Showing papers on "Hydraulic machinery published in 1997"

Electokinetic high pressure hydraulic system

Abstract: A compact high pressure hydraulic system having no moving parts for converting electric potential to hydraulic force and for manipulating fluids. Electro-osmotic flow is used to provide a valve and means to compress a fluid or gas in a capillary-based system. By electro-osmotically moving an electrolyte between a first position opening communication between a fluid inlet and outlet and a second position closing communication between the fluid inlet and outlet the system can be configured as a valve. The system can also be used to generate forces as large as 2500 psi that can be used to compress a fluid, either a liquid or a gas.

Experiments and simulations on the nonlinear control of a hydraulic servosystem

Abstract: Presents the derivation, simulation and implementation of a nonlinear tracking control law for a hydraulic servosystem. An analysis of the nonlinear system equations is used in the derivation of a Lyapunov function that provides for exponentially stable force trajectory tracking. This control law is then extended to provide position tracking. The proposed controller is simulated and then implemented on an experimental hydraulic system to test the limits of its performance and the realistic effects of friction.

Power conversion system for bi-directional conversion between hydraulic energy and electrical energy

Abstract: A bi-directional power conversion system interconnects hydraulic and electrical power systems on-board a vehicle such as an air-craft, whereby the power conversion system can selectively convert available electrical power to needed hydraulic power or vice versa. The power conversion system includes a hydraulic machine (15) connected to the hydraulic system (10) of the vehicle, an electrical machine (20) connected to the electrical system (3) of the vehicle through a power converter and control unit (22), a rotational drive shaft (14) mechanically interconnecting the hydraulic machine (15) and the electrical machine (20), and a priority and safety control unit (26) that controls the operation of the system. In a first operating mode, for example in the event of a failure of a primary electrical generator (2), the hydraulic machine (15) operates as a hydraulic motor driven by available hydraulic power from the hydraulic system (10) to drive the electrical machine (20) which operates as an electrical generator to provide electrical power into the electrical system (3). In a second operating mode, for example in the event of a failure of a primary hydraulic pump (9), the electrical machine (20) operates as an electric motor driven by electric power from the electrical system (3) to drive the hydraulic machine (15) operating as a hydraulic pump to provide hydraulic power into the hydraulic system (10). A hydraulic valve arrangement (18) and an electrical switch arrangement (21), as well as pressure and speed regulators are controlled by the control unit (26), and the system operation is monitored by sensors connected to the control unit (26), to activate the appropriate operating mode.

Vehicle hydraulic braking systems incorporating micro-machined technology

Abstract: Hydraulic or electro-hydraulic braking systems which include at least one wheel braking device and micro-machined technology, such as microvalves, are described herein. The use of the microvalves helps to eliminate audible noise produced in the hydraulic systems as well as allows for reduced package size of the system. In particular, many of the braking systems described herein have Anti-lock Braking System (ABS) capabilities, and as such employ apply microvalves, dump microvalves and changeover microvalves. The microvalves may be digitally or proportionally controlled for selectively controlling the pressure supplied to the wheel brake cylinders.

Control scheme for pressure relief

Abstract: A control scheme is provided that controls the maximum pressure level in desired locations of a hydraulic system. This control scheme eliminates the need of separate line relief valves that many times create pressure spikes in the hydraulic system. In one example, the control scheme functions to sense the operating pressure at the desired location and compares it to a differential pressure and a desired input command during one step or loop to establish a predicted pressure level. The predicted pressure level is compared to the pressure necessary to initiate movement of the valving element in an electrically actuated control valve mechanism. The result is used to move the valving element to a predetermined position if the predicted pressure level is less than cracking pressure level and the differential pressure is greater than zero. If the predicted pressure level is higher than the cracking pressure level, an output control signal is boosted in order to move the valving element to an open position in a much quicker time period to offset the over pressure condition before a pressure spike occurs.

ABS valve body heat sink for control module electronics

Abstract: A hydraulic valve body for an electro-hydraulic control unit forms a heat sink for the control unit electronic components. The control unit can be included in an anti-lock brake system.

Hydraulic design of hydraulic machinery

Abstract: Two dimensional flow three dimensional flow boundry layer similarity laws and modelling performance cavitation flow induced vibrations rotodynamic pumps pelton turbines Francis turbine runner blades Axial flow turbines hydraulic design of Francis pump turbine hydraulic design of Axial flow pump turbine flow anlysis and computer aided design.

Auxiliary hydraulic control system

Abstract: An auxiliary hydraulic system for a working vehicle having an operator station is disclosed herein. The system includes a hydraulic pump for providing hydraulic fluid under pressure, auxiliary hydraulic fittings for connection to auxiliary attachments, and electrically-actuated auxiliary valve assemblies for controlling the supply of hydraulic fluid from the pump to the fittings in response to control signals. The system also includes an operator control console mounted at the operator station and including control levers moveable between different flow positions, flow limit input devices for setting flow limits for the control levers, and a console control circuit for generating command signals based upon the positions of the control levers and the flow limits. The command signals are transmitted to an auxiliary control circuit which generates the control signals in response thereto and applies the control signals to the auxiliary valve assemblies. Thus, the supply of fluid to the auxiliary valve fittings depends upon the positions of the control levers and the flow limits which are controlled by an operator from an integrated operator control console.

Pressure compensating hydraulic control valve system

Abstract: An improved pressure-compensated hydraulic system for feeding hydraulic fluid to one or more hydraulic actuators. A remotely located, variable displacement pump provides an output pressure equal to input pressure plus a constant margin. A pressure compensation systems requires that a load-dependent pressure be provided to the pump input through a load sense circuit. A reciprocally spooled, multi-ported isolator transmits the load-dependent pressure to the pump input but prevents fluid in the load sense circuit from leaving the load sense circuit and flowing through a relatively long conduit leading to the remotely located pump. In a multi-valve array, at least one valve section has a backflow-preventing shuttle valve which prevents backflow through the pressure compensation system if a main relief valve is operative.

Hydraulically powered fan and power steering in vehicle

Abstract: A hydraulic system for use in an automotive vehicle. A source of hydraulic pressure selectively operates in two modes. In one mode, it feeds a radiator cooling fan and a power steering system in parallel when a system pressure or flow exceeds a predetermined pressure rate. In another mode, it feeds the radiator cooling fan and the power steering system in series when the system pressure or flow is less than the predetermined pressure or flow.

Hydraulic system for motor vehicle

Abstract: A motor vehicle hydraulic system including a power steering pump, a reservoir, a steering assist fluid motor, and a second fluid motor for a radiator cooling fan. A flow control valve remote from the power steering pump divides the total fluid flow from the power steering pump into a high flow branch and a low flow branch. Fluid circulates in the low flow branch at a substantially constant flow rate for a proportional control valve for the steering assist fluid motor and returns to the reservoir through an unrestricted tubular boss on the reservoir. Fluid in the high flow branch issues as a jet stream from a nozzle on the reservoir into a venturi passage submerged in fluid in the reservoir. The venturi passage is connected to an inlet port of the power steering pump. The jet stream aspirates fluid from the reservoir into the venturi passage. The kinetic energy of the jet stream is converted into superatmospheric pressure at the inlet port of the power steering pump to suppress cavitation. Fluid from the low flow branch dwells in the reservoir for a time duration adequate for natural release therefrom of any entrained gas bubbles.

On-line condition monitoring and fault diagnosis in hydraulic system components using parameter estimation and pattern classification

Abstract: Safety and functionality of a fluid power control system can considerably be increased by implementing predictive maintenance routines. Modern predictive maintenance practices are based on automatic condition monitoring and fault diagnosis of the system components. In most cases, low-quality raw sensor data are directly monitored for constraint violations or threshold crossings. Subsequent fault diagnosis is often performed by a knowledge-based expert system based on "order-of-magnitude reasoning". This means that quantitative sensor data are first transformed into more understandable "linguistic terminologies" such as "low", high", etc., and are then assessed by production rules in order to diagnose system (or component) faults. A major problem with this technique is that it is not usually feasible to directly measure the desired quantity, e.g., the flow rate inside a valve. Another problem is the association of noise and variations with directly measured signals, which might be misinterpreted as faults, especially in highly dynamic systems. In practice, failure modes often involve a change in the model structure, which may be interpreted as change(s) in one or several system parameters. The theme of this thesis is on automatic generation of fault symptoms in the form of qualitative variation of system physical parameters by on-line processing of low-quality raw sensor data. To accomplish this, a novel model-based methodology has been proposed that has integrated four levels of information processing in a structured hierarchy: 1. State/parameter estimation of the hydraulic system components using state-space models, stochastic signal processing techniques such as Kalman filtering, and raw sensor data from the hydraulic system. 2. Monitoring and change detection in the identified parameters of the system components, using statistical tests, such as sequential probability ratio test. 3. Generation of fault symptoms in the form of qualitative changes in the physical parameter values, such as "increased", "decreased", etc. 4. Fault recognition by fault symptom classification using neural network pattern classifiers, 5. Fault diagnosis maintenance aiding using knowledge-based expert systems. ii By using a second-order linear system as an example, we have shown how each element of the proposed hierarchical methodology effectively processes the lower quality data received from the previous element and provides higher quality information for the next element in the hierarchy, so that an incipient fault or an abrupt failure can be successfully detected and diagnosed. The proposed fault detection and diagnosis (FDD) technique has also been applied on a real hydraulic test rig which has been built in the Robotics and Control Laboratory, at UBC. The hydraulic test rig has a two-stage proportional directional flow control valve, which has been thoroughly modelled for simulation of faults. A step-by-step methodology has been adopted to obtain the physical valve parameters from static measurements, as well as through numerical search techniques using dynamic measurements. In order to estimate the system parameters and states in real-time, nonlinear state-space models have been developed for various hydraulic components, including the two-stage servovalve, a hydraulic cylinder, and a manipulator. Extended Kalman Filtering (EKF) is applied on the state-space models to get the parameter estimates. Only low-cost robust sensors such as pressure transducers and position sensors have been used for this purpose. More expensive or hard-to-measure states such as flow rates and orifice areas are predicted using novel state-space models. One of the major achievements of this thesis has been incorporation of a novel state-space model for a valve orifice area that allows us not only to obtain accurate estimates of the flow rate through the valve, but also to detect several incipient faults and abrupt failures in the valve and its connecting ports. The valve orifice area is considered as a nonlinear unknown function of the valve spool position. No a priori knowledge about the orifice profile or the spool deadband size is assumed. The functional relationship, along with the deadband size are automatically revealed during the on-line estimation process, while the decision as to which port is open to the flow is made internally. Experimental results were promising and showed that the identified valve orifice area is an excellent measure in quick detection and diagnosis of incipient or gradual faults, as well as and abrupt failures, in servovalves and servo-actuator systems.

Hydraulic marine jack plate

Abstract: A powered jack plate for use with a marine outboard motor in a marine environment; the inward side of the jack plate is attached to the transom of a boat; the outboard motor is attached to the outward side of the powered jack plate; hydraulic power is the preferred power source, hydraulic fluid being supplied by a separate hydraulic pump; the jack plate comprises a pair of opposing supports which are interconnected by support bars; the opposing supports incorporate linear bearings in which rides a slide which is capable of vertical movement; the linear bearings are provided with grease fittings for positive lubrication; the outward side of the opposing supports is higher than the inward side thereby permitting maximum upward travel of the slide and the linear bearings are locked into the opposing supports via an undercut groove which is integral with these supports.

Pre-loaded elastomeric accumulator for hydraulic system

Abstract: A hydraulic control unit for a hydraulic vehicle control system, such as anti-lock brakes, includes a hydraulic accumulator including a housing that defines a cavity and a passageway that extends from the cavity and that is adapted for inner-connection with a host hydraulic circuit, preferably adjacent the high pressure outlet of the host system hydraulic pump. A closure member cooperates with the housing to substantially seal the cavity. A pre-loaded elastomeric member is disposed within the cavity and is compressible with increasing hydraulic fluid pressure to attenuate short duration pressure pulses therein. The elastomeric member is preferably enclosed within a rigid relatively porous member that, in combination with the elastomeric member, substantially fills the entire volume of the cavity and permits pressurized fluid to act on substantially the entire outer surface of the elastomeric member to minimize internal friction and hysterisis losses and provides the structure, along with the closure member, to pre-load the elastomeric member.

Auxiliary interlock control system for power machine

Abstract: A skid steer loader has an auxiliary coupling device connected to the hydraulic circuit of the skid steer loader. An auxiliary control circuit includes a hydraulic valve coupled between the hydraulic circuit of the skid steer loader and the auxiliary coupling device. The auxiliary control circuit is coupled to an operator input and controls flow of hydraulic fluid between the hydraulic circuit of the skid steer loader and the auxiliary coupling device based on a control signal received from the operator input. In addition, a controller is coupled to an operating mode sensor and to the auxiliary control circuit and provides an output to control operation of the hydraulic valve controlling flow to the auxiliary coupling device based on the status of the operating mode sensor.

Vehicle mounted high pressure cleaning apparatus

Abstract: A vehicle mounted high pressure water cleaning apparatus includes a water delivery system, hydraulic system, and an electrical system working together to provide, alternatively, high pressure water for a cleaning operation, or recirculation of high pressure water back to a water tank. The hydraulic system is operable to either direct water toward a cleaning operation, or to wind in or play out the water delivery hose while either supplying water to the delivery hose under pressure or recirculating the water back to the water tank.

Hydraulic door operating system

Abstract: A hydraulic system for opening and/or closing the rear lift gate of a vehicle uses a double or single acting gas charged hydraulic cylinder. If double acting, a second piston separates the head side of the cylinder into hydraulic and gas chambers. A unidirectional (for the single acting cylinder) or a bidirectional (for the double acting cylinder) drives a pump to operate the cylinder. A solenoid actuated on-off valve selectively communicates the ports of the cylinder with tank pressure. A gas charge accumulator may also be provided. In the double acting embodiment, a two way ball shuttle valve which is vented in the center provides alternating communication between the two cylinder ports.

Modelling of transient flow in hydraulic pipelines

Abstract: This paper describes a method of modelling time-varying flow in hydraulic pipelines which may be incorporated into time domain simulations of hydraulic systems operating with variable time steps. A previously reported finite element method is extended. New approximations to frequency-dependent friction for laminar and turbulent flow are presented. These are applicable to this finite element method as well as the method of characteristics and finite difference methods. Simulation results are compared against theory and excellent agreement is found.

Hill holding brake pressure as a function of hill gradient detected as a function of acceleration in a control system for automatic transmission

Abstract: A control system for an automatic transmission having a hydraulic power transmission for transmitting the rotation of an engine to a gear shifter; a clutch to be applied, when a forward drive range is selected, for connecting the hydraulic power transmission and the gear shifter to one another; a one-way clutch to be locked, when the clutch is applied, for establishing a first forward speed of the gear shifter; a brake for locking the one-way clutch, when applied, to block the backward rotation of the output shaft of the gear shifter; a first hydraulic servo for applying the clutch when fed with an oil pressure; a second hydraulic servo for applying the brake when fed with an oil pressure; a stopping state detector that detects the stopping state of a vehicle by determining the vehicle speed is substantially 0, the accelerator pedal is in a released state and the foot brake pedal is depressed; a gradient detector that detects the gradient load of an uphill, as applied to the vehicle; and a controller that controls the oil pressure to be fed to the first and second hydraulic servos on the basis of the signals from the stopping state detector and the gradient detector. The controller includes a decision maker that determines whether the road is uphill, on the basis of the signal from the gradient detector; a pressure reducing device that reduces the oil pressure to be fed to the first hydraulic servo, to bring the clutch into a substantially released state; a feed device that feeds an oil pressure, as regulated on the basis of the gradient detector, to the second hydraulic servo, to apply the brake at an engaging extent according to the gradient load; and a device for executing the reduction of the feed oil pressure to the first hydraulic servo by the pressure reducer and the feed of the regulated oil pressure to the second hydraulic servo by the oil pressure feeder, if it is detected by the stopping state detector that the vehicle is in the stopping state and if it is determined by the decision maker that the road is uphill.

Aircraft servovalve current rate limiter

Abstract: Aircraft flight path changes commanded by a pilot via the wheel, column and pedal (12) are converted to position sensor signals (14) and passed as the input to primary flight computer (26). The primary flight computer (26) converts these pilot inputs and the inputs from autopilot (25) into desired surface actuator commands and then transmits them to actuator control electronics (18). The actuator control electronics (18) also receives a position feedback signal, representative of the position of the aircraft control surface (42). The actuator control electronics (18) produces a control signal which is fed to the input of an actuator (32) which includes a hydraulic system (34). The actuator responds to control input signals to drive linkage (40) which then positions the control surface (42). A rate limiter (110) imposes maximum rate limits to the actuator input signal (30) to thereby reduce peak transient hydraulic fluid pressure in the hydraulic system (34) and corresponding return and pressure lines (36), (38) to specified maximum values.

Active tractor suspension system

Abstract: An active vehicle suspension employs a multi-point support system between a vehicle's chassis and cab. Each support point has an isolator which includes a linear hydraulic actuator that is connected at its quiet end to the payload by a passive vibration isolator and is connected at its vibrating end to the chassis. Each isolator also has a support spring to off-load the majority of the weight of the cab from the hydraulic actuator. An accelerometer is mounted to sense movement at a point between the linear hydraulic actuator and the passive vibration isolator. An electrical signal produce by the accelerometer is processed to operate a hydraulic valve that controls movements of the hydraulic actuator so that transmission of vibrations from the chassis to the cab is attenuated.

Application of a robust nonlinear fault detection observer to a hydraulic system

Abstract: This paper proposes a fault detection method for a fairly wide class of nonlinear systems based on a nonlinear observer. Various other methods proposed in the field are related to this method or are special cases of it. The observer is designed such that the error dynamics are independent of state, input, output and unknown disturbances. Necessary conditions are given for the observer to exist and to be robust with respect to an unknown input. Applications are made to a hydraulic system.

An auxiliary hydraulic power unit

Abstract: A hydraulic power unit (10) for supplying hydraulic fluid under pressure to auxiliary hydraulic equipment associated with a vehicle and to ancillary appliances. The hydraulic power unit includes a frame (20) which is adapted to be mounted on the vehicle. A combustion engine (30), a hydraulic pump (40), a hydraulic reservoir (42), a hydraulic distribution system (44) and an ancillary platform (22) are mounted on the frame. The ancillary appliances are mounted on the ancillary platform. The vehicle is a track drive excavator (100) with the auxiliary hydraulic equipment mounted on a hydraulically articulated boom (120). The auxiliary hydraulic equipment is a soil remediation apparatus for treating contaminated soil including a trenching tool (220), a treatment injection apparatus (270) and a vapor recovery hood (250); and the ancillary appliances include a treatment delivery system (48) connected to the treatment injection apparatus and a vapor recovery system (46) connected to the vapor recovery hood.

Control device for variable hydraulic machines

Abstract: A control device for variable hydraulic machines, and specifically for variable axial piston machines equipped with a servo system that is connected to a swash plate so that the discharge/displacement volume is infinitely variable. The hydraulic machine is equipped with a sensor that detects the piston displacement and is connected with an electronical control unit that controls the swash angle position of the swash plate and is pressure controlling the servo system by an electrohydraulic converter. A method for the infinite controlling of the volume flow of hydraulic machines, by which the servo system is connected to the swash plate of the hydraulic machine, and by which a conduction of a signal from a sensor to the control unit, a pressure controlling of the servo system by an electrohydraulic converter as well as the controlling of the swash angle position of the swash plate by the electronical control unit is realized.

Hydraulic lift system and method for retrofitting

Abstract: A high pressure, low volume hydraulic lift system and a method for retrofitting a low pressure high volume lift system are provided The lift system includes a low pressure high volume (LPHV) casing within which is mounted a high pressure ram The ram is equipped to move a plunger in an axial direction with respect to the casing, without the need for any further reinforcement of the existing casing The method for retrofitting is effected by removing the pre-existing structure of the LPHV system, cutting a hole in the upper portion of the pre-existing casing, and draining all hydraulic fluid Thereafter, the pre-existing gland flange and plunger are removed A high pressure low volume hydraulic cylinder and associated hydraulic line, are then installed in the casing of the pre-existing system The bottom of the high pressure hydraulic cylinder is mechanically locked to the base of the pre-existing outer casing The hydraulic line is attached to a new hydraulic compressor and a new plunger is added to the new hydraulic cylinder and, with it, an appropriate bearing and guide mechanism that uses the pre-existing casing as an outer guide means for the new plunger Once the hydraulic ram is installed, any holes cut in the slab are filled with concrete The lift system and method may be adapted for any type of pre-existing LPHV, such as that used in the automotive industry or in elevators When used in connection with an automotive lift, the pre-existing superstructure is then secured to the top of the new plunger and cylinder structure