Shir-Kuan Lin

Low dark current quantum-dot infrared photodetectors with an AlGaAs current blocking layer

Low dark current InAs/GaAs quantum-dot infrared photodetectors (QDIPs) are demonstrated. The dark current is reduced by over three orders of magnitude by using a thin AlGaAs current blocking layer. This thin AlGaAs layer reduces the dark current much more than the response signal. The responsivity at 0.5 V is 0.08 A/W with a peak detection wavelength at 6.5μm. The corresponding detectivity is 2.5×109 cm Hz1/2/W1/2, which is the highest detectivity reported for a QDIP at 77 K.

Nonovershooting and monotone nondecreasing step responses of a third-order SISO linear system

This paper presents the necessary and sufficient conditions for a third-order single-input/single-output (SISO) linear system to have a nonovershooting (or monotone nondecreasing) step response. If the transfer function of an overall system has real poles, a necessary and sufficient condition is found for the nonovershooting (or monotone nondecreasing) step response. In the case of complex poles, one sufficient condition and two necessary conditions are obtained. The resulting conditions are all in terms of the coefficients of the numerator of the transfer function. Simple calculations can be used to check a system for the nonovershooting (or monotone nondecreasing) step response. Another feature is that the conditions in terms of pole-zero configurations can be easily derived from the present results.

Design of a voice coil motor used in the focusing system of a digital video camera

This paper raises a valid method to design a voice coil motor (VCM) used in the focusing system of a digital video camera (DVC). A better VCM performance, such as lower battery consumption, higher efficiency, and shorter focusing time, can be achieved by turning the diameter of a winding coil, the thickness of the magnet, and the winding spaces in a VCM.

Deep level transient spectroscopy characterization of InAs self-assembled quantum dots

Deep level transient spectroscopy (DLTS) was used to obtain the energy level and the capture characteristics of InAs self-assembled quantum dots embedded in GaAs. A specially designed structure was used for the DLTS measurement for enhanced resolution. This structure allows us to detect capacitance relaxation signal from a single layer of quantum dots and to separate this signal from those of the DX centers inside the structure. The DLTS spectra with different filling pulses and different rate windows provide clear information on the energy level and the capture characteristics of the quantum dots.

An identification method for estimating the inertia parameters of a manipulator

This article presents an off-line identification method to estimate the minimal knowledge of the inertia parameters for determining the dynamic model of a manipulator. A new approach is proposed to find a set of the minimal knowledge of the inertia parameters. This set is recursively estimated by moving one joint at a time. The off-line identification procedure also provides a sufficient condition for a persistently exciting trajectory. A simulation example of Stanford arm illustrates the validity and simplicity of the identification procedure.

Low power consumption focusing actuator for a mini video camera

A novel low power consumption autofocusing actuator in a mini video camera is constructed in accordance with the result of a systematic design procedure of voice coil motors (VCM). This paper emphasizes the position control of such a VCM. The position feedback signals are provided by a magnetoresistive (MR) encoder. The position estimation algorithm (PEA) is developed to precisely decode the MR signals for the position of the moving part of the VCM. Different postures change the loading of the moving part of the VCM, so that an adaptive model-following control system based on the PEA is proposed to compensate for the loading variation. The experiments verify the fast dynamic performance and high power efficiency of the VCM.

Sliding-mode direct torque control of an induction motor

This paper proposes a new sliding-mode direct torque control (DTC) for an induction motor. This DTC is established by designing two sliding surfaces for the torque and the flux. The authors propose a novel sliding surface for the torque, which is based on the integral-sliding surface, whereas the sliding surface for the flux follows that of Benchaib et al. (1999). They also modify the flux observer of Benchaib and Edwards (2000) by using the adaptive sliding-mode method. This not only eliminates the estimation of the uncertainty bounds, but also improves the performance of sliding control. A practical application of the proposed DTC to the position control of a motor is also presented. Some experiments verify the control theory and demonstrate the usefulness of the proposed DTC.

Microprocessor Implementation of the Inverse Dynamical System for Industrial Robot Control

Abstract The inverse system problem of robot control is resurveyed. It is found, that the body-fixed coordinate system also plays an important role in computational efficiency of inverse dynamical formulations. The driving-axis coordinate system, whose origin locates on the driving axis of each link, is proposed to derive the recursive Newton-Euler formulation of manipulator inverse dynamics. The new algorithm with considering trivial calculations is implemented using the Assembly language on an INTEL 8086/8087 microprocessor (5 MHz clock). The measurement of computational efficiency shows that this software package marginally satisties the sampling rate criterion of robot control even with a 16-bit microprocessor

Fall detection for multiple pedestrians using depth image processing technique

A fall detection method based on depth image analysis is proposed in this paper. As different from the conventional methods, if the pedestrians are partially overlapped or partially occluded, the proposed method is still able to detect fall events and has the following advantages: (1) single or multiple pedestrian detection; (2) recognition of human and non-human objects; (3) compensation for illumination, which is applicable in scenarios using indoor light sources of different colors; (4) using the central line of a human silhouette to obtain the pedestrian tilt angle; and (5) avoiding misrecognition of a squat or stoop as a fall. According to the experimental results, the precision of the proposed fall detection method is 94.31% and the recall is 85.57%. The proposed method is verified to be robust and specifically suitable for applying in family homes, corridors and other public places.

A Novel Twelve-Step Sensorless Drive Scheme for a Brushless DC Motor

This paper presents a novel twelve-step sensorless drive scheme for a three-phase brushless DC motor, which combines the traditional six-step 120deg and 180deg conduction modes and has varied active angular period. The proposed scheme is implemented on a single FPGA-chip. Several experiments for various active angle periods from 124deg to 168.75deg are undertaken. The experimental results show that the torque constant is larger for the larger active angular period