Suppressing Initial Force Overshoot Using Admittance Filter and ASMC under Contact Location Uncertainty

This paper proposes a control method to mitigate initial force overshoot caused by contact surface position estimation errors. The proposed method adds a compensation term based on Adaptive Sliding Mode Control (ASMC) to a conventional admittance control structure. Also, to maintain position tracking performance under model uncertainty, a hierarchical control structure is designed by combining a Time-Delay Control (TDC)-based internal position controller. Simulation results show that the proposed method reduces the maximum overshoot from 76.6% to 32.1% compared to conventional admittance control, and shortens the peak time from 0.254 s to 0.126 s. Furthermore, the settling time is reduced from 3.51 s to 1.467 s at the 2% criterion and from 2.113 s to 0.832 s at the 5% criterion, improving transient response stability and convergence speed. II. METHOD Figure1. The proposed control system architecture for overshoot suppression. This section presents the proposed hierarchical control framework designed to suppress initial force overshoot under contact location uncertainty. The overall structure This research was supported by the Regional Innovation System & Education(RISE) program through the Gyeongbuk RISE CENTER, funded by the Ministry of Education(MOE) and the Gyeongsangbuk-do, Republic of Korea.(2026-RISE-15-115) and the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT)(No. RS-2023-00219725). consists of an external force control loop and an internal position control loop. The dynamics of an n-DOF robotic manipulator are described as: M(qt)q̈t+ C(qt, q̇t)q̇t+ G(qt) + F(q̇t) = τt, (1) where M(qt) is the inertia matrix, C(qt, q̇t) is the Coriolis matrix, G(qt) is the gravity vector, F(q̇t) represents friction. The contact force is modeled as: ft,ext= Ke(xt−xe), (2) Where xe denotes the environment position. In practice, uncertainty in xe leads to excessive penetration during initial contact, resulting in force overshoot. To achieve robust position tracking under model uncertainty, a TDC scheme is adopted. The system dynamics are reformulated as: q̈t= Ht+ M̂−1τt, (3) Where Ht represents unknown dynamics and disturbances. TDC estimates Ht using time-delayed information and compensates for it. The control input is designed as: τt TDC= −M̂q̈t−L+ τt−L+ M̂(q̈t,d+ Kdėt+ Kpet). (4) This enables stable and accurate trajectory tracking without requiring an exact dynamic model. For contact force tracking control, we use admittance control as a basic method. The admittance filter generates a position compensation term: Xa(s) = 1 ms2 + bsEf(s), (5) Suppressing Initial Force Overshoot Using Admittance Filter and ASMC Under Contact Location Uncertainty Sejik Oh1, Yi Gyeom Kim1, Hyojin Jo1, Dogyun Park1, and Nam Kyu Kwon2 1 Department of Robot and AI Convergence, Yeungnam University, Gyeongsan 38541, Republic of Korea; sjo7565@yu.ac.kr, dlrua01@yu.ac.kr, hynn0254@yu.ac.kr, pdk4634@yu.ac.kr 2 Department of Electronic Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea; namkyu@yu.ac.kr ICRA2026 Late Breaking Results Poster presented at 2026 IEEE International Conference on Robotics and Automation (ICRA 2026) June 1-5, 2026. Vienna, Austria