Tethered Mobile Robot’s EKF-based Cable Length Estimation and Control

In industrial environments such as large-scale facilities, mobile robots are increasingly being used to automate welding tasks. Because these robots rely on supply cables for power, communication, and welding equipment, cable length must be properly regulated in response to robot motion. Insufficient cable release can cause excessive tension, robot tipping, motor overload, and cable damage, while excessive release can lead to cable entanglement, floor dragging, and path interference. This paper proposes an extended Kalman filter (EKF)-based cable length estimation and safety control method for a tethered mobile welding robot. The EKF estimates the deployed cable length while accounting for encoder bias, load-cell bias, and slip velocity, and compensates for slip-induced length errors using feeder velocity and measured tension. Based on the estimated length, cable slack is calculated and controlled by a proportional-integral (PI) controller combined with a safety layer that considers tension level, tension rate, slack lower bound, and motor peak constraints. Simulations under radial motion, random motion, high-friction ground, and sensor offset conditions show that the proposed method maintains stable slack and prevents excessive tension compared with encoder-based and conventional EKF methods.