Search PubMed⌕ Search

PubMed · 10401926

Feedforward neural network with adaptive reference pattern layer.

Abstract

A hybrid neural network architecture is investigated for modeling purposes. The proposed hybrid is based on the multilayer perceptron (MLP) network. In addition to the usual hidden layers, the first hidden layer is selected to be an adaptive reference pattern layer. Each unit in this new layer incorporates a reference pattern that is located somewhere in the space spanned by the input variables. The outputs of these units are the component wise-squared differences between the elements of a reference pattern and the inputs. The reference pattern layer has some resemblance to the hidden layer of the radial basis function (RBF) networks. Therefore the proposed design can be regarded as a sort of hybrid of MLP and RBF networks. The presented benchmark experiments show that the proposed hybrid can provide significant advantages over standard MLPs and RBFs in terms of fast and efficient learning, and compact network structure.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M Lehtokangas. 1999. Feedforward neural network with adaptive reference pattern layer.. https://doi.org/10.1142/s0129065799000022

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Analysis of the reflexive feedback control loop during posture maintenance.

In previous work it has been shown in posture experiments of the human arm that reflexive dynamics were substantial for narrow-band stochastic force disturbances. The estimated reflex gains varied substantially with the frequency content of the disturbances. The present study analyses a simplified linear model of the reflexive feedback control loop, to provide an explanation for the observed behaviour. The model describes co-activation and reflexive feedback. The task instruction 'minimize the displacements' is represented mathematically by a cost function that is minimized by adjusting the parameters of the model. Small-amplitude displacements allow the system to be analysed with a quasilinear approach. The optimization results clarify the limited effectiveness of reflexive feedback on the system's closed-loop behaviour, which emanates from the time delay present in the reflex loops. For low-frequency inputs less than 5 Hz, boundary-stable solutions with high reflex gains are predicted to be optimal. Input frequencies near the system's eigenfrequency (about 5 Hz), however, would be amplified and result in oscillatory behaviour. As long as the disturbance does not excite these frequencies, boundary stability will be optimal. The predicted reflex gains show a striking similarity with the estimated reflex gains from the experimental study. The present model analysis also provides a clear explanation for the negative reflex gains, estimated for near-sinusoidal inputs beyond 1.5 Hz.

Feedback↗

The role of target position in smooth pursuit deceleration and termination.

Subjects smoothly pursued a target moving horizontally at 15 deg/s. After pursuit for 1 s, the target jumped 3 deg ahead of the fovea. At the moment of the jump, target velocity became 0 and 'effective visual feedback' assumed a value of either 0 (target retinally stabilized), -0.2, -0.4, or -1.0 (target fixed in space). With 0 visual feedback the eye continued to move smoothly at a moderate velocity, an apparent response to target position relative to the fovea. When negative visual feedback was present eye velocity decreased. With -0.2 and -0.4 feedback, this decrease was not a simple exponential, but often consisted of an initial fast decrease followed by slower decrease. With -1.0 feedback, eye velocity quickly decreased in an approximately exponential manner, and stopped. We were able to simulate these pursuit responses using a simple model of the pursuit system. Key features of the model are: (a) a target-velocity channel whose output decreases with target offset from the fovea, and whose gain switches from high to low as pursuit velocity approaches zero; (b) a target-position channel with a saturation non-linearity at 1-3 deg; and (c) a positive feedback loop with gain of less than 1.0. All of these features are essential to simulate the pursuit responses, especially with visual feedback values of -0.2 and -0.4. Our results and model suggest that target position serves as an important stimulus in guiding smooth pursuit as pursuit velocity decreases, and especially during pursuit termination.

Feedback↗