EE50235 Autonomous Systems Engineering 2021
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EE50235
Autonomous Systems Engineering
1 (a) The basic principle of a Watt's speed governor for an engine is illustrated in the
schematic diagram of Figure 1.
(i) Explain the principle of this control system.
(ii) Use a standard block diagram to describe this control system, and
label controller, actuator, plant, sensor, and disturbance in your answer.
Fly ball
[5 marks]
Figure 1. Watt’s Fly Ball Governor for engine speed control
(b)
Figure 2: Block Diagram
The block diagram of a system is shown in Figure 2.
(i) Draw a signal flow graph based on the block diagram.
(ii) Derive the transfer function of Y(s)/R(s) using Mason’s gain formula.
(iii) Derive the transfer function of Y(s)/N(s). Determine a condition, so
that the disturbance N(s) does not affect the output Y(s).
(c) Continued on next page.
(c) Proportional-Integral-Differential (PID) control is a popular control method in control engineering.
(i) Discuss the effects of all the P, I and D settings on three measures of system performance: stability, accuracy, and speed of response.
(ii) In Figure 3, what is the primary problem on the system performance
if the controller Gc is not used? Design a PID controller Gc to solve the problem. Note, you may implement your controller with a single term, P, I, or D; or a combination of terms, PI, PD, ID, or PID. Calculate the steady-state error of the system with the controller you have
designed for a unit-step input.
[7 marks]
Figure 3. Block diagram of a system.
2 (a) Figure 4 is a block diagram of a control system. R(s) is the reference input, (s)
is the disturbance, and Y(s) is the output. The steady-state error is -0.1. Calculate the value for Kp and Kd .
W(s) =
+ +
- |
Figure 4. Block diagram of a system
[5 marks]
(b) A mechanical system is shown in Figure 5. There are two springs, one mass,
and one damper. The displacement of the mass is x, and the displacement of the damper is z. For this system, the input is fa and the output is z. The differential equations are given. Develop a state space model for this system.
Figure 5. A mechanical system.
[6 marks]
(c) The state space for a system is given below:
(x = Ax + Bu
〈
ly = Cx + Du
where
「−3 0 1] 「0]
A = 2 −2 0 , B = 0 , C = [1 2 0] , D=0
|L0 0 3」| |L2」|
Y(s)
Obtain the transfer function
(d) Regarding vision-based control for a robotic arm,
(i) Explain the two types of configuration: end-point closed-loop and end-point open-loop.
(ii) Explain the two types of visual servo control: Position Based Visual
Servo (PBVS) and Image-Based Visual Servo (IBVS).
[5 marks]
[4 marks]
3 (a) The block diagram of a control system is given in Figure 6.
Figure 6. Block diagram of a control system
(i) Use Routh Criterion to determine the range of K for the closed-loop system to be stable.
(ii) Determine the value of K when the output of the system is sustainable oscillation. [6 marks]
(b) Under a unit-step input signal, the responses of two transfer functions are shown
in Figure 7.
(i) Select the transfer functions that match the figures (A) and (B). Explain the reasons.
(ii) In Figure 7 (A), give the overshoot percentage, peak time, delay time,
and rise time. Approximate values are acceptable.
(A) (B)
Figure 7. Responses under unit-step signal
(a)G1 = , (b)G2= , (c) G3 = , (d) G4 =
[6 marks]
(c) Develop an artificial neural network (ANN) as a feedforward controller to control the end-effector of a robotic arm to track a desired trajectory.
(i) For a robotic arm, explain the four terms: forward dynamics, inverse dynamics, forward kinematics, and inverse kinematics.
(ii) Which part(s) should the ANN realise among the four parts: forward dynamics, inverse dynamics, forward kinematics, and inverse kinematics? Give the reasons. What are the input variable and the output variable of ANN in this case?
(iii) If a PID controller is added, which is combined with ANN, a hybrid controller can be developed. Plot a block diagram to describe this hybrid control system. Show advantages of this hybrid controller in comparison with a single ANN controller.
[8 marks]
4 (a) Design a piezo-electric pressure sensor system that could be mounted on a
robot hand to accurately detect whether the robot is gripping an object. How would you measure the data from the sensing system? How would you use the data from the sensing system to control the robot hand and ensure that the object does not get crushed? Use text and diagrams to answer these questions.
(b) You have been asked to design a robot capable of performing a mission
autonomously, with the mission profile power demand shown in Figure 8. What is the minimum capacity of battery required to provide sufficient energy to complete the mission if the battery has a nominal voltage of 15.3V.
Figure 8.- Mission Profile Power Demand
(c) Let us suppose that we have a wheeled robot with two motors and two light sensors (Figure 9). The light intensity is measured in the range of 0 (low intensity) to 255 (high intensity), which can be used to control the motors’ speed with values from 0 (low speed) to 255 (high speed). Design a fuzzy logic system to control the motors’ speed based on the light intensity to implement the robot behaviour of escaping from the light. Also explain what changes you would do to implement the robot behaviour of being attracted to the light. Describe the complete process for the design of the fuzzy logic system. Use text, diagrams and mathematical expressions to answer this question.
Figure 9.- Robot behaviours and fuzzy logic
5 (a) Explain how vision and touch sensing can be used together in a humanoid robot
to make it capable of exploring and interacting with the surrounding
environment and learning. [4 marks]
(b) Calculate the values of G(u, v), which is a 5x5 Gaussian filter. This filter uses a
standard deviation of 1.5 and u and v take the values -2, - 1, 0, 1 and 2. Show the values of the Gaussian filter. Next, apply G(u, v) to the image matrix below and show the resulting filtered matrix.
Image matrix
[5 marks]
(c) Design a fuzzy logic controller to control the speed of an autonomous vehicle. The diagram of this system is shown in Figure 10. The controller has 2 inputs, and 1 output.
The car increases its speed when no curve is detected, and the speed decreases when the angle of the detected curve is big. You can use the variables slow, medium and fast for the memberships of the speed of the car. For the type of curve detected you can use the variables big, medium and no curve for the membership functions. Your answer should include a fuzzification methodology, membership graphs, rules set, a fuzzy matrix table, aggregation and a defuzzification method. Make use of diagrams, tables and formulas to design the components of your fuzzy logic controller. Also, explain what modification you would implement in the fuzzy logic controller to allow the autonomous car to achieve a highly smooth control signal and response.
Figure 10.- Speed control for autonomous vehicle
[11marks]
2023-01-19