A double-tracked robot is designed from mechanical and control perspectives,which consists of two segments connected with a swing joint. As the angle between the two segments of the robot platform can be changed,the r...A double-tracked robot is designed from mechanical and control perspectives,which consists of two segments connected with a swing joint. As the angle between the two segments of the robot platform can be changed,the robot can move like a four-tracked robot on many terrains. The center of gravity（ CG） kinematics model is established,which plays an important role in the process of traveling over obstacles and climbing up stairs. Using this model,the CG change situation and the maximal height of the climbable obstacle are obtained. Then the relationship between the robot pitch angle and the height of the obstacle is established. Finally,a reasonable system structure for the robot is designed and its kinematics analysis for obstacle-surmounting capability is conducted through experiments.展开更多
在无人矿用卡车的轨迹跟踪任务中,露天矿的地形信息繁杂且路面类型多样,导致跟踪精度与横向稳定性之间的矛盾突出;此外,无人矿卡轮地交互的动力学特性复杂,矿卡的轨迹跟踪面临建模难度大的挑战。针对以上问题,提出了一种基于稳定性评价...在无人矿用卡车的轨迹跟踪任务中,露天矿的地形信息繁杂且路面类型多样,导致跟踪精度与横向稳定性之间的矛盾突出;此外,无人矿卡轮地交互的动力学特性复杂,矿卡的轨迹跟踪面临建模难度大的挑战。针对以上问题,提出了一种基于稳定性评价的无模型自适应控制(Stability-based Model Free Adaptive Control,SMFAC)方法,以数据驱动的方式实现对行驶稳定性和跟踪精确性的协调控制。在Pacejka轮胎公式的基础上引入路面附着系数对矿卡的影响,结合简化的动力学方程构建矿卡的质心侧偏角-质心侧偏角速度相平面,并对不同环境工况的稳定域边界实现动态辨识,实时求解矿卡的稳定系数。基于径向基网络构建Actor-Critic无模型轨迹跟踪控制器,Actor网络依据系统状态计算控制量,Critic网络评估实时控制量的价值并对价值函数进行拟合;结合稳定系数设计学习过程中的网络误差,以最小化误差函数为目标求解隐藏层权值的更新律,通过矿卡与环境的交互迭代出轨迹跟踪的最优策略。基于CarSim与MATLAB/Simulink搭建轨迹跟踪联合仿真系统,以验证所提出的SMFAC方法的有效性。结果表明:相比于无模型的PID算法与有模型的MPC与LQR算法,所提方法在低速与高速的情况下均可兼顾角度跟踪精度与横向跟踪精度,在双移线、单移线、曲线工况中均取得最优轨迹跟踪性能。此外,SMFAC方法可抑制输出动作的波动,生成较为平滑的行驶轨迹,保障了无人矿卡的操纵稳定性。展开更多
基金Supported by the National Natural Science Foundation(61273344)Ph.D. Program Foundation of Ministry of Education of China(20121101110011)+1 种基金Fundamental Research Fund of Beijing Institute of Technology(20130242009)State Key Laboratory of Robotics and Systems(HIT)(SKLRS-2011-ZD-06,SKLRS-2013-MS-10)
文摘A double-tracked robot is designed from mechanical and control perspectives,which consists of two segments connected with a swing joint. As the angle between the two segments of the robot platform can be changed,the robot can move like a four-tracked robot on many terrains. The center of gravity（ CG） kinematics model is established,which plays an important role in the process of traveling over obstacles and climbing up stairs. Using this model,the CG change situation and the maximal height of the climbable obstacle are obtained. Then the relationship between the robot pitch angle and the height of the obstacle is established. Finally,a reasonable system structure for the robot is designed and its kinematics analysis for obstacle-surmounting capability is conducted through experiments.
文摘在无人矿用卡车的轨迹跟踪任务中,露天矿的地形信息繁杂且路面类型多样,导致跟踪精度与横向稳定性之间的矛盾突出;此外,无人矿卡轮地交互的动力学特性复杂,矿卡的轨迹跟踪面临建模难度大的挑战。针对以上问题,提出了一种基于稳定性评价的无模型自适应控制(Stability-based Model Free Adaptive Control,SMFAC)方法,以数据驱动的方式实现对行驶稳定性和跟踪精确性的协调控制。在Pacejka轮胎公式的基础上引入路面附着系数对矿卡的影响,结合简化的动力学方程构建矿卡的质心侧偏角-质心侧偏角速度相平面,并对不同环境工况的稳定域边界实现动态辨识,实时求解矿卡的稳定系数。基于径向基网络构建Actor-Critic无模型轨迹跟踪控制器,Actor网络依据系统状态计算控制量,Critic网络评估实时控制量的价值并对价值函数进行拟合;结合稳定系数设计学习过程中的网络误差,以最小化误差函数为目标求解隐藏层权值的更新律,通过矿卡与环境的交互迭代出轨迹跟踪的最优策略。基于CarSim与MATLAB/Simulink搭建轨迹跟踪联合仿真系统,以验证所提出的SMFAC方法的有效性。结果表明:相比于无模型的PID算法与有模型的MPC与LQR算法,所提方法在低速与高速的情况下均可兼顾角度跟踪精度与横向跟踪精度,在双移线、单移线、曲线工况中均取得最优轨迹跟踪性能。此外,SMFAC方法可抑制输出动作的波动,生成较为平滑的行驶轨迹,保障了无人矿卡的操纵稳定性。
