IEEE Access (Jan 2021)
Design of an Artificial Muscle Pressure Supply Mode Based on the Connected Structure
Abstract
This paper proposes an air pressure supply structure for artificial muscles. The main body of the structure comprises a hollow tube, an electromagnet in the outer layer, and a magnetic piston in the inner diameter of the tube. At both ends, a hose interface connects the air inlet of the artificial muscle. Under the action of controlling changes in current, the electromagnet nested in the outer wall causes the movement of the piston by changing the force between the electromagnet and the magnetic piston and by changing the law of air pressure in the tube. Because the inside of the tube is a closed space, the movement of the magnetic piston in the tube causes a change in the volume of the gas at both ends, thus forming pressure differences of different sizes and directions. Therefore, this air supply, with specific oscillatory characteristics, can be used to produce the desired movement of artificial muscles. Through system modeling, theoretical analysis, and simulation experiments of the connected pressure supply structure, we verified that the system has inherent characteristics similar to a spring damping structure. In view of the inherent characteristics of this kind of structure, this paper introduces the trend of input and output changes by considering the deviation value, details how to improve the traditional neural network PID control algorithm, and discusses the intelligent optimization of controller parameters. Simulation results show that the improved control method can effectively overcome the nonlinear and coupling characteristics of the system, and the gas supply structure can provide a continuous pressure supply curve of an arbitrary waveform and a frequency within a certain amplitude range. The designed air supply structure was applied to a quadruped robot, using its oscillating characteristics to generate rhythmic movement. Compared with the traditional pressure control method, the piston was driven to produce reciprocating motion by fully exploiting the energy stored in the compressed gas, so as to reduce the external energy input and reduce the comprehensive energy consumption of the system. In addition, the control algorithm improved in this paper can meet diverse pressure requirements for driving artificial muscles. Moreover, the independent control of leg support force and stiffness can be realized by combining it with the antagonistic joints. This structure can be widely used in the pressure supply of outdoor robot artificial muscle.
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