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Design of Actuator Servo Controller
Published in Abdullah Al Mamun, GuoXiao Guo, Chao Bi, Hard Disk Drive, 2017
Abdullah Al Mamun, GuoXiao Guo, Chao Bi
The head positioning servomechanism of an HDD uses the VCM actuator to move read-write head from one track to another and to regulate its position over the center of the track. Position feedback used by the servo loop is extracted from the readback signal obtained by the read head scanning the servo sector. Design objectives of the servo controller are fast movement of read/write head from one track to another during track seek and minimum variance regulation of the position of the head during track following. Various sources of disturbances and noise have detrimental influences on the performance of the servomechanism and the objectives of the servo controller must be fulfilled in presence of those influences. Moreover, a cost effective realization of the controller puts additional constraints on designer’s choice of sophisticated and complex algorithms. To make such cost effective realization possible the designer must avoid a complex model of the process, leaving significant parts of plant dynamics unmodeled. The HDD servo controller is often implemented using fixed point digital signal processors (DSP), and low cost analog-to-digital converter (ADC) and digital-to-analog converter (DAC). This chapter explains issues related to design of digital controller, highlights factors to be considered while implementing such controllers, and provides different algorithms to solve problems specific to HDD servomechanism. Design considerations for track seek mode are already presented in chapter 2. Primarily the issues relevant to track-following controller are focused in this chapter, but some of these issues are equally important for the seek mode.
Control Systems
Published in Albert Thumann, D. Paul Mehta, Handbook of Energy Engineering, 2020
The control of physical systems with a digital computer is becoming more and more common. Aircraft autopilots, mass transit vehicles, oil refineries, paper-making machines and countless electromechanical servomechanisms are among the many existing examples. Furthermore, many new digital control applications are being simulated by microprocessor technology, including on-line computer controllers in automobiles and household appliances. Among the advantages of digital logic for control are the increased flexibility of the control programs and the decision-making or logic capability of digital systems.
IoT End Devices
Published in Rebecca Lee Hammons, Ronald J. Kovac, Fundamentals of Internet of Things for Non-Engineers, 2019
Servomechanism—Actually, an actuator and sensor combined. It uses error-sensing negative feedback to correct the action of an actuator. This controls position, speed, and other parameters. Your car cruise control mechanism is a form of this, as it keeps the speed set at what you desire by monitoring current speed and comparing it to set speed (Figure 5.15).
Gap-metric-based robustness analysis of nonlinear systems with full and partial feedback linearisation
Published in International Journal of Control, 2018
A. Al-Gburi, C. T. Freeman, M. C. French
Many approaches exist to add robustness to state feedback linearisation, including applications to systems with structured or unstructured uncertainties. Most research to date is for systems with structured uncertainties, for example, systems of the form where ‖κ(x)‖ < M ∀x and M < ∞. In the work presented in Spong and Vidyasagar (1987), a robust state feedback controller is designed to control a nonlinear robotic system. Assuming that the plant nonlinearities are bounded, the stability of this system was established using the small gain theorem. In Spong, Thorp, and Kleinwaks (1984), a state feedback controller was designed for a robotic manipulator with structured bounded uncertainties. However, this controller was designed using Lyapunov's direct method and did not account for actuator saturation. To solve this problem, an optimal decision strategy was incorporated to realise a robust unsaturated controller. Meanwhile, Khalil (1994) used a state feedback controller to drive the states of the system to a region of attraction and then enlisted a servomechanism to recover robustness and asymptotic tracking properties. Kravaris (1987) proposed a robust nonlinear state feedback control design based on input–output linearisation, and robustness of the closed-loop system was guaranteed using Lyapunov-based analysis.
Boundary output tracking for a flexible beam with tip payload and boundary nonlinear disturbance
Published in Applicable Analysis, 2022
In this paper, we designed a new infinite-dimensional ESO without high gain to estimate the total disturbance of a flexible beam with payload and boundary nonlinear disturbance. Based on such ESO, we construct a servomechanism corresponding to the given reference signal and a servomechanism-based output feedback control law such that the performance boundary output tracks exponentially the reference signal. Moreover, we proved that closed-loop system under such control law is bounded such that our control strategy makes sense. The Riesz basis approach is crucial to the verification of the semigroup generation and exponential stability of an important couple system.
Proportional-integral-proportional control and compensation design for low-speed motions of permanent magnet synchronous motor driven servomechanism with position-dependent disturbance
Published in Journal of the Chinese Institute of Engineers, 2022
A position-dependent disturbance implies an external disturbance, such as that related to the motor angular position, which significantly influences the low-speed motion performance of a PMSM-driven servomechanism. Therefore, based on the PIP feedback control that is generally used in servomotor drivers, a control and compensation design was developed that improves the low-speed motion performance of a PMSM-driven servomechanism and without excessively increasing the computational burden of the servomotor driver.