刘军, 袁俊, 蔡骏宇, 陶昌岭, 王利明, 程伟. 基于GPS/INS和线控转向的农业机械自动驾驶系统[J]. 农业工程学报, 2016, 32(1): 46-53. DOI: 10.11975/j.issn.1002-6819.2016.01.006
    引用本文: 刘军, 袁俊, 蔡骏宇, 陶昌岭, 王利明, 程伟. 基于GPS/INS和线控转向的农业机械自动驾驶系统[J]. 农业工程学报, 2016, 32(1): 46-53. DOI: 10.11975/j.issn.1002-6819.2016.01.006
    Liu Jun, Yuan Jun, Cai Junyu, Tao Changling, Wang Liming, Cheng Wei. Autopilot system of agricultural vehicles based on GPS/INS and steer-by-wire[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(1): 46-53. DOI: 10.11975/j.issn.1002-6819.2016.01.006
    Citation: Liu Jun, Yuan Jun, Cai Junyu, Tao Changling, Wang Liming, Cheng Wei. Autopilot system of agricultural vehicles based on GPS/INS and steer-by-wire[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(1): 46-53. DOI: 10.11975/j.issn.1002-6819.2016.01.006

    基于GPS/INS和线控转向的农业机械自动驾驶系统

    Autopilot system of agricultural vehicles based on GPS/INS and steer-by-wire

    • 摘要: 研究旨在设计出一套农用车辆自动导航控制系统,让机器人代替农民进行田间作业,实现农用车辆自动驾驶,从而可以有效提高农业机械的作业精度、生产效率和使用安全性,并且为精细农业研究提供技术支持,改善农业生产的方法。该文通过GPS/INS(global positioning system/ inertial navigation system)组合导航技术实时获得载体的导航信息(位置、速度、航向、姿态),根据导航信息与预设轨迹参数计算出载体的目标前轮转向角,并以该目标前轮转向角与当前前轮转角的差值作为控制输入,实现对转向执行电机的精确控制,从而实现载体的路径跟踪控制。同时对整个系统的软硬件进行设计,并对系统控制策略进行仿真和试验验证。最终结果表明,本文所设计的组合导航系统定位精度高,其定位精度可达到0.1~0.5 m;路径跟踪系统误差小,当车速分别为0.5 m/s和1 m/s时,路径跟踪的最大横向误差分别为0.16 m和0.27 m ;整个系统响应速度快,可达到0.1s。通过将GPS/INS组合导航技术与线控转向技术相结合,能够实现农用车辆的自动驾驶。

       

      Abstract: The application of the path tracking technology on agricultural vehicle makes the robot replace farmers for field operation, and the accuracy, production efficiency and dependability about farming automation are improved effectively.Meanwhile the labor time, labor intensity of drivers and the production cost are saved.The path tracking of agricultural vehicle was studied in an operating condition, and a variety of sensors were installed on the car features of the external environment.Then it generated a four-element in state space by the target path which was given for controling the agricultural vehicles to track the target path automaticly according to the theory of optimal navigation control.The location method of GPS/INS was selected, the navigation system was developed, and the experiment was finished in 2014.According to the needs of automatic walking positioning system, a variety of sensors has been chosen, including the inertial sensor, angle sensor and GPS sensor.Then the serial program was writen to collect the signal from the sensors and calibrate them.In order to meet the requirements of vehicle navigation system, the positioning system with low cost and high precision was developed.The hardware of the system consisted of two GPS modules, two Zigbee wireless transmission modules and an inertial sensor.The data from the sensors are filtered and fused, and finally accurate, reliable vehicle position data was got.The tracking controller based on preview control was designed to obtain the future values and target values of the vehicle.With the target path and its curvature, the feed forward control value was got.There was an error between the current state and the state of vehicle target path that was needed to use LQR for elimination.The performance of the path following controller was simulated by Matlab, then the maximum lateral error was 0.16 m and 0.27 m at the speed of 0.5 m/s and 1 m/s respectively.The results showed that the control method was feasible.The steering control system was designed based on steer-by-wire(SBW) after the study of vehicle navigation control principle.SBW removed out mechanical connection between steering wheel and steering front wheel.It used motors to control front wheel angle and simulated force characteristic.Compared with traditional steering system, SBW had characteristics of ideal steering ratio and active steering control according to vehicle state parameters, and improved safety of driving and handling stability.The strategy of BLDCM was designed in order to make actual front angle follow the desired angle better.PID control and sliding mode variable structure control were applied in strategy of BLDCM and the result of simulation showed that sliding mode variable structure control was better than PID control.This paper designed the electronic control unit of SBW based on chip of MC9S12XET256, mainly including peripheral circuit of MCU, CAN communication circuit, drive circuit of BLDCM, power circuit, signal acquisition and processing circuit, current sampling circuit of motor.Based on the requirement of joint simulation, we designed a bench test for control strategy and hardware, software of ECU in 2015.The results of test bench showed that angle correction was similar with the result of simulation and sliding mode variable structure control was better than PID control in following front angle.Finally, the vehicle steering control test and the vehicle path tracking control test were carried out based on vehicle test platform, which was built personally.The vehicle path tracking system was based on the Windows platform, using Microsoft Visual Studio as the development environment.The integrated navigation system was validated and the test data showed that the integrated navigation system had a high positioning accuracy and the steering system had a reliable tracking performance.The final navigation and positioning accuracy of integrated navigation system was around 0.1 m to 0.5 m and the response speed of the whole system was about 0.1s .The results proved that the system could meet the requirements of agricultural vehicle path tracking control system.

       

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