A generalized control framework of assistive controllers and its application to lower limb exoskeletons

Various control methods have been studied for the natural assistance of human motions by exoskeletal robots, i.e., wearable robots for assisting the human motions. For example, impedance control and compliance control are widely used for controlling interaction forces between a human and a robot. When an accurate measurement of the human muscular force is available (e.g., electromyography), a direct use of the estimated human joint torque is possible in the control of an assistive robot. The human motions in a daily living, however, are so complex that they are constituted by multiple phases, such as walking, sitting, and standing, where the walking can be further categorized into multiple sub-phases. Therefore, a single control method cannot be the best option for all the motion phases; a switch in the control algorithms may be necessary for assisting human movements in multiple motion phases. In this paper, a generalized control framework is proposed to incorporate the various assistive control methods in one general controller structure, which consists of Feedforward Disturbance Compensation Control, Reference Tracking Feedback Control, Reference Tracking Feedforward Control, Model-based Torque Control. The proposed control framework is designed taking into consideration of the linearity of each control algorithm, and thus it enables the continuous and smooth switching of assistive control algorithms, and makes it possible to analyze the stability of the overall control loop. The proposed method is implemented into a lower-limb exoskeleton robot and is verified by experimental results.     

Multichannel image contrast enhancement based on linguistic rule-based intensificators

This study follows the direct approach to image contrast enhancement, which changes the image contrast at each its pixel and is more effective than the indirect approach that deals with image histograms. However, there are only few studies following the direct approach because, by its nature, it is very complex. Additionally, it is difficult to develop an effective method since it is required to keep a balance in maintaining local and global image features while changing the contrast at each individual pixel. Moreover, raw images obtained from many sources randomly influenced by many external factors can be considered as fuzzy uncertain data. In this context, we propose a novel method to apply and immediately handle expert fuzzy linguistic knowledge of image contrast enhancement to simulate human capability in using natural language. The formalism developed in the study is based on hedge algebras considered as a theory, which can immediately handle linguistic words of variables. This allows the proposed method to produce an image contrast intensificator from a given expert linguistic rule base. A technique to preserve global as well as local image features is proposed based on a fuzzy clustering method, which is applied for the first time in this field to reveal region image features of raw images. The projections of the obtained clusters on each channel are suitably aggregated to produce a new channel image considered as input of the pixelwise defined operators proposed in this study. Many experiments are performed to demonstrate the effect of the proposed method versus the counterparts considered.     

FPGA implementation of reversible watermarking in digital images using reversible contrast mapping

Reversible contrast mapping (RCM) and its various modified versions are used extensively in reversible watermarking (RW) to embed secret information into the digital contents. RCM based RW accomplishes a simple integer transform applied on pair of pixels and their least significant bits (LSB) are used for data embedding. It is perfectly invertible even if the LSBs of the transformed pixels are lost during data embedding. RCM offers high embedding rate at relatively low visual distortion (embedding distortion). Moreover, low computation cost and ease of hardware realization make it attractive for real-time implementation. To this aim, this paper proposes a field programmable gate array (FPGA) based very large scale integration (VLSI) architecture of RCM-RW algorithm for digital images that can serve the purpose of media authentication in real-time environment. Two architectures, one for block size (8 × 8) and the other one for (32 × 32) block are developed. The proposed architecture allows a 6-stage pipelining technique to speed up the circuit operation. For a cover image of block size (32 × 32), the proposed architecture requires 9881 slices, 9347 slice flip-flops, 11291 number 4-input LUTs, 3 BRAMs and a data rate of 1.0395 Mbps at an operating frequency as high as 98.76 MHz.     

松辽盆地梨树断陷小宽断层走滑位移量恢复研究

小宽断层是梨树断陷内一条重要的走滑断层,是在火石岭时期区域NW向拉张应力产生的基底断层基础上发育形成,受营城组末期区域左旋走滑作用开始走滑活动,在登娄库末期强烈走滑,最终在嫩江组末期区域NW向挤压反转作用下定型。本文通过对小宽断层特征的详细分析,利用地层厚度对比法,以营城组厚度为参照,选取不同距离进行反推厚度对比,分析表明,小宽断层走滑位移在3~5km之间。     

In situ mechanical compression of polycrystalline BaTiO3 in the ESEM

Ferroelectric BaTiO₃ was mechanically compressed in situ, in an environmental scanning electron microscope equipped with a compression stage and domain wall motion was recorded using orientation contrast imaging. Before and after the experiment, the sample was characterized by electron backscatter diffraction (EBSD) in order to determine the misorientation between single domains which was 90° in every case. During the compression test, the microstructure changed from a banded twin structure to lamellar twinning.     

Effect of cycle time and duty cycle on psychophysically determined acceptable levels in a highly repetitive task

Psychophysical methodology has been used to develop guidelines for lifting and more recently similar methods have been applied to repetitive upper limb movements. While a range of cycle times are usually used, there is often no control for duty cycle. The purpose of this paper is to present psychophysically determined acceptable torques for a common upper limb task, with both cycle time and duty cycle conditions set by the researcher. Eight female participants, sitting at adjustable workstations, performed a simulated in-line screw running task. A computer-controlled torque motor applied a torque every 3, 6, 12 or 20?s with a duty cycle of 25, 50 or 83%. The participants worked with one set of conditions each day and self-selected the highest torque that they felt was acceptable without developing undue pain and discomfort. Duty cycle was found to significantly affect the amount of torque selected. With duty cycle controlled, cycle time was no longer found to have any significant effect on selected torque. Acceptable torques for 25, 50 and 83% duty cycles were 1.09, 0.9 and 0.73 Nm. Discomfort and stiffness were concentrated on the back of the hand and on the thumb web. These findings suggest that increased perception of discomfort with increased frequency (decreased cycle time) may be related to decreased rest/recovery time for muscles.     

The predictive validity of the RSI QuickScan questionnaire with respect to arm,shoulder and neck symptoms in computer workers

The aim of this study was to determine whether results from the RSI QuickScan questionnaire on risk factors for arm, shoulder and neck symptoms can predict future arm, neck and shoulder symptoms in a population of computer workers. For this prospective cohort study, with a follow-up of 24 months, 3383 workers who regularly worked with a computer were approached. Generalised estimating equations (GEE) with 6, 12, 18 and 24 months time lags were used to determine whether high exposure was related to symptoms at follow-up. The results showed that high scores on 9 out of 13 scales, including previous symptoms, were significantly related to arm, shoulder and neck symptoms at follow-up. These results provide support for the predictive validity of the RSI QuickScan questionnaire.

Practitioner Summary: The results showed that high scores on 9 out of 13 scales, including previous symptoms, were significantly related to arm, shoulder and neck symptoms at follow-up. The RSI QuickScan questionnaire may be recommended as a tool in the identification of computer workers who should be targeted with interventions aimed at prevention of future symptoms.     

Analysing observer preferences when presenting a product in a rendered scene: 2D vs. autostereoscopic 3D displays

ABSTRACT

This research compares the way the image of a product included within a rendered scene shown on an autostereoscopic 3D display is rated versus the same image shown in a 2D display. The purpose is to understand the observer's preferences and to determine the features that a composition should have to highlight the product and to make its presentation more attractive to observers, thereby helping designers and advertisers who use both displays to prepare images to make them more effective when visually presenting a product.

The results show that observers like the images on autostereoscopic 3D displays slightly more than those presented by means of 2D displays. On both displays the product is perceived more quickly when it is larger than the other elements and is shown with greater chromatic contrast, but a composition is seen as more attractive when the chromatic relationship between all the elements is more harmonious.     

Morphological contrast index based on the Weber's law

In this article, a morphological contrast index based on the Weber's law is proposed to quantify the contrast in a processed image. This measure involves the contours of the image along with its background. The proposal made here is applied to detect the image with higher contrast, and also identify the enhanced image most similar to the original. Moreover, the contrast index is compared with other four indexes reported in the current literature. © 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 137–144, 2012     

航空精密铸件射线CR成像检测研究

根据ASTM E192验收标准,对某精铸件加工的孔型和槽型缺陷,分别采用CR和C7胶片进行射线检测对比.由于CR图像灰度范围宽,细节影像不易直接观察,采用多尺度对比度增强算法提取细节信息进行增强放大,人眼可直接从增强后的图像识别细节信息.CR与C7胶片检测对比试验结果表明,CR图像的质量已达到C7胶片的检测质量,可降低检测成本和提高检测效率,能代替C7胶片实现该精铸件的数字射线照相检测.