![Taking LT of both equations considering initial conditions to
zero [i.e. h1(0)=h2(0)=0].](https://image.slidesharecdn.com/waterlevelcontroller-141210173941-conversion-gate02/85/Water-level-controller-24-320.jpg)
Water level controller
- 1. TANK WATER LEVEL CONTROLLER. SHEKHAR GEHLAUT. AKANSHA RAUTELA ADITYA GOEL
- 2. WATER LEVEL CONTROLER • Water level controller is used to control the water level in a tank. • In many industries like chemical, there is a restriction on liquid level of a container in such cases level controller can maintain level of the liquid at desired value.
- 3. WATER LEVEL CONTROL. • There are two methods to control the water level. i. Manual. ii. Automatic.
- 5. Working of manual method. • The purpose of this system is to maintain the liquid level (h) in the tank as close to the desired liquid level H as possible, even when the output flow rate is varied by opening the valve. • In manual method a human controls the liquid level close to the desired level using a sight tube. Using sight tube human compares the present level by the desired level and adjust the valve accordingly.
- 6. Drawbacks of manual method. • Error due to human. • Error due to time wasted in opening and closing of valves. • So there is a need of automatic(human less) system to increase the accuracy.
- 8. Working of automatic method. • In the automatic method human is replaced by a controller to increase the accuracy. The liquid level is sensed by a float and sensed level is then fed to the controller, controller compares the sensed level with desired level and error signal is generated, according to that error signal actuator controls the output valve.
- 9. Advantage of automatic method. • 1- error is reduced by human by a controller. • 2- automatic method is more reliable as compared to manual method, it is more stable also. • 3- it is costly comparatively but accuracy and stability provided by this method can cover the cost.
- 10. Laminar v/s Turbulent Flow • Laminar Flow • Flow dominated by viscosity forces is called laminar flow and is characterized by a smooth, parallel line motion of the fluid • Turbulent Flow • When inertia forces dominate, the flow is called turbulent flow and is characterized by an irregular motion of the fluid.
- 11. Resistance of Liquid-Level Systems • Consider the flow through a short pipe connecting two tanks as shown in Figure. • Where H1 is the height (or level) of first tank, H2 is the height of second tank, R is the resistance in flow of liquid and Q is the flow rate.
- 12. Resistance of Liquid-Level Systems • The resistance for liquid flow in such a pipe is defined as the change in the level difference necessary to cause a unit change inflow rate.
- 13. Resistance in Laminar Flow • For laminar flow, the relationship between the steady-state flow rate and steady state height at the restriction is given by: • Where Q = steady-state liquid flow rate in m/s3 • Kl = constant in m/s2 • and H = steady-state height in m. • The resistance Rl is
- 14. Capacitance of Liquid-Level Systems • The capacitance of a tank is defined to be the change in quantity of stored liquid necessary to cause a unity change in the height. • Capacitance (C) is cross sectional area (A) of the tank.
- 15. Capacitance of Liquid-Level Systems
- 16. Modelling
- 17. Modelling • The rate of change in liquid stored in the tank is equal to the flow in minus flow out. • The resistance R may be written as • Rearranging equation (2)
- 18. Substitute qo in equation (3) After simplifying above equation Taking Laplace transform considering initial conditions to zero
- 19. The transfer function can be obtained as
- 20. Modelling • The liquid level system considered here is analogous to the electrical and mechanical systems shown below
- 21. Modelling • Consider the liquid level system shown in following Figure. In this system, two tanks interact. Find transfer function Q2(s)/Q(s).
- 22. Modelling • Tank 1 Pipe 1 • Tank 2 Pipe 2
- 23. Modelling • Tank 1 Pipe 1 • Tank 2 Pipe 2
- 24. Taking LT of both equations considering initial conditions to zero [i.e. h1(0)=h2(0)=0].
- 25. From Equation (1) Substitute the expression of H1(s) into Equation (2), we get
- 26. Using H2(s) = R2Q2 (s) in the above equation
- 28. SIMULATION AND RESULTS • RESULT 1— CONTROLLER GAIN GAIN 2 CONCLUSION P=50 5 0.0035 Settling time=3 I=300 5 D=0 Overshoot=1 Undershoot=1 Max overshoot=1.2
- 30. SIMULATION AND RESULTS • RESULT 2 • — CONTROLLER GAIN GAIN 2 CONCLUSION P=50 3 0.0035 Settling time=4 I=300 3 D=0 Overshoot=1 Undershoot=1 Max overshoot=1.4
- 32. SIMULATION AND RESULTS • RESULT 3— CONTROLLER GAIN GAIN 2 CONCLUSION P=50 10 0.0035 Settling time=2 I=300 10 D=0 Overshoot=1 Undershoot=1 Max overshoot=1.1
- 34. SIMULATION AND RESULTS • RESULT 4— CONTROLLER GAIN GAIN 2 CONCLUSION P=100 5 I=200 5 D=0 0.0035 Settling time=2.5 Overshoot=0 Undershoot=0
- 36. SIMULATION AND RESULTS • RESULT 5— CONTROLLER GAIN GAIN 2 CONCLUSION P=100 1 0.001 I=200 1 0.002 D=0 0.0035 Settling time=aprox 0 Overshoot=0 Undershoot=0
- 38. SIMULATION AND RESULTS • RESULT 6— CONTROLLER GAIN GAIN 2 CONCLUSION P=100 1 0.5 Settling time=3 I=200 1 Overshoot=1 D=0 Undershoot=1