Search

This study focuses on a wheeled mobile robot used for detection, weeding and information monitoring in agriculture. However, it is difficult to reach satisfactory motion mode switching (MMS) performance. This paper aimed at exploring the optimal control parameters guaranteeing smooth MMS of four-wheel steering. Single factor tests were first conducted using a test-bench. A binary quadratic general rotation combination test was designed to obtain the optimal parameters. An entropy weight method was introduced to construct the four indexes as a comprehensive index. The optimal combination of the parameters was obtained, based on the regression equation. The results showed that the two factors and their interaction had a significant impact on the comprehensive index (p < 0.05). The best combinations of the speed of the stepper motor and locking voltage were 56 r·min−1 and 3.96 V for 15° steering, 72 r·min−1 and 4.35 V for 30°, and 107 r·min−1 and 5.50 V for 45°, respectively. A verification test was performed using the prototype of the robot chassis. The results demonstrated that the MMS process was smooth and stable, and the proposed method was effective. This study is a beneficial exploration of the experimental method concerning wheeled robots. [ABSTRACT FROM AUTHOR]

Traditional underwater robots have many shortcomings in terms of resistance to sea currents, stability and functionality. In order to improve the efficiency and quality of underwater operations, this paper proposes and designs a new underwater robot, the navigation and crawl underwater unmanned vehicle (NCUUV), it has two motion modes: swimming and crawling. In order to enable the robot to have the ability to switch motion modes, this paper designed a motion mode switching mechanism, and verified the effectiveness of the mechanism through experiments, which proved that the mechanism has good motion reliability and accuracy. In order to control NCUUV to smoothly switch the motion mode, a controller based on the central pattern generator (CPG) was developed. The upper controller reconstructs the CPG network in the middle controller according to the feedback information of the acoustic rangefinder. The CPG network in the middle controller has two configurations: a triangular fully symmetrical network and a hexagonal fully symmetrical network, and the CPG network can be freely changed between the two configurations according to the instructions of the upper controller. These two configurations control NCUUV's swimming and crawling respectively, so as to realize the smooth switching between swimming and crawling. The experimental result shows that this control mechanism of motion mode switching can enable NCUUV to stably realize motion mode switching and the switching process is smooth and reliable.

A flexible chassis (FC) is a type of electric vehicle driven by in-wheel motors that can be used in narrow conditions in agricultural facilities. The FC is composed primarily of four off-center steering mechanisms (OSMs) that can be controlled independently. Various FC operation modes can be achieved including cross motion (CM), in-place rotation (IR), diagonal motion (DM), and steering motion (SM). However, it is difficult to achieve satisfactory motion mode switching (MMS) results under traditional distribution control methodologies due to a lack of linkage relationships between the four OSMs. The goal of this study was to provide a coupling control method that can cope with this problem. First, dynamic MMS models were derived. Then, an MMS coupling error (CE) model was derived based on coupling control and Lyapunov stability theory. Second, a fuzzy proportional integral derivative (PID) controller with self-tuning parameters was designed to reduce the CE during MMS. A fuzzy PI controller was also employed to improve response times and decrease OSM tracking motion steady-state error. Finally, MATLAB/Simulink simulations were performed and experimentally validated on hard pavement. The results showed that the proposed methodology could effectively reduce CE and guarantee MMS control stability while substantially shortening response times. The proposed methodology is effective and feasible for FC MMS. [ABSTRACT FROM AUTHOR]