Download
pdt 380 automations in agricultural systems n.
Skip this Video
Loading SlideShow in 5 Seconds..
Powerpoint Templates PowerPoint Presentation
Download Presentation
Powerpoint Templates

Powerpoint Templates

6 Vues Download Presentation
Télécharger la présentation

Powerpoint Templates

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. PDT 380 AUTOMATIONS IN AGRICULTURAL SYSTEMS Powerpoint Templates

  2. DRIVE SYSTEM AND ACTUATORS- HYDRAULIC AND PNEUMATIC CIRCUIT CONTROL

  3. introduction

  4. Actuators in agriculture • Actuator solutions in spreaders adjusting the amount of fertilizers. • Sprayer, actuator control height and angle of outlet nozzle. • In chopper, actuator used to adjust the outlet direction. • Electric actuators – used to improve ergonomics and comfort in a number of applications such as adjustment of steering wheels, seats and ventilation.

  5. Sensor vs Actuator • A sensor • monitors the variable such as pressure and temperature and send a signal to a transmitter or indicator. • An actuator • Hardware devices that convert a controller command signal into a change in a physical parameter. • The change is usually mechanical (eg: position or velocity). • An actuator is a transducer because it changes one type of physical quantity into some alternative form. • An actuator is usually activated by a low-level command signal, so an amplifier may be required to provide sufficient power to drive the actuator.

  6. Actuation Systems • Practically every industrial process requires objects to be moved, manipulated, held, or subjected to some type of force. • The most commonly employed methods for producing the required forces/motions are: • Air – Pneumatics • Liquids – Hydraulics • Electrical – motors, solenoids. • Mechanical

  7. The task considered is how to lift a body by a distance x mm. such tasks are common in manufacturing industries.

  8. Electric Actuators - motor

  9. Drives & Control Engineering for Actutors

  10. Pneumatic & hydraulic actuation systems

  11. Actuate large valve & high-power control device PNEUMATIC SIGNALS Compressibility of air More high-power control device - expensive HYDRAULIC SYSTEMS Oil leaks – causes hazard

  12. Pneumatic Vs Hydraulic • Application • Hydraulics are used for power and precision. • Pneumatics are used for light weight and speedy applications. • Material used in the construction of the components. • Hydraulic components are mainly made from steel. • Pneumatic components are made from plastic and non-ferrous materials. • However, the materials used in the system may have to withstand some of the following conditions: • Heat • Cold • Mechanical damage • Dust • Chemical attack

  13. Pneumatic Vs Hydraulic • When either pneumatic or hydraulic systems are equally for an application the following should be considered. • Hydraulics generally calls for a greater capital outlay. • Hydraulic power generally cheaper on an energy basis. • Installation of hydraulic equipment generally requires a power pack for each machine. • Hydraulics with multiple machines generally requires a power pack for each machine. • Pneumatic machinery can be plugged into a ring main.

  14. Pneumatic Vs Hydraulic Comparison Table

  15. Pneumatic Vs Hydraulic Comparison Table (con’t…)

  16. Hydraulics Definition • Is the science of transmitting force and/or motion through the medium of a confined liquid. • Power is transmitted by pushing on a confined liquid.

  17. Fundamental laws of Hydraulics • All hydraulic systems operate following a defined relationship between area, force and pressure. • Laws have been established to explain the behavior of hydraulic systems. • Hydraulic systems use the ability of a fluid to distribute an applied force to a desired location.

  18. Pressure Where Force is in newtons (N) and Area is in square meters (m2). 1 Pascal (Pa) =1 N/m2. 1 bar= 100,000 Pa= 105 Pa. 10 bar= 1 MPa (mega Pascals)

  19. Pascal’s Law • Pascal’s law states that: “The pressure in a confined fluid is transmitted equally to the whole surface of its container” • When forceF is exerted on areaA on an enclosed liquid, pressureP is produced. The same pressure applies at every point of the closed system Pascal’s law.

  20. Hydraulic systems - used pressurized incompressible liquids as transmission media • Works on the principle of Pascal’s law which says that the pressure in an enclosed fluid is uniform in all the directions.

  21. Hydraulic Systems Smooth out any short term fluctuations – output oil pressure • Hydraulic systems schematic diagram. Release pressure – rise about safe level. Prevent the oil being back to the pump

  22. Schematic Diagram

  23. Common examples of hydraulic systems include: Hydraulic jack • In a hydraulic jack, a small piston (pumping piston) transmits pressure through the oil to a large piston (power piston) through a check valve, resulting in the weight being lifted as shown in Fig.1.3. (a) Hydraulic jack (b) Hydraulic jack schematic diagram

  24. Basic Component of Hydraulics System • Movable piston • Storage tank • Filter • Hydraulic pump • Pressure regulator • Control valve

  25. Hydraulic system components • Power input device: The pump and motor together are called the power input device; the pump provides power to the hydraulic system by pumping oil from the reservoir/tank. The pump’s shaft is rotated by an external force which is most often an electric motor.

  26. Hydraulic system components • Control device: Valves control the direction, pressure, and flow of the hydraulic fluid from the pump to the actuator/cylinder. • Power output device: The hydraulic power is converted to mechanical power inside the power output device. The output device can be either a cylinder which produces linear motion or a motor which produces rotary motion. • Liquid: the liquid is the medium used in hydraulic systems to transmit power. The liquid is typically oil, and it is stored in a tank or reservoir. • Conductors: The conductors are the pipes or hoses needed to transmit the oil between the hydraulic components.

  27. Hydraulic power pack • The hydraulic power pack combines the pump, the motor, and the tank. The hydraulic power pack unit provides the energy required for the hydraulic system. The parts of the hydraulic power pack unit. The main parts of the hydraulic power pack

  28. Hydraulic Power Unit The hydraulic power unit (power supply unit) provides the energy required for the hydraulic installation. Its most important components are the reservoir (tank) , drive (electric motor), hydraulic pump, pressure relief valve (safety valve), filter and cooler. The hydraulic power unit may also act as a carrier for other devices (gauges, directional control valves).

  29. Reservoir The hydraulic reservoir contains the hydraulic fluid required the operate the installation. Within the reservoir, air, water and solid matter are separated out of the hydraulic fluid. The size of the reservoir will depend on the practical application involved; for stationary systems, the volume of fluid delivered by the pump in 3 to 5 minutes can be taken as a guide. In mobile hydraulic systems, on the other hand, the reservoir contains only the maximum quantity of hydraulic fluid required.

  30. Function of Reservoir 1. Provide storage for the hydraulic fluid (oil). 2. Help dissipate heat produced in the oil. Many restrictions to flow and internal friction in components and piping produced heat in the oil. Steel wall of the reservoir can help dissipate undesirable heat. 3. Allows air bubbles to rise to the surface of oil. Without reservoir, air bubbles trapped in the hydraulic components which may results to component failure. 4. Allows dirt and contamination to settle to the bottom of reservoir. Contamination level in the hydraulic system must be carefully monitored and controlled to avoid catastrophic failures.

  31. Pumps • Function • Hydraulic pumps convert mechanical energy from a prime mover (engine or electric motor) into hydraulic (pressure) energy. • Then, the pressure energy is used to operate an actuator. • Principle • Pumps push on a hydraulic fluid and create flow. • They operate on the displacement principle. • Fluid is taken in and displaced to another point. • Type of Pumps • Positive-displacement : • A pump that causes a liquid to move by trapping a fixed amount of fluid • and then forcing (displacing) that trapped volume into the discharge • pipe. • Non Positive-displacement : Pumps that discharge liquid in a continuous flow. [penggerak utama] Question : What is/ are the difference(s) between a compressor and a pump?

  32. Hydraulic Systems • Hydraulic pumps. • Gear pump – two close meshing gear rotated. • Vane pump – spring loaded sliding vanes. • Piston pump • Radial piston pump - cylinder block is rotate. • Axial piston pump – move axially.

  33. Hydraulic Systems • Gear pump • Advantages • Widely used • Low cost • Robust • Weaknesses • Leakage • Limit efficiency • Gear wheels rotate in opposite direction. • Fluid forces through pump, become trapped between gear teeth. • Fluid transferred fro the inlet port to be discharged at the outlet port.

  34. Hydraulic Systems • Vane pump • Advantage • Leakage less than gear pump. • Spring loaded sliding vanes slotted in a driven motor. • Rotor rotates – vanes follow contours of the casing. • Fluid trapped between successive vanes and casing. • Transported round from inlet to outlet.

  35. Hydraulic Systems • Radial piston pump • Axial piston pump • Cylinder block rotates – hollow pistons with spring return, to move in and out. • Fluid drawn from inlet port. • Fluid transported round for ejection from the discharge port. • Piston move axially in a rotating cylinder block – move by contact with the swash plate. • Shaft rotates – move the pistons. • Air sucks (piston opposite the inlet), air expelled (opposite the discharge port.

  36. Non Positive-displacement Pumps • Non Positive-displacement • Pumps that discharge liquid in a continuous flow. • Use an impeller or propeller to move fluid by momentum. • Example : Centrifugal pump, Propeller pump uses in coolant pump or water pump on radiator-cooled engine. • Centrifugal Pump • A centrifugal pump converts the input power to kinetic energy in the liquid by accelerating the liquid by a revolving device - an impeller. • A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure of a fluid.

  37. Positive-displacement Pumps • Type of Positive-displacement Hydraulic pumps • Geared Pump • Vane pumps • Piston type • Many type of pumps are exist but the purpose is only one : • To displace fluid and create flow • Hydraulic pumps are rated by the amount of fluid can be displace for each revolution of pump shaft. • Unit : cm3/rev. • For positive-displacement pump, the theoretical flow rate of a constant flow is calculated in liters/minutes. DNT241 Electro Pneumatics & Hydraulics

  38. Vane Pumps Vane – a flat or curve blade, wing [sayap] The rotor has a permanent offset or eccentricity so that, as it turns, the space between the vanes gets larger and then smaller. When the space is getting larger, oil is drawn in. When the space is getting smaller, oil is pushed out. Animation : http://www.vikingpump.com/en/products/vanepumps/vaneAnimation.html

  39. Radial Piston Pump Keyword : Reciprocate – menyaling, salingan, membalas Animation : http://home.planet.nl/~brink494/radpm_e.htm The cam ② is a part of the main shaft ① and when it rotates, the pistons are made to reciprocate inside cylinder ④ which lay on a radial line. When the piston moves inwards, the space in the cylinder fills with oil thru the suction valve ⑦ and the suction port, s. When the piston moves outwards, the oil is trapped inside and forced out to the pressure port, p.

  40. Gear Pump Animation : http://www.pumpschool.com/principles/eg_ani.htm http://home.kpn.nl/rbrink1955/index.html The input shaft ③ carries the driving gear ⑦ that turns the idler gear ⑧. Oil from suction port, S is carries around in the space between the gears and the pressure port, P. The gears mesh and form a barrier so the oil is forced out.

  41. Advantage Positive Displacement • They can operate at very high pressures of up to 800 bar (used for lifting oils from very deep oil wells). • They can achieve a high volumetric efficiency of up to 98%. • They are highly efficient and almost constant throughout the designed pressure range. • They are a compact unit, having a high power-to-weight ratio. • They can obtain a smooth and precisely controlled motion. • By proper application and control, they produce only the amount of flow required to move the load at the desired velocity. • They have a great flexibility of performance. They can be made to operate over a wide range of pressures and speeds.

  42. Pump Performance

  43. Flow Rate / Pump delivery • The theoretical delivery from any hydraulic pump can be calculated by: • where, • QT : Theoretical pump delivery [L/min] • DP : Pump displacement [cm3/rev] • NP : Pump speed [rpm or rev/min]

  44. Pump Performance