ee323 mini-project - line tracing robot

EE323 Mini-Project – Controller Design for Guided Vehicle

Dr. Praneel Chand - 2015 1

School of Engineering and Physics

EE323 – Digital Control Systems

Mini-Project – Controller Design for Guided Vehicle

Introduction:

Controllers and compensators are employed in range of industrial and research

applications. Industrial applications can include regulating the temperature of fluids in

tanks or furnaces, controlling the speed of conveyor belts, or controlling the

movement of guided vehicles in a factory. In research, controllers and compensators

are widely used in the design and development of mobile robotic devices for various

applications such as exploration, search and rescue, surveillance, or object

manipulation and transport.

The specific objectives of this project are to:

1. Develop mathematical models of digital control systems.

2. Analyse mathematically modelled and physical digital control systems using

first principles of mathematics and engineering sciences and modern tools.

3. Design and test digital controllers and compensators for modelled and physical

systems using first principles of mathematics and engineering sciences and

modern tools.

4. Function as an individual, and as a member or leader of a team.

5. Produce written reports and oral presentations of practical work.

6. Apply project management techniques to the planning and execution of future

work.

Each group is required to submit a technical report (refer to

http://www.monash.edu.au/lls/llonline/writing/engineering/technical-report/index.xml

for more information about technical reports) and give a 20 minute presentation of

their work.

Specifications:

In this mini-project, you will design and implement a controller for a guided vehicle

to meet the given performance specifications. The project has three major

components. Firstly, you are required to familiarize yourself with a Lego robotic

guided vehicle that will be given to you. Secondly, you are required to design a digital

controller for the guided vehicle using an appropriate control theory design method.

Finally, you are required to implement your fuzzy controller on the Lego NXT brick

using Robot C. You may need to re-design your controller if it does not perform

satisfactorily.

The control system performance requirements are as follows:

Requirements for following a straight line/path:

Zero steady state error

2 % settling time ≤ 2 seconds

Vehicle speed at least 70%

Requirements for following curved lines/path:

http://www.monash.edu.au/lls/llonline/writing/engineering/technical-report/index.xml



Mean Absolute Error (MAE) ≤ 10 degrees

Vehicle speed at least 70%

You should be able to account for and apply the fundamental steps of a formalized

design process learned in any of your engineering courses (e.g. MM101, EE312,

EE323, EE314) which must incorporate (but not necessarily be limited to) the above

specifications.

Some hints to familiarize with the guided vehicle system are provided in Appendix 1.

Assessment:

This project is worth 15% of your course. Each group will be required to submit a

report and also give a presentation of their work. Please refer to Table 1 for the

assessment scheme. The due date for the project and report is Week 14 Tuesday. No

extensions will be given so time management is an important issue which you all have

to plan from now onwards.

Course coordinator



Table 1: Project Assessment Scheme

COMPONENT ELEMENT SUB ELEMENTS TOTAL

MARK

A: PRESENTATION Technique tools used to present eg

PowerPoint, CAD packages etc 0.25

Content Introduction, body of presentation

and conclusion 1.5

Demo System setup, operation,

functionality

2

Question & Answers Clarifications on content & results 1.5

PRESENTATION TOTAL 5.25

B: REPORT structure & clarity & use of English

presentation references identified

appendices / bibliography 0.25

acknowledgements

diagrams, photos, tables, graphs

introduction report objective

awareness in the wider context

background knowledge (literature

review)

1

methodology Design details of your control

system solution.

Design & simulation of control

system in MATLAB

Hardware implementation details of

control system

2.25

results & discussion tables & graphs

simulation results

hardware results

videos/photos of system in operation

2.25

Discussion: Performance of control

system in simulations & hardware

with respect to the specified

performance requirements

finale Conclusions: implications

suggestions: future work 1

abstract

REPORT TOTAL 6.75

C: MANAGEMENT Initial Plan & Weekly

plan achievements

Initial plan

Work done each week vs weekly

plan

1.5

MANAGEMENT TOTAL 1.5

D: TEAMWORK Teamwork

Effectiveness

Project carried out by ALL members

Workload and variety on each

member

Leadership by each member for

different tasks

Scheduled meetings and minutes

1.5



recording – contribution of each

member identified

TEAMWORK TOTAL 1.5

OVERALL TOTAL 15

Appendix 1:

Familiarization with Lego Robot Guided Vehicle & Mathematical Modelling

About the Lego Robot NXT Guided Vehicle:

o An assembled Lego robot NXT vehicle will be given to you. It consists

of an Lego Mindstorms NXT Brick, two NXT motors, and a light

sensor array

Information about the NXT brick: the orange button turns the

brick on and used to enter menus or run a program. The grey

button below the orange one is used to exit menus or programs.

The left and right triangle buttons are used to move left or right

in menus.

o Note the ports of the NXT Brick to which the motors and the light

sensor array will be connected. You will need this information for your

program.

o Open Robot C on the desktop PC. You can now connect to the Lego

NXT Guided Vehicle Brick and download programs. Refer to the

section on Getting Started with the NXT (PDFs) in

http://www.robotc.net/support/nxt/ .

o Try to create a simple program to run the vehicle forward for 2 seconds

at 25% speed.

o Robot C has a good help menu which can be useful for creating

programs. Read though the software help pages.

o Other sources of help

http://www.robotc.net/education/curriculum/nxt/

http://cdn.robotc.net/code_listing/nxt/nxt.html

o Information on the light sensor array is available at:

http://www.mindsensors.com/index.php?module=pagemaster&PAGE_

user_op=view_page&PAGE_id=168 . The Robot C drivers for the

sensor and user guide are available there. READ THE USER GUIDE.

Mathematical model of Guided Vehicle:

o Consider a line-following robot similar to Figure 1. The robot has

rotational inertia J and two motors/wheels that can produce a

differential torque T(t) to change the orientation angle θ(t) of the robot

via Newton’s 2nd law:

2

2( ) ( )

dJ t T t

dt (1)

The differential torque T(t) in (1) produced by the motors can be

described by:

http://www.robotc.net/support/nxt/



http://www.mindsensors.com/index.php?module=pagemaster&PAGE_user_op=view_page&PAGE_id=168

http://www.mindsensors.com/index.php?module=pagemaster&PAGE_user_op=view_page&PAGE_id=168



( ) [ ( ) ( )]m e

dT t K V t K t

dt (2)

Where V(t) in (2) is the differential voltage applied to the motors and

Ke (t) in (2) is due to the EMF voltage generated by the rotational

speed of the motors.

The transfer function of the line-following robot is given by:

2( ) ( )m

m e

Ks V s

Js K K s

(3)

o The motor constants Km and Ke have been obtained by experiment by

Bradley et al (http://www.dit.upm.es/~str/papers/pdf/bradley&12a.pdf

[see Table 1on pg. 4] ).

o Motor power % vs rpm graphs have also been obtained by experiment

(http://www.philohome.com/nxtmotor/nxtmotor.htm ). Note the

voltage source of your NXT motors. This is what 100% power (or

100% duty cycle) corresponds to.

o You will need to experimentally determine/estimate the inertia of the

guided vehicle. Ask some mechanical engineering staff for hints.

o Depending on the placement of the light sensor array you will have to

determine the relationship between the light sensor array reading and

the offset (angle) of the robot from the path (line). This offset is then

used to apply corrections to the guided vehicle’s heading.

Figure 1: Line-following robot (Source: toddthahn.com)

Implementing Control of the Lego Robot Guided Vehicle via Robot C

In this implementation you will write a Robot C program to represent the controller

designed in Part 2. The help sources identified in Part 1 will be useful:

The Robot C software has a good help menu which can be useful when

learning to write programs.

o Other sources of help



http://www.dit.upm.es/~str/papers/pdf/bradley&12a.pdf

http://www.philohome.com/nxtmotor/nxtmotor.htm





You will also need to incorporate data logging in your Robot C program so that you

collect data to plot response graphs for analysis. This means you will have to write

data to a file during the hardware tests and read this data file later after testing is

complete.

ee323 mini-project - line tracing robot

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