Motion Synthesis and Coordinated Control in the Multi-Axle-Driving-Vehicle

Abstract

Multi-axle-Driving-vehicle is a kind of the mobile robot and it also belongs to the construction machinery which generally has heavy load-capacity and huge size. As shown in Fig.1 and Fig.2, both hoisting-girder transporter and DCY900 transportation vehicle are multi-axle-driving vehicles. In order to decrease the ground-contacting pressure, the ground-clearance of the vehicle chassis and the size of the tyre, and to increase the loadingcapacity and the passing performance of the vehicle, the multi-axle driving and independently controlled steer axles are employed, and also distributed electro-hydraulic proportional control is applied to the heavy type of vehicles. Such a large-scale vehicle has to deal with the complex motion control problem. The controlled output motions of multiple axles should meet certain matching condition or corresponding relationship so as to make the whole vehicle to realize the expected contouring motion trace. For example, all the powered steer axles have to be coordinately controlled in real time in order to achieve smooth and accurate steering motion without slipping and sliding. Besides the steering function, the steer axles are also designed to automatically level the vehicle body when it moves in an uneven terrain. It follows that the motion synthesis and coordinated control methods should concurrently cope with the tasks and motions of multiple subsystems. Conventionally, coordinated control of a simple mechatronics system is realized through a centralized control scheme in which each of the actuators is directly linked to the controller through cable in a point-to-point manner. However, for a complex multi-tasking mechatronic system with a large number of subsystems and actuators, such a control scheme is impractical. This is especially true for a large-scale multi-axle vehicle because it is huge in size and has many distributed subsystems to be arranged anywhere in the vehicle. If a centralized control scheme is employed, it will result in a very messy wiring scheme. Thanks for the advanced network technologies, which provide us an effective way to realize coordinated control for the multi-axle driving vehicles. In a network environment, all the control devices such as sensors, actuators, and controllers are distributed and simply linked together through network interfaces (e.g., Field-bus, Industrial Ethernet, and mobile net) so as to achieve coordination and resources sharing efficiently. In convention, a network-based mechatronic control system is called an NCS (Networked Control System), which has many advantages over a centralized control system, e.g., low installation cost, ease of system maintenance, simplicity in failure diagnosis, and high flexibility in system management