An Integrated Linear-Drive Joint with Hybrid Control for High-Precision Robotics

Aiming at the problems that electric cylinders have complex structures, large volumes, and low efficiency, making them unsuitable for high-precision applications in robot linear joint modules, this paper designs a high-precision linear-driven robotic joint system and proposes a new method for integrating the motor rotor with a long nut. Through theoretical analysis of the working mechanism and structure of the electromagnetic linear actuator, a multi-field coupled mathematical model involving mechanics, electricity, and magnetism is established. A co-simulation test platform based on Simulink-Adams is built to verify the reliability of the system. Based on MATLAB/Simulink, a dual-loop proportional-integral-derivative (PID) control algorithm and a sliding-mode variable-structure control algorithm with a nonlinear extended state observer are designed and simulated, enabling the linear actuator to adjust its stroke and frequency according to different operating conditions. Simulation results show that the proposed control algorithms can meet the variable operating condition requirements of the linear joint actuator, and the motion is smooth under loaded conditions. This study provides a new approach for the research on lightweight, high-energy-efficiency, and high-precision linear driving and control technologies for robotic linear joints.