Path-tracking control represents a crucial technology for achieving autonomous driving in tracked vehicles. This paper presents a novel cascade control approach based on a port-controlled Hamiltonian model that incorporates position, velocity, and flow loops to improve the robustness and stability of path-tracking in tracked vehicles. Firstly, the nonlinear kinematic model undergoes an equivalent transformation to tackle the challenge of converting the hydraulic-tracked vehicle kinematic model into a port-controlled Hamiltonian model. The effectiveness of this substitution is evaluated through a phase portrait analysis. Subsequently, an interconnection and damping assignment passivity-based controller is formulated to achieve position control and generate a desired velocity reference. Leveraging the dynamics of the tracked vehicle, a velocity controller is developed to calculate the desired vehicle torque and hydraulic motor angular velocity, facilitating velocity tracking. Flow control is realized through a novel passivity-based L2-gain robust control method designed in conjunction with the port-controlled Hamiltonian model. This method empowers the electro-hydraulic servo system to track the desired angular velocity at the expected torque, mitigating the adverse impact of the electro-hydraulic servo system on the tracking performance of tracked vehicles. Finally, a comprehensive comparison is made with two existing control strategies. The results show that the overall performance of the controller is improved by 20.3% and 10.92%, and the tracking accuracy is improved by 15.01% and 5.97%, respectively.

The motors and reducers of traditional industrial robots are installed at the joints, which leads to large moment of inertia and difficult to effectively improve the dynamic performance of the robots. In particular, the residual vibration at the end of the robots will significantly reduce its working efficiency and fatigue life. Therefore, this paper proposes a new method to reinstall the motor and reducer near the frame, which can effectively suppress the residual vibration of the robots and simultaneously reduce the moment of inertia. Taking the series industrial robot as the research object, four types of CM robots are designed based on the theory of a multi-DOF controllable mechanism (CM). The motor and reducer of the robot are reinstalled near the frame through different branch chains, and their moments of inertia are calculated and compared. The dynamic equations of residual vibration of the four CM robots considering concentrated mass are established based on the finite element method (FEM) and Timoshenko space beam element (SBE) model, and the correctness of the equations are verified by experiments. The results show that the installation position of motor and reducer has a significant influence on the value of moment of inertia of the robot. The motor and reducer of configuration D are reinstalled near the frame by three branches, which can effectively reduce the attenuation time and amplitude of residual vibration at the end of the robot. The research provides a new idea for improving the dynamic performance of industrial robots.

The stiffness distribution (SD) of robot has a great influence on the robot pose accuracy, but the calculation efficiency and accuracy of stiffness distribution are still low.This study presents a finite element fitting method with an extremely small number of computational cells. It was developed based on experimental results of robot stiffness. This method can be employed to establish single- and multi-source fitted SD (FSD) (S-FSD and M-FSD) models for host–parasite (H–P) robots. The computational efficiency and correctness of the FSD models were verified by case studies.The configurations of six evolutionary mechanisms of an H–P robot were subjected to an SD analysis. A comparison of the six configurations shows that adding parasitic branched chains can improve the SD of the H–P robot to varying degrees. In particular, the most notable improvement was for H–P mechanism. Specifically, by averaging the stiffness of all positions, the average-stiffnesses of H–P mechanism in the x-, y-, and z-directions were 104.10%, 1427.78%, and 1101.62% of those of the host mechanism, respectively. In the SD diagram, the medium- and high-stiffness regions of mechanism F are large and distributed in a banded pattern between the highest pose point and the furthest pose point, whereas its low-stiffness region is small and concentrated near the nearest pose point.