Tilt Servo Research Articles

Real-time Ball Detection and Tracking using Raspberry PI

This paper presents a real-time system for ball detection and tracking system which is reliable in any conditions. Images from the webcam are processed by openCV library running on a Raspberry Pi to move the camera pan and tilt servo and two DC motors to drive the robot body using the Arduino Nano microcontroller. The webcam is integrated in a robot prototype to represent the wheel football robot type. The results show that a ball tracking webcam system is obtained with the capability to detect a ball with a diameter of 17cm within a maximum distance of 200 cm, a stable ball reading when the light intensity is at 32 lux and above. Furthermore, the experimental results demonstrated the system’s robustness in detecting and tracking ball in different distance and ligthing conditions.

Design and Experimental Investigation of Three Degrees of Freedom Nanoscale Microsuspension Actuators

Nanoscale actuators are one of the key technologies in high-precision servo systems. For optical storage systems, the performance of the actuator determines the maximum storage capacity and read/write speed. This article introduces a three-degrees of freedom nanoscale microsuspension actuator. Compared with an actuator from a traditional optical storage system, the proposed actuator can hold dual objective lenses with large apertures, the load capacity of which is increased by 3.14 times. With dual objective lenses operating at the same time, the actuator can achieve a large range of layer jumps. Thanks to the four-sided magnetic circuit and the overall structure, the actuator has an operating bandwidth greater than 10 000 Hz for dynamic performance, can compensate systematic errors in nanoscale, and provides a radial tilt servo direction. We have derived the actuator a unified electromechanical dynamic model, an equivalent stiffness model, an equivalent damping model, and a magnetic circuit analysis model in detail. Compared with other analysis models of microsuspension actuator, the proposed models provide a theoretical guidance for the determination of each key parameter, and can effectively improve design efficiency. The theoretical models and design method of the actuator are also applicable to microactuators design and active vibration isolation design of other high-precision servo systems. The simulation and experimental results verify the good dynamic performance of the actuator and show the effectiveness of the principal analysis and design method.

Pan-Tilt Modelling for Face Detection

Object detection is one of the important application in the surveillance system. In system design, a model is needed to be used for the compensator design process. The black-box modeling method is used so that we can get the mathematical model of the plant without using physics laws, while it is used an experimental approach so that it takes input and output data from the open-loop system response. In modeling the system, two datasets are required to estimate the model and validate the data. In the process, Arduino Mega controller commanded to transmit Pulse Width Modulation (PWM) signals on the pan and tilt servo motors. The command sets motion to pan and tilt systems which installed a camera in it, and the dataset retrieval process can be performed. In this case, the PWM signal as input and the center coordinates of the face (pixels) as outputs based on the viola jones method for the image processing of the open-loop system. The results of the mathematical model of the system show that the data obtained is quite accurate, it is proved from the estimation and data validation that has been done.

Image compensation using wavelet transform for tilt servo control in holographic data storage system

A holographic data storage system is very important in the division of a mass storage device. In this regard, tilt servo control is the main problem in the study of holographic data storage system. Tracking servo and tilt servo control are very important research area in holographic data storage system. In this paper, we propose two algorithms. The first algorithm is image compensation using the wavelet transform method and the second algorithm is intelligent servo control using fuzzy rules for the exact tilt control in the holographic data storage system. We need to obtain a good pattern in binary data using a CMOS camera. We have developed two step-by-step operations. Firstly, to obtain exact image data, image data compensation carried out by the wavelet transform method. Finally, we have realized an intelligence control model using fuzzy rules, which was generated by a subtractive clustering algorithm. Therefore, we control radial and tangential tilt servo control using fuzzy rules in a holographic data storage system and perform image data compensation by the wavelet transform method. Our system does not require responses in the tilt servo control system. Therefore, this system has the advantage terms of time. Consequently, the practical pattern of tilt servo control was found by an intelligence algorithm through image processing in the holographic data storage system.

Intelligence control system compensation by DNA coding method in holographic data storage system

A holographic data storage system is one of the next-generation information-storage devices. Many researchers study a holographic data storage system. But the holographic data storage system, there are a lot of difficulties to study. One of them, tilt servo control in holographic data storage system is very difficult. In this paper, we proposed intelligent compensator for given problem that is tilt servo control in holographic data storage system. We have found pattern of tilt servo control which is between radial and tangential angle in holographic data storage system through fuzzy system. Fuzzy rules were generated by DNA coding method for tilt servo control. And then, tilt servo control is controlled by fuzzy rules.

Generation of fuzzy rules and learning algorithm for servo control in holographic data storage system

Today many media of information storage device are formed as disks. Hence, next generation removable data storage media are shaped as disk types too. The holographic data storage system also uses a disk type photopolymer media. And then, holographic data storage system is most advanced optical memory system. Tracking servo and tilt servo control are very important research in holographic data storage system. In this paper, we propose intelligent servo control by fuzzy rules in holographic data storage system. Hence, we have found pattern of tilt servo control in holographic data storage system through fuzzy system and genetic algorithm. Fuzzy rules were generated by genetic algorithm for controlling tilt servo. Therefore, we control tilt servo using fuzzy rules in holographic data storage system. Consequently, Image input---output patterns of tilt servo control was found by intelligence algorithm in holographic data storage system.

Tilt Servo Control by Intelligent Algorithm in Holographic Data Storage System

Tracking servo and tilt servo control are very important research in holographic data storage system. In this paper, we propose intelligent servo control by fuzzy rules in holographic data storage system. Hence, we have found pattern of tilt servo control in holographic data storage system through fuzzy system. Fuzzy rules were generated by subtractive clustering algorithm for controlling tilt servo. Therefore, we control tilt servo using fuzzy rules in holographic data storage system. Consequently, practical pattern of tilt servo control was found by intelligence algorithm in holographic data storage system.

Pattern analysis for tilt servo control in holographic data storage system

Today many media of information storage device are formed as disks. Hence, next generation removable data storage media are shaped as disk types too. The holographic data storage system also uses a disk type photopolymer media. And then, holographic data storage system is most advanced optical memory system. In 1948, Dennis Gabor made the insightful observation that the phase formation in a diffracted wavefront could be recorded by interference with a coherent background. It was not until the early 1960s with the invention of the laser that the technology became practical for storing and retrieving images, and the concepts of holographic data storage were established by van Heerden. In his seminal paper in 1963 on the theory of optical information storage in solids, van Heerden postulated that the recording of interference patterns in a three-dimensional medium could be used as a means of storing and retrieving information (Holographic data storage, Springer, New York, 2000). Tracking servo and tilt servo control are very important research in holographic data storage system. In this paper, we propose intelligent servo control by fuzzy rules in holographic data storage system. Hence, we have found pattern of tilt servo control in holographic data storage system through fuzzy system. Fuzzy rules were generated by subtractive clustering algorithm for controlling tilt servo. Therefore, we control tilt servo using fuzzy rules in holographic data storage system. Consequently, practical pattern of tilt servo control was found by intelligence algorithm in holographic data storage system (Holographic data storage, Springer, New York, 2000).

Development of dynamic tilt control method and servo algorithm in gap servo NFR

In the NFR system, since the gap between SIL and disc is under 100 nm, the traditional servo method can not be applied, and its modification is necessary for the stable servo performance. The gap error servo method is well-known as a typical servo in the NFR system (Verschuren et al. in JJAP 44:3554–3558, 2005) for focusing direction, and pull-in procedure (Zijp et al. in IEEE Trans Magn 41(2):1042–1046, 2005) and hand-over (Lee et al. in JJAP 44(5B):3423–3426, 2005) methods are also good approaches for the stable servo in the near field. We can obtain a good servo performance using the gap error servo method, and its experimental result shows that it is consistent with the previous researches. In case of the track servo, 1-beam push pull was generally used for the traditional ODD. However, it contains a DC offset components with lens movement, and thus, we can not have a good RF signal and track error signal simultaneously. Therefore, in this paper we introduce the modified servo method, which uses gap error lens position and the successful servo result for surface disc and 1.7 μm cover layer disc. Test was performed with a 4-axis actuator, and it gives a good performance not only for gap and track servo, but also for radial and tangential tilt. Finally, we suggested the decoupling method between track-shift and tilt components using the gap error differential signal and the simple slit structure. Based on the experimental result, it was verified that slit structure can eliminate the track-shift component effectively.

Tilt Error Measurement and Compensation Method for the Holographic Data Storage System Using Disturbance Observer

Tilt error can affect a serious effect to holographic data storage system using angle(polytopic) multiplexing. Because the tolerance about tilt error is very tight it is important to measure the tilt error and compensate it. In this paper, tilt error measurement system with additional red laser and reflection geometry is suggested and servo control experiments are conducted. A servo controller to compensate tilt error is designed using disturbance observer. Amount of tilt is decreased smaller than 0.01 degree and signal-to-noise ratio is increased with the tilt servo controller when 0.216 degree of tilt disturbance is applied.

Servo Technologies in a Near-Field Optical Disk Drive System

A near-field optical disk drive (NFDD) system has been predicted as a storage system with a capacity higher than 100 Gbytes in a 12-cm-sized disk and with a data transfer rate higher than 100 Mbps. The major advantage of an NFDD system with a solid immersion lens is that it is possible to utilize the technologies accumulated through conventional optical drive systems. However, the working distance in an NFDD system is only 25 nm or less, which is much smaller than that in a conventional optical disk drive system. The nano-working distance must be successfully maintained without regard to any tilts over the entire disk radius. In this study, we discuss the servo technologies in the NFDD system by focusing on the tilt servo technology which contributes to the stable gap servo performance over the entire disk radius. First, we evaluate the tilt in the NFDD system by utilizing the optically detected tilt error. Second, we propose specifications for an NFDD system on the basis of the results. We also report a tilt servo system that satisfies the specifications and discuss its effect from the viewpoint of drive performance over the entire disk radius. In addition, we suggest a novel gap servo technology utilizing the tangential tilt information and discuss its performance.

Innovative Three-Axial Actuator for High-Density Optical Drive

As the density in optical data storage systems increases, a drive capable of tilt control thus becomes necessary in order to improve the tilt margin as the coma aberration is accordingly increased. In this paper, we propose an innovative three-axial actuator based on a traditional four-wire scheme with an additional pair of tilting magnets. The proposed coil-driven servo can independently compensate plusmn1 tilt degree associated with a torque variation of less than 5%. The driving forces of the focusing and tracking are kept constant while the tilt servo is activated.

Radial and Tangential-Tilt Servo Using Four-Axis Actuator

A two-axis tilt servo using a four-axis object-lens actuator was developed. The four-axis actuator can tilt the object lens in the radial and tangential directions, and can move it to allow axial tracking or radial tracking. The tilt servo was applied on an optical disc system for next-generation digital versatile discs using a blue-violet laser, and the effect of disc-tilt compensation was determined experimentally. These experiments show that the tilt servo with the four-axis object lens actuator reduces tilt by 0.1 deg in the cases of a disc tangential tilt to 0.43 deg and a disc radial tilt to 0.47 deg.

Radial Tilt Detection Using One Beam and Its Compensation in a High-Density Read Only Memory

To increase the capacity of the optical disc, the shortening in the wavelength of the laser diode and the increase of the numerical aperture of the lens have been attempted for several years. Unfortunately, the efforts have generated adverse effects of comatic aberration caused by disc tilt. To solve this problem, a few detection and compensation methods of disc tilt have been proposed for random access memory (RAM) discs. However, no clear approach has been taken yet in the case of read only memory (ROM) disc. In this paper, we propose a method to detect the radial tilt in a high-density ROM disc using differential phase detection (DPD) signals generated by an 8 divided photodetector. The developed radial tilt servo with a 3-axis lens actuator compensates the detected radial tilt. Its effects on the tracking servo which arise when the actuator rotates are introduced. Finally, the feasibility of the proposed method is verified through experiments on a high-density ROM.

Force Characteristics of Slim Pickup Actuator to Improve Actuating Performances

Recently, there has been a trend to lower the tilt margin in multifunctional rewritable optical disk drives and many attempts have been made to construct a servo system to compensate the tilt in such devices as compact disk-rewritable (CD-RW) or digital versatile disk-random access memory (DVD-RAM) drives in view of rewritable disks. However, in the slim-type drives for Notebook PCs, it is very difficult to realize mechanisms for tilt servo without accompanying impairment of the gain property, due to spatial constraints. In this paper, we suggest a method of controlling the driving force to diminish the variance of mechanical tilt over the entire movable range of wire-spring-suspension-type actuators, and propose a process for precise analysis of driving force. In addition, based on the results of force analysis, we present the conditions that minimize the phase disturbance in subsidiary resonances which have adverse effects on the servo performance of slim-type pickup actuators.

Tilt Servo Using Modal Wavefront Actuator

In this paper, a new approach of disk tilt servo by using piezoelectric modal wavefront actuator is proposed. A compatible configuration of commerical optical pickup head (PUH) is presented with a piezoelectric folding mirror. Based on this device, the innovation has the advantages of high bandwidth, linear control, simple drive line and high spatial wavefront resolution.

The Applications of a Liquid Crystal Panel for the 15 Gbyte Optical Disk Systems

We have studied the next-generation digital versatile disk (DVD) using a blue laser and investigated the application of a liquid crystal (LC) panel to the high-density disk. The LC panel can easily shift the optical path length of light beams making it possible to cancel out wavefront aberrations. First, the authors applied an LC panel to a tilt servo system. Compared with a mechanical tilt servo system, the LC tilt servo is expected to be more compact and reliable. We also developed a system for sensing the amount of disk tilt by comparing the signal levels of crosstalk from adjacent tracks. Consequently a tilt servo without any extra sensors was achieved. Another application of the LC panel is for the compensation of spherical aberrations. It was confirmed, by simulations and experiments, that the LC panel was practically useful for correcting disk thickness error which has been determined to become more serious when a blue laser was used.

The Path from a Digital Versatile Disc (DVD) using a Red Laser to a DVD using a Blue Laser

The next generation digital versatile disc(DVD) using a blue laser is required to have 15 Gbytes capacity so that it can reproduce motion picture expert group 2(MPEG2) video stream with a main profile at a high level format for a maximum of 133 min. To achieve this goal, further improvements are necessary in both the recording and the reproducing systems. For the recording system the authors developed a super resolution recording material and an electron beam recording system. For the reproducing system the authors devised four technologies: a Viterbi decoder, a liquid crystal tilt servo system, a cross talk cancel system and a tangential adaptive equalizer. By combining these with a pick up head of 430 nm vavelength/0.6 NA lens and a 0.6-mm-thick substrate, the authors confirmed sufficient tilt margins in the case of 12.7 Gbytes (radial tilt margin: ±1.61°, tangential tilt margin: ±0.48°). Our next target is to work on the 15 Gbytes capacity.