Abstract
Considering the joint elasticity, a novel dynamic parameter identification method is proposed for general industrial robots only with motor encoders. Firstly, the unknown parameters of the elastic joint dynamic model are analyzed and divided into two types. The first type is the motion-independent parameter only including the joint stiffness, which can be identified by the static force/torque-deformation experiments without the dynamic model. The second type is the motion-dependent parameter composed of the rest of the parameters, which needs the dynamic excitation experiments. Therefore, these two types of parameters can be identified separately. Meanwhile, it is found that the rotor inertia parameters can be obtained from the manufacturer, which reduces the identification difficulty of other parameters. After obtaining the rotor inertia and joint stiffness, an approximate processing algorithm is proposed considering the motor friction to establish the linear identification model of other parameters. Hence, the least squares can be employed to identify the parameters, and the independence of the inertia and joint viscous friction parameters are not affected. Meanwhile, the exciting trajectories can be optimized throughout the robot workspace, which reduces the effect of measurement noise on identification accuracy. With the proposed separated identification strategy and approximate processing algorithm, the dynamic parameters can be obtained precisely without double encoders on each joint. Finally, a series of simulations are conducted to evaluate the good performance of the proposed method.
Highlights
With the increasing applications of industrial robots in modern manufacturing field, a lot of advanced motion control methods based on the torque input have been proposed and applied to satisfy the demand for high speed and high accuracy, which requires the complete and accurate dynamic model of robot.[1,2,3,4] the dynamic model is the basis for the characteristic analysis of robot.[5]
Simulation tests are conducted to evaluate the good performance of the proposed dynamic parameter identification method for the elastic joint dynamic models (EJDM)
The real values of joint stiffness and rotor inertia are given in Table 3, where the setting of rotor inertia value is referenced to Panasonic MSME series motors with approximately 2–4 kW power
Summary
With the increasing applications of industrial robots in modern manufacturing field, a lot of advanced motion control methods based on the torque input have been proposed and applied to satisfy the demand for high speed and high accuracy, which requires the complete and accurate dynamic model of robot.[1,2,3,4] the dynamic model is the basis for the characteristic analysis of robot.[5]. To cope with this problem, the elastic joint dynamic models (EJDM) of robots are established, and some identification methods have been proposed. Because of the unknown rotor inertia, joint stiffness, and motor friction parameters, the linear IDIM is difficult to establish.
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