Discrete Time Delay Control for Current Tracking of Joint Motors with Estimation Error Compensation

High-performance torque and position control of robots relies on the high-precision current tracking control of joint motors. Among various control methods, time delay control (TDC) has attracted growing interest due to its advantages such as low dependency on parameters, computational simplicity, and good tracking performance for both high- and low-frequency signals. However, existing TDC algorithms for current control lack specificity to robotic operating conditions, and the inherent time delay estimation (TDE) errors reduce the current tracking accuracy. Therefore, this paper proposes a discrete time delay control (DTDC) algorithm with TDE error compensation to achieve higher precision in current tracking control. Firstly, the key factors affecting the current tracking accuracy of joint motors are analyzed based on actual operating conditions. Then, a direct TDE error compensation method is designed from the perspective of gradient descent, and a new DTDC control law is derived based on this, with its stability rigorously proven. Next, the effectiveness of the proposed method is demonstrated through a comparative analysis of transfer functions. Additionally, the direct compensation characteristics of the proposed method are highlighted, followed by the parameter sensitivity analysis and tuning guidelines. Finally, experiments are conducted on a 3.1-kW surface-mounted motor platform and a robotic joint module platform to verify the effectiveness of the proposed DTDC method through comparative analysis.