A single-acting hydraulic cylinder controlled by an 3-way directional valve. It drives a load consisting of a mass, viscous friction, and preloaded spring. The pump unit is assumed to be powerful enough to maintain constant pressure at the valve inlet.
A closed-loop actuator that consists of a proportional 4-way directional valve driving a double-acting hydraulic cylinder. The cylinder drives a load consisting of a mass, viscous and Coulomb friction, constant force, and a spring. The actuator is powered by a variable-displacement, pressure-compensated pump, driven by a constant velocity motor. Pipelines between the valve, cylinder, pump, and the tank are modeled using the Hydraulic Pipeline blocks.
The actuator consists of a proportional 4-way directional valve driving a double-acting hydraulic cylinder. The cylinder drives a load consisting of a mass, viscous and Coulomb friction, constant force, and a spring. The actuator is powered by a variable-displacement, pressure-compensated pump, driven by a constant velocity motor. Pipelines between the valve, cylinder, pump, and the tank are simulated with the Hydraulic Pipeline blocks.
The use of a 2-way valve in a closed-loop circuit together with a double-acting hydraulic cylinder, fixed orifice, mass, spring, damper, and control blocks.
The use of a 3-way valve to control the motion of a hydraulic differential cylinder. The valve connects cylinder port B either to tank or to cylinder chamber A through the fixed orifice. The cylinder extends when its ports are both connected to the pressure source due to difference in piston areas. Orifice B controls the extension speed. The cylinder retracts if chamber B is connected to tank.
The use of a double-acting hydraulic cylinder. The clamping structure is simulated with the spring and damper installed between the cylinder case and the reference. The cylinder performs forward and return strokes caused by the change of pressures at ports A and B. The cylinder load consists of inertia, viscous friction, and constant opposing load of 400 N.
A closed-circuit hydraulic actuator driven by a variable-speed motor. The actuator is arranged as a closed system with two replenishment valves (check valves) and a spring accumulator serving as a replenishment reservoir. The motor velocity is controlled by the difference between the commanded and actual actuator position. The actuator acts against a spring, damper, and a time-varying load.
The model consists of a double-acting hydraulic cylinder controlled by an open-center 4-way directional valve and a power unit built of a flow rate source and a pressure-relief valve. The cylinder is loaded with an active force in 10000 N trying to extend the rod. In other words, the cylinder experiences an overriding load while extending. To hold the rod in place while the directional valve is in the neutral position and prevent losing control of the cylinder extension, the counterbalance valve is used. The valve controls the return flow from port A. The valve pilot port P is connected to cylinder port B, thus making it impossible for the cylinder to move until pressure at port B builds up to certain level.
An actuator built of a double-acting hydraulic cylinder, directional valve, flow control, block of counterbalance valves, power unit, and a control unit.
A custom hydraulic cylinder model that omits the effect of fluid compressibility in the cylinder chambers. The double-acting cylinder connected to a 4-way valve to model a simple closed-loop actuator.
A hydraulic cylinder equipped with a custom model of snubbers (cushions) on both sides of the cylinder. The snubbers are implemented as two-chamber cushions separated by the cushioning bush as the piston comes close to the end of the stroke. The cushioning provides hydraulic braking as the cylinder reaches the end of its stroke, absorbing some of the kinetic energy of the system before the piston reaches the end stop.
An actuator built around a telescopic hydraulic cylinder, which is equipped with three rods interacting with each other through hard stops. The effective areas of the rods are set to 20, 16, and 12 cm^2 respectively, which causes the first rod to move first, followed by the second, and then by the third rod. The actuator is controlled by a 2-position 3-way valve, which connects the actuator chamber to the tank at neutral position. As the control signal is applied to the valve, the actuator chamber is connected to the pump and the actuator starts extending. The rods are retracted by external load when the chamber is connected to the tank. The power unit relief valve is set to 50 bar, and maximum load to be handled by the actuator is 2500 N.
A digital hydraulic actuator that consists of 3 double-acting cylinders mounted in the same shell and interconnected through the hard stops. The gap between the leftmost piston and the shell is equal to 2^0*base_length, the gap between the first and the second pistons is set to 2^1*base_length, and the gap between the second and the third pistons is set to 2^2*base_length. The piston area in the rightmost chamber is half the size of the areas of the other chambers. The rightmost chamber is permanently connected to the pump while the other three chambers are connected either to pump or tank depending on the 2-position 3-way electro-hydraulic valves. As a result, 2^3 discrete positions can be reached within 2^3*base_length range.
A typical hydraulic cylinder actuator used to operate friction clutches, brakes and other devices installed on rotating shafts. The key element of the actuator is a piston that moves back and forth under pressure provided through the central drill in the shaft and through channels in the clutch. In the example, the actuator acts against a preloaded spring, which tends to push the piston against the clutch wall.
An oscillating hydraulic mechanism that consists of a single-acting hydraulic rotary actuator, winch, flow control valve, two-position electro-hydraulic valve, and power and control units. The mechanism maintains oscillating vertical motion of the weight by raising it to 25 cm and then allowing it to fall. To raise the weight, the electro-hydraulic valve is energized and connects the power unit to the hydraulic actuator inlet. As the weight reaches 25 cm the valve is deenergized, connecting the actuator chamber to tank.
A sequence circuit that is based on four check valves installed in both pressure and return lines of the second rotary actuator. The cracking pressure of all the valves is set higher than any load pressure of Rotary Actuator 1, but lower than pressure that develops in its chambers at the end of the stroke when Rotary Actuator 1 reaches its hard stop. As a result, the Rotary Actuator 2 starts moving only after the Rotary Actuator 1 completes its stroke.
A transmission built of a variable-displacement pump, and a fixed-displacement hydraulic motor. Pipelines between the source and motor are connected by two replenishing valves (check valves) and a charge pump on the pump side and two pressure-relief valves on the motor side. The motor drives a mechanical load consisting of inertia, viscous friction, and time-varying torque. The system is tested with varying pump flow rate and motor torque load.
The usage of secondary control in hydrostatic transmissions with a variable-displacement motor. It uses a pressure-compensated variable-displacement pump, a variable-displacement motor, and is controlled by a secondary control unit. The secondary control unit is a servo-cylinder controlled by a proportional 4-way valve. The servo-cylinder drives the control member of the variable-displacement motor, which is represented by a mass, spring, and damper. The hydrostatic transmission is used in a closed-loop control system with an angular velocity feedback. It drives a winch which lifts a mass and acts against a viscous damper. A dynamic compensator is included in the secondary control unit to improve system stability.
A hydrostatic transmission with a shuttle valve in the control unit. The 4-way directional valve that controls the motor is actuated by a valve actuator whose input is controlled by two 2-position valves (Shuttle A Valve, Shuttle A1 Valve). The shuttle valve installed between the actuator and the 2-position valves allows the 4-way directional valve to be opened by opening either 2-position valve, and those valves are opened by signals S1 and S2. A fixed orifice is connected to the P port of the two-position valves to decrease flow consumption of the control circuit. Another fixed orifice introduces a small leak from the valve control chamber to avoid this chamber being isolated from the main flow. The motor is connected to pressure line at 1 second and 5 seconds by activating each of the two-position valves.
Two valve actuators with different values for switching-on time and switching-off time. Valve Actuator 1 is set to start from the retracted position, while Valve Actuator 2 from the extended position. Both actuators are driven with the same pulse signal.
A use of a double-acting valve actuator. All three actuators are driven by the same pulse signals. A pulse is first applied to port A and after 1.5 s delay a pulse is applied to port B. Actuator A is set to start from the "Extended positive" position, while actuator C starts from the "Extended negative" position. As a result, actuators A and C move to the neutral position at the start of simulation and reach this position before the first pulse is applied. The actuators strokes, switch-on, and switch-off times are set to different values to illustrate the effects of these parameters.
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