Dynamic Three-dimensional Environment Research Articles

Motion planning for an under-actuated autonomous underwater vehicle based on fast marching nonlinear model-predictive quantum particle swarm optimization

The motion planner determines the autonomy of the autonomous underwater vehicle. However, many studies often ignore the characteristics of autonomous underwater vehicles and the underwater environment, resulting in unreasonable trajectories. To solve this problem, this paper plans the motion force through prediction and optimization to integrate the characteristics of the autonomous underwater vehicle. The fast travel algorithm is modified to take advantage of favorable currents and output arrival times, taking into account the peculiarities of the underwater environment. A novel objective function is proposed, which incorporates the arrival times to imply the requirements of obstacle avoidance and distance optimization. A penalty item is included in the objective function to avoid strong side flow. At the same time, the force and its changing rate limited in appropriate ranges are also included to balance energy consumption. In order to meet the high running time requirements in practical applications, the warm-start improved quantum particle swarm optimization is introduced into force optimization. Simulation studies are performed on a self-developed autonomous underwater vehicle. The method has good application effects in multi-island areas, ocean currents, and dynamic three-dimensional environments. Comparative simulations show that the planner plans shorter paths with good robustness and adaptability.

English

Reconstruction of a maxillofacial skeletal defect in the recent past has witnessed a paradigm shift in the process of treatment planning. It has now become a collaboration between the surgeon and the bioengineer to provide a customised stable reconstruction. Understanding maxillofacial skeleton from an architectural and biomechanical perspective would not only guide the surgeon in planning a reconstruction but also the bioengineer to select the biomaterial and design an ideal reconstruction. This paper intended to provide an insight into scientific concepts which needed to be considered during the designing of biomaterials for reconstruction of maxillofacial skeletal defects. Any object in the world, from a mechanical perspective is seen only as a material of varying physical and chemical (organic / inorganic) properties dwelling in a dynamic three-dimensional environment. Bone continuously has been re-modelling by adapting to the dynamic loading environment through an established force distribution pattern of equilibrium. 1 Hence, for a patient requiring reconstruction of defects of varying dimensions within the craniomaxillofacial skeleton, its architectural complexity should be seen from both the surgeon’s and bioengineer’s perspective. Such multidisciplinary approach would provide a customized comprehensive reconstructive and rehabilitative solution.

The relationship between reflex eye realignment and the percept of single vision in young children

Effective binocular vision is dependent on both motor and perceptual function. Young children undergo development of both components while interacting with their dynamic three-dimensional environment. When this development fails, eye misalignment and double vision may result. We compared the range of image disparities over which young children display reflex motor realignment of their eyes with the range over which they report a single versus double percept. In response to step changes in the disparity of a 2.2° wide stimulus, 5-year-olds generated an adult-like reflex vergence velocity tuning function peaking at 2° of disparity, with a mean latency of 210 ms. On average, they reported double vision for stimulus disparities of 3° and larger, compared to 1° in adult reports. Three-year-olds also generated reflex vergence tuning functions peaking at approximately 2° of disparity, but their percepts could not be assessed. These data suggest that, by age 5, reflex eye realignment responses and percepts driven by these brief stimuli are tightly coordinated in space and time to permit robust binocular function around the point of fixation. Importantly, the plastic neural processes maintaining this tight coordination during growth control the stability of visual information driving learning during childhood.

A real-time path planning algorithm for cable-driven parallel robots in dynamic environment based on artificial potential guided RRT

This paper deals with the collision-free path planning of cable-driven parallel robots (CDPRs) in a dynamic three-dimensional environment. The proposed algorithm is based on the artificial potential field (APF) approach which provides a simple and effective path planning method. However, the APF approach is easy to cause the robot oscillation and hard to reach the goal when it is applied in a dynamic environment. To overcome these two problems, the rapidly exploring random tree (RRT) was used to provide a random disturbance in order to reduce oscillations and reach the goal in less time. Due to the particularity of CDPRs, the proposed algorithm consider the wrench feasible workspace (WFW) and various collision conditions caused by the cable. The proposed algorithms were evaluated with three kinds of simulations. According to the simulation results, the proposed algorithms found an optimized path with less time cost was reduced about 27% compared with the APF approach. Furthermore, the oscillation phenomenon in the APF approach was effectively mitigated by 49%. Finally, the experimental result demonstrates the validity of the proposed algorithm.

Binocular viewing geometry shapes the neural representation of the dynamic three-dimensional environment.

Sensory signals give rise to patterns of neural activity, which the brain uses to infer properties of the environment. For the visual system, considerable work has focused on the representation of frontoparallel stimulus features and binocular disparities. However, inferring the properties of the physical environment from retinal stimulation is a distinct and more challenging computational problem-this is what the brain must actually accomplish to support perception and action. Here we develop a computational model that incorporates projective geometry, mapping the three-dimensional (3D) environment onto the two retinae. We demonstrate that this mapping fundamentally shapes the tuning of cortical neurons and corresponding aspects of perception. For 3D motion, the model explains the strikingly non-canonical tuning present in existing electrophysiological data and distinctive patterns of perceptual errors evident in human behavior. Decoding the world from cortical activity is strongly affected by the geometry that links the environment to the sensory epithelium.

The Importance of the Interaction Between Ocular Motor Function and Vision During Human Infancy.

Numerous studies have demonstrated the impact of imposed abnormal visual experience on the postnatal development of the visual system. These studies have provided fundamental insights into the mechanisms underlying neuroplasticity and its role in clinical care. However, the ocular motor responses of postnatal human infants largely define their visual experience in dynamic three-dimensional environments. Thus, the immature visual system needs to control its own visual experience. This review explores the interaction between the developing motor and sensory/perceptual visual systems, together with its importance in both typical development and the development of forms of strabismus and amblyopia.

Regulation of mechanotransduction: Emerging roles for septins.

Cells exist in dynamic three‐dimensional environments where they experience variable mechanical forces due to their interaction with the extracellular matrix, neighbouring cells and physical stresses. The ability to constantly and rapidly alter cellular behaviour in response to the mechanical environment is therefore crucial for cell viability, tissue development and homeostasis. Mechanotransduction is the process whereby cells translate mechanical inputs into biochemical signals. These signals in turn adjust cell morphology and cellular functions as diverse as proliferation, differentiation, migration and apoptosis. Here, we provide an overview of the current understanding of mechanotransduction and how septins may participate in it, drawing on their architecture and localization, their ability to directly bind and modify actomyosin networks and membranes, and their associations with the nuclear envelope.

UAV formation control design with obstacle avoidance in dynamic three-dimensional environment.

This paper considers the artificial potential field method combined with rotational vectors for a general problem of multi-unmanned aerial vehicle (UAV) systems tracking a moving target in dynamic three-dimensional environment. An attractive potential field is generated between the leader and the target. It drives the leader to track the target based on the relative position of them. The other UAVs in the formation are controlled to follow the leader by the attractive control force. The repulsive force affects among the UAVs to avoid collisions and distribute the UAVs evenly on the spherical surface whose center is the leader-UAV. Specific orders or positions of the UAVs are not required. The trajectories of avoidance obstacle can be obtained through two kinds of potential field with rotation vectors. Every UAV can choose the optimal trajectory to avoid the obstacle and reconfigure the formation after passing the obstacle. Simulations study on UAV are presented to demonstrate the effectiveness of proposed method.

A novel fuzzy control algorithm for three-dimensional AUV path planning based on sonar model

A novel fuzzy control method is presented for AUV (Autonomous underwater vehicles) path planning in both static and dynamic three-dimensional environment. First, on the basis of the forward looking sonar model, the virtual acceleration and velocity of AUV in both horizontal and vertical plane can be gotten through the fuzzy system. Then the velocity synthesis approach is applied to generate the real control variables in the body-fixed frame. In addition, a fuzzy-inference system with an accelerate/break (A/B) module is developed for real-time navigation, which enables AUV to avoid dynamic obstacles automatically. Finally, simulation results indicate the effectiveness and feasibility of the proposed approach.

WARP Is a Novel Multimeric Component of the Chondrocyte Pericellular Matrix That Interacts with Perlecan

WARP is a novel member of the von Willebrand factor A domain superfamily of extracellular matrix proteins that is expressed by chondrocytes. WARP is restricted to the presumptive articular cartilage zone prior to joint cavitation and to the articular cartilage and fibrocartilaginous elements in the joint, spine, and sternum during mouse embryonic development. In mature articular cartilage, WARP is highly specific for the chondrocyte pericellular microenvironment and co-localizes with perlecan, a prominent component of the chondrocyte pericellular region. WARP is present in the guanidine-soluble fraction of cartilage matrix extracts as a disulfide-bonded multimer, indicating that WARP is a strongly interacting component of the cartilage matrix. To investigate how WARP is integrated with the pericellular environment, we studied WARP binding to mouse perlecan using solid phase and surface plasmon resonance analysis. WARP interacts with domain III-2 of the perlecan core protein and the heparan sulfate chains of the perlecan domain I with K(D) values in the low nanomolar range. We conclude that WARP forms macromolecular structures that interact with perlecan to contribute to the assembly and/or maintenance of "permanent" cartilage structures during development and in mature cartilages.

Perspective Guidance Displays Show the Way Ahead

LITTLE over two decades ago, programmable electronic flight instrument display systems (EFIS) were introduced in commercial aviation aircraft such as the Boeing B757/767. The introduction comprised three new instruments: the primary flight display (PFD), replacing the traditional attitude director indicator (ADI); the navigation display (ND), replacing the horizontal situation indicator (HSI); and the engine indicating and crew alerting system (EICAS), replacing the engine gauges and a whole slew of other indicators and controls. This introduction changed the face of the cockpit flight instrument panels in civil aviation, earning its nickname of “glass cockpit”. However, more than the mere looks of the flight deck changed. The flight management system (FMS) got a central role in the flight practice, and piloting changed, from interaction with the aircraft supported by some automation to interaction mainly with the automated systems. The introduction of the glass cockpit and the new way of flying civil transport aircraft through automation was reluctantly accepted by the pilot community. Besides early complaints about the readability of EFIS displays, the main issues were the problems of keeping the pilot in the loop, and explaining what the automation is doing at any time, supporting the flight crew “mode awareness”. Still, as accident statistics now show, safety has increased and nowadays flight decks with EFIS and FMS are the norm for commercial and business aviation, and are introduced even in general aviation. With the introduction of the glass cockpit came an increased level of navigational situation awareness, in particular through the added functionality of the navigation display. Its forebear, the HSI, showed an abstract presentation of relative bearings to selected beacons and the distance expressed in dots to VOR radials or the localizer. The ND replaced this by a much more intuitive display of relative geographical position with respect to waypoints on the planned route, approach fixes, markers, and the runway centerline. A planned approach was now visible on the display rather than just on an approach plate. As altitude and speed constraints could be assigned to waypoints in an approach procedure, the energy management during an approach, which depended so far on rough mental computations, was significantly improved as well. Although the electronic instruments offer much more functionality and integrated information than their electromechanical counterparts, they still are not more than two-dimensional “orthogonal” presentations of attitude and geographical position which the pilot must mentally integrate. There must be a world of possibilities in the electronic instrumentation that we have only begun to explore. Unlike autonomous robotic vehicles, humans are capable of interpreting and moving through dynamic three-dimensional environments with little or no conscious mental effort. This talent to intuitively do things right, to not become disoriented or collide with obstacles while moving through the most complex of environments, is a product from ages of evolution. Besides mental reasoning, judgment and a talent for producing solutions when confronted with unforeseen situation (in other words, improvisation) this represents one of the important assets of the human pilot. However, it was up to now not exploited to its fullest potential because of the “unnatural” way of presenting the information to the pilot. Therefore, the current practice to have different abstract, two-dimensional presentations of the aircraft guidance and navigation situation needs to be revised. A future primary flight display should present the aircraft’s spatio-temporal situation, i.e. its motion in space and time, in a way that is intuitively understandable, that supports pilots in their manual and supervisory control tasks, enhances their situation awareness even more, and is compatible with the various tasks imposed by the air traffic management system, now and in the future. Advances in this field have been made with perspective flight-path displays such as the “tunnel-in-thesky,” the “pathway-in-the-sky,” or the “highway-in-the-sky”. These displays integrate the guidance information with