Synchronization in multi-motor hydromechanical systems

Introduction. The paper submits the analysis of existing design solutions of flow dividers used to synchronize hydraulic drives of working bodies of technological and mobile machines. The market demands for multithreaded throttle flow dividers without valves with the controlled division ratio, such as multi-axle vehicle chassis, are identified. The objective of the work was to analyze the possibility and rationale for developing a throttle four-way flow divider without valves with sensing elements of the Venturi tube type. The solution should provide the synchronicity of movement (rotation) of more than three working bodies of technological and mobile machines.Materials and Methods. A patent search for the designs of hydraulic flow dividers is carried out, and systems that require the division of the hydraulic fluid flow into more than two executive bodies are considered. An upgrade option, which allows dividing the flow into four branches, is proposed for the design of a three-channel throttle flow divider without valves.Results. The urgency of developing a multithreaded throttle flow divider without valves for application in industrial and mobile machines is validated. Two types of four-flow dividers are considered, their weaknesses are indicated. It is noted that the development of a multithreaded throttle flow divider based on the designs created in 1989 and 1991 will reduce the number of hydraulic pumps and get rid of the series connection of double-flow dividers. In this way, it is possible to reduce pressure losses in the hydraulic system and implement adaptive control of hydraulic motors of multi-motor mobile machines. The possibility to obtain a divider/combiner into four flows by adding an outlet chamber connected to the membrane chamber through a channel entering the Venturi nozzle on the basis of a three-flow throttle divider is shown. The principle of operation of such equipment is described.Discussion and Conclusions. The principles of construction of throttle flow dividers without valves are considered. An upgrade option is proposed to increase the number of division channels from three to four. However, to validate the operability of this design, a numerical analysis of the various modes of operation of the divider is required — calculation of the reduced volumetric stiffness of its working cavities. The information obtained can be used to modernize the hydraulic units of technological and mobile machines, increase their reliability, manufacturability, and efficiency. The issues that need to be solved in further research are identified.

Characteristics of Hydraulic and Electric Servo Motors

Until the 1970s, hydraulic actuators were widely used in many mechanical systems; however, recently, electric motors have become mainstream by virtue of their improved performance, and hydraulic motors have largely been replaced by electric motors in many applications. Although this trend is expected to continue into the future, it is important to comprehensively evaluate which motor is most suitable when designing mechanical systems. This paper presents the results of a survey of the performance of electric and hydraulic servo motors and aims to provide quantitative data that can be used as a reference for selecting appropriate motors. We surveyed AC, AC direct, brushless DC, and brushed DC electric motors and swash plate-type axial piston, bent axis-type axial piston, crank-type radial piston, and multistroke-type radial piston hydraulic motors. Performance data were collected from catalogs and nonpublic data. We compared and evaluated the characteristics of these diverse servo motors using indexes such as torque, rotating speed, output power, power density, and power rate.

Analysis of the Heating Process of Hydraulic Motors during Start-Up in Thermal Shock Conditions

Conditions that prevail during harsh winters and hot summers pose a serious challenge for machine designers building devices suitable for operation in extreme weather. It is essential for the designers and the users to define the principles and conditions for the safe operation of machines and devices with hydraulic drive in low ambient temperatures. Bearing in mind the above, the author tested the hydraulic motors in thermal shock conditions (cold motors were fed with a hot working medium). This enterprise required the design and construction of a specialized stand for testing hydraulic motors, including satellite motors, in thermal shock conditions. The stand was equipped with the apparatus and a system for measuring the temperature of the moving parts of the satellite motor. The experimental tests were conducted in the laboratory of the Faculty of Mechanical Engineering and Ship Technology at Gdańsk University of Technology. The paper presents the results of tests of a correctly and incorrectly operating satellite motor during start-up in thermal shock conditions. The results concerned the course of oil temperatures, temperatures of heated elements, oil pressures, and the pressure drop in the motor. The influence of the oil pressure drop in the motor on its temperature increase was determined. The distributions of the temperature fields of the heated elements of the satellite motor during start-up in thermal shock conditions were derived by means of computer simulation. The utilization of the distribution of the temperature fields of the motor elements enables the evaluation and analysis of the work of this unit. The conducted tests may determine the conditions for the proper operation of hydraulic motors started in thermal shock conditions.

Measuring system for monitoring the polydimensional deformation of superstructures of bridges and over-bridges improvement of volume hydraulic drive construction and road machines using flow shareholders

Due to its advantages, the hydraulic drive is widely used in road construction machines. Depending on its design, the share of the hydraulic drive, which is the most expensive unit of a road construction machine, accounts for thirty to eighty percent of all failures. Reliable hydraulic drive, provides, to a large extent, the reliability of the whole machine and the efficiency of the construction organization as a whole. The efficiency of the hydraulic drive of construction machines, and, as a consequence, the machines themselves, is ensured by a set of measures, among which the most important is the quality design, manufacture and operation, combined into a single structural system. Depending on the quality of cleaning of the working fluid, the service life of hydraulic machines can be increased or decreased several times. Accumulation of pollutants in the hydraulic drive, the hardness of which is significantly higher than the hardness of metals, causes rapid wear of the surfaces of hydraulic units and the service life is rapidly reduced. Cavitation in the pump is accompanied by a pulsation of fluid pressure and noise. These pulsations are due to the return flow of fluid from the discharge cavity of the pump, which is accompanied by hydraulic shocks and as a result of alternating shocks, a pressure pulsation in the discharge line of the pump. The amplitude of these pulsations can, under known conditions, reach a value that causes the destruction of the pump. The possibility of cavitation can be reduced by rational choice of modes of operation of the hydraulic system and the correct design of its units, but this phenomenon can be completely eliminated only by using auxiliary pumping pumps, as well as increasing the pressure in the suction line of the pump. On the basis of the analysis of perspective directions of improvement of the hydraulic drive of the excavator the following improved scheme of it is developed. Usually only high-flow hydraulic motors can be used in flow dividers. But in our case it is necessary that the device had, first of all, small mechanical losses and small cost, and accuracy of division of working liquid which follows on filters can be small. In the volume flow divider, hydraulic motors are used: gear, piston, vane, screw, roller. The simplest dividers of volume type are paired (connected by shafts) hydraulic motors of lamellar (vane) and roller types. Hydraulic motors in this scheme are flow measuring devices (dispensers), which supply for one revolution the volume of liquid, equal without taking into account the leaks in the hydraulic motor, its working volume. The use of a flow divider as a source of hydraulic energy makes it possible to improve the hydraulic drive by combining in a single system the purification of the working fluid and the ejector feed of the pump. The most promising, in terms of cost, are flow dividers based on vane and rotary hydraulic motors..

Model-Based Control of a Mobile Platform With Independently Controlled In-Wheel Hydraulic Motors

Wheeled mobile platforms are important subsystems of heavy-duty working machines, but precise motion control of vehicles with multiple actuated wheels can be challenging, as linear controllers relying solely on velocity feedback could lead to excessive slippage of the wheels in face of varying terrain conditions. When aiming for more advanced control tasks as opposed to path-following, torque control of individual wheels could become necessary in order to distribute the traction effort in a desired fashion between each wheel. Studies on dynamic-model-based control of wheeled mobile robots concentrate on eletrically driven platforms that exhibit more linear behaviour than hydraulic drives, and dynamics of hydraulic motors are rarely addressed in the control design. In this paper, a model-based control design is pursued for a four-wheel vehicle actuated by in-wheel hydraulic motors, all independently controllable by high-bandwidth valves. Experiments on a heavy-duty mobile platform, equipped with wheel odometry, pressure transducers and satellite positioning, are conducted to study the feasibility of the proposed controller.

RESEARCH OF TRANSIENT PROCESSES OF PRESSURE CHANGE WHEN OPERATING A HYDRAULIC SYSTEM WITH FOUR CONNECTED HYDRAULIC MOTORS

The publication is devoted to the study of the quality of the hydraulic system with four series-connected hydraulic motors. These hydraulic systems can be used to drive the working bodies of agricultural machines, have significant advantages in their layout, but at the same time and disadvantages, the elimination of which requires a detailed study of the processes occurring during the operation of this type of system. The analysis of the previous works of scientists in this area allows us to conclude that it is possible to conduct theoretical research in this direction. A mathematical model of the proposed hydraulic system has been developed, which takes into account the effect of external load on the shafts of hydraulic motors, the inertia of the system, the effect of leaks from the connections of the elements of the hydraulic system and possible overflows of the working fluid from the high-pressure zone to the low-pressure zone. At this stage, wave processes occurring in the cavities of the hydraulic system were not taken into account. The solution of the resulting system of differential equations was carried out using the Runge-Kutta-Feldberg method with automatic change of the integration step in the mathematical package MathCad. The resulting transient processes were analyzed for the amplitude of pressure surges and the frequency of its change. Carrying out this analysis allows you to obtain comprehensive information about the nature of transient processes in the hydraulic system in order to find such a ratio of design and technological parameters, in which the system under study met the requirements regarding the quality of work as part of a technological machine. During the research, special attention was paid to the processes occurring at the moment of starting the hydraulic system, and the moment of application of the technological load.

The Many Inputs To Creating a Single Moving Form, the V&A Swingbridge

<p>The moving bridges within the V&amp;A Waterfront, Cape Town, South Africa, are a recognised part of its identity and a memorable part of any visitor’s experience. One of its moving footbridges, a cable stayed swing bridge was recently replaced with a new wider swing bridge. The new 4 m wide bridge doubles the previous crossing’s capacity and improves access across the cut to the expanding Clock Tower Precinct. Moving bridges are an integration of many functional design requirements and, in the V&amp;A, important experiences and place-makers for visitors. This paper tells the story of how, from the integration of needs and opportunities, the design of the new bridge developed. The finished form is cable-stayed with a single plane of four locked coil cables connecting to the deck’ central, upstand spine beam. A reclining pylon is a continuity of the main central beam and its stiffness transfers the cable loads into the piled substructure. The superstructure rotates on a 3550 mm diameter, internally geared, three-row roller slew bearing that is driven by four hydraulic motors with a maximum output torque of 42 kNm each. Performing to the same high standards of its predecessor, the new footbridge opens and closes up to sixty times a day, carrying up to</p><p>2.4 million people per year. The need to maintain access across the cut meant it was installed and commissioned within one month of the removal of the previous bridge.</p>

Performance Features of Tooth Gearing in Gear Hydraulic Machines

The paper presented determines that the rotation velocities of gears and radii connecting the axes of rotation of the gears with the point of their teeth gearing are not equal with each other. It is explained by the relative slip of involute gear profiles during their rolling. This phenomenon will become a prerequisite for further development of creation of mathematical models in the context of theory of gear hydraulic machines. The models can explain a number of specific phenomena in the operation of gear hydraulic machines, such as pressure and input pulsations, dynamics of hydraulic oil in the cut-off plane, combined torque pulsations in gear hydraulic motors and others.