In the present paper, the job shop scheduling problem with no intermediate buffers, i.e. the blocking job shop scheduling problem, is investigated. Since there are no buffers between operating machines, the machines are blocked by the products that the machines operated until those products are passed to the products’ downstream machines. Under the condition where blocking is considered, complicated calculations must be performed to evaluate semi-active schedules when a partial change of a schedule, or exchange of an operation order of jobs on a specific machine, is planned. Furthermore, because some or most of the partial changes result in infeasible schedules, it will be an advantage to know the feasibility of the changes before the time adjustments for the semiactive schedule. To deal with the feasibility problem, a new optimization problem using an artificial variable is proposed for the feasibility evaluation of a partial change of a schedule. The proposed method utilizes the mixed integer programming problem of the blocking job shop scheduling problem, with the integer variables given so that the problem becomes a simple linear programming problem solved by the simplex method. By using the information before the change of the schedule, namely the basic variables and the deformed constraints, the optimization is performed efficiently beginning at a close solution of the present evaluation. Moreover, the semi-active schedules are determined within a few steps after the evaluation, which eliminates the calculation of determining the schedule separately. To demonstrate the behavior of the proposed method, examples of calculation procedures are described in a precise manner. In addition, numerical examples are shown to verify the advantages of the proposed evaluation method.
This paper presents a multi-dimensional loading material testing machine based on a hexapod parallel mechanism. We designed a model-based PID closed-loop control method using feedbacks from six uniaxial force sensors installed on limbs. Three simulations were proceeded to estimate the feasibility of this control method. Furthermore, we established two series of experiments, including multi-dimensional loading experiments and standard tension tests. The former experiment results demonstrate the multi-axial loading capacity since the actual multi-axial output wrench has the deviation less than 5% of the desired ones. The latter experiments reveal that the uniaxial tension test is not considerably influenced by the redundant degree of freedoms, because the tensile-test results are relatively identical to those results achieved by universal material testing machine. Both experimental results suggest that this proposed material testing machine are feasible to perform multi-dimensional material tests, as well as standard uniaxial tests.
According to the requirements on operating and controlling interventional catheter, a new design scheme for interventional catheter with a cable-driven active catheter system was proposed. A kinematics and dynamics model based on screw theory was achieved for special configuration on active catheter. Further, the control model of cable length was constructed through the relationship between driving cable length and motion state of the system. Thereby, the variation of the cable length in the planning task using this model was analyzed, which was verified by experiment. In view of the complexity of the system, dynamic characteristics using Kane's equation based on screw theory is analyzed in this paper. The needed driving torques of every joint are calculated in the environment of Mathematica when active head-end system is moving along planned trajectory, which provides theoretical basis for design and control of the system.
Chatter is one of the main limitations to milling performances. Prediction of such unstable phenomenon via stability lobe diagrams requires the measurement of the Frequency Response Functions (FRFs) for each tool and machine tool setup. This paper presents a hybrid FE-experimental approach to identify tool-tip FRFs with only one set of measurements, taking into account tool change without any other experimental test. Machine tool dynamics is modeled using a Finite Element (FE) approach. Machine, spindle and tool-holder are described by a lumped model characterized by frequency-dependent stiffness, while the tool is FE modeled. Lumped model and tool are connected by means of stiffness matrices extracted using the Craig-Bampton dynamic reduction method. The obtained simplified model of machine tool enables chatter prediction by means of stability lobe diagram for different tool without the need for extensive experimentation. Once a new tool is clamped no other measurements are needed, just the new tool FE model. Experimental validation under different conditions is provided, showing accuracy and reliability of proposed approach.
Ductile grinding of brittle materials has been demonstrated in achieving desired machining quality without deteriorating surface and subsurface quality and any post processing work. However, it is still in a low efficiency in micro-machining or conventional grinding. In this paper, a high speed diamond grinder was exploited to explore ductile grinding of SiC at a relatively higher material removal. A combination of ground surface, subsurface and grinding chips SEM observations are given to explain the high speed grinding mechanism for SiC. This study indicates that ductile grinding of SiC can be achieved through a combination of the increase of the wheel speed and the control of grinding depth. Moreover, the critical chip thickness for ductile grinding of SiC can be greatly improved under a higher grinding speed comparing to conventional speed grinding. Correspondingly, the material removal volumes can be substantially enhanced in high speed grinding while not affecting subsurface and surface integrity.
In face-to-face conversation, embodied rhythms between speech and body movements such as nodding are mutually synchronized between talkers such as a speaker and a listener. This synchrony is called entrainment in communication and it generates the sharing of embodiment in human interaction. Embodied communication, which is closely related to behavioral and physiological entrainment, is an essential form of communication that forms the basis of interaction between talkers through mutual embodiment. In particular, nodding has an important role as a regulator in embodied interaction and communication. The detection of nodding is useful for an estimation of the activity of conversation. In this paper, we develop a nodding detection system using a nodding detection model based on an analysis of the head movement involved in nodding. This model detects nodding based on the rotational movement of the head, which is estimated from the face tracking of the Active Appearance Model. The effectiveness of the system is demonstrated by comparing the result of the nodding detection results with visual inspection. The developed nodding detection system is demonstrated in an actual event for children.
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