Pneumatic Power Research Articles

A modified Wells turbine for wave energy conversion

The method of wave energy conversion utilises an oscillating water column (OWC). The OWC converts wave energy into low-pressure pneumatic energy in the form of bi-directional airflow. Wells turbine with its zero blade pitch setting has been used to convert this pneumatic power into uni-directional mechanical shaft power. Measurements in OWC based wave energy plants in India and Japan show that the airflow velocity is not equal in both directions. The velocity is more when the airflows out to the atmosphere (exhalation) than in the reverse direction. It may be advantageous to set the rotor blade pitch asymmetrically at a positive pitch so as to achieve a higher mean efficiency in a wave cycle. Towards this objective, performance characteristics of a turbine with different blade setting angles in steady flow were found by experimentation. Quasi-steady analysis was then used to predict the mean efficiency for a certain variation of air velocity with time. This variation with time was taken as pseudo-sinusoidal wherein the positive part of the cycle was taken as a half sine-wave whose amplitude is greater than that of the negative half sine-wave. Such a variation is representative of what happens in reality. For exhalation velocity amplitude to inhalation velocity ratios 0.8 and 0.6, a rotor blade setting angle of 2° was found to be optimum.

Effect of guide vanes on the performance of a self-rectifying air turbine with constant and variable chord rotors

A Wells turbine is a self-rectifying air flow turbine capable of converting pneumatic power of the periodically reversing air stream in Oscillating Water Column into mechanical energy. The Wells turbine has inherent disadvantages; lower efficiency, poorer starting characteristics, higher axial force and low tangential force in comparison with conventional turbines. Guide vanes before and after the rotor suggest a means to improve the tangential force, hence its efficiency. Experimental investigations are carried out on a Wells turbine with the constant chord and variable chord blade rotors fitted with inlet and outlet guide vanes to understand the aerodynamics. Experiments were also conducted for the above said rotors with various stagger angles to validate the design stagger angle. In addition, the starting and running characteristics of the rotors have been studied and compared with the case without guide vanes. Studies were done at various flow coefficients covering the entire range of flow coefficients over which the turbine is operable. The efficiency, starting characteristics of the turbines with guide vanes have improved when compared with the respective turbines without guide vanes.

シリコーンゴムボールを用いた面駆動型ソフトアクチュエータの開発

Recently, robots have been expected to be used in various fields such as not only usual manufacturing industry but also medical welfare, agriculture, security system and so on. Especially, in the coming advanced aged society, the demand of robot will be more increased in medical welfare and human assist technology. In such a field, since robots must work together with human or contact with a human body directly, they are required safety and flexibility.In this study, in order to realize a flexible mechanisms satisfying the above requirements, a soft actuator has been developed. It is composed of a body made of silicone rubber and driven with a pneumatic power. Both the elasticity of rubber material and the air compressibility are effective to realize such a soft actuator. The developed planar type soft actuator has two layer structure built up with silicone rubber hemispheres and balls, which may be available to carry fragile and shapeless objects, furthermore, to execute flexible contacting tasks for human body. This paper describes a principle of operation, a control method and a fundamental control performance of the proposed actuator.

Intelligent proportional pneumatic valves and drives for field bus applications

The continuous trend within the factory automation and process control to use intelligent peripheral field devices increasingly leads to an extended function range of proportional pneumatic valves and drives. Typical requests in his area are:-interfacing to a digital communication system-line-up support-diagnostic and service functions-error messages/alarm-compatibility/exchangeabilityIn the area of process control there is a demand to lower the installation costs and to transfer the energy and the control signal via the same wire. For this reason the presented valve is characterised by a reduced electrical power consumption. The pilot control stage operates according to the spool valve principle and reduces the pneumatic power consumption substantially, too. The maximum electrical power consumption of the entire valve including the connection of the field bus and the electrical amplifier stage amounts to less than 1W.

Configuration and Optimal Control of Hydraulic/Pneumatic Hybrid Actuator with 2-DOF

A pneumatic actuator outputs large power in proportion to weight and can be installed in an inexpensive, light and compact configuration. From the standpoint of controllability, however, it is weak due to nonlinearity by compression and delayed transfer of air, it has a problem of poor accuracy in position control. To solve such problem, we propose a hydraulic/pneumatic hybrid actuator that has a pneumatic cylinder and hydraulic cylinder in parallel and uses the hydraulic cylinder as damper. We demonstrate that it can be used in practice and structurally applying it to a manipulator with 2-DOF. It also demonstrates that high-speed and stable control can be achieved by applying optimal control method.

NOVEL DESIGN FEATURES OF THE KANTROWITZ CARDIOVAD (KCV)

The purpose of this communication is to describe the current configuration of the KCV undergoing clinical trial. The KCV is an electrically powered, pneumatically driven LVAD which provides on demand diastolic augmentation to the failing left ventricle. Its physiologic function is analogous to that of the intraaortic balloon pump (IABP). The KCV consists of: a pumping chamber implanted into the wall of the descending thoracic aorta, a percutaneous access device (PAD), and a drive unit. The fusiform, 16 cm long pumping chamber is made of polyurethane; its blood-contacting surface is textured with integrally cast fibrils. The autologous cell coated PAD conveys pneumatic power to the pump and the ECG from the patient. The patient can disconnect the drive unit at the PAD and be untethered for hours. The drive unit acquires the ECG, measures aortic pressure, determines timing, and generates the requisite controlled pulses of air to inflate the blood pump. Two drive units have been developed. One operates from rechargeable batteries, weighs 5 pounds, and can be worn in a vest. The other is powered by 110 VAC and is built into a wheeled hard-shell suitcase. Both drive units provide only an ON/OFF switch and alarms as the patient user interface. Device operation can be monitored, automatically stored logs of events can be examined, and parameters can be reprogrammed via a serial port. The clinical results of an ongoing trial of the KCV are presented in a companion submission. The study has demonstrated that the equipment achieves its design goals. The patient or his caregivers can easily operate the KCV system. The embedded computer automatically adjusts to changes in heart rate and blood pressure as well as arrhythmia. The serial port allows a trained operator to customize parameters to the needs of a specific patient.

Power management and distribution system for a more-electric aircraft (MADMEL)

A five-phase Power Management and Distribution System for a More-Electric Aircraft (MADMEL) program was awarded by the Air Force to Northrop/Grumman Military Aircraft Division in September 1991. The objective of the program is to design, develop, and demonstrate an advanced electrical power generation and distribution system for a More-Electric Aircraft (MEA). The MEA emphasizes the use of electrical power in place of hydraulics, pneumatic, and mechanical power to optimize the performance and life cycle cost of the aircraft. This paper presents an overview of the MADMEL program and a top-level summary of the program results, development and test of major components to date. In Phase I and Phase II studies, the electrical load requirements were established and the electrical power system architecture was defined for both near-term (NT-year 1996) and far-term (FT-year 2003) MEA application. The detailed design and specification for the Electrical Power System (EPS), its interface with the Vehicle Management System, and the test set-up were developed under Phase III. Phase IV, fabrication and testing of the subsystem level hardware, has been completed. Overall system level integration and testing, Phase V, is scheduled to be completed by September 1999.

Development of In-Pipe Mobile Robot Using Pneumatic Soft-Actuator

In this paper, soft-actuators are developed, which are made of a silicon rubber and are driven with a pneumatic power. The silicon rubber has a flexibility, and the pneumatic power has a compressibility. Using these characteristics, soft-actuators can be realized. A rubber can be molded in some shapes and designs, and rubber actuators can move in extending and bending.An in-pipe mobil, robot is composed of two holding actuators and a traveling actuator. The robot is fixed by holding actuators on both sides, a traveling actuator is equipped between holding actuators. The influence of the tube length (from servo valve to robot) is compensated by an improved control system. The compensator comprises of expresses the transfer function which is identified characteristics of the robot. Owing to the softness of the actuator and the pneumatic compliance, the robot can travel in an arbitrary shape pipe, such as a circle or a non-circle. The validity of this robot is confirmed through some experiments.

A BASIC STUDY ON OPTIMAL DESIGN OF OPTO-PNEUMATIC SERVO SYSTEM

An optical servo system is a new control system which can be used in hazardous environments where electromagnetic noises and radiations exist. In our previous study, we have realized an opto-pneumatic control system which executed a cart positioning using optical control signals instead of electric signals in ahazardous area. However, the response of the system was slower than a usual electro-pneumatic control system, because the response time of the optical servo valve which converted optical signal to pneumatic fluid power was longer. In the next step, we have proposed an analytical model of the valve in order to improve the dynamics of the valve. In order to design the valve, it is necessary to analyze the characteristics of moving rubber membranes in the valve in detail. In this paper, we propose an analytical model of the membranes. And we investigate the relation between design parameters of the valve, such as an equivalent spring constant, damping coefficient and so on, and structural parameters of the membranes, such as a diameter and thickness.

Air Force Application of Advanced Magnetic Materials

ABSTRACTA national initiative is underway to develop and test a more electric aircraft (MEA) and is being led by the U.S. Air Force Research Laboratory at Wright-Patterson Air Force Base, Ohio. The MEA concept is based on utilizing electric power to drive aircraft subsystems which are currently driven by a combination of hydraulic, pneumatic, electric and mechanical power transfer systems. A major objective of this effort is to increase military aircraft reliability, maintainability and supportability and to drastically reduce the need for ground support equipment. These improvements will be realized through the further advancement of key MEA technologies, including magnetic bearings, aircraft integrated power units (IPU), and starter/generators (IS/G) internal to an aircraft main propulsion engine. These advanced developments, as well as weapon and space power applications, are the driving force for the new emphasis on high temperature and high strength magnetic materials for power applications. In determining the best magnetic material for an application it is typically necessary to conduct an engineering trade-off analysis which takes into consideration mechanical behavior, electrical loss, and magnetic properties under the conditions of actual usage. New materials solutions are required to meet these challenges, as designers often find the magnetic material performance to be the technological limitation.

Effect of guide vanes on the performance of a variable chord self-rectifying air turbine

Wells turbine is a self rectifying air flow turbine capable of converting pneumatic power of the periodically reversing air stream in Oscillating Water Column into mechanical energy. One of the principal reasons for the low efficiency of the Wells turbine is its lower tangential force compared to its axial force. Guide vanes before and after the rotor suggest a means to improve the tangential force, hence its efficiency. Experimental investigations are carried out on the Wells turbine with a variable chord (VACR) blade rotor fitted with inlet and outlet guide vanes to understand the aerodynamics especially improvement in efficiency and starting characteristics. Numerical simulation has been made to clarify the unsteady characteristics of the turbine with guide vanes. Studies are done at various flow coefficients covering the entire range of flow coefficients over which the turbine is operable. The efficiency, starting characteristics of the Wells turbine has improved when compared with the turbine without guide vanes.

Performance Prediction of Contrarotating Wells Turbines for Wave Energy Converter Design

Wave energy can be captured and converted to a vertical pistonlike oscillatory motion by semiinsertion of a chamber with a submerged opening into the ocean. The roof of the chamber will open onto a ducted Wells air turbine, which will be driven by the oscillatory airflow developed by the forcing action of the surface of the Oscillating Water Column (OWC) inside the chamber. The design of such an OWC conversion plant is considered with particular reference to the air turbine stage and its synthesis into the system. Consequently, a semiempirical method for predicting the performance of the contrarotating Wells turbine configuration is presented, notably, detailing aerofoil performance into the stall region. The predicted turbine performance is subsequently utilized to facilitate the design of a 310 kW plant, including efficient accommodation of the pneumatic power levels for maximal aerodynamic conversion.

On a methodology for discrete–continuous scheduling

Discrete–continuous problems of scheduling nonpreemptable jobs on parallel machines are considered. The problems arise e.g. when jobs are assigned to multiple parallel processors driven by a common electric, hydraulic or pneumatic power source. Existing models have assumed job processing rates as a function of the number of jobs currently being processed, or equivalently the number of machines currently in operation. In this paper a more general model is proposed in which processing rates of a job assigned to a machine depend on the amount of a continuous, i.e. continuously divisible resource (e.g. power) allotted to this job at a time. Thus the problem consists of two interrelated subproblems: (i) to sequence jobs on machines, and (ii) to allocate the continuous resource among jobs already sequenced. We provide a comprehensive analysis of the problem. This includes properties of optimal schedules, efficiently (in particular analytically) solvable cases, formulations of the possibly simplest mathematical programming problems for finding optimal schedules in the general case, heuristics and the worst-case analysis. Although our objective function in this paper is to minimize makespan of a set of independent jobs, the presented methodology can be applied to other criteria, precedence-related jobs, and many resource types (apart from, or instead of machines).

A skeletal framework artificial hand actuated by pneumatic artificial muscles

Describes a method and a process for developing a soft artificial hand similar to a real human hand and its small-size soft actuator. For the soft actuator, we took a pneumatic artificial muscle and succeeded in reducing it to a diameter of 3.5 mm. The pneumatic artificial muscle allows the artificial hand not only to move softly and powerfully by pneumatic power but also works as a sensor. As a frame for the artificial hand, we used the skeleton model of human hand in order to make the hand similar to real human hand in structure as well as motion.

Design synthesis of oscillating water column wave energy converters: Performance matching

The matching of a Wells air turbine to an oscillating water column (OWC) is addressed, with particular reference to design synthesis at the Islay prototype wave power converter. The level of damping applied by the turbine must optimize the hydraulic performance of the OWC in order to facilitate efficient conversion from wave power to pneumatic power. Furthermore, a Wells turbine is only able to convert pneumatic power to mechanical power over a limited range of flow coefficients. Therefore, the efficient operational range of the turbine must extend over a sufficient and optimal proportion of the range of flow coefficients generated by the OWC. Suitable analytical models that describe the behaviour of the system are presented and subsequently the wave conditions and conversion performance at the Islay plant are outlined in order to exemplify the design synthesis to be achieved.

Inverse formulation for viscous two-dimensional and axisymmetric flow problems

The inverse problem of a viscous axisymmetric flow is formulated using the orthogonal curvilinear coordinate system, including a two-dimensional flow. The Stokes stream function or stream function and the coordinate which is constant along the orthogonal trajectories of streamlines or stream tubes are the independent variables. The Navier-Stokes equations and the vorticity transport equation are transformed into the orthogonal coordinate frame for an incompressible flow. The axisymmetric laminar jet leaving a Poiseuille tube for an inviscid outer fluid phase is solved numerically using parabolic differential equations which are simplified by a boundary-layer-type analysis under the influence of both gravity and surface tension. Furthermore, the potential flow is calculated to obtain the optimum shape of a spool value which is universally used as a control valve for hydraulic and pneumatic power applications.

Theoretical and Experimental Investigations of an Opto-Pneumatic Detector

The following is a theoretical and experimental study of an opto-pneumatic detector (OPD) used in an opto-pneumatic interface. This interface is capable of changing an optical signal into a pneumatic one, that can be amplified and then applied to pneumatic power stages. The opto-pneumatic interface offers the greatest promise in the automation of installations located under fire and explosive-hazardous conditions and under conditions where there are electromagnetic or radiation field actions, whereby electrical communication channel application is undesirable or impossible, and where pneumatic channels do not provide the required speed of response. The OPD is made up of a cell where an infrared light signal cuts into a black-body, increases its temperature, and generates a pressure signal in the chamber. The work has been carried out using different absorption body thickness, gas chamber volumes, different optical signal frequencies, and different fluid loads of the OPD. Following this, a mathematical model for numerical computation has been elaborated. The theoretical results were compared with the experimental results. [S0022-0434(00)00101-5]

Lineår modelling of oscillating water columns including viscous loss

Wave-energy converters of the oscillating-water-column (OWC) type with pneumatic power take-off may be modelled by the so-called ‘applied-pressure’ (or ‘pressuredistribution’) description. For wavelengths which are not too short, the alternative ‘rigid-pistoa’ description is also applicable. The paper presents a transformation between the two descriptions. A mechanical mass-spring equivalent model of the OWC is also presented together with analog electric circuit diagrams. Some account of viscous energy loss is taken into consideration by introducing a mechanical loss resistance into the rigid-body description, and corresponding analog electric circuit elements for both descriptions are included. Some methods are presented to determine experimentally the mechanical loss resistance for a two-dimensional OWC.

Robots and food—low margins need different solutions

Examines the effectiveness of using expensive robotics equipment in the food industry where profit margins are low and labour is less expensive than in other industries. Looks at the work undertaken at the Silsoe Research Institute into developing appropriate low‐cost technology for basic food applications. Projects discussed include robotic teat cups for milking cows and a robotic mushroom harvesting; both using pneumatic power transmission. Concludes that food production will become an important application for robotics when it is generally accepted as cost effective.

Muscle- and Pneumatic-Powered Counterpulsating LVADs: A Pilot Study

There is a worldwide interest in supporting the failing heart with a skeletal muscle by either wrapping it around the natural heart (dynamic cardiomyoplasty) or by constructing a skeletal muscle ventricle (SMV) used for counterpulsation. Conventional cardiomyoplasty in many clinics carries an operative mortality rate of 15-20% partly because it requires 6 weeks to train the muscle to contract continually. A flexible, pear-shaped blood pump with an inflatable air chamber was designed and made around which a muscle can be wrapped. The advantage of our design is that it can also be driven by pneumatic power, immediately supporting the circulation of a seriously ill patient while that patient is still on the operating table. After a period of time to allow for revascularization and the subsequent training of the muscle, the external pneumatic power can be gradually discontinued. Then the assisted patient becomes tether-free. If, at any time, the muscle power fails, the pneumatic-powered mechanism can be reactivated. In the preferred approach, the blood pump is connected to the aorta for diastolic counterpulsation. A muscle can either be wrapped around the blood pump directly, or around one of two separate muscle pouches connected to the blood pump. To facilitate surgery, a large pouch is inserted under the musculus latissimus dorsi, which is connected to a blood pump. When stimulated, the muscle will contract over the pouch compressing it and providing power to the blood pump. If it is found that the pressure generated in the pouch cannot meet the aortic blood pressure, it can be augmented by using a pressure amplifier.(ABSTRACT TRUNCATED AT 250 WORDS)