Question

8 In order to prevent greenhouses becoming too hot in sunny weather, an automatic window can be installed. This opens automatically if the temperature reaches a pre-determined value. The higher the temperature the greater the opening becomes. Other than the heat produced by the sun, there is no external power source (a) Rescarch and describe how this mechanism works (b) State whether this is open or closed loop control. give reasons for your answer (c) Represent the system with a block diagram A direct acting proportional pressure controller has a gain of 3, a range of 0-40 bar and is set to control at 25 bar. When the measured value and the desired value are equal, the output signal is 60%. Determine the input pressure required to produce controller output values of 10% and 90% 9. 10. The mass M shown in FIGURE 5 is to be held in position by two hydraulic pistons (A and B) which exert forces F and F (respectively) onto the mass. The total for Fr (where FT-F+F2) is to be controlled at a constant valuc. The force F2 is uncontrolled, it is set at a nominal value however this may vary due to changes in the pressure of the hydraulic fluid supplying piston B. A control loop is to be used to maintain the total applied force Fr by controng the milude of F

Answer 1