eod-robot

Imperial College London | Mechanical Engineering | Embedded Control for Microcontrollers (ECM) 2019-2020 | Explosive Ordinance Disposal Robot

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Overview

Authors: Lim Siew Han & Justin Kek

IDE: MPLAB X IDE v4.20 Compiler: XC8 (v2.00) Microchip: PIC18F4331 Programmer: PICkit3

School: Imperial College London | Department: Mechanical Engineering | Module: Embedded C for Microcontrollers | Class: MEng Graduating 2021

Instructor: Dr Ravi Vaidyanathan | Due Date: 10 December 2019 | Last Updated: 9 December 2019 1300 |

Description: The given objective was to design code to drive a vehicle from a given start position towards a beacon which emits
50 ms infrared (IR) pulses every 250 ms. The vehicle should then collect information from a radio-frequency identification (RFID) card and display it upon returning to its initial position. The vehicle consists of two IR sensors, one RFID sensor, and a liquid crystal display (LCD) screen. The IR sensors are front facing and positioned side by side in the middle. Each IR sensor is isolated from the other by a cardboard tube with an inner lining of aluminium foil. The RFID sensor is wired below the IR sensors and suspended by a cantilever arm to match the length of the isolation tubes. The IR and RFID sensors are held together by a 3D printed housing made from polylactide (PLA).

Input: IR sensor signal, RFID signal

Output: RFID information on LCD screen

Main File: main.c

Source Files: functions.c, dc_motor_funct.c, lcd_funct.c

Required Features Not Included: The program adheres to all requirements

Known Bugs:

After fresh run, upon entering standby mode, motors run at full speed
- Attempted solutions: Using stop_all() in standby loop

Improvements for future work:

When RFID is retrieved, steering may not stop immediately as it depends on when the interrupt stops the main program (i.e., if interrupt triggers within __delay_ms(), delay continues running before exiting loop.
- Solution: Write new function delay_ms() which incorporates a conditional while loop to delay only when RFID is not not retrieved. For example:
```
      delay_ms(&G_rfid_retrieved, &G_time_ms, 400);
      void delay_ms(unsigned char *flag, unsigned int *time_ms, 
         unsigned int delay) 
      {
        *time_ms = 0; // reset timer
        while ((*flag == 0) | (*time_ms < delay));
      }
```

Program Flowchart

Main Flowchart

Initial Centering Flowchart

Method by which the robot locates and determines the general direction of the explosive device.

Steering Flowchart