| Heave compensation system for underwater robots to enhance the safe operation and retractable capability is of great significance. Electro-hydraulic position control system is is a major component of active heave compensation system. Having less power loss, strong anti-pollution and adaptive ability to the complex working conditions, the electro-hydraulic proportional valve is chosen to composed electro-hydraulic proportional position control system. Up to now, there have been a lot of research results for the electro-hydraulic proportional position control technology itself alone. However, due to its specific application background and characteristics, the electro-hydraulic position control system for active heave compensation system need to be specially designed.This project is part of the National High Technology Research and Development Program Project: "Reasearch on key technologies of underwater ROV system". The objective is to design a electro-hydraulic proportional postion control system for heave compensation system.Considering both the application background for compensation system and convenience for system upgrading, a modular closed-loop electro-hydraulic proportional position control system has been designed.The major work of this paper includes:(1) Design the overall structure of the system. The system is divided into several major parts: actuators, displacement sensors, digital PWM proportional valve amplifier module, signal conversion module, main controller module and monitoring computer module.(2) Design some parts of the system hardware, including the digital PWM proportional valve amplifier module, signal conversion module and the relay driver module. The AVR microcontroller is chosen to be the controller of PWM amplifier. The actual output current is obtained by low edge current measurement method. MOSFET is used for the power amplifier device. The module mentioned above compose a closed-loop current control system. The AVR microcontroller is chosen to be the controller of signal conversion module, where sensor data are sampled thoough the AD port, the electromagnetic direction valve is controlled through the IO port connecting to relay driver board and current control commands from main controller thorough RS232 bus are sent to the proportional valve amplifier through I2C bus. Meanwhile, in the relay driver module, optocoupler and MOSFET are used for the functions of isolution and power amplifier, respectively.(3) Design all required software of the system modules. Software on the PWM amplifier implements not only the function of the digital PID control algorithm, the feedback data sampling, and data communication, but also the driver of I2C interface. Moreover, a software tool on PC for amplifier debugging has been designed based on MFC. The embedded operating system uC/OS-II is ported to the ARM MCU of the main controller module in order to improve the real time performance and reduce the complexity of software design. Electro-hydraulic proportional position control algorithm is implemented by this module. Meanwhile, the system monitoring software on PC has been designed. The software designed based on MFC provids the following function: control algorithms adjusting, system testing, system real-time monitoring and so on.(4) Research on the control system strategy. Application of the PID control algorithm in the electro-hydraulic proportional position control system and PWM amplifier has been studyed. Moreover, a discrete-time indirect adaptive fuzzy sliding mode control (DTIAFSMC) algorithm has been proposed, and then both simulation and experiment reaserch on its application in electro-hydraulic proportional position control system has been provided. The experiment results show that this postion control system can fulfill basic position trailing function. |
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