The design of the robot system is realized based on the embedded PC104 industrial computer and C8051F047 single-chip microcomputer

1. Introduction

High-voltage transmission lines and tower accessories are exposed to the field for a long time, due to the continuous mechanical tension, electrical flashover, material aging and other damage, such as broken strands, wear, corrosion, etc., if not repaired and replaced in time, the original small damage and defects may expand, and eventually lead to serious accidents. Therefore, power companies need to conduct regular inspections of line equipment, detect and evaluate early damage and defects in a timely manner, and arrange necessary maintenance and repair according to the assessment results, so as to ensure the safety and reliability of power supply. The traditional manual inspection method not only has a large workload but also difficult conditions, especially for the inspection of transmission lines in mountainous areas and large rivers, etc., there are great difficulties, and even some inspection projects are difficult to complete by conventional methods. Therefore, the use of robot automatic line inspection has become a necessary means to ensure the safe operation of high-voltage transmission lines.

The high-voltage transmission line patrol robot belongs to the research category of special robots, which mainly completes high-altitude operations such as non-destructive testing of high-voltage power supply cables, detection of insulation characteristics of overhanging insulators, transmission performance testing of transmission line accessories, mechanical connection firmness inspection, and cable foreign body removal. In 1988, Sawada and others of Tokyo Electric Power Company in Japan developed a fiber optic composite overhead ground line inspection mobile robot, which can crawl along the ground wire, and when encountering obstacles, it can be assisted by an arc arm to cross. Montambault and others at the Quebec Institute of Hydropower in Canada successfully developed a remote-controlled robot for power lines in 2000, which can eliminate ice accumulation on power transmission lines and can be used as a line inspection platform. The domestic research on transmission line patrol robots is still in its infancy, and only Wuhan Water Conservancy University, Shandong University, and the Chinese Academy of Sciences have done some research.

2. Robot Overview

Due to the many types of cable accessories and complex shapes of high-voltage transmission lines, obstacle crossing has become the primary function of the line patrol robot. The robot described in this article adopts three free-swinging booms to span the cable attachment, and swings three booms when encountering obstacles, so that the three booms pass through the obstacles in turn. As shown in Figure 1, the robot can crawl on high-voltage transmission cables such as quadruple split, di-split, and single-strand, and can autonomously span cable accessories such as overhanging insulators, isolation rods, anti-vibration hammers, wire clamps, etc., and has the detection function of transmission cables. The comprehensive performance indicators of the robot are as follows: 1) Body shape: 850×300×700mm; 2) Body weight: 45Kg; 3) Cable diameter adaptability Ф10-Ф25mm; 4) Moving speed: 0-25m/min; 5) Climb angle 0-30°; 6) Control mode: autonomous operation and master-slave remote control operation; 7) Fault handling: manual/automatic.

The design of the robot system is realized based on the embedded PC104 industrial computer and C8051F047 single-chip microcomputer

3. Design of control system

The control system of the robot is divided into two parts: the ontology control system and the ground monitoring system, as shown in Figure 2. The ontology control system is used to plan the motion trajectory of the robot, control the motion components of the robot, ensure that the robot can reliably and quickly cross obstacles, and realize the long-distance transmission of commands and data with the ground base station; The ground monitoring system realizes the manual/automatic control of the robot and monitors the stable operation of the robot. The design of automatic and manual control systems for the robot increases the flexibility and reliability of the robot, when one of the systems fails, another control system can be started, and in some special occasions only the manual system can be used, which reduces the difficulty of the robot's field operation and increases the applicability of the robot.

3.1 Design of robot body control system

The control system of the robot body is based on the embedded PC104 industrial computer, and is equipped with the input and output expansion board HT-750 and the A/D acquisition expansion board PM-516. Using PC104 as the core module allows you to focus on the design of software and interfaces, and PC104 is easy to develop, maintain and expand. PC104 is fully compatible with the general PC and PC/AT standards (IEEE P996), can quickly master the use of its software and hardware, and has special requirements for embedded control, providing a standard system platform for embedded applications.

3.1.1 Fault detection

There are many types of transmission cable accessories and complex shapes, which brings great difficulties to the robot to judge the type of obstacles. Therefore, it is necessary to carry a variety of sensors, integrate a variety of line fault detectors into the mobile platform of the line patrol robot, and use multi-sensor information fusion technology to improve the efficiency, precision and accuracy of fault detection. The main sensors are CCD vision module, infrared temperature sensor, ultrasonic sensor, etc.

The visual inspection CCD module uses the COM2 serial port on PC104 to identify various accessories of the high-voltage transmission line, finds the area where the target (anti-vibration hammer, insulator, connecting fittings, isolation rods and other accessories) is located from the original image, uses image processing technology to extract the feature size of the obstacle, automatically judges the obstacle type and distance on the transmission line, and provides obstacle crossing information to the robot motion control unit to form the next obstacle crossing strategy. In addition, visual inspection can generally find overhead line surface faults, such as transmission line surface damage, connecting fittings loose, etc.; The infrared temperature sensor uses the characteristics of the high-voltage transmission line to produce abnormal temperature rise at the fault point to detect the abnormal temperature rise of the cable. In this paper, PerkinElmer's A2TPMI-334 sensor is used to detect abnormal temperature rise in cables to detect cable faults.

3.1.2 Motion control

Due to the complex action of the robot, most of the boom line patrol robots adopt a multi-motor drive scheme, that is, 6 motors are used to realize the rotation of the swinging boom and the walking wheel. This scheme robot is more flexible, but the multi-motor increases the weight of the robot, which is not conducive to the balance of the robot itself. In this paper, two motors are used to realize the required action, the swing of the three booms is controlled by three electromagnetic clutches and the motor 1 in Figure 2, and the robot is controlled to walk by the motor 2. In order to increase the flexibility of detection, two liftable sensor brackets are added to the robot, which are driven by motor 3 and motor 4 respectively. The drive block diagram is shown in Figure 3, using a high-performance microcontroller C8051F047 from Silicon Lab and an H-bridge assembly LMD18200T to drive the motor. LMD18200T is the United States National Semiconductor Corporation (NS) launched a special H-bridge assembly for motion control, which integrates CMOS control circuit and DMOS drive circuit, with a peak output current of up to 6A, a continuous output current of 3A, a working voltage of up to 55V, and a temperature alarm and overheating and short-circuit protection functions. The continuous locked-rotor current of the motor selected in this paper is about 3A, so the selection of LMD18200T chips can meet the requirements of use.

Motor 1 and motor 2 use digital PID algorithm to regulate speed. The digital PID algorithm is a commonly used control algorithm, which compares the value of the photoelectric encoder at equal intervals with the given speed value, and changes the duty cycle of the PWM of the C8051F047 through the PID algorithm to realize the closed-loop control of the motor, namely:

The design of the robot system is realized based on the embedded PC104 industrial computer and C8051F047 single-chip microcomputer

　　(1) where Kp is the scale coefficient, Ki is the integration coefficient, Kd is the differential coefficient, and T is the sampling period. The motor 3 and the motor 4 are only used to control the lifting of the support, and there is no specific requirement for speed, so only the number of encoder pulses needs to be collected.

3.1.3 Data Transfer

When the robot crawls, it should send its own status information, collected data, captured pictures and other information to the monitoring system; In special cases, the monitoring system also sends instructions to the robot, which requires the transfer of data between the two. The design transmission distance is 2Km, and a pair of wireless data transmission modules SRWF-108 are used to complete this function. The SRWF-108 of the robot body occupies the COM1 port on PC104, with a baud rate of 9600bps, 8 bits of data, and three formats: status frame, instruction frame and file frame.

3.1.4 Power supply design

The line patrol robot works at high altitude and can only use its own power supply. In this paper, 4 12V lead-acid batteries are used, and the power conversion chips such as B1205S, B1212S, and LM2678 are used to obtain the +12V, ±5V and other levels required by the system. In order to ensure that the robot has sufficient energy, it is necessary to monitor the battery power, this paper uses DS2438Z chip, the DS2438Z chip is a new generation of intelligent battery monitoring chip launched by DALLAS company, which has the advantages of powerful function, small size, low price, etc., and uses 1-Wire bus to transmit data, hardware wiring is simple, can be used to detect battery temperature, voltage remaining power and other parameters. When the battery is found to be insufficient, the robot body will send an alarm to the monitoring system to prompt the battery to be replaced.

3.1.5 Control system software

The software of PC104 control system is programmed in C language, which has a short development cycle and high efficiency. The program needs to realize the functions of data acquisition, system status detection, serial communication, action output, fault handling, abnormal situation handling, power supply monitoring, etc., and its program flow diagram is shown in Figure 4. The data transmission with the monitoring system can be queried or interrupted, the advantage of the query mode is that it is easy to program, but it will occupy more system resources, and the interrupt mode is the opposite. In addition to serial communication, the robot also needs to complete motor control, fault handling and other functions, so the query method is not suitable to be used, and the interrupt mode is used in this article. Initialize the COM1 and COM1 interrupt handlers [5] as follows:

void InitCOM() /* Initialize the COM1 serial port and set the serial port parameters*/

｛ outportb（0x3fb，0x80）; /*will set the baud rate*/

outportb（0x3f8，0x0c）; /*Baud rate 9600*/

　　outportb（0x3f9，0x00）;

outportb（0x3fb，0x03）; /*8 data bits, 1 stop bit, no parity*/

outportb（0x3fc，0x08|0x0b）; /*Set MCR*/

outportb（0x3f9，0x01）; /*on-interrupt*/}

　　void interrupt far asyncint（）

　　｛ char ch;

ch=inportb（0x3f8）; /*ch is the received character data */

　　…… ……｝

3.2 Design of the monitoring system

The monitoring system is developed with Visual Basic 6.0 software, VB has the advantages of object-oriented visual design tools, event-driven programming mechanism, powerful database manipulation function, Active technology and application integrated development environment. According to the requirements of the robot system, a more complete monitoring system has been developed by adopting the idea of modularization, which has strong scalability, and has the functions of battery power monitoring, motion status monitoring, cable fault database query, manual automatic switching, etc. You can save the fault information of the power transmission line in the Access database, and query the fault type and time.

4. Conclusion

In this paper, a robot control system with PC104 module as the core is proposed, which solves the problem of autonomous obstacle crossing of the robot, and can identify some cable accessories, carry out wireless data transmission, check the cable condition, etc., and provide convenience for the automatic detection of high-voltage transmission lines.

This article is from: Electronics Enthusiast