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HOME > No.33, Jun. 2023 > High-speed, high-precision positioning of stages with unknown vibration characteristics

High-speed, high-precision positioning of stages with unknown vibration characteristics

Simple design of high-speed, ultra-precise positioning control system without dynamic model Kaiji Sato
Professor Kaiji Sato (Center) and his lab members
Professor Kaiji Sato (Center) and his lab members

A research team led by Professor Kaiji Sato (Robotics and Mechatronics Laboratory, Department of Mechanical Engineering, Toyohashi University of Technology) revealed a method for designing with ease an ultra-precise positioning control system on the order of 10nm, even if the dynamic model and model parameters of the motion mechanism and the machine base on which it is installed are unknown. This design method provides a control system with an NCTF controller that compensates for unknown nonlinear characteristics, including frictional characteristics, to reach the target position with high speed and high precision and a vibration suppression compensator that quickly compensates for unknown vibration characteristics caused by high-speed driving. Its design is simple, and it can be designed without expertise in control system design or mechanical characteristics.

Overview of the ultra-precision stage used in the experiment
Overview of the ultra-precision stage used in the experiment

In industrial machinery such as machine tools and semiconductor manufacturing equipment, positioning accuracy and high-speed response of the mechanism are basic and important characteristics that affect the performance of the equipment. However, as the required accuracy becomes higher, the micro-dynamic characteristics caused by the mechanism and the machine base on which it is placed (which were not previously an issue) become problematic. A high-speed response generates a large reaction force, which excites each part of the mechanism. The use of active damping devices and hardware improvements are effective in suppressing micro-vibrations, but they limit the range of applications and increase costs. Using a controller that uses detailed mechanical property information is also effective, but it requires more labor and time, and requires the assistance of an expert to make adjustments. Therefore, we propose a method to effectively suppress vibration and achieve ultra-precision positioning by simple controller design and adjustment, while using the hardware as it is, without the need for mechanical property information in advance.

Configuration of proposed control system
Configuration of proposed control system

The control system consists of Nominal Characteristic Trajectory Following (NCTF) proposed by Professor Sato and the vibration suppression compensator consisting of a bandpass filter and a differential compensator, and is determined sequentially. The role of the compensator is straightforward, there are few variables to adjust, and it is easy to determine without expert knowledge. The former can be designed by incorporating an open-loop response waveform for a given input signal and adjusting the two gains step-by-step. The latter is completed by determining the two gains sequentially. The resulting control system achieves ultra-precise positioning even for mechanisms with marked nonlinear characteristics such as frictional characteristics. The latter can also be used in combination with other control systems. The effectiveness of the proposed control system design method has been demonstrated by experiments.

Benefit of proposed control system
(a) Error of conventional NCTF control system
(b) Error of proposed control system
Benefit of proposed control system
(a) Error of conventional NCTF control system
(b) Error of proposed control system

There is increasing demand for high acceleration, high speed, and improved accuracy in industrial machinery, making it an important issue when developing high-performance industrial machinery. This research was carried out jointly by Professor Kaiji Sato who wants to make use of the insights of his university laboratory in the real world and NEOMAX Engineering which wants to solve problems in cooperation with universities. This paper shows the achievement of the original goal and the basic results.

In the paper, the control system is adjusted to suppress two types of vibration with different properties. There are also scenarios where vibration with many different frequencies occurs, scenarios where the criteria of the vibration to be suppressed are different, and scenarios where the nature of the vibration is different. We want to increase the number of scenarios that can be addressed, and ultimately reveal how to solve these problems holistically.


Kaiji Sato, Ryouhei Hisamatsu, Kaoru Akamatsu (2023). Controller design for high-speed, ultra-precision positioning of a linear motion stage on a vibrating machine base stage control on a vibrating base. Precision Engineering,



佐藤 海二



制御系は、佐藤教授が提案しているNominal Characteristic Trajectory Following (NCTF) 制御系と、バンドパスフィルタや微分補償器からなる振動抑制補償器より構成され、順次決定されます。補償器の役割は単純明快で、調整する変数が少なく、専門的知識なしで簡単に決定できます。前者は、指定の入力信号に対する開ループ応答波形を組み込み、2個のゲインを手順通りに調整することで設計できます。後者は2個のゲインを順次決定すれば完了します。得られた制御系は,摩擦特性に代表される顕著な非線形特性を持つ機構でも超精密な位置決めを実現します。また後者は他の制御系と組み合わせて利用することも可能です。提示された制御系設計法の有効性は、実験により実証されています。



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Researcher Profile

Kaiji Sato
Name Kaiji Sato
Affiliation Department of Mechanical Engineering
Title Professor
Fields of Research Precision Mechatronics / Robotics /Control Engineering/ Actuator