1. Proportional and Servo Valves
MECH1300
Electronic Control of Fluid Power
Topics
Solenoid Valves
Proportional and Servo Valves
Pump Controls
Chapter 13

2. Electronic Control of Fluid Power
MECH1300
Electronic Control of Fluid Power
Use a central processing unit – usually a PLC
PLC’s monitor the input and generate the output
Sensors – The interface between the physical components and the electronics. They take a physical parameter (position, speed, acceleration, pressure flow, temperature, gas) and convert it to an electrical signal.
Transducers – Any device that converts energy from one form to another. Ex: a pressure transducer takes fluid pressure and converts it to electrical energy (voltage)

3. Electronic Control of Fluid Power
MECH1300
Electronic Control of Fluid Power
Control Systems –
Open Loop – Don’t have sensors that determine what is going on, but reliance is based on the fact that the control valve causes the desired result.
Closed Loop – Results are read by a sensor, which allows the control system to compensate or adjust errors

4. MECH1300
Solenoid Valves
Switches that are shifted by electrical current that is applied to a coil of wires.
The magnetic field is used to attract a movable element called a plunger, which is made of magnetic material
The attraction between the coil and plunger create the shifting used for actuation (in the valve spool)
Commonly used in hydraulics and pneumatics to shift two-way and three-way directional control valves and some pressure control valves

5. MECH1300
Solenoid Valves
Hydraulic solenoid valves are usually armature type (allows hydraulic fluid to circulate through the solenoid case), it helps carry away the heat generated by the current.
Solenoids can be pilot-operated
Can be AC or DC and in a variety of voltages
Two states, shifted or not shifted

6. Proportional and Servo Valves
MECH1300
Proportional and Servo Valves
Proportional Valves – Electronically controlled, but they are able to position the valve between the open and closed positions, allowing for precise flow and directional control. The flow rate is proportional to the input current.
Servo Valve – Electronically controlled, but uses feedback for self regulation

7. MECH1300
Pump Controls
A more efficient way to control flow and pressure is to control it at the source (the pump)
Electrohydraulic pumps control the pressure and flow output of the pump
Only the power required by the load is produced at the pump, reducing waste