In the complex industrial production workshop environment, the robot can complete the workshop environment monitoring task well through the complex workshop environment, and return the environmental data to the host computer through the wireless Wi-Fi module, providing an effective workshop unmanned monitoring scheme, improving the work efficiency and ensuring the safety of personnel and equipment. In the chemical industry, food industry, textile industry, in order to ensure the storage environment, process, equipment performance, etc., there are certain requirements for environmental conditions, it is necessary to monitor the environment of the workshop to ensure the normal production activities. In some industries, workshops may produce some pollutants that cause damage to personnel health and equipment, and it is also necessary to monitor these pollutants. In order to solve the above problems, an intelligent environment detection system based on STM32 and Aliyun is designed, but its acquisition node is relatively fixed and not flexible enough. An intelligent vehicle for environmental information collection is designed, but its chassis uses tracks, its moving speed and efficiency are low, and its large volume is not suitable for the workshop environment. Using sensor network to monitor, a large number of sensors and server systems need to be deployed, and the cost is high, which is not conducive to promotion. In order to solve the above problems, this paper designs a workshop environment monitoring robot based on ARM core microprocessor. The robot uses a two-wheeled balanced chassis, which has the advantages of high efficiency, flexibility, fast moving speed and strong passing performance. The robot is equipped with a gas sensor module, a temperature and humidity sensor module, a camera and Wi-Fi map transmission module, and an attitude sensor module. The robot overcomes the above shortcomings, has strong practicability, and provides a guarantee for industrial production. 1 Overall system design The overall structure of the robot system is divided into hardware layer and software layer. The hardware layer includes motion layer, control layer, communication layer and perception layer. The perception layer mainly includes various sensors to monitor and collect environmental information, the control layer is a microcontroller based on the ARM core, the motion layer includes the chassis motor of the robot movement, and the communication layer is a Wi-Fi graph transmission module. The main control of the robot system uses STM32F407 processor based on ARM core. This series MCU has rich peripheral interfaces and on-chip resources, outstanding low power consumption performance and rich development routines. MCU is responsible for communication and control with all levels of robot hardware. It includes robot motion control, motor current command sending, gas sensor, temperature and humidity sensor data collection and processing,Wi-Fi module data upload control. Data acquisition and processing of body attitude sensors. 2.1 Power Module Design The system needs three kinds of power supply of 3.3V, 5V and 24V, so the 24V lithium polymer battery is used as the power source of the robot system. The power supply of the system is divided into three levels: 24 V power input, TPS54540 synchronous buck 5 V power supply, MT2492 synchronous buck 3.3 V power supply. MT2492 is A synchronous buck converter developed by Xi 'an Aerospace Mincore Co., Ltd. with an output current of 2 A, and the output voltage is configured through the feedback resistance network. According to the calculation formula provided in the data manual, the feedback resistance network is configured as RHS = 67.5 KΩ. RLS=15ΚΩ.2.2 Attitude sensor Module design The robot uses a balanced chassis, in order to keep the chassis balanced and upright, the robot chassis attitude needs to be measured. The attitude sensor module uses the MPU6050 chip for attitude detection. The chip is InvenSense's IMU (inertial measurement unit) product, which can simultaneously detect three-axis acceleration, angular velocity motion data, and temperature data. The official DMP library can be used to process the sensor data, and the Euler Angle of the three axes can be calculated directly through the motion data of acceleration and angular velocity, and the attitude data of Yaw, Pitch and Roll of the chassis can be directly obtained. After the DMP unit of the chip completes the calculation of attitude data, it will trigger the interrupt of the microcontroller through the INT pin, and then send the data to the microcontroller through the 12C interface, and receive the attitude sensor data in the interrupt service function. 2.3 Gas sensor module Design The robot has the function of harmful gas detection, which can monitor the concentration of harmful gas in the workshop in real time. MQ135 gas detection module is used for harmful gas detection. The gas sensing material used in this sensor is tin dioxide (SnO2), which has a low conductivity in clean air. When there is pollution gas in the environment where the sensor is located; The conductivity of the sensor increases with the increase of the pollutant gas concentration in the air. The MQ135 sensor has high sensitivity to nitrogen, sulfide and benzene vapors, and is also ideal for monitoring smoke and other harmful gases. The change of conductivity can be converted into a digital signal corresponding to the gas concentration through the integrated gas sensor module detection circuit, and the trigger threshold is set through the potentiometer. When the harmful gas concentration exceeds the threshold, the module outputs a high level, and the single-chip microcomputer directly reads the module signal output through 10.
2.4 Temperature and humidity sensor module design In order to ensure the production needs and monitor the temperature and humidity of the workshop, the robot is equipped with DHT12 temperature and humidity sensor module, which is a digital signal output sensor integrated with a microprocessor. The temperature sensor, humidity sensor and an 8 bit high performance microcontroller are integrated in the sensor. The sensor element includes a capacitive humidity sensing element and an NTC temperature measuring element. The module uses the integrated microprocessor internal analog-to-digital converter for data acquisition, data output through the 12C interface. The sensor module has low cost and can perform relative humidity and temperature measurement simultaneously, which greatly reduces the production cost of the robot. The robot needs to be remotely controlled and data uploaded. Considering that the robot works in the workshop environment, the Wi-Fi camera graph transmission module is selected to upload the images collected by the camera and the robot data at the same time. The camera image transmission module uses ESP32-CAM, the module is based on ESP32 microprocessor, the processor computing power of up to 600DMIPS, the module integrates Wi-Fi image transmission, serial port transmission and camera, can directly view the image and upload data in the host computer software. The module adopts 802.1.1 communication standard, and the transmission speed can reach 150 Bit/S. The module uses 5 V power supply, the serial port baud rate is set to 115 200, and the robot sensor data is uploaded through the serial port for transmission. When in use, the client is connected to the wireless hotspot of the module and the corresponding client of the module is started. The data is transmitted directly in the form of string, and the refresh frequency is 20 Hz, which not only ensures the real-time performance of data upload, but also avoids taking up too much upload channel bandwidth. In the data uploaded by the serial port, /N is the starting bit of the data, "harmful gas", "temperature", "humidity" is the data name, and the data name followed by a number is the value of the data. The software of the robot system includes the initialization program, the sensor data acquisition program, the host computer data upload program, the remote control program, and the chassis control program. Because the robot software contains multiple threads, the software system is developed based on Freertos. Through the time slice scheduling function of Freertos, the parallel processing on the millisecond time scale is realized. The software initialization program initializes each peripheral of the MCU, makes each sensor enter the working state, initializes Freertos, and runs each thread. The sensor data acquisition program processes the data collected by each sensor and sends it to the host computer through the serial port after processing it into a string. The remote control program will set the motion state of the robot chassis through the data collected by the serial port to realize the motion control of the robot chassis. The chassis control program controls the movement of the chassis through the chassis controller. The balanced chassis uses the chassis controller to control the motion of the chassis. In order to ensure the performance and stability of the chassis, the combination of sliding mode control and PID control is adopted. The chassis controller uses the sliding mode controller to stabilize the Angle of the balanced chassis, and the PID controller to stabilize the speed of the balanced chassis. The sliding mode controller and the PID controller compose a cascade structure. The digital PID controller can be obtained by the discretization of the PID controller in the continuous domain, and the trapezoidal method is used here to obtain the discretization. 4 Workshop environment monitoring robot test In order to verify the overall function and passing performance of the robot, the laboratory environment was selected to verify the robot function. The passing performance of the robot is first experimented. The road environment of the workshop is simulated, and a drop with a height of 150 Mm is set on the forward path of the robot. The observed robot motion attitude is shown in Figure 6: Robot posture through the drop when the robot passes through the drop, due to the interference of the drop, the posture of the robot is offset, and it quickly recovers the upright and stable state after touching the ground. The data acquisition function of the robot was tested. After the robot is powered on, the robot is placed in the laboratory environment for testing, and the connection between the system and the host computer is established through the Wi-Fi module, so that the data acquisition and upload functions of the robot are in normal working state. The returned data collected in the host computer is shown in Figure 7:
The sensor data collected by the host computer is transmitted back to the host computer of the robot through the serial communication function of the Wi-Fi module, and the environmental data collection and upload function is realized. Based on the ARM core microprocessor, the software and hardware system of the workshop environment monitoring robot is designed. The experimental results show that the robot chassis has strong passing performance and can adapt to the complex workshop environment. The robot can measure environmental data through the sensors carried on it, and can return the collected data in time to complete the workshop environmental monitoring task. It has strong practicability, meets the environmental monitoring needs in the workshop of industrial production process, and provides a guarantee for industrial production.
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