Determination of Discharge Coefficient for Ball Valves With Calibrated Inserts

The valve coefficient was measured for 1, 1-1/4, 1-1/2 and 2 nominal ball valves. A recently designed orifice insert was used with these valves to obtain smaller valve coefficients. Orifice inserts were threaded into the body of a ball valve just upstream of the ball itself. The valve coefficient was measured for every insert used with these valves, and an expression was determined to relate the orifice diameter to other pertinent flow parameters. Two dimensionless groups were chosen to correlate the collected data, and expressions were developed that can be used as aids in sizing the orifice insert needed to obtain the desired valve coefficient. The study has shown that a 2nd order polynomial equation as well as a power law equation can both be used to predict the desired results. Knowing pipe size and schedule, the diameter of the orifice insert needed to obtain the required valve coefficient can be approximated with minimum error. An error analysis performed on the collected data shows that the results are highly accurate, and that the experimental process is repeatable.

Hydraulic Components Contribution to Total Power Losses and Acceleration of an Open Loop System With Long Hose

This paper is concerned with forest logging machinery. A great deal of final felling in cut-to-length method done by harvester, which fells, delimbs and cuts the trees to pre-selected lengths. Two important criteria of a harvester head are that it has to be energy efficient and it has to be as fast as possible. To minimize losses in hydraulic systems the main demand is to reduce pressure losses in high power valves and outer components as much as possible. Each orifice in the flow path results in power losses. This work is an experimental study on power losses and acceleration of hydraulic motor in a system with long hoses. Main hydraulic components included are hydraulic pump, cartridge valve, pipe line and hydraulic motor. The results show that pre-activating the pump improves the system speed. To reduce losses, optimization of valve block, cartridge valve orifices are needed. Accumulators are favourable if combined with high stand-by pressure.

Wireless Starting System and Emergency Stop for Teleoperated Hydraulic Mobile Machine

A small general-purpose teleoperated hydraulic mobile machine is studied at the Institute of Hydraulics and Automation at the Tampere University of Technology. Thanks to teleoperation, the operator of the machine is able to be in safe place during the driving when necessary. However, the actions of the machine can be dangerous for the people or the objects in the environment if problems appear for instance in the control system. On that account, safety issues must be considered carefully. Special attention has to be paid to stop the machine and start the engine again once the machine has recovered from an error situation. The goal of this paper is to describe the design and implementation of different kind of solutions to start and stop the machine wirelessly. The emergency stop can be activated through the wireless connection by the operator or by the automatic diagnostic system of the hydraulic mobile machine. The control system monitors the state of several hydraulic components such as hydraulic valves and motors by means of sensors during the operations of machine. The machine is teleoperated by using WLAN (Wireless Local Area Network) connection. The developed wireless starting system and emergency stop is totally independent of the WLAN link. In the first prototype of the wireless starting system and emergency stop, the wireless connection is carried out by using commercial, cost effective RF (Radio Frequency) modules. The data transfer protocol which is used by the modules is designed for this application. Protocol implementation is carried out with microcontrollers. Another version of the wireless starting system and emergency stop is carried out by using radio modems. The modems have better properties than the cost effective RF modules used in the first prototype due to their higher RF output power. Programmatically carried out automatic emergency stop, which stops the machine, if the WLAN connection between the control station and the machine breaks, is discussed. In that case, the independent wireless emergency stop connection is not needed. Implementations of the system are introduced in this paper. Also, some testing results and user experiences are described. Properties of these different implementations are compared: cost of the system, range, reliability and complexity of the implementation. By means of the studied results the most suitable solution to start the engine and stop the actions of the machine is chosen.

Self-Calibration of Push-Pull Solenoid Actuators in Electrohydraulic Valves

System parameters for solenoid actuators are important for high performance control and for self-sensing. Due to the non-linearities in the solenoid actuators, parameter identification procedures that aim to obtain the electro-mechanical property can be complex and time consuming. In this paper, a self-calibration procedure for solenoid actuators in push-pull configurations is proposed. Utilizing the fact that the inductances of the solenoids share the same parameters as those for the electromagnetic force, the parameters for the electromagnetic force can be obtained from the easily obtainable electrical signals such as the voltage and current signals, and two inexpensive on-off sensors. The calibration procedure involves only actuating the solenoid actuator back and forth. Simulation study is presented to verify the method.

Multi Criteria Design Improvement of Commercial Loader Crane

An approach to systematically deriving the optimal use of operator-in-the-loop machinery is presented. The operation is considered as a set of design variables that similarly to classical design variables such as geometry and materials may be manipulated with a view to reach certain performances. The emphasis of the paper is on mobile loader cranes and an example on the development of the lifting capacity diagram of such a crane is used to illustrate the potential benefits of employing the presented approach. In general, physical data is not given for the loader crane due to limited space, however, the authors will be happy to provide more details for anyone interested.

A Compressible Fluid Power Dynamic Model of a Liquid Propellant Powered Rifle

This paper presents a dynamic model of the interior ballistics of an experimental liquid propellant-powered rifle. The liquid propellant-powered rifle described utilizes a misture of Hydroxyl Ammonium Nitrate (HAN) and hydrocarbon fuel to replace gunpowder typically used in such firearms. The motivation for such a development is to discard the need for a shell casing whereby carrying only propellant and bullets will reduce both the mass and volume per shot carried by the soldier. A first-principles dynamic model of the interior ballistics is derived as a compressible fluid power problem with the chemical liberation of heat within the chamber modeled via a condensed-phase reaction rate law. The model is used to predict the overall performance in terms of ballistic kinetic energy as well as draw design insight regarding the role of friction, chamber geometry, and the profile of chamber pressure with respect to time. Simulation results are presented as well as preliminary experimental results from a proof-of concept device.

An Optimisation Approach Applied to Design the Hydraulic Power Supply for a Forklift Truck

This paper describes the first part of a method that may be used in the design of the most energy efficient hydraulic open-circuit systems, when also considering the operational aspects of the system given in the design specifications. The method builds on a numerically based multi-level optimisation approach, and is in the current paper exemplified through the design of the hydraulic power supply for a forklift truck. The paper first describes the prerequisites for the method and then explains the different steps in the approach to design the hydraulic system. Finally the results of the optimisation example for the forklift truck are presented along with a discussion of the method.

Condition Monitoring of an Electrohydraulic Position Control System Using Artificial Neural Networks

This paper investigates the condition monitoring of a servo-valve-controlled linear actuator system using artificial neural networks (NNs). The aim is to discuss techniques for the identification of failure characteristics and their source. It is shown that neural networks can be trained to identify more than one fault but these are larger and require more training patterns than networks for single fault diagnosis. This leads to much longer training times and to problems with scaleability. Therefore a modular approach has been developed. Several networks were trained each to identify an individual fault. The parallel outputs of these nets were then used as inputs to another network. This additional network was able to identify not only the correct faults but also the actual fault levels.

Modeling and Control of an Electro-Hydraulic Poppet Valve

This paper explores the dynamic modeling of a novel two stage bidirectional poppet valve and proposes a control scheme that uses a Nodal Link Perceptron Network (NLPN). The dynamic nonlinear mathematical model of this Electro-Hydraulic Control Valve (EHCV) is based on the analysis of the interactions among its mechanical, hydraulic, and electromagnetic subsystems. A discussion on experimental approaches to determine the model parameters is included along with model validation results. Finally, the control scheme is developed by proposing that the states of the EHCV follow a set of desired states, which are calculated based upon the desired valve flow conductance coefficient KV. A simulation is presented at the end to verify the proposed control scheme.

Automated Sizing Procedure of Servo-Driven Robot for Pallettes Handling

A procedure for the automated sizing of spatial servo mechanisms is presented. The design performance is measured by means of a work task moving a payload from one point to another within a certain time. The design variables are composed of continuous and discrete parameters with the latter associated with the servo motor and planetary gears making up the servo drive. The costs are identified as the main objective for minimization whereas a number of side constraints related to accuracy, fatigue, vibrations and thermal conditions are presented and formulated mathematically. The two-level design procedure generates design from a motor and gear database that a subsequently subjected to minimization with a view to eliminate any constraint violations. The least costly of the feasible design are considered the optimal.