UNIVERSITY OF BOLTON SCHOOL OF ENGINEERING · PDF fileBSc (Hons) Mechatronics Top-Up Semester 1 Examination 2016/2017 Advanced Mechatronic Systems ... 1 A unit ramp function 2 1 s

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UNIVERSITY OF BOLTON

SCHOOL OF ENGINEERING

BSC (HONS) MECHATRONICS TOP-UP

SEMESTER 1 EXAMINATION 2016/2017

ADVANCED MECHATRONIC SYSTEMS

MODULE NO: MEC6002

Date: Wednesday 11 January 2017 Time: 10:00 – 12:00 INSTRUCTIONS TO CANDIDATES: There are 6 questions. Answer 4 questions. All questions carry equal marks. Marks for parts of questions are shown

in brackets. This examination paper carries a total of

100 marks. All working must be shown. A

numerical solution to a question obtained by programming an electronic calculator will not be accepted.

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School of Engineering BSc (Hons) Mechatronics Top-Up Semester 1 Examination 2016/2017 Advanced Mechatronic Systems Module No. MEC6002

Q1

a) A robot control system can be represented by the block diagram shown in

Figure Q1(a). Using block diagram reduction techniques, find the θo for this

control system if a unit step input is applied.

Figure Q1 (a) A robot control system. Where θi(s) is the input and θo(s) is the

output.

(15 marks)

b) A DC motor of a mechatronic control system is a first order system. It’s time constant is 0.7 seconds. If the speed of the DC motor is suddenly increased from being at 0 rpm to 500 rpm, what will be the speed indicated by the speedometer after 0.6 seconds ?

(4 marks)

c) A spring-damper system has the following transfer function:

Please sketch the output displacement over the time when the impulse input is

applied to the system.

(6 marks)

Total 25 marks

Please turn the page

θi(s

) θo(s

)

82

5)(

ssG

i

o

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Q2.

(a) The differential equation for a mechatronics system is :

Where θo is the output and θi is the input.

(i) Find the transfer function of this system. (4 marks)

(ii) Find the damping factor. (2 marks)

(iii) Find the damped frequency. (3 marks)

(iv) Find the Percent Overshoot. (3 marks)

(v) Find the 5% settling time ts. (2 marks)

(b) Explain, helped by sketch, the steady state error in an output of the

biomechatronic control system.

(4 marks)

(c) Apply Routh-Hurwitz stability criterion to determine the range of values of K for

a robot control system with the transfer function of T(s)

which will result in a stable response.

(7 marks)

Total 25 marks

Q3 (a) Using a block diagram to define a closed loop mechatronic control system. In

the diagram, you need clearly indicate the basic elements and their input and output signals for each block. (4 marks)

Question 3 continued over the page

iooo

dt

d

dt

d

2953

2

2

Ksss

s

s

ssT

i

o

334

5

)(

)()(

23

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Question 3 continued

(b) As a mechatronic system design engineer, you are working on the design of the following two systems:

A smart wheelchair

A prosthetic limb

i) From sensor listed below, select two sensors for the smart wheelchair and two sensors for the prosthetic limb and briefly explain reasons for selecting them: Myoelectrodes Gyroscope Linear Transducers Touch Pads (FSR) Voice Vision Accelerometer Laser rangefinder (8 marks)

ii) Currently, brushed DC motors have been used for both these two systems. Make comments on using brushed DC motors, and provide suggestions for using alternative actuators (at least Three actuators).

(5 marks)

iii) Describe how brain-computer interface can be applied into these two systems.

(8 marks)

Total 25 marks


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Q4 A simplified model of a smart wheelchair control system is shown in Figure Q4

and the wheelchair dynamics are given by:

)94(

6)(

sssGP

Figure Q4 A Smart Wheelchair control system

The system responses for a unit step input are required as:

The maximum overshoot is less than 30%

The rise time is less than 0.4 seconds

The steady-state error is 0. a) If a PID controller Gc(s) with Kp = 2, Ki = 8, and Kd = 5 is applied into

the system, examine the actual system’s percent overshoot, rise time and steady-state error under the PID controller and check whether the design criteria have been achieved or not. (15 marks)

b) If the design criteria haven’t achieved by using the PID controller provided above, explain the procedure to modify the PID controller

(3 marks)

c) Describe, helped by sketches, how the error item is handled by proportional, integral and derivative controller. (7 marks)

Total 25 marks


Output X(s)

- +

Input R(s)

Wheelchair Dynamics Gp(s)

Wheelchair Controller

Measurement = 1

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Q5 (a) Using block diagrams, briefly explain an analogue closed loop control

system and a digital closed loop control system. Assume that input, output and sensor signals for both control systems are all analogue signals. (6 marks)

(b) Explain what is meant by a zero-order hold (ZOH) system. (4 marks) (c) A controller has a 10 bit Analogue to Digital Converter with the signal

range between -8 Volt to +8 Volt: (i) What is the resolution of the AD converter? (2 marks)

(ii) What integer number represented a value of +6 Volts?

(2 marks) (iii) What voltage does the integer 200 represent? (2 marks)

(iv) What voltage does 1010101101 represent? (2 marks)

(d) If the controller consists of a Digital to Analogue Converter with zero

order element in series with the processing centre which has a transfer function

2)8(

)(

s

ssGp

find the sampled-data transfer function, G(z) for the digital control system . The sampling time, T, is 0.3 seconds. (7 marks)

Total 25 marks


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Q6 Figure Q6 (a) illustrates a rotational mechanical system with a compound gear train.

Figure Q6 (a) A rotational mechanical system

Where the first driver Gear A has 10 teeth, Gear B 20 teeth, Gear C 12 teeth and Gear D 24 teeth.

(i) If the maximum angular acceleration of the load needs to be 10 rad/s2, determine the maximum torque of the motor. (6 marks)

(ii) Determine the power needed to accelerate the whole system

from rest so that the final angular velocity of the load L is 20 rad/s. (5 marks)

(c) A DC motor has an inertia Im of 0.01 kgm2. The nominal speed of motor is

3000 rpm and can generate a maximum torque of 15 Nm. It is connected to a uniformly distributed arm. Figure Q6 (b) shows the motor power system. The inertia of the load IL is 1.0 Kgm2, and the torque required by the load is 60 Nm.

Question 6 continued over the page

D Tm

Im = 2 Kgm2

L

IL = 48 Kgm2

A

B C

Gear Train

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Question 6 continued

Figure Q6 (b) The motor power system

(i) Ignoring the viscous friction in the system, determine the gear ratio for the system. (8 marks)

(ii) If the viscous friction has been measured as bm = 0.01 Kgm/s

and bL = 0.02 Kgm/s, and using the gear ratio determined by (i) above, what is the maximum torque of the motor required for the system? (6 marks)

(25marks)

END OF QUESTIONS

L

m

DC Motor

Load

Gears

Tm

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FORMULA SHEETS

G(s) = )()(1

)(

sHsGo

sGo

(for a negative feedback)

G(s) = )()(1

)(

sHsGo

sGo

(for a positive feedback)

Steady-State Errors

)]())(1([lim0

ssGse iOs

ss

(for an open-loop system)

)]()(1

1[lim

0s

sGse i

os

ss

(for the closed-loop system with a unity feedback)

)](

]1)()[(1

)(1

1[lim

1

10

s

sHsG

sGse i

sss

(if the feedback H(s) ≠ 1)

])1)((1

)([lim

12

2

0d

sss

sGG

sGse

(if the system subjects to a disturbance input)

Laplace Transforms A unit impulse function 1

A unit step function s

1

A unit ramp function 2

1

s

First order Systems

)1( / t

ssO eG (for a unit step input)

)1( / t

ssO eAG (for a step input with size A)

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Performance measures for second-order systems

dtr = 1/2

dtp =

P.O. = exp %100))1(

(2

ts = n

4

d = n(1-2)

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UNIVERSITY OF BOLTON SCHOOL OF ENGINEERING · PDF fileBSc (Hons) Mechatronics Top-Up Semester 1 Examination 2016/2017 Advanced Mechatronic Systems ... 1 A unit ramp function 2 1 s