Gear Reduction Unit Research Articles

Planetary vertical concrete mixers: Simulation and predicting useful life in steady states and in perturbed conditions

A simulation environment for the dynamics of planetary concrete mixers has been developed, it is a model-based method using the lumped parameters analysis and integrating the theory of classical mechanics and life analysis. The aim of this work is to give a fast and easy to use tool capable of predicting the behaviour and the useful life of concrete mixers through geometrical and physical parameters. Simulations were conducted in steady states and in perturbed conditions. The gear reduction unit is the part of the mixer under most stress. Results were compared with data obtained from costumers on building sites.

Multiobjective optimization of three-stage spur gear reduction units using interactive physical programming

The preliminary design optimization of multi-stage spur gear reduction units has been a subject of considerable interest, since many high-performance power transmission applications (e.g., automotive and aerospace) require high-performance gear reduction units. There are multiple objectives in the optimal design of multi-stage spur gear reduction unit, such as minimizing the volume and maximizing the surface fatigue life. It is reasonable to formulate the design of spur gear reduction unit as a multi-objective optimization problem, and find an appropriate approach to solve it. In this paper an interactive physical programming approach is developed to place physical programming into an interactive framework in a natural way. Class functions, which are used to represent the designer’s preferences on design objectives, are fixed during the interactive physical programming procedure. After a Pareto solution is generated, a preference offset is added into the class function of each objective based on whether the designer would like to improve this objective or sacrifice the objective so as to improve other objectives. The preference offsets are adjusted during the interactive physical programming procedure, and an optimal solution that satisfies the designer’s preferences is supposed to be obtained by the end of the procedure. An optimization problem of three-stage spur gear reduction unit is given to illustrate the effectiveness of the proposed approach.

DIRECT-DRIVE MOTOR SYSTEM WITH PARTICLE-TYPE ER FLUID DAMPER

In most of robotic systems in industrial applications, vibratory problems occur at high-speed motion, because of elasticity of drive systems like reduction gear units and mechanical structures. Also friction and backlash in the drive systems cause serious problems. On the other hand, since direct-drive (DD) motor systems do not use reduction gears, those are effective for high-speed and high-precision control. In DD motor systems, however, low damping ratio, or large time delays of computers and amplifiers causes another type of problem at precise positioning phase. In this study, a particle type ER fluid damper was introduced to a DD motor system to compensate damping ratio mechanically. Because controlling viscosity of ER damper according to status of motion did not disturb advantage of the DD system that can move fast, the performance of the DD system was improved. The effectiveness of the proposed system was confirmed experimentally. The method of our study can contribute to expansion of usability of ER fluid dampers on industrial applications not limited to DD systems.

The Frog Keeps Zanjeros Cranking

The “Frog” is the nickname for a gear reduction unit used to open gate valves that eliminates hand and back strain. To operate, set the Frog on the existing vault lid, fitting the female gate wrench part over the square nut on the top of the valve stem. The stem should be an extension from the valve in the vault. Tack weld the Frog to the existing lid. Fit a T‐handle gate wrench over the square nut on top of the Frog and turn it to open the valve. The chain will provide the leverage needed to open the gate valve.

Dynamic Analysis of a Multi-Shaft Helical Gear Transmission by Finite Elements: Model and Experiment

A dynamic model of a multi-shaft helical gear reduction unit formed by N flexible shafts is proposed in this study. The model consists of a finite element model of shaft structures combined with a three-dimensional discrete model of helical gear pairs. Bearing and housing flexibilities are included in the model as well. Eigenvalue solution and the Modal Summation Technique are used to predict the free and forced vibrations of the system. Results of experimental study on a helical gear-shaft-bearing system are also presented for validation of the model. It is demonstrated that the predictions match well with the experimental data in terms of excited modes and the forced response given in the form of the dynamic transmission error. Forced vibrations of an example system formed by three shafts are also studied to demonstrate the influence of some of the key system parameters.

COMPARISON OF TWO-INERTIA SYSTEMS WITH TORQUE/ACCELERATION FEEDBACKS

Most robots are driven through reduction gear units. Because of the flexibility of the drive system, the vibratory behavior is caused. The drive system of the robot joint can be modeled as a two-inertia system. In this paper, we consider the two-inertia system with the torque, motor-acceleration and load-acceleration feedbacks. First, it is explained that the inertia-ratio is a very important factor. Second, it is shown that these feedbacks can change the inertia-ratio. Next, the performances of I-P speed control systems with feedbacks are compared. Finally, the experiments are performed. As a result, the torsion vibrations are suppressed effectively.

Tradeoff analysis in minimum volume design of multi-stage spur gear reduction units

The problem of minimum volume preliminary design of simple and multiple-stage spur gear reduction units has been a subject of considerable interest, since many high-performance power transmission applications (e.g., automotive and aerospace) require low weight. One of the principal steps in traditional design procedures relates to the determination of an “optimal” value of diametral pitch at which tooth bending fatigue failure and surface fatigue failure are equally likely. The purpose of this paper is to present a generalized optimal design formulation with multiple objectives which is, in principle, applicable to a gear train of arbitrary complexity. The methodology is applied to the design of two-stage and three-stage spur gear reduction units, subject to identical loading conditions and design criteria. The approach serves to extend traditional design procedures by demonstrating the tradeoff between surface fatigue life and minimum volume using a basic multiobjective optimization procedure. This information allows the designer to judge overall trends and, for example, to assess the penalty in surface fatigue lifetime which would occur for a given weight reduction.

Development of Actuator with ER Damper and Examination of Its Basic Characteristics

Most industrial robots are driven through reduction gear units by servomotors. Due to the elasticity of the drive systems including these reduction gear units, the vibratory behaviors are caused. ER fluids are the substances that can change their viscosity by applying an electric field. Because the damper with an ER fluid can change the damping coefficient, the characteristics of robots are improved by using ER damper. In this paper, we develop a new actuator with a rotary-type ER damper. The two-inertia-system with the ER damper is analyzed. The experiments are carried out and the effectiveness is confirmed.

Development of an Actuator with ER Damper and Its Basic Experiments

Most industrial robots are driven through reduction gear units by DC or AC servomotors. The elasticity of the drive systems including these reduction gear units cannot be ignored when the high-speed and precise motion control is required for robots. Due to the elasticity of the drive systems, the vibratory behaviors are caused, and the control performances of robot systems are deteriorated. In this study, we develop a new actuator, which consists of an AC servomotor, a harmonic drive gear and an ER damper. Since the gap between electrodes of the ER damper is 80 [Rm], only the voltage of 80 [V] is needed for the electric field of 1 [kV/mm]. And this ER damper consumes little electric power. The actuator is installed to the one-link robot arm. The mathematical model of the robot arm is derived, and the eigenvalues of the robot system are analyzed. The experiments are conducted, and the effectiveness of the actuator is shown.

Development of High-Performance Actuators Using ER Fluids

We developed ER actuators with high performance. An ER actuator consists of ER clutch, reduction gear unit and electric motor. The electrodes of the output-shaft side in the developed ER actuators are made of light material such as CFRP, and the moment of inertia of the ER actuators with respect to the output-shaft becomes very small. As a result, the large torque/inertia ratio can be obtained, compared with conventional actuators. When comparing with powder clutches in which the torque/inertia ratio is considered to be extremely high, the torque/inertia ratio of small-size ER actuators is not inferior. Considering the slow response property of powders in powder clutches, it can be stated that ER actuators are devices with extremely high response characteristics. Firstly we discuss the design and structure of ER actuators. Secondly the experimental results are presented. Then, the control experiments are executed. The developed ER actuators are used in order to develop the new force display system which has high-fidelity force-presentation ability.

Elastodynamic response of a d.c motor driven flexible mechanism system with compliant drive train components during start-up

The aim of this paper is to demonstrate the importance of system approach to elastodynamic modeling of high speed, flexible mechanisms when response is determined during start-up. A mechanism system consisting of a four-bar (4R) linkage and a drive train comprised of a d.c. motor, gear reduction unit, coupling, and connecting shafts is investigated considering: (a) rigid drive train and linkage, (b) rigid drive train and flexible linkage and (c) flexible drive train and linkage. Analysis results lead to the proposition that the response of a linkage mechanism is more accurately estimated if the linkage and its auxiliary components are modeled as one integrated system.

The U5.0 Undulator for the Advanced Light Source

The U5.0 Undulator, an 89 period, 5 cm period length, 4.6 m long insertion device has been designed, is being fabricated, and is scheduled for completion in early 1992. This undulator will be the first high brightness source, in the 50 to 1,500 eV range, for the Advanced Light Source at the Lawrence Berkeley Laboratory. A hybrid magnetic configuration using Nd–Fe–B permanent magnet material and vanadium permendur poles has been selected to achieve the field quality needed to meet performance requirements. The magnetic structure is modular with each half consisting of five assembly sections, which provide the periodic structure, and end structures, for entrance and exit correction, mounted on a steel backing beam. Each assembly section consists of 35 half-period pole assemblies bolted to a mount. The required 0.837 T effective peak field at a 1.4 cm gap has been verified with model measurements. Vertical field integral correction is accomplished with the end structures, each having an arrangement of permanent magnet rotors which will be adjusted to minimize electron beam missteering over the undulator operating field range. To reduce the effect of environmental fields, the steel backing beams are connected through parallel, low-reluctance, Ni–Fe hinges. The magnetic structure is connected through four rollernuts to the drive system that provides gap adjustment with an arrangement of roller screws, chain drives, a gear reduction unit, and a stepper motor driven by a closed loop control system. Magnetic structure and drive system support are from a 2.4 m high structure which includes a support base with four vertical supports. The vacuum chamber design is a two-piece machined and welded 5083-H321 aluminum construction of 5.1 m length. Pumping is with a combination of ion, titanium sublimation pump and nonevaporable getter pumps. Magnetic design, subsystem design, and fabrication progress are presented.

Mass and rated characteristics of planetary gear reduction units

A sample of planetary gear reduction units for industrial appliances is analysed from a statistical point of view. A correlation between the variables ‘mass/rated torque’ M/T and ‘rated torque’ T of the above machines is pointed out, which is independent of the number of stages z. Parallel correlations for single values of z are moreover pointed out between the variables P t/T 2/3 and T, where P t is the thermal capacity, with natural cooling, of the above machines. The results are compared with those found for a sample of ordinary gear units, chosen and analysed with the same criteria. The well-known advantages of planetary over ordinary gear units, as far as mass is concerned, are confirmed but a corresponding disadvantage is pointed out as far as thermal capacity is concerned.

Weight and rated characteristics of machines: positive displacement pumps, motors and gear sets

Resuming a previous study [1] samples of positive displacement hydraulic machines and gear reduction units are analyzed, in order to find out correlations between their weight and rated characteristics. The particular tendencies of the positive displacement hydraulic machines resulting from the former work are confirmed and specified in this one. As far as the gear reduction units are concerned, correlations between the variables “weight/rated torque” W/ T and “rated power” P pointed out; they are well defined for single fields of output rotation speed. Some hypotheses about the interpretation of those correlations are advanced and further developments stated.

Weight and rated characteristics of machines—A statistical-descriptive analysis

A sample of machines, in which mechanical power enters or leaves through a rotating shaft and no reduction gear unit or other device converts the power mechanical factors, is analyzed from a statistical-descriptive point of view. With the only exception of the hydraulic positive displacement machines, a general correlation between the variables “weight/rated torque” W/T and “rated power” P of the above machines is pointed out, which is independent of the type of machine and of its angular velocity. Parallel correlations for single ranges of angular velocity are, moreover, printed out between the variables “weight/rated power” W/P and “rated power” P. The results are compared with those found in the technical literature, covering narrower fields of mahines.

A mechanically-actuated wave mattress.

A polio victim who has been in a negative pressure ventilator ("iron lung") since 1950 was in need of an activated mattress to combat the hallucinatory effects of complete immobilization and to assist with body pressure distribution. A mechanical method was used to give the patient's mattress a moving wave form of vertical amplitude 50mm with a period variable from 50 seconds to infinity. His arms rested on separate supports which oscillated 180 degrees out of phase with the trunk support. The device is powered by a 12 volt electric motor operating through two mechanical reduction gear units. It differs significantly in design and purpose from pneumatic ripple mattresses.

Three-dimensional photoelastic study of the load-carrying capacity/face width ratio of Wildhaber-Novikov gears for automotive applications

Wildhaber-Novikov gears are becoming more and more popular for heavy load applications. They have been tried as speed-reducing gears, in spite of heavy noise generation, in aircraft jet engines, marine engines and agricultural machinery. These circular-arc gears, though stronger than involute geras, have the disadvantage of needing larger face width. Axial face width required can be minimized only at the expense of load-carrying capacity. This is not a serious disadvantage with stationary engines. But in the case of automotive applications, this fact limits the load-carrying capacity of Wildhaber-Novikov gears, since space problem is very critical in these applications and large face widths, therefore, cannot be used for such gear-reduction units. The face width is determined by the helix angle and, therefore, a thorough investigation of the dependence of the load-carrying capacity on helix angle is necessary, if these special types of gears have to make headway into the automotive field.

Development in Central Gear Drives for Large Mills

Cement manufacturers have in the past demanded larger and larger mill units. The demand has forced gear manufacturers to produce matching gear reduction units. The past developments in drive units and what can be expected in the future are described.

L'aménagement de la vallée de l'Authion

The Authion river valley runs alongside the river Loire for 60 kilometres above Angers and is separated from the latter river by a dyking system. High water in the Loire causes very severe flooding in spite of isolation gates designed to prevent back-flow into the Authion, since the former river is then at a higher level than the latter which, therefore, no longer has an outlet for its flow. As a result of these conditions, activities in this region have suffered a severe setback ; in an attempt to remedy the situation, a development plan has been prepared which is mainly based on resettlement of horticulturists displaced by growing urban development in the Anjou region. Adequate control of water levels was an absolute prerequisite for implementation of this plan, which meant tint major river engineering works would have to be provided for. In addition, action was required under the following headings: a) Land management, mainly in the form of highly-specialised new farms and improvement of existing farms. b) Assistance for resettled horticulturists. c) Professional training schemes. d) Overall rural development planning for the region. The main hydraulic structure is a pump station transferring water from the Authion to the Loire, which is located just above the confluence of the two rivers and is designed to operate when flood flow in the Loire prevents gravity outflow from the Authion. Rated capacity of the plant is 60.3 m3/sec for a geometric lift of 4.5 m. It comprises four identical bays each equipped with a vertical pump driven by an electric motor. Leading particulars of this equipment are as follows : a) Bergeron single-cell centrifugal pumps with concrete volutes and 2.7 m diameter cast-iron impellers, performance data as follows : Speed : ... 74.5 rpm ; ... 93 rpm Discharge at 4 m lift : 7.25 m3/sec ; 12.65 m3/sec b) Rheinstahl 8:1 planetary reduction gear unit. c) CEM 5.5 kV, 800 kW two-speed motor. d) Self-priming siphon transferring flow over the dyke between the Authion and Loire. The pump station is fully automatic in operation, being controlled by stage data in the uppermost flooding area of the Authion 9 kilometres upstream. It is designed for an average 52 days' operation in the year, i.e. a total flow output of 128 million cubic metres and a total power input of 1.1 million kWh. It was built in several stages from 1972 to 1974 at a total cost of 14.2 million French Francs.

Paper 6: Design of an Artificial Elbow: An Electromechanical Solution

This paper presents an outline of the power and energy requirements of a human elbow and gives a discussion on the means by which these requirements can be met. Reasons are given for the choice of a system using batteries for energy storage and direct electric drive by a motor and gearbox. The gearbox is of an unusual type, using ‘harmonic drive’ elements, which permit the motor to be installed transversally at the elbow. The gear reduction unit is described in detail. The paper also discusses the problems inherent in controlling a motor with large stall current in such a way that most efficient use is made of the energy stored in the battery, and two control circuits are described which meet the requirements.