Autonomous Robot Design: Sensor Mechanisms and Control Loops
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Autonomous Robot Behaviors and Sensor Mechanisms
Robot Light-Seeking Mechanism (Initial Description)
When the robot is connected, one motor begins to rotate forward and the other remains stationary. Therefore, the robot turns on itself (1). When the front light sensor detects a light source or a clear zone (such as a flashlight, a white wall, or a window), the motor activates, causing the robot to move toward the light (2). If the robot detects no light, the sensor monitors the motor stops, and the robot starts to spin again until it detects light.
Robot Crawler (Line Follower)
When the robot is placed on a white surface, the high-brightness Light Emitting Diodes (LEDs) reflect light, which is detected by the Light Dependent Resistors (LDRs). The transistors become saturated, and the activated relays cause both motors to rotate, moving the robot forward.
If one of the sensors is placed over a black line, the corresponding LDR no longer receives reflected light. The corresponding transistor goes to cut-off, the relay is deactivated, and the motor next to that sensor reverses direction. This correction adjusts the robot's path.
Robot Obstacle Avoidance (White Wall Detection)
If the robot has no obstacle in front, both wheels rotate forward and the robot moves (1). In this state, infrared (IR) radiation reaches the receiver.
When the robot approaches a white wall, the infrared sensor detects the signal reflected from the wall (2). The control circuit then reverses the direction of rotation of the motor on the opposite side, causing the robot to change direction. Note: If the wall is dark, the infrared radiation will not be reflected, and the robot will run into it.
Detailed Light-Seeking Robot Operation
- No Light Detected: When neither sensor detects light, the robot moves backward. If a light source (like a lantern) is introduced, the robot moves toward the light.
- Right Sensor Detects Light: When only the right sensor detects light, the motor reverses direction opposite the turn, causing the robot to turn toward the right and head toward the light.
- Both Sensors Detect Light: As the robot turns, both sensors eventually detect light. The right motor reverses its direction of rotation, causing the robot to move forward, seeking the light source.
- Left Sensor Detects Light: If only the left sensor detects light, the right motor turns forward and the left motor reverses. The robot then moves left.