A novel strategy to design time invariant motion controllers for underactuated mobile systems is applied to the position and attitude control of an underactuated 3D vehicle. The idea consists in defining a velocity ve...
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ISBN:
(纸本)0780365763
A novel strategy to design time invariant motion controllers for underactuated mobile systems is applied to the position and attitude control of an underactuated 3D vehicle. The idea consists in defining a velocity vector field such that an ideal, fully actuated system would exponentially achieve the control objective by simply following such field. Then a steering law for the given underactuated system is designed such that it is exponentially stabilized parallel to the above mentioned velocity vector field. For the particular problem here addressed, due to the use of polar like coordinates, this method yields a discontinuous control law. Both the design process and the resulting solution have a most clear physical interpretation. Important practical requirements as approaching the target on a null curvature path, avoiding cusps in the whole path and moving in only one given forward direction are easily satisfied within this framework.
The statistical properties of saccadic time intervals recorded in eye movements in human subjects were calculated. The probability density function of the inter-spike intervals exhibits a Poisson-type behavior with a ...
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ISBN:
(纸本)0780370449
The statistical properties of saccadic time intervals recorded in eye movements in human subjects were calculated. The probability density function of the inter-spike intervals exhibits a Poisson-type behavior with a maximum located at time lags around 600 ms. Such a value agrees well with the frequency of the theta rhythm observed in the visual cortex of mammals, in particular, rabbits. EEGs were recorded from 8/spl times/8 arrays of subdural electrodes at high density (6/spl times/6 mm) in rabbits trained to discriminate visual stimuli in a classical aversive paradigm. EEG patterns had the form of amplitude and phase modulation of this. The covariance between the spatial events revealed striking peaks in the theta range (2-7 Hz), even when the autospectrum of the EEG failed to show a prominent peak. Comparable sequences of spatial EEG patterns in the olfactory system occur at frequencies in the theta range, reflecting the driving by respiration. These multiple sets of observation suggest that the visual system may be driven by surges of sensory input that are occasioned by saccades. Further studies are indicated to analyze this relationship by cross correlating simultaneous recordings of saccades and scalp EEGs from the occipital leads.
Inverse kinematics computation using an artificial neural network that learns the inverse kinematics of a robot arm has been employed by many researchers. However, the inverse kinematics system of typical robot arms w...
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ISBN:
(纸本)0780365763
Inverse kinematics computation using an artificial neural network that learns the inverse kinematics of a robot arm has been employed by many researchers. However, the inverse kinematics system of typical robot arms with joint limits is a multivalued and discontinuous function. Since it is difficult for a well-known multilayer neural network to approximate such a function, a correct inverse kinematics model cannot be obtained by using a single neural network. In order to overcome the discontinuity of the inverse kinematics function, we proposed a novel modular neural network system that consists of a number of expert neural networks. Each expert approximates the continuous part of the inverse kinematics function. The proposed system uses the forward kinematics model for selection of experts. When the number of the experts increases, the computation time for calculating the inverse kinematics solution also increases without using the parallel computing system. In order to reduce the computation time, we propose a novel expert selection by using the performance prediction networks which directly calculate the performances of the experts.
In the paper,we exhibit the usefulness of nonlinearity in two aspects:analysis of nonlinear dynamics and nonsmooth feedback *** illustrative examples are given to show how the new bifurcation p
In the paper,we exhibit the usefulness of nonlinearity in two aspects:analysis of nonlinear dynamics and nonsmooth feedback *** illustrative examples are given to show how the new bifurcation p
We propose a method to detect and identify faults in wheeled mobile robots. The idea behind the method is to use adaptive estimation to predict the outcome of several faults, and to learn them collectively as a failur...
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We propose a method to detect and identify faults in wheeled mobile robots. The idea behind the method is to use adaptive estimation to predict the outcome of several faults, and to learn them collectively as a failure pattern. Models of the system behavior under each type of fault are embedded in multiple parallel Kalman filter (KF) estimators. Each KF is tuned to a particular fault and predicts, using its embedded model, the expected values for the sensor readings. The residual, the difference between the predicted readings (based on certain assumptions for the system model and the sensor models) and the actual sensor readings, is used as an indicator of how well each filter is performing. A backpropagation neural network processes this set of residuals as a pattern and decides which fault has occurred, that is, which filter is better tuned to the correct state of the mobile robot. The technique has been implemented on a physical robot and results from experiments are discussed.
Read and spontaneous discourses are two different but very significant speech styles to be investigated. So phonetic labeling on read and spontaneous discourse corpora are made one is ASCCD, a 10 hours read discourse ...
ISBN:
(纸本)7801501144
Read and spontaneous discourses are two different but very significant speech styles to be investigated. So phonetic labeling on read and spontaneous discourse corpora are made one is ASCCD, a 10 hours read discourse corpus and the other is CASS, a 4 hours spontaneous discourse corpus. First the principles and conventions of transcription are presented. Then, these two speech styles are compared from phonetic and syntactic point of view, including the statistic results of different phonetic units got from the annotated corpora.
Weighted relative accuracy was proposed in [4] as an alternative to classification accuracy typically used in inductive rule learners. Weighted relative accuracy takes into account the improvement of the accuracy rela...
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Designing a parallel computer would be much easier if one interconnection network was for all applications and platforms. However, unfortunately, no such network exists. For a fixed application domain and fixed platfo...
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