Research on the multi-degree-of-freedom and large-displacement motion control of the levitated object makes a contribution to broadening the application field of the Maglev technology. A one-dimensional motion control system and method of the Maglev ball are investigated in this paper. The Maglev ball motion control system is required to have a large operating range. In order to meet this requirement, a novel Maglev system based on double linear hall sensors is designed and implemented. The step-by-step control based on the Proportional-Integral-Derivative (PID) controller is proposed as one method to realize the large step response of the levitated object. The controlled object responds to the successive small step input rather than the large step input. Then, the mathematical model of the system is set up based on the electromagnetic force equation and controller parameters are tuned by following the mathematical model of the Maglev system at different positions. The experimental data show that the position accuracy of the Maglev control system using the PID controller reaches ±0.02 mm. Moreover, step-by-step control can not only safely realize large-displacement motion of the levitated object but also effectively reduce the overshoot of the step response and make the step response process smoother.
In this paper, an external magnetic driving method of a maglev ball based on force imbalance is first proposed to meet the requirement that the maglev ball is moved linearly in the axis direction of the electromagnetic actuator in the non-liquid environment. This method is expected to be better applied in the fields of industrial and medical miniature curved tube. The maglev ball is a magnetic levitated object. Based on the interpolation algorithm, the two-dimensional stepwise levitation motion trajectory of the maglev ball is designed as the target curve of the motion. The maglev ball can be driven with a large range along a specified motion path. Compared with the 1.0 mm step input, the overshoot of a 0.2 mm step input is decreased by 73.7% and 73.6% in the descending phase and the ascending phase, respectively. Therefore, fluctuation of the step response of the maglev ball is improved by smaller step control. However, the larger the step input, the faster the speed and the larger the levitation gap. Under the condition of a 1.0 mm step input, the maximum levitation gap can be up to 20.487 mm, and the speed of the maglev ball can reach 3.086 mm/s. Compared with static levitation control, the position of the maglev ball is fluctuated severely due to radial runout under motion control conditions, and the position accuracy can reach ±0.03 mm.
Accurate large-displacement magnetic levitation actuation and its stability remain difficult in non-liquid environments. A magnetic levitation actuation and motion control system with active levitation mode is proposed in this paper. The actuating force of the system is generated by the external magnetic field. A neural network proportion-integration-differentiation (PID) controller is designed for active actuation, and a force imbalance principle is built for the step motion mode. Dual electromagnetic actuators are configured to generate a superimposed magnetic field, ensuring that the electromagnetic force on the ball is more uniform and stable than single actuators. Dual-hall-structure sensors are used to measure displacement, thereby reducing overshoot and ensuring stability whilst motivating the ball. Due to the high adaptability of the neural network to complex systems with nonlinear and ambiguous models, the PID controller composed of neurons has stronger adaptability through tuning the PID controller parameters automatically. Furthermore, the proposed controller can solve the shortcoming that the deviation between the controlled object and the steady-state operating point increases and the tracking performance deteriorates rapidly. The strong robustness and stability in active levitation and motion control is achieved during both ascending and descending processes.
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