Image Identification of a Moving Object Based on an Improved Canny Edge Detection Algorithm

Edge detection plays an increasingly critical role in image process community, especially for moving object identification problems. For this case, the target object can be captured straightly via the edges beside which there is an obvious jump of grey value or texture. Nowadays, Canny operator has gained great popularity as it shows higher anti-noise performance and presents better detection accuracy in comparison with other edge detection operators like Robert’s, Sobel’s, Prewitt’s etc. However, the Gaussian filter associated with the classic Canny operator is sometimes too simple to decrease the all-type-noise. Additionally, in order to enhance the detection accuracy and lower the pseudo-edges detection ratio, two thresholds, high and low, are chosen artificially which have actually limited the adaptability of the algorithm. In this work, a compound filter, Gaussian-Median filter, is proposed to improve the smoothing effect. The self-adaptive multi-threshold Otsu algorithm is realized to determine the high/low threshold automatically according to the grey value statistic. Image moment method is conducted on basis of the detected moving object edges to locate the centroid and to compute the principal orientation. The experimental results based upon locating the edges of both static and moving objects proved the good robustness and the excellent accuracy of the proposed method.

An Improved Analytical Model of Friction and Ball Motion in Linear Ball Bearings With Application to Ball-to-Ball Contact Prediction

The friction behavior of rolling ball machine components like linear ball bearings is very important to their functionality. For instance, differences in linear velocity of balls induces ball-to-ball contact in certain circumstances, resulting in significant increases and variations in friction. In this paper, an improved analytical formula for determining the linear velocity of balls in four-point-contact linear ball bearings is derived as a function of contact angle deviations and contact forces. The analytical formula is validated against a comprehensive friction model in the literature and shown to be in good agreement, while an oversimplified analytical model proposed by the authors in prior work is shown to be inaccurate. A case study is presented where insights gained from the derived analytical formula are used to mitigate velocity difference of balls in a linear ball bearing which otherwise would experience ball-to-ball contact.

Minimum Energy Control of Redundant Systems Using Evolutionary Bi-Level Optimization

Redundant manipulators are mechanical systems with more degrees of freedom than required for their task. The paper considers the problem of energy minimization, given a required task, for such systems. The problem is formulated as a constrained optimal control with additional inequality constraints. A dynamic projection enables transforming the problem into an equivalent unconstrained, reduced order one. The solution scheme presented here combines the problems of path planning and tracking control. It includes decomposition of the problem into a bi-level structure. The parametric, higher-level problem is solved using a genetic algorithm and the lower level one is solved using optimal control. Comparison with full optimal control solutions shows the superiority of the combined evolutionary algorithm in terms of computational feasibility and overall energy savings.

A Game-Theoretic Approach to Defending Nuclear Instrumentation and Control Systems From Cyber-Threats

Cyber-physical systems consist of interconnected physical processes and computational resources. Because the cyber and physical worlds are integrated, the system’s physical assets are vulnerable to cyber-attack. An attacker who is able to access control inputs and mask measurements can damage the system while remaining undetected. By masking certain measurement signals, an attacker may render part of the state space unobservable, meaning that it is impossible to reconstruct those states. This is called an observability attack. A game-theoretic approach is presented to analyze observability attacks. The attacker’s strategy set includes all possible combinations of masked measurements. The defender’s strategy set includes redundant sensing and direct measurement of state variables. Attacker and defender payoffs are quantified using the responses of the observable and unobservable states. The observability attack game is analyzed for a nuclear balance of plant system. Combinations of sensor omissions are analyzed to find observability attacks with high impact and low detection. The effects of sensor augmentation are examined. A pure strategy Nash equilibrium is identified.

Dynamic Analysis for Motor-Powered Periotomes in Dentistry

A periotome is a hand-held manual instrument that dentists use during tooth extraction. Using the sharp blade at the tool tip, dentists cut the periodontal ligaments that bonds the alveolar bone and the cementum surrounding the roots of teeth. Since this procedure usually requires dentists to repeatedly apply a certain level of force on the hand-held tool during the long-time procedure, it leads to dentists’ fatigue on their hands, inaccurate hand motion, and patients’ discomfort. Motorized periotomes can significantly improve the tooth extraction procedure by decreasing the force required from a dentist and reducing the procedure time. In this paper, we consider simple designs for motor-powered periotomes focusing on dynamic behaviors. Since the motor inside the tool creates motion and the hand-held tool moves as a result of dynamic response, the analysis requires detailed consideration of many factors such as tool mass, hand stiffness and damping. The motion of the tool tip should be monitored in this analysis to maximize the cutting performance. The analysis results will be used for choosing design options and parameters. This approach will be demonstrated using dynamic modeling and computer simulations.

Developing an Advance Tire Hydroplaning Model Using Co-Simulation of Fully Coupled FEM and CFD Codes to Estimate Cornering Force

Hydroplaning is a phenomenon which occurs when a layer of water between the tire contact patch and pavement pushes the tire upward. The tire detaches from the pavement, preventing it from providing sufficient forces and moments for the vehicle to respond to driver’s control inputs such as breaking, acceleration and steering. This work is mainly focused on the tire and its interaction with the pavement to address hydroplaning. Fluid Structure Interactions (FSI) between the tire-water-road surfaces are investigated through two approaches. In the first approach, the coupled Eulerian-Lagrangian (CEL) formulation was used. The drawback associated with the CEL method is the laminar assumption and that the behavior of the fluid at length scales smaller than the smallest element size is not captured. As a result, in the second approach, a new Computational Fluid Dynamics (CFD) Fluid Structure Interaction (FSI) model utilizing the shear-stress transport k-ω model and the two-phase flow of water and air, was developed that improves the predictions with real hydroplaning scenarios. Review of the public literature shows that although FEM and CFD computational platforms have been applied together to study tire hydroplaning, developing the tire-surrounding fluid flow CFD model using Star-CCM+ has not been done. This approach, which was developed during this research, is explained in details and the results of hydroplaning speed and cornering force from the FSI simulations are presented and validated using the data from literature.

Improving Motion Stability of the Plane 3-RPR Parallel Manipulator at Singular Configuration

Kinematic parameters have significant influences on the motion stability of parallel manipulators at singular configureations. Taking the plane 3-RPR parallel manipulator as an example, the motion stability at different types of singular configurations corresponding to the angular speed and velocity of the movable platform are investigated. At first, the second order of uncoupled dynamics equation for the 3-RPR parallel manipulator is established with the aid of the second class Lagrange approach. According to the Lyapunov first approximate stability criterion, the approximate conditions for the 3-RPR parallel manipulator with a stabile motion at singular configurations are determined based on the Gerschgorin circle theorem. Next, the exact Hurwitz criterion is utilized to study the motion stability and the load capability of the manipulator corresponding to the angular speed and velocity of the movable platform, as well as the directions of the external forces at two kinds of singular configurations: with a gained rotation-type DOF, and with a gained translation-type DOF, respectively. The results show that increasing both the angular speed and the velocity of the mass center of the movable platform can efficiently improve the motion stability of the 3-RPR parallel manipulator at singular configurations.

Numerical Modeling and Analysis of Nonlinear Dynamic Response for a Bolted Joint Beam Considering Interface Frictional Contact

For an assembled structure with many bolted joints, predicting its dynamic response with high fidelity is always a difficult problem, because of the nonlinearity introduced by friction contact between jointed interfaces. The friction contact results in nonlinear stiffness and damping to a structure. To realize predictive simulation in structural dynamic design, these nonlinear behaviors must be carefully considered. In this paper, the dynamics of a multi-bolt jointed beam is calculated. A modified IWAN constitutive model, which can consider both tangential micro/macro slip and nonzero residual stiffness at macroslip phase, is developed to model nonlinear contact behaviors due to joint interfaces. A whole interface element integrating the proposed constitutive model is developed. The element is used to model the nonlinear stiffness and damping caused by bolted joints. The interface element is placed between the two contact interfaces. The other part of the beam is modeled by linear beam elements. A Matlab code is developed to realize the proposed nonlinear finite element dynamic analysis method. A hammer impact experiment for the bolt-jointed beam is conducted under different excitation force levels. The calculated nonlinear numerical results are compared with experimental results. It is shown that the effect of joint nonlinearity on structural dynamics can be observed from the response predicted by the proposed method. The numerical results agree well with the experimental results. This work validates the necessary of using nonlinear joint model for dynamic simulation of jointed structures.

Motion Capture of the Selective Hand Picking Movements As the Basis for the Design of Mechanically Assisted Picking Tools in Coffee Plantations in Colombia

Besides oil, coffee is one of the most traded commodities worldwide. Colombia is known as the producer of the highest quality coffee in the world, thanks to its smooth taste and aroma. One of the key elements that are responsible for the quality of Colombian coffee is its harvesting method, in which it is enforced that only mature fruits are harvested. Given the terrain conditions in which coffee trees grow, the preferred harvesting method in Colombia is selective hand picking, in which each coffee grain is individually teared off from the branch that is attached to. This work focuses on the analysis of the motion of a human hand performing the action of manual selective coffee harvesting. The analysis is based on the data collected from a custom made motion capture system, which consists of a glove capable of sensing the angular movement of the joints, and accelerations at the tip of the fingers, by means of a set of flex sensors and accelerometers, respectively. The methods followed in this investigation include the study of the biomechanics of the hand, as applied to the motion of hand picking of coffee, which proved to be fundamental for the analysis of the experimentally measured data. After processing the experimental data, the patterns of movement done by a human coffee harvester can be simulated and replicated, which allows identifying trajectories that a good harvester follows, as compared to other harvesters, which collect smaller amounts of grains during the same period of time. After having parameterized the motion of efficient selective hand picking, the results from this investigation serve as the basis for the design and optimization of an electromechanical tool to assist in the process of coffee harvesting, which minimizes the amount of green beans removed from the branches of the coffee trees.