COMPONENTS USED
Stinger Base Kit
MBED microcontroller
Micro SD Card & Adapter
SRF05 SONAR Rangers
VS1053 MP3 Decoder
CMPS03 Electronic Compass
HS-322HD Servo
COM Port
IR Distance Sensors
BLOCK DIAGRAM AND OPERATION
Figure 1: Block diagram of Seeing i-Robot
The working of the robot mainly involves three operations:
1.Sensing
2.Control signal generation
3.Control of the robot
Sensing
SONAR rangers are mainly used to sense any obstacle on the path of the robot. In order to make sure that the robot detects obstacles at the floor level as well as obstacles that are raised at a height, two sonar rangers have been used. One sonar ranger is mounted such that it’s beam is parallel to the floor whereas, the other ranger makes an angle of around 60 degrees with the floor. This ensures proper sensing.
Control Signal Generation
Once the MBED receives the sensor data from the sensors, it processes them to decide the angle at which the robot should make a turn inorder to avoid the obstacle. The MBED also controls the servo on which the sensors are mounted.
Control of the robot
Serial COM port has been used to communicate with the motors in the Stinger robot base. Depending on the position of the obstacle detected and availability of free space, the robot is instructed to move or turn.
Operation
The SONARs continuously sense for any obstacles on the robot’s path. If an obstacle is detected, the servo on which the SONARS are mounted is rotated. If a free path is found, the stinger robot is directed to turn in that direction and move. While it moves, the servo continuously searches whether the obstacle has been crossed. Once it has been crossed, the MBED directs the stinger robot to turn, so that it can head back in the original direction. At each move, the robot gives instruction for which an MP3 decoder has been used which decodes files stored in a SD card using an adapter.
ALGORITHM
if( no obstacle detected )
Go straight
else if( obstacle detected at least three times )
Stop
if( free path found around the obstacle )
Turn and move along the path until the obstacle has been bypassed
Get back to original path
ISSUES FACED
LV-MaxSonar-EZ1 from MaxBotics were unreliable
Positioning of sensors in order to have better coverage
Detecting obstacles at a height
Maintaining direction while avoiding obstacle
Controlling the speed of motors in the Stinger robot kit
FUTURE WORK
Read MP3 files from MBED’s local memory
Integrate GPS for outdoor navigation
Voice commands by user
Detecting walls when the robot approaches it at an angle greater than the critical angle
Improve obstacle avoidance
