Abstract: Autonomous shoveling of loaders is the key technology to realize automatic and intelligent operation,and the tracking control of the target working trajectory is one of its core parts.The actual trajectory of the bucket in the pile is related to the indicators such as the operation output,so it is of great significance to realize the effective tracking control of the target working trajectory.The PID and other control methods without system models have problems such as large overshoot amplitude and buffeting under the system constraints.Since the Model Predictive Control (MPC) has the advantage of effectively dealing with system constraints to make the system operate smoothly,it was introduced into the motion control of the loader's working mechanism and a trajectory-tracking control method was proposed for the working mechanism based on the Nonlinear Model Predictive Control (NMPC).A kinematic model of the working mechanism in the drive space was established.Then,the description of the working trajectory was given.Furthermore,a trajectory-tracking controller for the working mechanism was designed based on the NMPC method.Finally,the Simulink/ADAMS co-simulation was carried out with the general PID as the comparison group.The analysis showed that under the same system constraints,for the different target trajectories,the maximum absolute error of the bucket-tip displacement based on the designed controller didn't exceed ±0.052m,which was 71% lower than the PID controller,and the maximum absolute error of the bucket angle didn't exceed ±2.58°,which was 16% lower than the PID controller.Moreover,the designed controller had a smoother control effect.The designed controller had better performance than the PID controller in dealing with system constraints and smoothness.

Key words: loader, working mechanism, PID control, model predictive control, nonlinear model predictive control

摘要： 装载机自主铲掘是实现自动化、智能化作业的关键技术,而实现对目标作业轨迹的跟踪控制是其核心部分之一,铲斗在料堆中的实际运动轨迹关系着作业产量等指标,因此实现对目标作业轨迹的有效跟踪控制具有重要意义。对于PID等无系统模型控制方法在系统约束下存在较大超调幅度及抖振等问题,鉴于模型预测控制(MPC)具有可有效处理系统约束使系统平稳运行的优点,将MPC思想引入到装载机工作机构运动控制中,提出了一种基于非线性模型预测控制(NMPC)的工作机构作业轨迹跟踪控制方法。首先建立了工作机构在驱动空间下的运动学模型,其次给出了作业轨迹描述,进而基于NMPC方法设计了用于工作机构作业的轨迹跟踪控制器,最后以常规PID为对照组进行了Simulink/ADAMS联合仿真。分析发现,在相同系统约束下,针对不同目标作业轨迹,相比PID控制,所设计控制器的斗尖位移最大绝对误差不超过±0.052m,同比降低了71%,铲斗转角最大绝对误差不超过±2.58°,同比降低了16%,且具有更平顺的控制效果。研究表明,所设计控制器在处理系统约束和平顺性方面相比PID控制器具有更优秀的表现。

关键词: 装载机, 工作机构, PID控制, 模型预测控制, 非线性模型预测控制