农业工程学报
農業工程學報
농업공정학보
2015年
10期
198-203
,共6页
赵翾%杨珏%张文明%曾珺
趙翾%楊玨%張文明%曾珺
조현%양각%장문명%증군
车辆%控制%模型%铰接车%轨迹跟踪%硬件在环仿真
車輛%控製%模型%鉸接車%軌跡跟蹤%硬件在環倣真
차량%공제%모형%교접차%궤적근종%경건재배방진
vehicles%control%models%articulated vehicle%path tracking%Hardware-In-the-Loop
针对农用轮式铰接车辆驾驶员工作条件恶劣的问题，该文提出了一种应用于无人驾驶系统的滑模变结构控制铰接车精确轨迹跟踪的方法。首先推导出了铰接车的运动学模型，根据该模型建立实际行驶轨迹与参考轨迹偏差的模型，之后针对偏差模型设计滑模变结构路径跟踪控制器，该控制器使用Ackermann公式设计，控制律采用指数趋近律使系统有较快的响应和较小的抖振，同时，为了进一步抑制滑模控制器固有的抖振问题，将趋近律中的符号函数替换为连续函数，以避免趋近律数值产生阶跃变化，并用Lyapunov函数证明了其稳定性，最后在硬件在环仿真中验证了控制器的实时性和路径跟踪质量。结果表明，该控制器在硬件在环仿真环境下可将横向位置偏差、航向角偏差、曲率偏差分别控制在0.21 rad(12°)、100 mm、0.17rad(1°)、0.005 m-1附近，各向偏差均在10 s内达到平衡，且误差控制在5%以内，铰接车能有效跟踪参考路径。该研究为农用轮式铰接车辆实现无人驾驶提供参考。
針對農用輪式鉸接車輛駕駛員工作條件噁劣的問題，該文提齣瞭一種應用于無人駕駛繫統的滑模變結構控製鉸接車精確軌跡跟蹤的方法。首先推導齣瞭鉸接車的運動學模型，根據該模型建立實際行駛軌跡與參攷軌跡偏差的模型，之後針對偏差模型設計滑模變結構路徑跟蹤控製器，該控製器使用Ackermann公式設計，控製律採用指數趨近律使繫統有較快的響應和較小的抖振，同時，為瞭進一步抑製滑模控製器固有的抖振問題，將趨近律中的符號函數替換為連續函數，以避免趨近律數值產生階躍變化，併用Lyapunov函數證明瞭其穩定性，最後在硬件在環倣真中驗證瞭控製器的實時性和路徑跟蹤質量。結果錶明，該控製器在硬件在環倣真環境下可將橫嚮位置偏差、航嚮角偏差、麯率偏差分彆控製在0.21 rad(12°)、100 mm、0.17rad(1°)、0.005 m-1附近，各嚮偏差均在10 s內達到平衡，且誤差控製在5%以內，鉸接車能有效跟蹤參攷路徑。該研究為農用輪式鉸接車輛實現無人駕駛提供參攷。
침대농용륜식교접차량가사원공작조건악렬적문제，해문제출료일충응용우무인가사계통적활모변결구공제교접차정학궤적근종적방법。수선추도출료교접차적운동학모형，근거해모형건립실제행사궤적여삼고궤적편차적모형，지후침대편차모형설계활모변결구로경근종공제기，해공제기사용Ackermann공식설계，공제률채용지수추근률사계통유교쾌적향응화교소적두진，동시，위료진일보억제활모공제기고유적두진문제，장추근률중적부호함수체환위련속함수，이피면추근률수치산생계약변화，병용Lyapunov함수증명료기은정성，최후재경건재배방진중험증료공제기적실시성화로경근종질량。결과표명，해공제기재경건재배방진배경하가장횡향위치편차、항향각편차、곡솔편차분별공제재0.21 rad(12°)、100 mm、0.17rad(1°)、0.005 m-1부근，각향편차균재10 s내체도평형，차오차공제재5%이내，교접차능유효근종삼고로경。해연구위농용륜식교접차량실현무인가사제공삼고。
The articulated frame steering vehicles (ASV) are widely implemented in agriculture, mining, construction and forestry sectors due to their high maneuverability. The ASVs, however, are known to possess lower dynamic stability and yield high magnitude of whole-body vibration, which are reported to be harmful to the operators. Automatic driving system is thus necessary for the ASVs to exclude the human driver from detrimental operations, especially for the agricultural ASV. In order to enable the automation of ASV, path tracking strategies are essential to maintain the normal work of the vehicles. As the ASV dynamics significantly are different from the conventional vehicles with front wheel steering, the path tracking controller derived for conventional vehicles is considered not to be applicable for the ASVs. Moreover, large variations of the vehicle load and the off-road excisions challenge the robustness of path tracking algorithms. In this paper, a path tracking strategy is proposed for the ASVs on the basis of sliding mode control (SMC). The kinematic model of the ASV is derived neglecting the vehicle dynamics. Three measurable errors are defined to indicate the deviation of real path from reference path, i.e. lateral displacement error, orientation error and curvature error. These errors serve as the inputs in order to synthesize the SMC. The exponential reaching law is selected in order to increase the reaching speed and reduce chattering. The sign function of exponential reaching law is replaced by a continuous function to further suppress the chattering. Lyapunov function is then utilized in order to assess the system stability. The system transition performances in terms of response time, setting time and overshooting are tuned via pole placement method. The differential transformation method is implemented to determine the poles, in order to obtain the transition performances while preserving the system stability. Ackermann’s formula is used to improve traditional pole placement algorithm and further design the control law. The open loop eigen-polynomial of the system is thus not requisite. Furthermore, the hardware-in-the-loop (HIL) simulation is conducted to evaluate real-time performance of the proposed control law. The HIL platform is set up on the basis of national instruments PXI-8110 and cRIO-9024 as well as a host computer. The real-time ASV kinematic model established in the MapleSim platform is downloaded into the PXI-8110 as the simulation plant, and the SMC path tracking algorithm compiled by Simulink is embedded to the cRIO-9024 as the real electronic control unit. The host computer couples the real-time vehicle model and the path tracking algorithm via the LabVIEW platform and displays the simulation status as the upper monitor. The path tracking algorithm then controls the vehicle to follow a circle path in real time. The results suggest that the simulated vehicle path is smooth and almost identical to the reference path. The 3 kinds of errors achieve steady state in 10 s. The proposed SMC controller is then demonstrated to be robust even neglecting the vehicle dynamics. The results also suggest that the SMC with Ackermann’s formula can fulfill the prescribed request of the dynamic and the steady performance. The real-time performance of the path-tracking is even better than the off-line simulation. The simulation duration 60 s is equal to the calculating duration in the HIL simulation that means the time is synchronous. Compared with the real vehicle test, the HIL simulation is economical and efficient. This research can provide a reference for the design of agricultural ASV automatic driving system.
