Study On4-DOF Parallel Mechanism Platform Horizontal Stabilization Control

With the development of modern industry, there is more and more high demand for the stability of motion carrier. In the process of transportation, a stable platform is requir ed to all of the carried such as people, instrument, equipment, and valuable goods and so forth. Therefore, as for the platform, demand for the control technique of horizontal stabilization become more and more pressing in the engineering sector. In this paper,4-DOF parallel mechanism platform has carried on the research of horizontal stabilization control. On the basis of analyzing characteristics and motion of parallel mechanism, fuzzy control method is proposed to be used to control the MIMO coupling process, and realize horizontal stabilization control using experimental platform, and achieved good control effect at last.Primarily, this paper introduces the main structure of4-DOF parallel mechanism platform, and analyzes its degree of freedom and position inverse solution and position forward solution, provides the measuring and calculating method of platform pose parameters. Starting from the characteristics of horizontal stabilization control, analyzes the requisite hardware configuration of platform control system, and introduces the hardware of4-DOF parallel mechanism platform control system. On this basis, control strategy is discussed. Analysis of the traditional control strategy indicate its shortcomings, fuzzy control method which does not depend on accurate model of the controlled object, is proposed to be applied to the design of horizontal stabilization control system.Afterwards, this paper analyzes the coupling characteristics of the platform which is treated as a MIMO coupling controlled object. Under appropriate approximation, relationship matrix between the increments of control output and variation of platform pose parameters is received and coupling information of the controlled system is obtained from the specific numerical relationship. Moreover, it is on this foundation that the demand for design is moderately resolved. In the design of fuzzy control system, compensation decoupling and fuzzy compensator is introduced to design the decoupling link, improving the decoupling capability of the fuzzy control system effectively. Finally, according to the demand of platform horizontal stabilization control and the design of fuzzy control system, control software is developed and control algorithm is fulfilled by utilizing Visual C++on the host computer. Non-disturbance leveling experiment and stochastic disturbance horizontal stabilization control experiment are carried out on the4-DOF parallel mechanism experimental platform. Experimental results show that:(1) Horizontal stabilization control system, designed in this paper, is effective and stable, and able to effectively respond to the coupling characteristics of MIMO controlled process. In the non-disturbance leveling experiment, experimental data, obtained in numerous experiments, are quite approximate. There was no instability. In the stochastic disturbance horizontal stabilization control experiment, control system is able to effectively respond to stochastic disturbance, and keep the platform pose a certain degree of horizontal stabilization.(2) Control system is of good control effect. In terms of the non-disturbance leveling, average leveling time of50leveling experiment was0.61s, average leveling precision of lateral inclination leveling experiment was0.17°; of longitudinal inclination leveling experiment was0.18°; of vertical offset leveling experiment was0.68mm; of comprehensive deviation leveling experiment was0.075of pose parameter standard deviation. In terms of the stochastic disturbance horizontal stabilization control, under the maximum amplitude that the disturbance source is able to provided, control system can cope well with the disturbance of0.2Hz and lower frequency, reaching more than20dB of isolation degree. Horizontal stabilization control system showed good control performance facing disturbance with low-frequency and large amplitude.