is made possible by the use of a mechanical knee-joint which, when locked, cannot be flexed any more, but is still free to extend under the patient's control. The prosthesis described in this paper employs a rather unconventional control system. Pulse triggering, instead of pulse integration, is used. A logic device inhibits the detection system once the knee lock has occurred; the whole system is automatically re-set as soon as the patient fully extends the artificial leg. A patient can be trained to use the leg for climibing stairs in a matter of hours.

Improvements in the integrating photometer for X-ray crystal analysis

Some improvements in the integrating photometer are described; mainly the substitution of a mechanical clutch with a magnetic release for the original magnetic clutch.