1. Two-legged self-balancing System
Sponsored by UVATT
Supervisor: Stephen Neville
Robert Prinz
Mark Kuoppola
Tifenn Vialatte

2. Tilt Sensor Single axis (1-D) Output: analog (0 to 5V)
Zero Angle Voltage = 2.5V
Sensitivity = 35 mV/˚

3. H-bridge Motor Speed Controller
Average voltage across armature changes as the duty cycle changes.
Direction of the motor can be changed by switching the polarity of the armature (by switching the corresponding MOSFETs).
FORWARD
MOSFET
State Q4 ON Q2
OFF Q1
PWM Q3
REVERSE

4. Overall System Block Diagram
Serial Cable
Tilt Sensor
MC 1488
Serial Input Buffer
Real-time operation
Matlab
Fuzzy logic controller
Arc 1489
Serial Output
Motor Controller
LED display
A-D converter
TTL Serial Data
Output process
PIC Processor
Computer
Port C
RB7 – RB4
Input 1: Tilt
Output 1: Duty-cycle

5. Fuzzy Logic Controller
Solution 1
Classical inverted pendulum: 2 inputs, 1 output
Membership functions:
Inputs: Tilt in degrees, change of tilt
Output: motor duty cycle
Solution 2 (selected for testing)
Similar to fuzzy air conditioning system
Membership functions:
Input: Tilt in degrees
Output: motor duty cycle P Z N PB NB

6. Fuzzy Logic Controller (Cont’d)
Overall controller Layout
Membership functions
Tilt
Motor duty cycle
Rules
Rules in action

7. Serial Port Communication
+12V
0 V
-12V
Start ……. 7 Stop
TTL  RS232 ; RS232  TTL
MC1488:RS232 line driver
MC1489: RS232 line receiver
TTL
5 V
0 V
Start ……. 7 Stop
Bit Bit
Logic
TTL
RS232
<1.2V
>+3V 1
>3.3V
<-3V
Interrupt on RB0
Rotate right through carry

8. Membership functions: initial conditions established
System Path: Overview
PIC sends tilt value to computer
MC 1488 TTL to RS232 Converter
A-to-D on PIC
Tilt
Serial Data Transmission
Membership functions: initial conditions established
Input to Matlab Fuzzy Inference System (FIS)
Received bytes buffer on computer
Value read from buffer
Union of consequents defuzzified (centroid method)
Union of fuzzy consequents fired by rules
Output value saved to motor-duty
Output to RS232 Serial cable
MC1489 RS232 to TTL converter
External interrupt input on PIC processor
PIC duty cycle values updated then output to motor controller
Motor controller H bridge pulsed at duty cycle
New tilt
To beginning

9. System Path: Input Side
PIC
PIC MC
1488
Converts TTL signal to RS232 Data stream
Data
Comm
Tilt variable digital serial data stream generated
8-bit resolution
Tilt voltage correspond to 8-bit value between 0 and 255
Serial Cable
Tilt value
PIC MC
1488
Motor Duty
Initial Conditions
Fuzzy Inference System

10. System Path: Output SideMC
1489
PIC
Serial Cable
Quad line receiver
Converts RS232 to TTL data stream
External Interrupt on falling edge of start bit
RS232 Signal of motor-duty
PIC
Data Comm
Duty cycle input to transistor controlling the H-bridge
Start bit ignored
Data bits sampled and saved
Wheels turn, aligning robot