Embedded System Design - Servo Control of DC motors The design of real-time control software to give PD positional control of a mobile robot

2017

Zeeshan Mustafa Latif Ansari BEng (Hons) Electronic Engineering, Birmingham City University

1/20/2017

s09466807 Page 1

Contents Page Numbers

Introduction…………………………………………………………………….2

Section 1: Hardware Design…………………………………………………3

Block Diagram of DC-Motor Servo Controller……………………….3

Functional Specification of the Block Diagram……………………...3

Rationale for the choice of processor………………………………..5

Schematic for Single Channel DC-Motor Servo Controller………..6

Algorithm – Flowchart………………………………………………….7

Pulse Width Modulation………………………………………………..8

H-Bridge – Rotation…………………………………………………….9

DC-Motor Characterisation……………………………………………9

Mouse Position and Speed Measurement…………………………..9

Pulse Counter…………………………………………………………10

Data Acquisition……………………………………………………….10

RS232…………………………………………………………...10

Section 2: Software Design…………………………………………………11

Proportional and PD Controller (Track)…………………………….11

Speed Profiler…………………………………………………………15

A 4 Cell Profiled straight……………………………………………..15

A Profiled 90 degree rotation………………………………………..16

Summary……………………………………………………………………...17

References……………………………………………………………………17

Appendix……………………………………………………………………...18

s09466807 Page 2

Introduction

The report aims at gaining clear understanding of architecture and then building the latest

design (using Servo control of DC motors) of “MYTEE-Mouse” which is a successor to the

previously made robots - “Heretic” and “Robotic” at Birmingham City University“. To put it

more precisely, it is the design of real-time control software to give PD positional control of a

mobile robot (MYTEE-Mouse). This assessment mainly involves the position encoder of

mouse, motor drive, real-time system and closed loop control theory. Design consists of two

major parts which are given below:

Hardware Design

This part was initiated by functional specification with block diagram for a single channel DC-

motor servo controller, using the minimum number of components and an appropriate

processor of PIC 8-bit range which was chosen to be PIC18F4523. It then included a

rationale for the choice of processor, a schematic of the design and finally the development

of algorithms and description to clearly show that the design could function. Design will be

undertaken by keeping in mind the important factors i.e. Forward and Rotational profile to

drive mouse from start to finish, application of PWM to the DC motors, use of encoders to

measure the speed and position of mouse, measurements of distance by using IR sensors

and how to control the position by using the PID controller and Speed profiler. Following this,

the software design begins.

Software Design

The Software design for servo control of DC motors began with the development of program

codes in order to demonstrate how the MYTEE-Mouse can be implemented to prove its

functionality into the maze. This part, in detail, included an introduction to servo control on

MYTEE-Mouse, lab reports with data acquired and analysed (using graphs) on “PID

controller” and “Speed Profiler“ and description of the final software design to accomplish

three milestones (specified in assessment brief) which are stated below:

(a) a 4-cell profiled straight;

(b) a profiled 90 degree rotation;

(c) Sequencing of a, b in order to complete a 4x4 cell rectangle and return to the start

point.

s09466807 Page 3

Section 1: Hardware Design

Block Diagram of DC-Motor Servo Controller

Functional Specification of the Block Diagram

MYTEE mouse can be defined as a mobile device that with applied codes to its

microcontroller (being PIC18F4523 for this time), it should demonstrates some operations

such as following the wall with specific dimensions, on a unknown route, to start on a

specific point and while following the path on maze by sensing the walls on sides and in front

it reaches its pre-defined destination.

In past, two micro mouse have been built by BCU; first one was called Robotic which had

numerous interconnections which were prone to faults i.e. motor control used a MOSFET

chopper transistor with relay direction change, motor assemblies were sourced externally,

wall-sensors were top-of-the-wall devices that added greatly to the mass and turning

moment of the mouse. It was a poor designs but it performed the job required of it (Dr Wilcox,

2017

The second one was called Heretic or SMA (Student Mouse A) which was proved to be a

very successful design; it had fully symmetric array of 9 IR-sensors, an RF-link and a wire-

link for RS232 communications with a host PC, H-Bridge motor control, low-inertia DC

motors with spur an pinion gearing and high resolution encoders for wheel position

measurement. It also had reduced battery size and came out to be a much more compact

low-level design. Its applications included its use in maze-solving and in an open-

environment for co-operative and swarm research activities (Dr Wilcox, 2017).

Then another mouse was developed based on SMA which had its name changed from SMB

(Student Mouse B) to MyTEE-Mouse due to the formation of the new faculty (TEE). The

DC-Motor Servo Controller

(Microcontroller - PIC18F4523)

Motor

Encoder

H-Bridge

Power

Power Supply

8 AAA

Rechargeable Batteries

Memory

EEPROM

FRAM

Communication

ICD

Connector

RS232 Cable

PIC

PICKIT2

Debugger

s09466807 Page 4

microcontroller being used for this design is PIC18F4523 which operates at frequency of

64MHz is responsible for providing commands (that specify their operations) to its

peripherals.

Since the micro mouse operates at 5V and batteries come with supply voltage of 9.5V, a

potential divider network is required to keep voltage stabilised at 5V. Micro mouse is

connected with 8 AAA rechargeable batteries for power supply which can be charged with

the voltage supply that is set at 14.4V.

A high current half-H Driver motor (named L293D) was used to drive the left and right

motors. L293D supports bi-directional drive of two DC motors with PWM speed control

whereas in this exercise only single channel DC servo is required. When driver input controls

the direction of the motor, the PWM for the motor is applied to the enable input of the H-

bridge (Dr Wilcox, 2017). It offers the benefits of bi-directional (forward and backward) drive

currents up to 600mA per driver at voltages between 4.5V to 36V (Texas, 2017).

The mouse is connected with three pushbuttons and two LEDs. Green LED and Red LED

are connected with PB2 and PB2 respectively. When PB1 is pressed, the red LED lights up

and the mouse stars calibrating and when PB2 is pressed the green LED lights up and

mouse starts moving whereas the third pushbutton is used to stop the mouse. The mouse

can also store information about sensor readings which is achieved by connecting mouse to

“Tera Term” and when Reset pushbutton is pressed - following which the PB2.. The micro

mouse can also be turned “ON” and “OFF” by the use of power-ON switch that is connected

to it.

In order for the microcontroller to be programmed or debugged an insulation-displacement

contact (14-way IDC) connector is also used (while connected to the microcontroller) to

download the code from the MPLAB software and then to store it into the memory (EEPROM

and FRAM). EEPROM which stands for Electrically Erasable Programmable Read-Only

Memory is a non-volatile memory which is used in embedded systems to store small amount

of information while offering options to erase and reprogram individual byte of information

(tech, 2017).

FRAM (ferroelectric RAM) is a random access memory that combines the fast read and write

access of dynamic RAM (DRAM) with its ability to retain data when power is turned off.

Although, it cannot store as much data as DRAM and SRAM does but because it’s a fast

memory with very low power requirements it replaces EEPROM and SRAM for many

applications (what, 2017). Therefore, because of their unique features, both EEPROM and

FRAM are used to erase, reprogram or store code required for mouse operations. As

previously said information can be viewed through Tera Term when mouse is connected with

a RS232 and ICD connector.

It is worth mentioning that MyTEE-Mouse also has 6 wall sensors which are 3 pairs of IR

phototransistors and photo-emitters. Sensors indicate the position of the mouse by

detecting the light from the IR emitters that is reflected from the walls of the maze. The first

forward-looking sensors’ pair detects the distance to the front wall, the second angled

sensors’ pair tracks the side wall and the third side looking sensors’ pair is used to detect the

wall openings for re-calibration purposes. In this exercise IR sensors are disabled (not in

use), instead simple Proportional- derivative Controller and Speed Profiler is being used for

s09466807 Page 5

a 4 cell profiled straight, a profiled 90 degree rotation and for sequencing so that mouse can

complete 4 × 4 cell rectangle and return to it start point (Dr Wilcox, 2017).

Out of the many advantages of MyTee-Mouse, the one that must be stated is that it is cheap

to design and build and it offers great functionality as a wall follower and maze solver for UK

level competition that takes place every year at BCU.

Rationale for the choice of processor

A processor can be defined as a logic circuitry that responds to and processes the basic

instructions that drive an electronic system (MyTEE-Mouse). The four primary functions of a

processor would include fetch, decode, execute and writeback (what, 2017).

The processor was chosen based on its peripherals, size, cost and other important features

i.e. FLASH, SRAM, EEPROM, USB interface, I/O pins, number of servos support, analogue

inputs, PWM, serial communication, external interrupt pins and boot-loader etc.

PIC stands for “Peripheral Interface Controller”, it’s a specialised family of microcontrollers

which are compact microcomputers designed to control the operations of embedded

systems in robots and most of the electrical/electronic devices. A microcontroller normally

includes processor, memory and peripherals. PIC microcontrollers are in fact quite cheap

and they can be bought as kits that can be assembled by the user or as pre-built circuits.

Microcontrollers are programmed and simulated using computers and “Circuit Wizard”

software. In this project the microcontroller being used is PIC18F4523 and software to

program it using “C code” is MPLAB IDE. When the program is simulated and it works, the

program is downloaded and saved into the memory of PIC18F4523 using a USB lead which

can then be run independently without using the USB cable.

Figure 1 PIC18F4523, (micro, 2017)

PIC18F4523 is a 40-pin device with flash memory of 32 kilobytes and RAM of 1536 bytes.

According to the datasheet developed by the company “MICROCHIP TECHNOLOGY” the

actual microprocessor “PIC18F4523” has the following features:

Its CPU has up to 10 MIPS (Million Instructions per Second) performance; it also includes a

C-compiler optimized RISC (Reduced Instruction Set Computer) architecture and an eight

times eight (8x8) Single Cycle Hardware Multiply.

Its system includes an internal oscillator which supports 31 KHz to 8MHz. It also has a

property that allows a safe shutdown if clock fails. This function is called Fail-Safe Clock

s09466807 Page 6

Monitor. Furthermore it has a watchdog timer with separate RC Oscillator and it operates at

voltage ranges from 2.0V to 5.5V.

Its “nanoWatt Power Managed Modes” includes Run, Idle and SLEEP modes. Idle mode

currents down to 5.8uA typical and Sleep mode currents down to 0.1uA typical.

Its analogue features include 12-bit ADC (Analogue to Digital Converter), 13 channels, 50K

samples per second and two Analogue Comparators multiplexing. It can also be

programmed to Low Voltage Detection Module and Brown-out-Reset Module.

Its peripherals include Master Synchronous Serial Port supports SPI and IC2 Master and

slave mode. It also has EUSART (Enhanced Universal Synchronous Asynchronous

Receiver Transmitter) module with a LIN (Local Interconnect Network) bus support. Finally it

consists of Four Timer modules, 5 PWM (Pulse Width Modulation) outputs and up to 2

Capture/Compare.

Development tools include Demo and Eval Boards, Emulation & Debuggers and

Programmers (micro, 2017).

Price: The chosen microcontroller is priced at £ 4.12 which is very economical for MyTEE-

Mouse.

Schematic of Single Channel DC-motor Servo Controller

s09466807 Page 7

Algorithm – Flowchart

s09466807 Page 8

Pulse Width Modulation The PWM was implemented using the CCP Modules to reduce the loading on the processor

and to leave two timers free for pulse counting, it is shown below:

Void OpenTimers2 (unsigned char config);

Void OpenPWM1 (char period); // PWM period = (PR2 register +1) ×4×Tosc×TMP2 Pre-

scalar Value

Void SetDCPWM1 (unsigned int dutycycle); // PWM Duty period = PWM Duty Value × Tosc

× TMR2 Pre-scalar Value

// PWM Duty range = (PR2 register + 1) × 4

These two PWM channels used timer2 as their clock. PR2 register or the Timer2 prescalar

can be altered to change the PWM frequency (where prescale can be either 1.4 or 16). The

speed of a DC motor is directly proportional to the applied voltage. In order to achieve the

full 10 bit range for duty cycle, the PR2 resistor is set to 225. Using low frequencies keeps

the motor on for longer whereas using high frequencies results in higher current applied to

the motor at the start, hence less current remains which keeps the motor on for short time.

High torque produced by this current at the start allows the motor to overcome the effect of

stiction thus allowing it to accelerate quickly.

In order to fulfil all the requirements given above, the PWM frequency of 2KHz is achieved

by setting the PR2 resistor and pre-scale value to 249 and 16 respectively which gives duty

gain of 0 to 1000 (the duty gain necessary to achieve 2KHz of PWM frequency).

The PWM frequency and period is calculated as shown below:

The frequency of MyTEE-Mouse is 32 MHz

Frequency

Timer2 (input clock) = 32MHz / 4 = 8 MHz per instruction cycle

Now divide 8 MHz by the Pre-Scale value of 16 = 8 MHz / 16 = 0.5 MHz

Again divide by 249 (TIMER 2 = 8 bit value) = 0.5 MHz / (249+1) = 2 KHz

So Frequency is 2 KHz

Period

Periods = 1 / frequency

So Period = 1 / 2 kHz = 500 us this is the PWM period time.

The PWM makes good use of duty percentage i.e. acceleration, deceleration and desired

speed can be produced by increasing or decreasing duty percentage where the duty cycles

of 0 and 1000 would indicate that the output is always low and high respectively.

s09466807 Page 9

H-Bridge - Rotation The rotation of the MyTEE-Mouse was controlled by using the H-Bridge method. The motor

driver L293D was used to drive a single channel DC-motors which has the maximum

operation frequency of 5 KHz – suitable for chosen PWM frequency of 2 KHz. As the name

states that the digital amplifier which is used produces digital output such as on/off or 1/0.

Whatever the input is loaded i.e. 40% duty cycle square wave would produce 40% in output,

thus restricting the power to the motor to a defined level.

DC-Motor Characterisation A single channel RF500-TB-12560 DC-motor Iis used for MyTEE-Mouse. The motor has

maximum speed of 3100rpm when no load applied on it. Its speed is achieved by voltage

and direction is determined by polarity – speed is proportional to the voltage and direction to

the polarity.

Figure given below helps us understand the relationship between the “ideal” and “actual”

response of the motor. The “Ideal response” line shows that the “Motor Speed” and “Applied

Voltage” are directly proportional to each other. Stiction must be eliminated for the motor to

reach its maximum speed. It can also be seen that once the ideal response settles down the

motor also slows down.

Figure 2 Motor drive, (Dr Wilcox, 2017)

In order to drive the motor at constant speed the coefficient factor (Kd) which is calculated

from the “Speed vs. PWM” graph, is used to convert the speed value to PWM. The motor

was driven by setting the PWM of the DC motor to duty of 50% for 4030 pulses. Tera Term

along with RS232 line and ICD connector was used to capture the data so that graphs can

be plotted which are given below:

Mouse Position and Speed Measurement Optical encoders will be used to obtain measurements of speed and position. MyTEE-Mouse

uses quadrature encoder HLC2705 for a single channels DC-motor servo controller. The 12-

tooth pinion gear which is fitted with 60-slot encoder disc. Encoder disc rotates an IR emitter

and a times-2 quadrature (HLC2705 – provides 120 pulses/revolution) giving 2*60*80/12 =

800 pulses per revolution of the wheel. As the wheel diameter is 45mm which gives a

circumference of pi*45mm = 141.37 and when divided by pulses per revolution of the wheel

i.e. 141.37/800 gives 0.18mm per pulse.

s09466807 Page 10

Figure 3 Motor-Gear- Encoder Assembly & HLC2705 Quadrature Detector Output, (Dr Wilcox, 2017).

Pulse counters One method that could have been used to drive the microcontroller (PIC18F46K42) timers

was by enabling their timers to count external pulses by using external inputs. As this

method only counts upwards that’s why the problems was resolved by using an alternative

method where combinations of interrupts were employed which can decide whether to

decrement (down) or increment (up) the count variable by changing the values of the counter

timers.

So the pulse counting was finally achieved by configuring the timer0 to produce an interrupt

by an external input. In MCC18 compiler “Timer libraries” and header file “Timer.h” were

used, and because the timer can only count 1 pulse that’s why timer mode was set to 8 bit.

Both the wheels were monitored by adding timer1 to their opposite wheels.

Data Acquisition The data acquisition is important for MyTEE-Mouse because it is possible to gain feedback

from sensor readings which can further help provide data for analysis and understanding of

the mouse operations. The data acquisition can be achieved from the mouse by using

RS232 cable when mouse is not moving or FRAM can be used to take data when mouse is

moving in the maze.

RS232

“A USART (Universal Synchronous/Asynchronous Receiver/Transmitter) is a microchip that

facilitates communication through a computer's serial port using the RS-232C protocol”

(what, 2017). The USART function baud rate was set to 115200 so that the mouse can be

connected to the serial port (RS232) for data to be acquired using the “Tera Term”. Two

parameters “config” (configuration byte) and “spbrg” (value written to the serial port baud

rate generator) were passed to “OpenUSART” function. Then the MyTee-Mouse is

connected to the serial port by using options from the Tera Term which is selecting “Set up”

> “Serial port” along with baud rate of 115200. The code and algorithm given below explains

how the “Data Acquisition” setup is done using the USART and RS232.

s09466807 Page 11

Wait for PB1 or PB2

If PB2 upload the FRAM

Else run main program

Section 2: Software Design

Proportional and PD Controller (Track)

This part talks about the movements of the micro mouse with respect to the speed and

distance of the wheels so that the position control (servo control) can be investigated.

As it usually happens, the measured position comes out to be different than the desired

position. The “steady-state error” is calculated by subtracting the measured position from the

desired position. This error is reduced (or corrected) by taking the feedback from the output

and putting it back into the input. This process of feeding back output into the input is known

as “closed loop gain”. The “steady-state error” is then multiplied with the “gain factor (KP)” to

turn the “position error” into PWM. The output here is actually this PWM which is fed back

into the motor driver as input.

Steady-state error = desired position – measured position

For the configuration of KP values of wheels, the left wheel was chosen and KP value was

first set to 5 with no forward move, after which the mouse was programmed. Then the left

wheel was moved (rotated) with hand. Rotation was observed with two effects: firstly, the

wheels turned easily and secondly they became harder to rotate because of the controller

which tried to return the wheels back to the zero position. As soon as the wheel was

released after rotating it a little error occurred between the two positions (desired and

measured). After which the PD controller was used to correct the error by increasing the

duty which eventually made wheel return back very much closer to its original position.

Wait for PB1 or PB2

PB2

RUN

UPLOAD

Initial Position Rotated by 112 pulses. Duty rises to

560 to attempt to correct the error.

Released… error = 20. PWM drive

of 100 is insufficient to overcome

stiction.

RESET

s09466807 Page 12

After this the measured position is increased (made higher than the desired position) which

makes the duty go down and that compensates the overshoot in measured position. After

some time, they start stabilising, resulting which they compensate the effect of each other.

This leads in conducting a couple of experiments so that KP value can be attained as shown

below:

While the mouse on the bench (stand), using results given above the higher KP i.e. 20

causes the wheels to start oscillating whereas very low KP i.e. 4 gives an error in the “settle

down position”. The appropriate value for KP was chosen to be 5.

In order to convert a simple “Proportional Controller” to a “Proportional-Derivative Controller”,

the KD derivative gain factor is used where a constant amount of time is added to the

-1000

-500

0

500

1000

1

28

55

82

10

9

13

6

16

3

19

0

21

7

24

4

27

1

29

8

32

5

35

2

37

9

40

6

43

3

46

0

48

7

51

4

54

1

Calculating Steady-state Error

dpl mpl el duty

s09466807 Page 13

desired position at regular intervals (delta t). The two main advantages that “Proportional-

Derivative Controller” offers are that it damps the oscillatory response and improves the

rising time. The different KD and KP values were chosen to conduct a couple of experiments

to decide the best values. Mouse was placed both on the stand and on the Track (Bench):

It can be seen in the graph above that the duty starts to go down so that it can compensate

the overshoot of the measured position and also after some time they begin to stabilize so

that they can compensate the effect of each other. Higher overshoot occurs due to increased

value of KD and wheels start to oscillate because of increased values of KD. Hence in order

to reduce the steady-state error and overshoot, the values of KD and KP were increased

respectively. The best results achieved, as shown above, were made possible by changing

the values of KD, KP and BIAS. This stiction problem is resolved using an offset (bias value)

which is added to the motor drive.

The different derivative gains KD and proportional KP and bias value were tuned so that

oscillation and overshoot can be reduced to minimum. Different KD, KP and a fixed value of

Bias (Bias = 250) was used to draw graphs as shown below:

Overshoot

On the Stand

s09466807 Page 14

The derivative gains KP = 50, KD = 60 and BIAS = 250 were found to be the best for

Forward and Rotational Profile; therefore these values were used for demonstration in

laboratory.

Overshoot

Overshoot Oscillation

s09466807 Page 15

Speed Profiler

The speed profiler is a technique or method to see how the speed varied over a period of

time. Stepper motors are driven with open-loop profilers where “Stepper Profiler" sets the

time period for the next step. For this project DC servos are being used where “Servo

Profiler” tells the “Position Controller” what position the motor is required to be at by the next

timer interval (δt). The DC servo system uses a scheduler that runs at a specified time

period (δt). Speed is measured as the number of encoder pulses needed in that period

(pulses/ δt) and the acceleration is measured as the rate of change of speed (pulses/ δt/ δt).

Therefore it controls the speed and acceleration.

NextSpeed = CurrentSpeed + Acceleration

NextPosition = CurrentPosition + NextSpeed

For the measurement of acceleration, the profiler performs this calculation at each δt and

passes the “NextPosition” value to the controller. NextPosition is the “Desired Position”

which is calculated using the SUVAT equations that use distance, initial speed, final speed,

acceleration and time. The SUVAT equation being used here is v2 = u2 + 2*a*s which leads

to the calculation of the deceleration required to get to the end-point by allowing it to

determine when to start deceleration.

Figure 4 Speed Profiler Diagram, (Dr Wilcox, 2017)

A 4-cell profiled straight

The micro mouse has a differential-drive configuration that works by the use of two motors

which drive both the left and right wheels. Both the motors are operated by a power driver

and controller. Motor speed plays a vital role in determining the direction of the mouse. If the

speed of both the motors is not the same then mouse moves in an arc or takes a turn;

increasing speed of one motor can make the mouse move in an arc and increasing speed of

one motor while decreasing speed of the opposite motor at the same time makes the mouse

take a turn.

When decelerating

Final velocity (v) < Initial velocity (u). This gives negative acceleration i.e. deceleration.

Required deceleration >= specified deceleration

s09466807 Page 16

The graphs below show the speed of both wheels as they execute forward profile (on the

stand) with “acceleration” of 60 pulses/ δt/ δt and “maxspeed” of 30 pulses/ δt. The left

position and right position are slightly different.

The graphs given below show the speed of both wheels as they execute forward profile (on

the track) with “acceleration” of 60 pulses/ δt/ δt and “maxspeed” of 30 pulses/ δt.

Both the results (on “stand” and on the “track”) were taken after tuning the mouse with the

same parameters of KPL, KPD, BIAS forward distance and rotation factor. Both the graphs

are quite similar except a little difference in oscillation which is negligible.

A profiled 90 degree rotation

For 90 degree rotation, the “RotationalProfile” was developed which is shown by code in the

appendix. As already stated above, for rotation to take place one wheel’s maximum speed is

increased while the other wheel’s maximum speed is decreased. As the distance between

the two wheels is 76mm. This leads to a mathematical calculation of profiled 90 degree

rotation which was performed based on the calculation done in the section given above

“Mouse Position and Speed Measurement”.

Rotation

Deceleration

Acceleration

s09466807 Page 17

The circumference can be calculated by 2d (d=diameter) and applying this will give a

circumference of 76*pi = 238.8mm. For quarter of the circle as it’s a 90 degree rotation, it will

be 238.8/4 = 59.7. As for 0.18mm per pulse of the encoder, it will be divided by 0.18 so

59.7/0.18 gives 331.65.

Two graphs are taken, one while the mouse is on the stand and the other when it’s on the

maze track. The graph below illustrates the left and right positions and left and right speeds

and the average left and right speed. It is obvious from the graphs that the left (lpos) and

right (rpos) positions are in opposite direction (negative and positive) to each other that

makes the wheel perform a profiled 90 degree rotation.

Summary/Conclusion

The project as it was based on MyTEEmouse robotic platform was very interesting. The real-

time control software has been developed to give PD positional control of a mouse and it has

fulfilled all the major requirements of the assessment brief. The mouse ran very smoothly in

the maze and demonstrated accurate 90 degree rotations. Author has acquired Great

knowledge and exceptional understanding was gained regarding all parts of the mouse.

Skills and knowledge gained can be used to work on similar (embedded system design)

projects in future. Although it’s only a beginning and there is still a lot to learn in this vast

world of embedded robotics.

References

[1 – 3] Dr Wilcox, T. (2017). Embedded System Design. [online] icity.bcu.ac.uk. Available at:

http://moodle.bcu.ac.uk/pluginfile.php/996054/mod_resource/content/2/MyTEEmouseUserGuideV

1_4.pdf [Accessed 1 Jan. 2017].

[4] Texas, I. (2017). L293x Quadruple Half-H Drivers. [online] Texas Instruments. Available at:

http://www.ti.com/lit/ds/symlink/l293.pdf [Accessed 1 Jan. 2017].

[5] tech, t. (2017). What is EEPROM (electrically erasable programmable read-only memory)? -

Definition from WhatIs.com. [online] WhatIs.com. Available at:

s09466807 Page 18

http://whatis.techtarget.com/definition/EEPROM-electrically-erasable-programmable-read-only-

memory [Accessed 1 Jan. 2017].

[6] what, i. (2017). What is FRAM (ferroelectric RAM)? - Definition from WhatIs.com. [online]

SearchStorage. Available at: http://searchstorage.techtarget.com/definition/FRAM [Accessed 1 Jan.

2017].

[7] Dr Wilcox, T. (2017). Embedded System Design. [online] icity.bcu.ac.uk. Available at:

http://moodle.bcu.ac.uk/pluginfile.php/996054/mod_resource/content/2/MyTEEmouseUserGuideV

1_4.pdf [Accessed 1 Jan. 2017].

[8] what, i. (2017). What is processor (CPU)? - Definition from WhatIs.com. [online] WhatIs.com.

Available at: http://whatis.techtarget.com/definition/processor [Accessed 1 Jan. 2017].

[9] micro, c. (2017). PIC18F4523 - 8-bit PIC Microcontrollers. [online] Microchip.com. Available at:

http://www.microchip.com/wwwproducts/en/PIC18F4523 [Accessed 1 Jan. 2017].

[10] Dr Wilcox, T. (2017). Embedded System Design. [online] icity.bcu.ac.uk. Available at:

http://moodle.bcu.ac.uk/pluginfile.php/996054/mod_resource/content/2/MyTEEmouseUserGuideV

1_4.pdf [Accessed 1 Jan. 2017]

[11] what, i. (2017). What is USART (Universal Synchronous/Asynchronous Receiver/Transmitter)? -

Definition from WhatIs.com. [online] WhatIs.com. Available at:

http://whatis.techtarget.com/definition/USART-Universal-Synchronous-Asynchronous-Receiver-

Transmitter [Accessed 6 Jan. 2017].

Appendix

/* AJW 28/11/16

/* Zeeshan Ansari 20/12/2016

left and right pwm drive

left and right position measurement

10ms scheduler

PD Servo control on left and right motor

BIAS: correction for stiction

Data acquisition to FRAM if FRAM macro is TRUE

Exit from cyclic exec and close FRAM if PB2 pressed during run

Profilers added

*/

s09466807 Page 19

#pragma config

OSC=INTIO67,PWRT=ON,WDT=OFF,BOREN=OFF,MCLRE=ON,PBADEN=OFF

#pragma config CCP2MX=PORTC,STVREN=ON,LVP=OFF,XINST=OFF,DEBUG=ON

// System header files

#include <p18f4520.h>

#include <delays.h>

#include <timers.h>

#include <usart.h>

#include <stdio.h>

#include <pwm.h>

/************************** User header files ***************************/

#include "myteemouse.h"

#include "globals.h"

#include "initcore.h"

#include "controller.h"

#include "ledpb.h"

#include "FRAMfileIO.h"

#include "profiler.h"

/************************** Macro definitions ***************************/

#define FRAM TRUE

/************************** Function Prototypes **************************/

void DelaySeconds (unsigned char del);

/*************************************************************************/

/* Cyclic executive - MAIN program

/*************************************************************************/

void main (void)

{

unsigned char end_of_move,i;

s09466807 Page 20

InitCore(); // Setup Myteemouse

InitLEDPB(); // initialise I/O

RedLED(ON); // indicate ready

if (FRAM)

OpenFRAMwrite(); // redirect stdout if FRAM true

while (!PB1() && !PB2()); // wait for either PB1 or PB2

if (PB2()) { // PB2: calibrate then run

RedLED(ON);

if (FRAM) PrintFRAM(); // Upload stored data

GreenLED(OFF);

RedLED(OFF);

} else {

GreenLED(ON); // indicate running

DelaySeconds(1);

ZeroCounters();

RedLED(OFF);

printf("lpos rpos\r\n"); // Print header for data

// START RECTANGLE LOOP

for (i=0; i<4; i++) {

// MOVE 1: MOVE FORWARD 4 CELLS

SetFwdProfile(4030,FWD,60,30,0); // move forward 4 cells

do { // Do ... while not done

if (tick) { // 10ms timeout?

tick = FALSE; // clear scheduler flag

end_of_move = ExecMove();

printf("%5ld %5ld\r\n",left.current_position,

s09466807 Page 21

right.current_position);

}

} while (!end_of_move);

// END OF MOVE 1

end_of_move = FALSE;

// MOVE 2: ROTATE 90 DEGREES

SetRotProfile(328,CW,60,30); // rotate right (90 degrees)

do {

if (tick) { // 10ms timeout?

tick = FALSE; // clear scheduler flag

end_of_move = ExecMove();

printf("%5ld %5ld\r\n",left.current_position,

right.current_position);

}

} while (!end_of_move);

// END OF MOVE 2

end_of_move = FALSE;

}

// END RECTANGLE LOOP

CloseFRAMwrite(); // write EOF

SetDCPWM1(0); // pwm off

SetDCPWM2(0); //

RedLED(ON); // indicate HALT

}

while(TRUE); // loop

}

s09466807 Page 22

/*************************************************************************/

void DelaySeconds (unsigned char del)

{

unsigned int i;

for (i=0; i<10*del; i++) {

Delay10KTCYx(80); // 100ms delay

}

}

/*************************************************************************/