ENGR 4000 Chapter 5: Fluid Actuation Systems

2. Actuation Systems Translate commands to action Input in one form, output in another form Hydraulic actuators: Chap 5 Mechanical: Chap 6 Electrical: Chap 7 Modeling: Chap 8

3. Pneumatic vs Hydraulic Common advantages Power actuation Move significant loads Pneumatic Compliance of air Mostly binary control Lightweight Hydraulic Expense Weight – heavy Precision control Fire hazard

4. Power Supply Hydraulic Power Supply Pump Check valve Accumulator Pressure relief valve Electrical Power Supply Generator Diode Capacitor Zener diode

5. Control Valves Directional control On-off (binary) Spool valve Most common Requires three ports Port 1 is air supply Port 2 goes to actuator Port 3 vents Only actuates in one direction Five port spool valve Port 1 is air supply Port 2 goes to actuator extension Port 3 vents actuator extension Port 4 goes to actuator retraction Port 5 vents actuator retraction

6. Control Valves Direction control Poppet valve Two ports Port 1 Supply Port 2 Actuator No return or venting Controls the flow of fluid medium

7. Hydraulic Symbols Tank Pressure Relief Dashed line is pilot actuated Two position two way valve NO, plunger activated, spring return… P for pressure port Three position four way valve 3 psn (boxes), P pressure, T tank, B port, A port, C1 solenoid, C2 solenoid, spring return Pressure Relief Valve Hydraulic fluid is virtually non compressible, if the fluid can't go anywhere the pump will stall, and damage to the pump and motor can result. All hydraulic systems must have a pressure relief valve in line with the pump. The pressure relief will drain into the tank. The dashed line indicates a pilot line, this is a small line that only flows enough fluid to control other valves. The pressure of this pilot line acts against the spring on the other side of this valve. When the pilot pressure exceeds the spring force then the valve spool shifts over and opens the valve, this allows flow to the tank. This causes a drop in the pressure on the pump side, which also reduces the pilot pressure. When the pilot pressure is less than the spring force the spring closes the valve. The relief valve in the position described above will control the maximum pressure in the hydraulic system. Directional control valves A directional valve will control which device the fluid will flow to. These valves are the primary devices used to sequence the motion of equipment. There are many different types of directional control valves. The valve is generally specified by number of positions and number of ways (ports). The valve is made up of two parts, the body and the spool. When valves shift the spool is moved in relation to the body, this opens and closes passages that the fluid flows through. Remember that the valve actuator always pushes the spool, this will help you read the drawings. You read the operation of a valve in a circuit in the following manner. The box(s) with arrows in it show the flow of fluid when the valve is shifted. The box without arrows and/or away from the actuator shows the flow, if any, in the neutral position. This is also the box you use to count the number of ports the valve has. Two(2) Position, Two(2) way This valve has two positions (2 boxes) and 2 ways (ports); thus 2 position, 2 way. It is shown with a manual actuator (on the right) and has a spring return to neutral. This valve is called normally closed because both ports are blocked when in neutral. It could be used on a safety device like a safety gate, if the gate isn't closed, actuating the valve, then the flow will be stopped, preventing movement of the connected device. Three(3) Position, Four(4) way This valve has three positions (3 boxes) and 4 ways (ports); thus 3 position, 4 way. It is shown with a closed center, when the valve is neutral all ports are blocked. The small boxes on each end with diagonal lines through them, C1 and C2, are electrical coils, this is an electrically actuated valve. The port marked P is Pressure and the port marked T drains to tank. The ports marked A and B connect to an external device, like a cylinder. When C1 is energized the valve will shift, putting pressure to the B port and draining the A port to the tank. Likewise when C2 is energized the pressure port connects to the A port and the B port drains to the tank. Pressure Relief Valve Hydraulic fluid is virtually non compressible, if the fluid can't go anywhere the pump will stall, and damage to the pump and motor can result. All hydraulic systems must have a pressure relief valve in line with the pump. The pressure relief will drain into the tank. The dashed line indicates a pilot line, this is a small line that only flows enough fluid to control other valves. The pressure of this pilot line acts against the spring on the other side of this valve. When the pilot pressure exceeds the spring force then the valve spool shifts over and opens the valve, this allows flow to the tank. This causes a drop in the pressure on the pump side, which also reduces the pilot pressure. When the pilot pressure is less than the spring force the spring closes the valve. The relief valve in the position described above will control the maximum pressure in the hydraulic system. Directional control valves A directional valve will control which device the fluid will flow to. These valves are the primary devices used to sequence the motion of equipment. There are many different types of directional control valves. The valve is generally specified by number of positions and number of ways (ports). The valve is made up of two parts, the body and the spool. When valves shift the spool is moved in relation to the body, this opens and closes passages that the fluid flows through. Remember that the valve actuator always pushes the spool, this will help you read the drawings. You read the operation of a valve in a circuit in the following manner. The box(s) with arrows in it show the flow of fluid when the valve is shifted. The box without arrows and/or away from the actuator shows the flow, if any, in the neutral position. This is also the box you use to count the number of ports the valve has. Two(2) Position, Two(2) way This valve has two positions (2 boxes) and 2 ways (ports); thus 2 position, 2 way. It is shown with a manual actuator (on the right) and has a spring return to neutral. This valve is called normally closed because both ports are blocked when in neutral. It could be used on a safety device like a safety gate, if the gate isn't closed, actuating the valve, then the flow will be stopped, preventing movement of the connected device. Three(3) Position, Four(4) way This valve has three positions (3 boxes) and 4 ways (ports); thus 3 position, 4 way. It is shown with a closed center, when the valve is neutral all ports are blocked. The small boxes on each end with diagonal lines through them, C1 and C2, are electrical coils, this is an electrically actuated valve. The port marked P is Pressure and the port marked T drains to tank. The ports marked A and B connect to an external device, like a cylinder. When C1 is energized the valve will shift, putting pressure to the B port and draining the A port to the tank. Likewise when C2 is energized the pressure port connects to the A port and the B port drains to the tank.

8. Hydraulic Symbols (cont.) Actuator Two ports, double acting: extension, retraction Pump Triangle points out for pump and in for motor, arrow indicates variable Mystery Valve Cylinder A cylinder is one of the devices that creates movement. When pressure is applied to a port it causes that side of the cylinder to fill with fluid. If the fluid pressure and area of the cylinder are greater than the load that is attached then the load will move. Cylinders are generally specified by bore and stroke, they can also have options like cushions installed. Cushions slow down the cylinder at the end of the stroke to prevent slamming. If the pressure remains constant a larger diameter cylinder will provide more force because it has more surface area for the pressure to act on. Hydraulic Pump A pump displaces fluid which creates flow. There are fixed displacement pumps and variable displacement pumps. The pump symbol is very similar to a hydraulic motor symbol, the difference is that the pump has the small triangle pointing out and a motor has the small triangle pointing in to the center. An angled arrow typically indicates that a device is variable, thus this is a variable volume pump. Fixed displacement pumps provide the same output volume with the same input RPM. Variable displacement pumps can change the output volume while maintaining the same input RPM. Hydraulic pumps are precision components and have very close tolerances, they must be treated with care. Three(3) Position, Four(4) Way This valve has three positions (3 boxes) and 4 ways (ports); thus 3 position, 4 way. It also is electrically actuated. The jagged lines next to the coil indicates springs, when the coil is de-energized the opposite spring will force the spool back to the center position. This valve also drains to tank when in neutral, this is a standard valve on molding machines. They drain to tank when de-energized for safety. Cylinder A cylinder is one of the devices that creates movement. When pressure is applied to a port it causes that side of the cylinder to fill with fluid. If the fluid pressure and area of the cylinder are greater than the load that is attached then the load will move. Cylinders are generally specified by bore and stroke, they can also have options like cushions installed. Cushions slow down the cylinder at the end of the stroke to prevent slamming. If the pressure remains constant a larger diameter cylinder will provide more force because it has more surface area for the pressure to act on. Hydraulic Pump A pump displaces fluid which creates flow. There are fixed displacement pumps and variable displacement pumps. The pump symbol is very similar to a hydraulic motor symbol, the difference is that the pump has the small triangle pointing out and a motor has the small triangle pointing in to the center. An angled arrow typically indicates that a device is variable, thus this is a variable volume pump. Fixed displacement pumps provide the same output volume with the same input RPM. Variable displacement pumps can change the output volume while maintaining the same input RPM. Hydraulic pumps are precision components and have very close tolerances, they must be treated with care. Three(3) Position, Four(4) Way This valve has three positions (3 boxes) and 4 ways (ports); thus 3 position, 4 way. It also is electrically actuated. The jagged lines next to the coil indicates springs, when the coil is de-energized the opposite spring will force the spool back to the center position. This valve also drains to tank when in neutral, this is a standard valve on molding machines. They drain to tank when de-energized for safety.

9. Review of symbols

10. Actuators Hydraulic Pneumatic Single acting Double acting Questions Actuation? Neutral position Sizing 1500 psi wp ±100 kip ±0.2 inches Find cylinder size, flow rate in gal/min

11. The electrical analogy

12. Hydraulic Symbols (cont.) Circuit: What does it do? When not activated, the cylinder has no pressure on either side since in neutral it is vented to the tank. How would you specify the valve if you desired the cylinder to “lock” in place when in neutral??? Answer: have a block P, T, B, A that has same symbol as P has now. Symbol for the fluid tank, source of hydraulic fluid and receptacle for overflow. Filter, must be sized for pressure and flow Motor, powers the pump (4). Must be sized horsepower and rpm wise for the pump and circuit. Based on pressure and pump flow rate, a minimum of 1.14 HP is required, choose 1.5 HP Constant displacement pump at 1.3 gpm, sized for pressure, flow rate, mechanical interface with motor (3) Pressure relief valve activated by pilot line (dash) and set for 1500 psi. Necessary since in neutral position all flow is cut off from actuators and other circuits. A better design would be to have an accumulator which would smooth out the fluctuations in the pressure and would shut off when pressure is reached. Three position, four port valve, shown in the neutral position. When activated by b electrical solenoid, P or pressure goes to B port and extends the cylinder, A port vents to the tank. When activated by a electrical solenoid, P or pressure goes to A port and extends the cylinder, B port vents to the tank. In the neutral position, both ports vent to tank, and the cylinder will move where ever loads force it. If it is desired to lock the cylinder in position, the center position should be changed to have the same symbol as is present for P. Double acting cylinder. 36” stroke means that it will extend a maximum of 36 inches. In extension the force exerted by the cylinder will be 18,850 pounds. In retraction the force will be 16,199 pounds (area of bore minus the area of the rod). Max time of extension is 90 seconds and speed of .4 inches/sec based on 1.3 gpm; retraction is faster being only 78 seconds or .46 inches per second. When not activated, the cylinder has no pressure on either side since in neutral it is vented to the tank. How would you specify the valve if you desired the cylinder to “lock” in place when in neutral??? Answer: have a block P, T, B, A that has same symbol as P has now. Symbol for the fluid tank, source of hydraulic fluid and receptacle for overflow. Filter, must be sized for pressure and flow Motor, powers the pump (4). Must be sized horsepower and rpm wise for the pump and circuit. Based on pressure and pump flow rate, a minimum of 1.14 HP is required, choose 1.5 HP Constant displacement pump at 1.3 gpm, sized for pressure, flow rate, mechanical interface with motor (3) Pressure relief valve activated by pilot line (dash) and set for 1500 psi. Necessary since in neutral position all flow is cut off from actuators and other circuits. A better design would be to have an accumulator which would smooth out the fluctuations in the pressure and would shut off when pressure is reached. Three position, four port valve, shown in the neutral position. When activated by b electrical solenoid, P or pressure goes to B port and extends the cylinder, A port vents to the tank. When activated by a electrical solenoid, P or pressure goes to A port and extends the cylinder, B port vents to the tank. In the neutral position, both ports vent to tank, and the cylinder will move where ever loads force it. If it is desired to lock the cylinder in position, the center position should be changed to have the same symbol as is present for P. Double acting cylinder. 36” stroke means that it will extend a maximum of 36 inches. In extension the force exerted by the cylinder will be 18,850 pounds. In retraction the force will be 16,199 pounds (area of bore minus the area of the rod). Max time of extension is 90 seconds and speed of .4 inches/sec based on 1.3 gpm; retraction is faster being only 78 seconds or .46 inches per second.

13. Mechatronics Project Design a 100 kip load frame Max load: ±100 kip Max stroke on actuator: 6 inches Capability to switch from a steady very slow pull to alternating pull (±100 kip) Cross head that clamps hydraulically and moves up and down hydraulically. Linear position sensing to ±2/10,000 inch or .5 micron if possible Load cell for ±5 kip, ±20 kip, ±100 kip interchangeable Control and data streaming via National Instruments & PC Data collection for strain gages, temperature sensors with up to 16 inputs. Max height is consistent with Technology building, maximize loading area. Minimum sinusoidal alternating load @ 10 hertz full range load and 100 hertz for lightest load. Requirements Team effort Control valves should be flow controlling, one valve body for ultra slow pull and one faster Separate analysis for each component Three bids for each component Briefing charts (Powerpoint) specifying features, capabilities, and capacities and component list.