Circuit design of embedded robot control system based on wireless communication

Wheeled mobile robot is an important part of the field of robot research. It integrates machinery, electronics, detection technology and intelligent control. It is a typical intelligent control system. The intelligent robot competition integrates high technology, entertainment and competition, and has become a high-tech confrontation activity widely carried out internationally.

Wireless communication interface design

The system uses the PTR2000 wireless communication data transceiver module produced by Xuntong Company. The circuit interface is shown in Figure 2. This module is developed based on the radio frequency device nRF401 produced by NORDIC. Its characteristics are: ① There are two channels to choose from, and the operating rate is up to 20 Kb/s; ② The reception and transmission are integrated, suitable for duplex and simplex communication, so the communication method Relatively flexible; ③ Small size, less peripheral components required, simple interface circuit, so it is particularly suitable for miniaturization requirements of robots; ④ Can be directly connected to the microcontroller serial port module, simple control; ⑤ Strong anti-interference ability; ⑥ Low power consumption, stable communication.

Design and implementation of ultrasonic ranging sensor

The two ultrasonic sensors are used to control the robot to avoid obstacles, predict the distance of the robot relative to the destination, and play a navigation role. The receiving part is connected to the capture and timing pins of the microcontroller. The entire ultrasonic detection system consists of ultrasonic transmitter, ultrasonic receiver and microcontroller control. The transmitting part consists of a high-frequency oscillator, a power amplifier and an ultrasonic transducer. After being amplified by a power amplifier, ultrasonic waves are emitted through an ultrasonic transducer.

Figure 5 shows an ultrasonic oscillation circuit composed of digital integrated circuits. The high-frequency voltage signal generated by the oscillator passes through the capacitor C2 to remove the DC content in the signal and feeds it to the ultrasonic transducer MA40S2S. Its working process: U1A and U1B generate a high-frequency voltage signal corresponding to the ultrasonic frequency. This signal is converted into a standard square wave signal through the inverter U1C, and then amplified by power. C2 isolates the DC signal and then adds it to the ultrasonic transducer. MA40S2S performs ultrasonic emission. If DC voltage is applied to the ultrasonic transducer for a long time, its characteristics will significantly deteriorate, so the AC voltage is generally treated with DC isolation. U2A is a 74ALS00 NAND gate, and the control_port (control port) pin is the control port. When control_port is high level, the ultrasonic transducer emits ultrasonic signals.

Figure 6 shows an ultrasonic wave receiving circuit. The ultrasonic receiving transducer is MA40S2R, and the signal received by the transducer is amplified by the integrated operational amplifier LM324. After three-stage amplification, the sinusoidal signal is converted into a TTL pulse signal through the voltage comparator LM339. INT_Port is connected to the interrupt pin of the microcontroller. After receiving the interrupt signal, the microcontroller immediately enters the interrupt and processes and judges the ultrasonic signal.

The overall design is carried out according to the functional requirements of the competitive robot, and each function is modularized. The hardware block diagram of the control system is shown in the figure. The central processing unit adopts a microcontroller structure to control the coordinated operation of peripheral devices. The steering gear controls the movement direction of the robot; the drive motor uses a small DC motor with an output shaft equipped with a photoelectric encoder to drive the wheel rotation. Electromagnets serve as actuators for robot clamping. It is equipped with two ultrasonic sensors, 8 photoelectric detection inputs and 8 switch detection interfaces.