Simcenter Amesim animations

Simcenter Amesim animations (by Massimo Rundo) used in the Fluid Power courses. Full HD videos, along with additional ones, are available only to students enrolled in the courses.

• Start circuit (352.86 kB)

  It shows the functioning of the circuit illustrated in the first lesson. The actuator's direction is determined by the 4/3 valve. It can be seen when the pressure relief valve regulates: when the directional control valve is closed and when the actuator has reached the endstop. The backpressure at the actuator's outlet port during the inward phase due to the unidirectional restrictor can be observed. Moreover, during the inward stroke, despite the smaller force, the delivery pressure is higher with respect to the outward stroke due to the smaller surface of influence.

• Basic open circuit hydrostatic transmission (218.32 kB)

  It shows the different behaviour of a hydraulic motor when operating with imposed flow rate (first part of the simulation) and imposed pressure drop (second part). In the first case, the speed is determined by the motor and remain constant, while in the second case, it is determined by the load. This behaviour can be analysed with the Politecnico’s functional blocks.

• Metering-compensator behaviour of a restrictor (346.20 kB)

  It shows the behaviour of a restrictor as compensator (first part of the simulation) and as metering (second part). In the first case, reducing the flow area increases pressure, but does not affect the actuator’s speed. In the second case, the regulation of the pressure relief valve forces the system to operate with imposed pressure, so further reduction of the area imposes a change in flow rate and therefore in the actuator’s speed.

• Relief valve transient (1.15 MB)

  It shows the influence of the diameter of the dynamic restrictor on the step response of a relief valve. The load flow area is suddenly reduced. With a 1 mm diameter, the response time is fast with few damped oscillations. With a 0.5 mm diameter, the valve responds slowly. With a 1.5 mm diameter, the valve is unstable, exhibiting significant oscillations.

• Interaction between pressure relief and pressure reducing valves (149.72 kB)

  It shows that when the pressure reducing valve regulates, upstream pressure is controlled by another component, in this case, the pressure relief valve, which must also regulate. If instead the pressure relief valve does not regulate, the pressure reducing valve does not regulate either, meaning it is fully open (in saturation). In fact, it can be observed that up to 4 seconds, the pressures correspond to the respective settings of the valves; after 4 seconds, the pressures decrease, indicating that neither valve is regulating.

• Restrictor vs. pressure-compensated flow control valve (286.15 kB)

  It compares a simple restrictor and a pressure-compensated flow control valve (RQ2) in controlling the speed of an actuator. With constant force, varying the flow area changes the speed. However, with a constant area, as the force on the actuator increases, the speed varies with a simple restrictor, while it remains constant with RQ2.

• Discretely variable flow generation unit (266.63 kB)

  It simulates a GAQVD (discretely variable flow generation unit). With low force on the actuator, both pumps are connected to the P port of the directional control valve and the speed of the actuator is high. As the force increased, the pump P2 is vented by the complete opening of the relief valve, thanks to the remote pilot, so that its absorbed torque is ideally zero, and the actuator moves at a lower velocity, being fed only by the pump P1. When the actuator reaches the end-stop, the relief valve RV1 regulates.

• Approximately fixed pressure flow generation group - 1 (193.84 kB)

  It simulates the GAPFA (approximately fixed pressure flow generation group) of a semi-automatic gearbox. A flow request is simulated every two seconds. The pump is activated only at the start of the simulation and when the accumulator pressure drops below a minimum level. The supply pressure is maintained in the range between pmin and pmax.

• Approximately fixed pressure flow generation group - 2 (191.58 kB)

  With respect to the case of GAPFA-selespeed-1, a continuous flow request is simulated, showing that the pressure is maintained “approximately constant”. At about 8 s, a failure of the pressure switch is simulated, leading to the regulation of the pressure relief valve (safety valve).

• Clamp and drill circuit (718.55 kB)

  It shows a typical use of sequence valves. The model simulates a hydraulic circuit of a machine tool for clamping and drilling a workpiece. When the directional control valve is energized, at first only the actuator U1 moves, since the pressure is lower than 50 bar and the sequence valve VS1 remains closed. When U1 is in contact with the workpiece, the pressure increases up to 50 bar, VS1 regulates and U2 moves. In the first part of the stroke of U1, the load is low and the pump delivery pressure is imposed by the setting of VS1. In the second part of the stroke, the load increases, VS1 is completely open, and the pump delivery pressure is determined by the load on U2. Sequential movement is also ensured during the retraction of the actuators, thanks to the second sequence valve VS2.

• Control of overruning load (442.95 kB)

  It shows the control of a differential actuator in four quadrants (two directions of movement and two directions of force) by means of overcentre valves (OVC). During the first outward stroke, the load is resistive, the flow occurs through the non-return valve of OVC2, while OVC1 is completely open. In the inward stroke, the direction of the force remains the same, which makes it an overrunning load, and the OVC2 regulates in order to generate a back-pressure. It can be observed that the velocity remains constant (imposed by the pump) and the actuator does not run away.
  In the second part of the simulation the cycle is repeated with difference directions of force.

• 2 actuators in parallel (208.55 kB)

  The model shows what happens when two actuators with different load are fed in parallel by a single pump. At the beginning only the actuator with the lowest load (M2) moves. In this phase the delivery pressure is imposed by M2 and it is not sufficient to balance the load on M1. Only when M2 has reached the end-stop, the delivery pressure increases and M1 moves. When M1 also reaches the end-stop, the relief valve regulates. Furthermore, the oscillations during the transient phase highlight that dynamics are also important in a fluid power system.