The frequency converter control method in positioning and stabilisation of a platform suspended on ropes in conditions of a time - variant centre of gravity

When handling materials in space it is required that the materials to be hoisted should be stabilised and their position precisely controlled. Attempts are made to minimise the dynamic loading during the start-up and braking phase and to reduce vibration of the material being handled, at the same time ensuring the minimal time of operation. When the admissible value of positioning and levelling errors are very small, some effective methods of drive control are required. This study investigates an asymmetrically loaded platform suspended on ropes and people moving with respect to it during the hoisting phase. The positioning and levelling errors are minimised by controlling voltage fluctuations of the current supplying asynchronous induction motors. The proposed solution uses an optimal LQR controller. Both free and forced vibrations of the platform are low-frequency vibrations, so the scalar method of controlling the output voltages are recommendable, where feedback loops in the electro-magnetic part of the system are neglected. The losses and time delays associated with modulation of the velocity characteristics of the induction motor being omitted, the optimal control strategy of frequency control is developed to effectively handle the control plant. This study has demonstrate