Advances in High-Performance Motion Control of Mechatronic Systems

Takashi Yamaguchi, Mitsuo Hirata, Chee Khiang Pang

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781351832175
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Mechanics

Mechatronic systems are used in a range of consumer products from large-scale braking systems in vehicular agents to small-scale integrated sensors in mobile phones. To keep pace in the competitive consumer electronics industry, companies need to continuously improve servo evaluation and position control of these mechatronic systems. Advances in High-Performance Motion Control of Mechatronic Systems covers advanced control topics for mechatronic applications. In particular, the book examines control systems design for ultra-fast and ultra-precise positioning of mechanical actuators in mechatronic systems.

The book systematically describes motion control design methods for trajectory design, sampled-data precise positioning, transient control using switching control, and dual-stage actuator control. Each method is described in detail, from theoretical aspects to examples of actual industry applications including hard disk drives, optical disk drives, galvano scanners, personal mobility robots, and more. This helps readers better understand how to translate control theories and algorithms from theory to design and implementation in realistic engineering systems. The book also identifies important research directions and advanced control techniques that may provide solutions for the next generation of high-performance mechatronics.

Bridging research and industry, this book presents state-of-the-art control design methodologies that are widely applicable to industries such as manufacturing, robotics, home appliances, automobiles, printers, and optical drives. It guides readers toward more effective solutions for high-performance mechatronic systems in their own products.

1

Introduction to High-Performance Motion Control of Mechatronic Systems

T. Yamaguchi

Ricoh Company Ltd.

CONTENTS

1.1 Concept of Advances in High-Performance Motion Control of Mechatronic Systems

1.1.1 Scope of Book

1.1.2 Past Studies from High-Speed Precision Motion Control

1.2 Hard Disk Drives (HDDs) as a Classic Example

1.2.1 Mechanical Structure

1.2.2 Modeling

1.3 Brief History of HDD and Its Servo Control

1.3.1 Growth in Areal Density

1.3.2 Technological Development in Servo Control

1.3.2.1 Application of Control Theories

1.3.2.2 Improvement of Control Structure

1.1 Concept of Advances in High-Performance Motion Control of Mechatronic Systems

In this chapter, the concept and scope of this edited book are described in detail. The differences and new findings from our previous edited volume in 2011 [1] are also highlighted and explained.

1.1.1 Scope of Book

First we will explain the purpose of editing this book. As depicted in the title, both mechatronics and motion control are well-known terminologies which have been comprehensively defined and explained in various texts, e.g. [2] to describe the design methodologies of most mechatronic products which have dynamics and require motion control. Mechatronics is usually defined as a synergistic combination of electronics, mechanics, computer, and control. An example of the definition of mechatronics by [3] is shown in Figure 1.1.

FIGURE 1.1
Definition of mechatronics [3].

Mechatronics is present mainly in systems with dynamical motion, and is an integrated methodology for motion control including the choice of sensors, actuators, processers, and machines to control the dynamics and motion. Mechatronics exists in a wide variety of products which include home and office appliances such as air conditioners, office automation equipment such as printers, precision devices, e.g., wrist watches and digital cameras, etc., and entertainment devices such as electronic musical instruments. On a larger scale, mechatronics also appears in cars, airplanes, machine tools, and robots, etc. On the other hand, motion control is an advanced technology applied to mechatronic systems for achieving desired motions such as fast movement, precise positioning or tracking, profile control, and force control for the above-mentioned products.

In this book, our focus is on specific mechatronics and motion control technologies, i.e., an object is moved from a current position to its target position based on a given performance index such as minimum time, and target positioning or tracking should be precise enough for the required tasks to be carried out by an end effector or some other mechanical components. Such actions are commonly seen in various mechatronic systems, e.g., robotic arm control, Read/Write (R/W) head-positioning control in Hard Disk Drives (HDDs) and Optical Disk Drives (ODDs), linear or XY table motion control in manufacturing equipment, autofocus control in digital cameras, and servo valve control in electro-hydraulic and pneumatic equipment, etc. Stationary motion control such as speed regulation of the HDD spindle motor under various disturbances can be considered as motion control as well, in which the desired motor speed is the reference that has to be tracked precisely. Hence, even though our focus is on a specific motion control, the domains of application are very broad.

The main concept of this book is on control systems design, and the above-mentioned motion control can be divided into the following four design phases given as [1]:

1. Design of reference trajectory;

2. Design of controllers to track the reference trajectory;

3. Design of transient or settling controller to minimize the tracking error caused by various unmodeled dynamics or unpredicted parametric variations in the plants; and

4. Design of controllers to suppress external disturbances to ensure that the controlled object remains on its target position.

In Phases 1 and 2, the reference trajectory and servo control are designed for fast-motion reference tracking. The reference trajectory should be designed based on the specifications of the overall control system, e.gs., minimum time, minimum energy, low or no harsh grating acoustic noise, etc. The servo control structure for this phase is designed based on Two-Degrees-of-Freedom (TDOF) control, and a key issue in the design of TDOF control is the precise realization of the inverse dynamics of the plant using the feedforward controller. When utilizing the power amplifier saturation for maximum acceleration, it is necessary to convert this nonlinear control action into linear feedback control so that appropriate robust stability and sensitivity characteristics are theoretically guaranteed after settling. Another key issue in these phases is on the handling of the various complicated plant dynamics such as friction and mechanical resonant modes. In this book, both the reference trajectory and controller design with specific considerations of the mechanical resonant modes are described in detail (see Chapter 2).

In Phase 3, a settling controller is designed for transition from fast motion reference tracking in Phases 1 and 2 to precise positioning in Phase 4. In motion control, it is common that a certain amount of tracking error exists when the actuator approaches the target position. This is due to effects of model mismatch, unknown disturbances, and unmodeled plant dynamics, etc., which are common issues in realistic industrial applications. While it is important for this tracking error to be reduced by the system as quickly as possible, it is generally not easy to handle the corresponding transient responses. In this book, it is shown that the initial values of the controller at mode-switching are design parameters which are independent of other control systems’ characteristics such as stability, and can be used to modify the transient response drastically to improve its settling time (see Chapter 3).

In Phase 4, a controller is designed for precise positioning by improving the disturbance suppression capabilities based on precise modeling of both the plant dynamics and disturbance spectra. In this book, controller design with consideration for both plant dynamics and disturbances located below and above the Nyquist frequency is described (see Chapter 4). In addition, the use of dual-stage actuation and multi-sensing servo systems are also powerful approaches for improving the disturbance suppression capabilities in mechatronic systems (see Chapter 5).

1.1.2 Past Studies from High-Speed Precision Motion Control

Many of the authors of this book were also involved in the authoring and editing of High-Speed Precision Motion Control in 2011 [1]. Control design technologies which are developed and applied to actual HDDs were documented in [1] by ten contributors who are actively engaged in the development of the HDD servo control systems in either academia or industries. The main topics covered include system modeling and identification, basic approach to motion control design, and control technologies for high-speed motion control, precision motion control, as well as energy-efficient and low acoustic noise control. Under the unified approach to high-speed precision motion control, the topics covered include TDOF control which includes Zero Phase Error Tracking Control (ZPETC) for the design of a feedforward controller, Proximate Time Optimal Servomechanism (PTOS)—an access servo control with saturation considerations, Initial Value Compensation (IVC) for settling controller design, classical controller design methods for tracking-following which include the phase compensator, Proportional-Integral (PI) controller, notch filter, observer-based state feedback, etc., as well as multi-rate controller and observer design.

For fast motion control, the control technologies covered are vibrationminimized trajectory designed based on Final-State Control (FSC) theory and Perfect Tracking Control (PTC) theory under multi-rate sampling condition. For precision motion control, the control technologies covered are phase-stable design for high servo bandwidth, robust control using ℋ_∞ control theory, multi-rate ℋ_∞ control, repetitive control, and Acceleration Feedforward Control (AFC). For energy-efficient and low acoustic noise control, the control technologies covered are short-track seeking control using TDOF control with IVC, controller design for low acoustic noise seek, and servo control design based on Shock Response Spectrum (SRS) analysis.

As such, a wide variety of control technologies which have been applied to HDDs was covered in [1], with detailed focus on unique designs which are specific to HDDs and newly de...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• List of Figures
• List of Tables
• Preface
• Editors’ Biographies
• Contributors
• 1 Introduction to High-Performance Motion Control of Mecha-tronic Systems
• 2 Fast Motion Control Using TDOF Control Structure and Optimal Feedforward Input
• 3 Transient Control Using Initial Value Compensation
• 4 Precise Positioning Control in Sampled-Data Systems
• 5 Dual-Stage Systems and Control
• 6 Concluding Remarks from Editors
• Index