Hyrdaulic Systems Simulation Tool

 Contents

 

 

Actuators

 

In the actuators library there ten blocks representing double acting actuators, single acting actuators, rotary actuators and hydraulic motors.

 

For the ‘Double Acting Actuator’ and the ‘Rotary Actuator’ the inputs and outputs to the block are:

 

the controlled flows from the valve (is a two elements vector)

the external force or torque acting on the actuator (a constant) [N] or [Nm]

the connection load or torque coming from the connected mass

the actuator position [m] or [rad]

the actuator speed [m/s] or [rad/s]

the pressures into the two actuator chambers (it a two elements vector)

 

If the actuator block is not connected to a second moving mass (from ‘Mass / Inertia’ sub-library), the connection load input shall be connected to a ground block (from ‘Utility’ sub-library).

 

 

For the single acting actuator the inputs and outputs to the block are:

the controlled flow from the valve (is a single element);

the external force acting on the actuator (a constant) [N];

the uncontrolled pressure acting on the second actuator chamber; it can be the supply pressure or the return pressure (the first and the second element of the output from the Accumulator block) or the atmospheric pressure (a constant);

the connection load coming from the connected mass.

the actuator position [m]

the pressures into the controlled actuator chamber

the actuator speed [m/s]

the flow of the uncontrolled pressure side

 

If the uncontrolled side of the single acting actuator is connected to the reservoir pressure, the last output, that is the second side flow, shall be connected to the reservoir block, while if the second side of the actuator is connected to the supply pressure, this signal shall be connected to the accumulator.

For every type of actuator, a variable hydraulic compliance, function of the position, is taken into account so it shall be defined the ‘lost volume’ that is the volume of the fluid inside the actuator at one end stroke plus the volume of the pipes.

 

 

For the ‘Hydraulic motor’ the inputs and outputs to the block are:

 

the controlled flows from the valve (is a two elements vector)

the external torque acting on the actuator (a constant) [Nm]

the system pressure (from accumulator)

the connection torque coming from the connected mass

the motor position [rad]

the motor speed [rad/s]

the pressures into the two actuator chambers (it a two elements vector)

For the motor model, the drag torque is represented by the following equation:

Drag = D × (rkm× w 1.4 + Ploss + (P1 + P2)× Cf)

where

D is the motor displacement

w is the angular speed

P1 and P2 are the input and output pressure

rkm, Ploss and Cf are constant input data that shall be set to match the efficiency curve of the motor.

 

For the internal leakage, both the case drain leakage and the inter-ports leakage (between P1 and P2) are evaluated.

 

For each of the above components, there are also a block that does not take into account the effect of the friction. If the friction is negligible, it is useful to use this kind of blocks because they increase the simulation speed.

 

 

 

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