Research on Vehicle Control Technology Using Four-Wheel Independent Steering System

The enhancement of vehicle handling stability and maneuverability through active and independent rear wheels control is presented. Firstly, the configuration of four-wheel independent steering prototype vehide is introduced briefly. Then the concrete overall design of the electronic controllers of four wheel independent steering system （4WIS） is formulated in details. Under the control strategy of zero sideslip angle at mass center, the mathematical model of 4WIS is established to deduce the equations of separated rear wheel steering angles. According to these equations, simulation analysis for 4WIS vehicle performances is finished to show that 4WIS vehicle can improve the maneuverability greatly at low speed and increase the handling stability at high speed. Finally, the road test of 4WIS vehide has performed to verify the correctness of simulation and show that compared with the conventional four wheel steering （4WS） vehicle, the 4WIS vehicle not only improves the kinematical harmony but also decreases steering resistance and lighten abrasion of tires.

Autonomous Tracking Control for Four-Wheel Independent Steering Robot Based on Improved Pure Pursuit

Autonomous tracking control is one of the fundamental challenges in the field of robotic autonomous navigation,especially for future intelligent robots.In this paper,an improved pure pursuit control method is proposed for the path tracking control problem of a four-wheel independent steering robot.Based on the analysis of the four-wheel independent steering model,the kinematic model and the steering geometry model of the robot are established.Then the path tracking control is realized by considering the correlation between the look-ahead distance and the velocity,as well as the lateral error between the robot and the reference path.The experimental results demonstrate that the improved pure pursuit control method has the advantages of small steady-state error,fast response and strong robustness,which can effectively improve the accuracy of path tracking.

Research on the Variable Steering Ratio of Four-Wheel-Steering Vehicle

The steering characteristic of a four-wheel-steering vehicle is numerically simulated for in-depth research of the handling stability of four-wheel steering. The research results show that the deteriorating tendency of the steering stability due to the increase of the vehicle speed is improved obviously in the case of four-wheel steering. The approach of variable steering ratio is discussed. The use of the variable steering ratio can not only raise the steering stability of vechicles at high vehicle speed, but also reduce the dicomfort and steering burden of drivers; and hence is helpful for the subjective evaluation of four-wheel steering vehicles.

Estimation of Vehicle Speed Based on Wheel Speeds from ASR System in Four-Wheel Drive Vehicles

Three major methods currently in the use of determining vehicle speed based on wheel speeds, the minimum wheel speed, minimum wheel speed corrected by slope method and the Kalman filter method, are analyzed, with merits and defects of each approach stated. Through simulations, the Kalman filter method based on minimum wheel speed shows improved accuracy, in addition to better adaptivity to vehicle reference speed. It also can be used to acceleration ship regulation （ASR） in part-time four-wheel drive vehicles.

Track Tension Analysis of Four-Wheel Drive Tracked Vehicles

The distribution of track tension on track link is complex when the tracked vehicles run at a high speed.A multi-drive track link structure,which changes the traditional induction wheel into the driving wheel was proposed.The mathematical model of the system was established and the distribution of track tension was studied.The combined simulation model of RecurDyn and Simulink of the structure with multi-drive track was established.The simulation results show that our proposed structure has more uniform tension distribution than traditional structures,especially under the high speed condition.The maximum tension can be reduced by 28 kN-36 kN and the transmission efficiency can be improved by10%-16% under high speed condition with this new structure.

Research Based on Innovation and Entrepreneurship Driven by "Four Wheels" and Combination of Professional Education and Teaching-- Taking the " Specialty of Computer Application Technology in Hunan Ap-plied Technology University" as an Example

Implementing innovation and entrepreneurship education by combining with professional education in universities and colleges is an important measure to promote higher-quality employment and entrepreneurship of the graduates. The problems existing in the fusing teaching of computer application technology and innovation and entrepreneurship education are analyzed in this paper. By taking Hunan Applied Technology University as an example and in view of the existing problems, the mode of reform driven by "four wheels","professional talent training scheme by integrating optimization, innovation and entrepreneurship","implementing the specific teaching by integrating imovation,entrepreneurship and professional education","building many forms and university-enterprise cooperation platforms for innovation and entrepreneurship" and "setting up reasonable management and incentive mechanism for teachers and students" are proposed, to realize the dynamic integration of professional education and innovation and entrepreneurship education for the specialty of computer application technology.

Design and test of flexible chassis automatic tracking steering system

In order to develop an innovative omnidirectional non-homonymic flexible chassis(FC),the four-wheel steering control method of FC was designed by a new concept called off-centered steering(OCS)and the automatic tracking steering system was analyzed.Novelty of this wheel concept lies in the non-conventional positioning of the steering axis and wheel axis.Additionally,the steering axis of steerable wheel was motorized with an on/off electrometrical brake to overcome a hyper-motorization issue inherent to the wheel’s geometrical properties and hold the steering position.Based on the off-centered steering characteristics of FC,the Wheatstone bridge was applied in the steering control system.The bridge resistances are used to track target steering angles and the actual steering angle,respectively.The output voltage of the bridge is exploited to adjust the wheel’s speed so that steering and automatic tracking could be achieved.Experiments at different speeds,loadings,and target steering angles were conducted.Results showed that the chassis can indeed be controlled independently and its steering range is from-90°to 90°,which indicated the automatic tracking steering system was effective.The electromagnetic lock(EL)can significantly improve the stability of the chassis and reduce the vibration.Loading has no significant effect on the accuracy of the steering angle and the time it takes to complete steering tasks.The time taken to complete a forward steering task showed a linear relationship with the required angles,but was independent of rotation speed;for backward steering,time was related to both target angles and rotation speed.The results presented in this research may provide a reference for the steering control strategies of the four-wheel individual drive and four-wheel(4WID/4WIS)vehicle in the future.

Development of a tomato harvesting robot used in greenhouse

A tomato harvesting robot was developed in this study,which consisted of a four-wheel independent steering system,a 5-DOF harvesting system,a navigation system,and a binocular stereo vision system.The four-wheel independent steering system was capable of providing a low-speed steering control of the robot based on Ackerman steering geometry.The proportional-integral-derivative(PID)algorithm was used in the laser navigation control system.The Otsu algorithm and the elliptic template method were used for the automatic recognition of ripe tomatoes,and obstacle avoidance strategies were proposed based on the C-space method.The maximum average absolute error between the set angle and the actual angle was about 0.14°,and the maximum standard deviation was about 0.04°.The laser navigation system was able to rapidly and accurately track the path,with the deviation being less than 8 cm.The load bearing capacity of the mechanical arm was about 1.5 kg.The success rate of the binocular vision system in the recognition of ripe tomatoes was 99.3%.When the distance was less than 600 mm,the positioning error was less than 10 mm.The time needed for recognition of ripe tomatoes and pitching was about 15 s per tomato,with a success rate of about 86%.This study provides some insights into the development and application of tomato harvesting robot used in the greenhouse.