Enhancement of cutting force observer by identification of position and force-amplitude dependent model parameters

Enhancing the multi-encoder-based cutting force estimation along the stationary axis of a machine tool with multiple inertia dynamics

“…Here, the gain characteristics of the LDOB and current-based impulse force estimation are compared. The impulse force in the Y-direction was estimated using the LDOB and current-based methods, as follows [16,19]:…”

“…In this method, the cutting force is estimated from the relative position between the motor and stage (i.e., the deformation of the ball screw) converted from the rotary and linear encoder signals without friction compensation. Additionally, Yamato et al [19] proposed a cutting force estimation method based on a load-side disturbance observer (LDOB [20]). The LDOB method, based on the load-side motion equation of the dual-inertia model, can estimate the cutting force based on the relative position similar to the cutting force estimation based on the vibration mode.…”

“…The measured FRFs through tap tests are fitted with the multi-degree-of-freedom (MDoF) curve fitting technique with a nonlinear least square method[22], and the modal parameters comprising the residues (𝛼 𝑚,𝑖 , 𝛼 𝑐,𝑖 , 𝛼 𝑎,𝑖 ), damping ratios (𝜁 𝑚,𝑖 , 𝜁 𝑐,𝑖 , 𝜁 𝑎,𝑖 ), and natural angular frequencies (𝜔 𝑚,𝑖 , 𝜔 𝑐,𝑖 , 𝜔 𝑎,𝑖 ) of 𝑖th mode (𝑖 = 1,2, ⋯ 𝑁) at the motor side, center point, and anti-motor side are identified. Although the position dependencies of the modal parameters in a ball-screw-driven stage are usually modeled as quadratic functions[19], they are simply modeled with linear interpolation in this study because we assumed that the proposed method is applied to a compact machine tool. Linear interpolation models for the modal parameters of the 𝑖th mode are constructed based on the identified modal parameters as follows: { 𝛼 𝑖 (𝑥 𝑡 ) =…”

Integrated Design of Spindle Speed Modulation and Cutting Vibration Suppression Controls Using Disturbance Observer for Thread Milling

“…However, some factors, such as friction and dynamics of the feed drive and spindle motors, could contaminate current signals and thus degrade the cutting force and cutting torque control performance. Therefore, as the cutting force and disturbance are related, a disturbance observer was adopted to estimate the cutting force in milling [24,25] and several studies have focused on the applications of chatter detection [26,27], machining type detection [28], cutting force monitoring [29], and tool fracture detection [30]. In this study, in contrast to previous studies, a feedback control method integrated with a DOB was developed to estimate and feedback cutting torque, modulate spindle speed, and make the cutting torque in thread milling achieve a preset torque command.…”