How the SmartCAR2.0 ultrasonic sensor works
The ultrasonic sensor in SmartCAR2.0 consists of a receiver and a transmitter on a board. The transmitter sends out ultrasonic waves, and the receiver picks up the data reflected back from obstacles. This ultrasonic sensor detects obstacles and enables autonomous obstacle finding. This chapter will continue to share the structure and operation of the ultrasonic sensor in SmartCAR2.0 .
This ultrasonic sensor detects obstacles by transmitting ultrasonic waves that are reflected back to the obstacle and the distance to the obstacle is determined by calculating the return time. The ultrasonic sensors are mounted on the front and rear of the vehicle-shaped robot. When the robot moves forward or backward, obstacles in both directions can be detected. The table below shows the specifications of the ultrasonic sensors installed on the SmartCAR2.0 vehicle-shaped robot .
Table 11-2-1 | Specifications of SmartCAR2.0 Ultrasonic Sensor
The image below shows the shape and Transduder characteristics of the ultrasonic sensor installed in the SmartCAR2.0 vehicle-shaped robot .
Figure 11-2-1 | SmartCAR2.0 Ultrasonic Sensor Appearance
The ultrasonic sensor drives two TXD lines at different locations in the transmitter to simultaneously drive the ultrasonic sensor transmitter, transmitting signals at 40kHz. Therefore, the signal generated and transmitted into the AT91SAM3X8EA is relayed to the transmitter, where the ultrasonic sensor emits ultrasonic waves. The receiver receives the reflected signal and calculates the presence and location of obstacles in front, behind, and behind it.
In other words, the 40kHz clock signal in reverse direction within the TXD line of the ultrasonic sensor's receiving unit is multiplied by 7-8. The waveform is then amplified by the UART (MAX232) to the RS232 level, and the ultrasonic sensor's transmitting module receives a request to transmit the ultrasonic wave. The transmitted ultrasonic wave, reflected by an obstacle, is transmitted to the receiving unit. The waveform received by this sensor is amplified by an OP (amplifier), and the waveform generated by analyzing the voltage is transmitted via an AVR. The diagram below shows the circuit diagram of the ultrasonic sensor mounted on a vehicle-type robot.
The ATmega16U2 communicates with the main MCU (AT91SAM3X8EA) via serial port to determine the defined values. The ultrasonic sensor installed in the SmartCAR2.0 vehicle-shaped robot can measure distances within 4cm to 50cm. Measurements beyond this distance will result in sensor value errors.
The SmartCAR2.0 is equipped with three forward-facing ultrasonic sensors, two rearward-facing sensors, and one on each side. The SmartCAR2.0 also features lithium battery level detection.
