1. Match the types of Control Systems given in the left column with their corresponding advantage/disadvantage given in the right column.

Transcription

1 1. Match the types of Control Systems given in the left column with their corresponding advantage/disadvantage given in the right column. A. Advantage of closed loop control systems B. Advantage of open loop control systems C. Disadvantage of Closed loop control system D. Disadvantage of open loop control system I. Easy to implement. Needs lesser number of components. The overall cost is lower. II. Easily affected by load disturbances. III. The control action is dependent on the output. IV. Implementation is more complex and overall cost is higher. a) A: III, B: IV, C: II, D: I b) A: III, B: IV, C: I, D: II c) A: II, B: III, C: IV, D: II d) A: III, B: I, C: IV, D: II Answer: (d) Advantage of closed loop control system: Control action is dependent on output. r + e C(s) u G(s) y - u C s e u C s r y If there is any change in output (y) it will affect the control input (u) and immediately takes the corrective action.

2 2. Suppose a company buys two types of band saw machines for cutting steel ingots brought in by customers to dimension namely, Manual and Automatic, taking loan from a bank to be paid back in 24 equal monthly instalments. From figures given below for each machine, compute the amount of profit/machine the company can earn from each type of machine in 2 years by cutting ingots for 200 hours/month assuming enough demand such that the machines cut every day neglecting times for maintenance. Manual Automatic Cost 10,00,000 20,00,000 Manpower 6 (@ 30000/month) 2(@ 40000/month) Average energy 3 kw 4 kw consumption ( Rs10/kWh) Rate of annual simple 20% /yr 20%/yr interest to be applied on the borrowed amount Cost of saw/month 10,000 30,000 Number of products manufactured/hr 3 10 Cutting charge /ingot a) Manual: 4,82,96,000, Automatic: 4,23,68,000 b) Manual: 42,96,000, Automatic: 8,23,68,000 c) Manual: 82,96,000, Automatic: 4,23,68,000 d) Manual: 82,96,0000, Automatic: 4,23,68,00 Answer: (c) Working hrs. : 200hr/month Working month : 24 months Manual Automatic Cost of the Machine 10,00,000/- 20,00,000/- Salary of employees ( ,000) = 4,32,000/- Total cost of energy ( ) = 1,44,000/- Total interest (10,00, ) = 4,00,000/- ( ,000) = 19,20,000/- ( ) = 1,92,000/- (20,00, ) = 8,00,000/-

3 Total cost of saw (24 10,000) = 2,40,000/- (24 30,000) = 7,20,000/- Total cost price 61,04,000/- 56,32,000/- Total selling price ( ) = 1,44,00,000/- Total profit ( 1,44,00,000-61,04,000) = 82,96,000/- ( ) = 4,80,00,000/- ( 4,80,00,000-56,32,000) = 4,23,68,000/-

4 3. What type of automation system would you recommend for manufacturing Fluorescent Tube Lights & Garments? Answer: (d) a) Fluorescent Tube Lights: Flexible & Garments: Fixed b) Fluorescent Tube Lights: Programmable & Garments: Flexible c) Fluorescent Tube Lights: Fixed & Garments: Programmable d) Fluorescent Tube Lights: Fixed & Garments: Flexible Fixed Automation: It is used in high volume production with dedicated equipment, which has a fixed set of operation and designed to be efficient for this set. Continuous flow and Discrete Mass Production systems use this automation. e.g. Distillation Process, Conveyors, Paint Shops, Transfer lines etc. A process using mechanized machinery to perform fixed and repetitive operations in order to produce a high volume of similar parts. Flexible Automation: It is used in Flexible Manufacturing Systems (FMS) which is invariably computer controlled. Human operators give high-level commands in the form of codes entered into computer identifying product and its location in the sequence and the lower level changes are done automatically. Each production machine receives settings/instructions from computer. These automatically loads/unloads required tools and carries out their processing instructions. After processing, products are automatically transferred to next machine. It is typically used in job shops and batch processes where product varieties are high and job volumes are medium to low. Such systems typically use Multi purpose CNC machines, Automated Guided Vehicles (AGV) etc.

5 4. Match the types of Production Systems in factories given in the left column with their corresponding products given in the right column A) Continuous Flow Process I. Pharmaceuticals B) Mass Manufacturing Of Discrete Products II. Garments C) Batch Production III. Steel D) Job Shop IV. Cycles Answer: (a) a) A: III, B: IV, C: I, D: II b) A: II, B: IV, C: III, D: II c) A: III, B: I, C: IV, D: II d) A: IV, B: II, C: I, D: III A) Continuous flow process: Manufactured product is in continuous quantities i.e., the product is not a discrete object. Moreover, for such processes, the volume of production is generally very high, while the product variation is relatively low. Typical examples of such processes include Oil Refineries, Iron and Steel Plants, Cement and Chemical Plants. B) Mass Manufacturing of Discrete Products: Products are discrete objects and manufactured in large volumes. Product variation is very limited. Typical examples are Appliances, Automobiles etc. C) Batch Production: In a batch production process the product is either discrete or continuous. However, the variation in product types is larger than in continuousflow processes. The same set of equipment is used to manufacture all the product types. However for each batch of a given product type a distinct set of operating parameters must be established. This set is often referred to as the recipe for the batch. Typical examples here would be Pharmaceuticals, Casting Foundries, Plastic moulding, Printing etc. D) Job shop Production: Typically designed for manufacturing small quantities of discrete products, which are custom built, generally according to drawings

6 supplied by customers. Any variation in the product can be made. Examples include Machine Shops, Prototyping facilities etc.

7 5. A,B and C are three different product manufacturing systems whose characterisation in terms of product quantity vs product variety is shown below. Choose the right option for automation system for A, B and C. a) A: Fixed Automation System, B: Flexible Automation System, C: Programmable Automation System. b) A: Fixed Automation System, B: Programmable Automation System, C: Flexible Automation System. c) A: Fixed Automation System, B: Flexible Automation System, C: Programmable Automation System. d) A: Flexible Automation System, B: Fixed Automation System, C: Programmable Automation System. Answer: (b) A) Fixed Automation: It is used in high volume production with dedicated equipment, which has a fixed set of operation and designed to be efficient for this set. Continuous flow and Discrete Mass Production systems use this automation. e.g. Distillation Process, Conveyors, Paint Shops, Transfer lines etc. A process using mechanized machinery to perform fixed and repetitive operations in order to produce a high volume of similar parts. B) Programmable Automation: It is used for a changeable sequence of operation and configuration of the machines using electronic controls. However, non trivial programming effort may be needed to reprogram the machine or sequence of operations. Investment on programmable equipment is less, as production process is not changed frequently. It is typically used in Batch process where job variety is low and product volume is medium to high, and sometimes in mass production also. e.g. in Steel Rolling Mills, Paper Mills etc. C) Flexible Automation: It is used in Flexible Manufacturing Systems (FMS) which is invariably computer controlled. Human operators give high level commands in the form of codes entered into computer identifying product and its location in the sequence and the lower level changes are done automatically. Each production machine receives settings/instructions from computer. These automatically

8 loads/unloads required tools and carries out their processing instructions. After processing, products are automatically transferred to next machine. It is typically used in job shops and batch processes where product varieties are high and job volumes are medium to low. Such systems typically use Multi purpose CNC machines, Automated Guided Vehicles (AGV) etc.

9 6. Name the subsystems A, B and C of a typical sensor system shown below. Physical medium A B C Fig.Q6 Typical Sensor System a) A: Sensing element, B: Signal Conditioning and Processing Element, C: Target Signal Handling Element b) A: Signal Conditioning and Processing Element, B: Sensing element, C: Target Signal Handling Element c) A: Signal Conditioning and Processing Element, B: Target Signal Handling Element, C: Sensing element. Answer: (a) 7. Name the levels A and B of a typical Automation Pyramid shown below. B Production control A Automatic control Sensors,actuators Fig.Q7 Typical Automation Pyramid a) A: Enterprise Management, B: Supervisory control b) A: Supervisory control, B: Process Control c) A: Supervisory Control, B: Enterprise Management Answer: (c)

10 8. State three major functions of the Supervisory Control Level of an Automation System a) Process Scheduling, Maintenance Management, Inventory Management. b) Set point generation, Process Monitoring, Operator Interface. c) Set point generation, Inventory Management, Operator Interface. d) Set point generation, Maintenance Management, Inventory Management. Answer: (b) 9. State three major functions of a Production Control Level of an Automation System a) Process Scheduling, Maintenance Management, Inventory Management. b) Set point generation, Process Monitoring, Operator Interface. c) Set point generation, Inventory Management, Operator Interface. d) Set point generation, Maintenance Management, Inventory Management. Answer: (a)

11 10. What is the highest level of automation pyramid is present in the system shown below Fig. Q10: Automatic bottle filling system a) Level 0 b) Level 3 c) Level 2 d) Level 1 Answer: (d) Reference Weight signal + - Controller Position of valve at the tank Belt Driving Mechanism Filled bottle Weight sensor

12 11. What is the highest level of automation pyramid is present in the system shown below a) Level 2 b) Level 3 c) Level 1 d) Level 0 Fig Q11: Water level controller Answer: (c) Desired level + - Controller Pneumatic valve Tank Actual level Float position