Embedded-based robot system circuit module design

Robots have many actions and functions to implement and require multiple sensors to detect the outside world and control the robot's position, movements and operating status in real time. All tasks in the system are ultimately run on the real-time operating system μC/0S-II, so not only the internal resources of the microcontroller must be considered, but also its portability and scalability. LPC2129 is a 32-bit arm7TDMI-S microprocessor produced by Philips Company. It is embedded with 256 KB high-speed Flash memory. It uses 3-stage pipeline technology to fetch, decode and execute instructions at the same time, and can process instructions in parallel to improve the CPU efficiency. Running speed. Because of its very small size, extremely low power consumption and strong anti-interference ability, it is suitable for various industrial controls. It has 2 32-bit timer counters, 6 PWM outputs and 47 general-purpose I/0 ports, so it is especially suitable for industrial control and small intelligent robot systems with lower environmental requirements. Therefore, by choosing LPC2129 as the main controller, an intelligent robot control system with simple design structure and stable performance can be obtained.

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 is separated by the capacitor C2 to remove the DC amount in the signal and is given to the ultrasonic transducer MA40S2S. Its working process: U1A and U1B generate The high-frequency voltage signal corresponding to the ultrasonic frequency 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 for ultrasonic emission. If DC voltage is applied to the ultrasonic transducer for a long time, its characteristics will be significantly deteriorated, 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 an integrated operational amplifier LM324. After three levels of 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.

Photoelectric detection module design

Design a photoelectric detection module to enable the robot to detect white guide lines on the ground. The photoelectric detection circuit mainly includes a transmitting part and a receiving part, and its principle is shown in Figure 3. The waveform modulation of the transmitting part adopts frequency modulation method. Due to the fast response speed of light-emitting diodes, their operating frequency can reach several megahertz or more than ten megahertz, and the modulation frequency of the detection system is in the range of tens to hundreds of kilohertz, so it can meet the requirements. The light source driver is mainly responsible for amplifying the modulation waveform to enough power to drive the light source to emit light. The light source uses an infrared light-emitting diode, which has a high operating frequency and is suitable for modulated light emission with a square wave waveform.

The receiving part uses photosensitive diodes to receive modulated light and convert the optical signal into an electrical signal. This electrical signal is usually weak and needs to be filtered and amplified before it can be processed. The modulated signal is amplified in the form of AC amplification, which can separate the modulated light signal from the background light signal, providing convenience for signal processing. The modulated signal processing part identifies the amplified signal and determines the characteristics of the detected object. Therefore, the essence of this module is to separate the "AC" useful modulated light signal from the "DC" useless background light signal to achieve the purpose of anti-interference.