在线重力补偿下工程机器人自主作业轨迹跟踪性能分析

Analysis on autonomous task trajectory tracking performance of construction robot with online gravity compensation

工程机器人自主作业时,工程机器人动臂举升、前臂摆动重心上升过程中需要克服自身重力做功,而在工程机器人动臂下降、前臂摆动重心下降过程中,自身重力要参与做功,影响工程机器人的运动速度,进而影响工程机器人自主作业的轨迹跟踪效果。针对这一问题,建立了工程机器人动臂、前臂的动力学模型,探讨采用最小二乘拟合法辨识动力学参数,进行工程机器人动臂、前臂的在线重力补偿,以消除在自主作业过程中重力做功对轨迹跟踪的影响。最后,在工程机器人试验台上进行了试验。试验结果表明,在线重力补偿可有效地补偿工程机器人自主作业过程自身重力,消除工程机器人动臂和前臂在运动过程中重力做功对自主作业轨迹跟踪过程的影响,有利于减小轨迹跟踪误差,提高工程机器人自主作业轨迹跟踪的性能。

By the visual feedback and the space position information of the target object of stereo vision camera, the construction robot can realize the autonomous task according to the kinematics analysis and trajectory planning. However, in the process of the autonomous task, because the link mass of construction robot is big, the driving force of the cylinder calculated by the pressure sensors attached at the cylinders will be divided into two parts, one is used for balancing the link gravity, and the other is used for driving the moving of the cylinder. Therefore, the construction robot will overcome the gravity to work in the process of gravity rising along with the lift of boom and swing of arm, and the links gravity of boom and arm will participate in working in the process of gravity fall along with the dropping of boom and swing of arm, this phenomena will influence the moving velocity of construction robot and the effect of the effect of trajectory tracking, especially in the lifting process, moreover, in the process of the links dropping of construction robot, it is dangerous to the construction robot because of the bigger links masses. Aiming at this problem, the dynamics models of construction robot were deduced followed by kinematics analysis, and the least squares method was used for identifying the dynamics parameters, and then online gravity offset method was purposed based on the dynamics parameters, which was used for eliminating the gravity impact from the driving force of the cylinders, and improving the trajectory tracking effect in autonomous task. Finally, experiment was finished on the construction robot test bench, and the experimental results show that the online gravity compensation algorithm could compensate the gravity of construction robot effectively, and eliminate the influence of gravity working to the trajectory planning of construction robot, and the tracking errors under online gravity compensation are smaller than no gravity compensation, therefore, the online gravity compensation will be propitious to reduce the trajectory tracking errors, and improve the trajectory tracking performance of autonomous task, at the same time, the gravity compensation algorithm has important significance to reduce the energy input and consume for the autonomous task of construction robot.