Yuan F. Zheng

Gait synthesis for the SD-2 biped robot to climb sloping surface

A scheme to enable the SD-2 biped robot to climb sloping surfaces is proposed. By means of sensing devices, namely position sensors on the joints and force sensors underneath the heel and toe, the robot is able to detect the transition of the supporting terrain from a flat floor to a sloping surface. An algorithm is developed for the biped robot control system to evaluate the inclination of the supporting foot and the unknown gradient, and a compliant motion scheme is then used to enable the robot to transfer from level walking to climbing the slope. While the robot walks on the slope, the gait synthesis is a simple modification to the one used for level walking. Experiments with the SD-2 biped robot show that the overall scheme, while simple to implement, is powerful and reliable enough to permit walking from level to slope or vice versa. Finally, it is argued that the proposed mechanism can be extended to quasi-dynamic and dynamic gaits. >

A robotic system for crystallizing membrane and soluble proteins in lipidic mesophases

A high-throughput robotic system has been developed for crystallizing membrane proteins using lipidic mesophases. It incorporates commercially available components and is relatively inexpensive. The crystallization robot uses standard automated liquid-handlers and a specially built device for accurately and reproducibly delivering nanolitre volumes of highly viscous protein/lipid mesophases. Under standard conditions, the robot uses just 20 nl protein solution, 30 nl lipid and 1 microl precipitant solution. 96 wells can be set up using the robot in 13 min. Trials are performed in specially designed 96-well glass plates. The slim (<2 mm high) plates have exquisite optical properties and are well suited for the detection of microcrystals and for birefringence-free imaging between crossed polarizers. Quantitative evaluation of the crystallization progress is performed using an automated imaging system. The optics, in combination with the slim crystallization plates, enables in-focus imaging of the entire well volume in a single shot such that a 96-well plate can be imaged in just 4.5 min. The performance characteristics of the robotic system and the versatility of the crystallization robot in performing vapor-diffusion, microbatch and bicelle crystallizations of membrane and soluble proteins are described.

Feature-based wavelet shrinkage algorithm for image denoising

A selective wavelet shrinkage algorithm for digital image denoising is presented. The performance of this method is an improvement upon other methods proposed in the literature and is algorithmically simple for large computational savings. The improved performance and computational speed of the proposed wavelet shrinkage algorithm is presented and experimentally compared with established methods. The denoising method incorporated in the proposed algorithm involves a two-threshold validation process for real-time selection of wavelet coefficients. The two-threshold criteria selects wavelet coefficients based on their absolute value, spatial regularity, and regularity across multiresolution scales. The proposed algorithm takes image features into consideration in the selection process. Statistically, most images have regular features resulting in connected subband coefficients. Therefore, the resulting subbands of wavelet transformed images in large part do not contain isolated coefficients. In the proposed algorithm, coefficients are selected due to their magnitude, and only a subset of those selected coefficients which exhibit a spatially regular behavior remain for image reconstruction. Therefore, two thresholds are used in the coefficient selection process. The first threshold is used to distinguish coefficients of large magnitude and the second is used to distinguish coefficients of spatial regularity. The performance of the proposed wavelet denoising technique is an improvement upon several other established wavelet denoising techniques, as well as being computationally efficient to facilitate real-time image-processing applications.

Combined spatial and temporal domain wavelet shrinkage algorithm for video denoising

A combined spatial- and temporal-domain wavelet shrinkage algorithm for video denoising is presented in this paper. The spatial-domain denoising technique is a selective wavelet shrinkage method which uses a two-threshold criteria to exploit the geometry of the wavelet subbands of each video frame, and each frame of the image sequence is spatially denoised independently of one another. The temporal-domain denoising technique is a selective wavelet shrinkage method which estimates the level of noise corruption as well as the amount of motion in the image sequence. The amount of noise is estimated to determine how much filtering is needed in the temporal-domain, and the amount of motion is taken into consideration to determine the degree of similarity between consecutive frames. The similarity affects how much noise removal is possible using temporal-domain processing. Using motion and noise level estimates, a video denoising technique is established which is robust to various levels of noise corruption and various levels of motion.

Optimal 3-D coefficient tree structure for 3-D wavelet video coding

An optimal three-dimensional (3-D) coefficient tree structure for 3-D zerotree wavelet video coding is considered in this paper. The 3-D zerotree wavelet video coding is inspired by the success of the two-dimensional (2-D) zerotree wavelet image coding. Existing 3-D zerotree wavelet video codecs use the either symmetric or symmetric-alike 3-D tree structure, which is a straightforward extension of the symmetric 2-D tree structure in the zerotree wavelet image coding. In this paper, we show that the 3-D zerotree coding does not need to be applied symmetrically along all the directions, as the 2-D zerotree image coding does. We find that an asymmetric 3-D tree structure working with a more flexible asymmetric 3-D wavelet transform can produce a higher compression ratio than traditional symmetric approaches. The new 3-D tree structure can be used to improve the rate-distortion performance of many existing 3-D zerotree wavelet video codecs without sacrificing other features such as scalability and computational efficiency. The new tree structure is applied to the 3-D set partitioning in hierarchical trees method and receives convincing peak signal-to-noise ratio improvements in experiments.

Arm-manipulator coordination for load sharing using variable compliance control

Coordination of a human arm and a manipulator to share a load is a new problem. In this paper, we propose a variable compliance control as a coordination mechanism for the arm and the manipulator. The compliance will be updated according to the force exerted by the manipulator. This coordination mechanism is proposed to accommodate with the uncertainties associated with the impedance of the human arm and the weight of the object. Furthermore, the stability of the system and the manipulation speed will be improved. The stability problem is studied using the small gain theorem. Experiments were conducted in our laboratory to prove the effectiveness of the proposed scheme.

Trajectory planning for two manipulators to deform flexible beams

The coordination of two manipulators to deform flexible beams is studied. Two coordination methods are identified. The first method allows the relative position of the two manipulators to be altered, but no relative orientation changes. The second method allows both the position and the orientation to be altered. By studying the mechanics of elastic deformations the performance of the methods, in terms of the interaction forces and moments between the object and the manipulators, is analyzed. The analysis shows that the second mechanism may result in less interaction forces and moments than the first. Optimal motion trajectories of the end-effectors to generate zero interaction moments in the second mechanism are then derived.<<ETX>>

Object Tracking in Structured Environments for Video Surveillance Applications

We present a novel tracking method for effectively tracking objects in structured environments. The tracking method finds applications in security surveillance, traffic monitoring, etc. In these applications, the movements of objects are constrained by structured environments. Therefore, the relationship between objects and environments can be exploited as additional information for improving the performance of tracking. We use the environment state to model the relationship between the objects and environments, and integrate it into the framework of Bayesian tracking. In this paper, distance transform is used to model the environment state, and particle filtering is employed as the paradigm for solving the Bayesian tracking problem. The adaptive dynamics model and environment prior are devised for the particle filter to fully utilize the environment information in the tracking process. Experiments on some video surveillance sequences demonstrate the effectiveness and robustness of our approach for tracking object motions in structured environments.

Automatic Liquid Handling for Life Science A Critical Review of the Current State of the Art

Liquid handling plays a pivotal role in life science laboratories. In experiments such as gene sequencing, protein crystallization, antibody testing, and drug screening, liquid biosamples frequently must be transferred between containers of varying sizes and/or dispensed onto substrates of varying types. The sample volumes are usually small, at the micro- or nanoliter level, and the number of transferred samples can be huge when investigating large-scope combinatorial conditions. Under these conditions, liquid handling by hand is tedious, time-consuming, and impractical. Consequently, there is a strong demand for automated liquid-handling methods such as sensor-integrated robotic systems. In this article, we survey the current state of the art in automatic liquid handling, including technologies developed by both industry and research institutions. We focus on methods for dealing with small volumes at high throughput and point out challenges for future advancements.

Arm-manipulator coordination for load sharing using compliant control

Arm-manipulator coordination is a new coordination problem in robotics. Human arm-manipulator coordination is superior to both arm-arm coordination and manipulator-manipulator coordination. Likewise, it is expected to have powerful impacts on many applications in the manufacturing, service, and construction industries. This paper introduces this problem and investigates the coordination using a compliant control method. There are several problems in this scheme. First, the stability problem is studied using the Routh-Hurwitz criterion. Then, a very important aspect of the arm-manipulator coordination problem, load sharing, is investigated. Experimental analysis proves the effectiveness of the proposed schemes.