Periodic/Aperiodic Motion Control Using Periodic/Aperiodic Separation Filter

Abstract

Motion control is a fundamental technique used in automated mechanical systems. Classically, velocity, force, and impedance are controlled in motion control systems, but simultaneous control is difficult. This article proposes periodic/aperiodic (P/A) motion control based on periodicity and aperiodicity of motion. The P/A motion control separately applies different control methods to P/A motions using P/A velocity and P/A force, which are extracted using a periodic/aperiodic separation filter (PASF) from velocity and force. Accordingly, six types of P/A motion controls are constructed in this article, which correspond to different combinations of the P/A velocity, P/A force, and P/A impedance controls. To construct the P/A motion control systems, acceleration control based on a disturbance observer is used. The ACS, which rejects disturbances, enables the P/A motion control design to ignore disturbances. The experiments were conducted to validate the six P/A motion controls, which simultaneously realized two P/A motion control objectives.

Harmonics Elimination by Periodic/Aperiodic Separation Filter for Chatter Detection

“…The flow of the proposed chatter detection algorithm is composed of the MEDOB (7) based on [14], the aperiodic-pass filter of the PASF S ai , MSD calculation (24), and comparison of the MSD with a threshold δ, as shown in Fig. 6.…”

“…Similar to the comb filter, a periodic/aperiodic separation filter (PASF) was proposed [9], which separates a signal into quasi-periodic and quasi-aperiodic signals defined in [8]. The first-order PASF can easily adjust its cutoff frequency and convergence speed [7], and the high-order PASF can perform more rigid harmonics elimination [8]. The PASF is composed of periodic-pass and aperiodic-pass filters, and the aperiodic-pass filter can be regarded as a generalized comb filter.…”

“…Lastly, the moving standard deviation (MSD) of the quasi-aperiodic force is computed and compared to a threshold for the detection. Moreover, for the PASF, we investigated a separation frequency that realizes a desired cutoff frequency for the firstorder PASF, the time constant of the first-order PASF on the basis of the previous studies [7,9], and highorder PASF based on [8]. They enable direct design of the cutoff frequency and time constant, and the high-order filter improves the harmonics elimination performance without deteriorating chatter signal extraction performance.…”

“…where the delay e −Ls multiplied by the reference current is the sum of the amplifier delay and the communication delay L := T c + T a . The block diagram of the MEDOB (7) is depicted in Fig. 2.…”

Separation and Estimation of Periodic/Aperiodic State

“…The proposed high-order IIR and FIR realization improves the separation performance of the PASF, and the proposed KF-PASF realizes the prediction and estimation of the states under noise. Furthermore, the proposed realization and KF-PASF are expected to improve the precision of the periodic/aperiodic separation control for robots (Muramatsu and Katsura (2020)); improve the accuracy of the aperiodic anomaly detection (Muramatsu et al (2021)); and eliminate harmonics noise similar to and better than the comb filters.…”