Ryo Torisu

Control System for Tractor-Platooning

A control system for two-tractor platooning was developed, which dealt with follow-up motions for both straight and curvous courses. Firstly, a trajectory of the leading tractor was dynamically obtained by processing the position points of the leading tractor with the method of least squares and curve fitting. Secondly, based on the vehicle kinematic model, a reference course for the following tractor was dynamically created from the trajectory of the leading tractor with a given lateral offset. Finally, an optimal path-tracking controller was designed to guide the following tractor along the reference course. Field tests were conducted on a flat meadow. The test results indicated that the following tractor followed up the leading tractor successfully. The mean and RMS lateral deviations for the straight course were 0.02 and 0.02 m, respectively, whereas those for the sinusoidal course were 0.02 and 0.04 m, respectively.

Neural Network Based Steering Controller for Vehicle Navigation on Sloping Land

Abstract This paper presents an autonomous guidance system of a wheeled tractor-like-robot on sloping terrain. A Neural Network (NN) vehicle model was developed for sloping land and trained using Back Propagation algorithm. Genetic algorithms were used to search the optimal steering values for different combinations of lateral and heading deviations. Using those values, a NN-based steering controller model was designed to generalize the optimal steering for different land-inclinations. Autonomous travel tests were conducted with a prototype test tractor along predetermined rectangular paths on sloping lands. It was found that the tractor could precisely follow the paths. The mean and standard deviation of the offsets along four linear directions of the rectangular path on 15° sloping land were 0.058 m and 0.063 m respectively, which are insignificant for tractor motion on agricultural farms.

Wavelet Analysis of the Nonlinear Dynamics of Farm Tractors

This paper discusses the application of wavelet in the analysis of time series data obtained from the experiments on the nonlinear dynamics of farm tractors. The experimental investigation was carried out by frequency response test. This was done by running the tractor on two types of artificial test tracks made of angle irons over a wide range of travel speeds. In the analysis, the wavelet used was Coiflets (Coif4) which is among one of the popular wavelets being used in the area of digital signal processing. By using simple linear models as well as nonlinear/chaotic models, the analysis of the experimental chaotic time series data is possible.

Trajectory Optimization for Nonholonomic Systems. Space Robot Case.

In this paper, we deal with trajectory optimization problems for free-floating space robots, where the bases are not controlled by external moments and forces. Robot arms are mounted on free-floating bases-for example, spacecrafts, space stations, and so on. First, we formulate the trajectory optimization problems as nonlinear optimal control problems. Next, applying optimal control algorithms, we numerically obtain optimal solutions in infinite dimensional function spaces. Finally, we demonstrate how to find global solutions through local solutions by some numerical simulations.