This paper proposes a smooth adjustment method for the instability problem that occurs during the start and stop of a multi-footed robot during attitude change. First, kinematics analysis is used to establish the mapping relationship between the joint angles of the robot support legs and the body posture. The leg joint angle is a known quantity that can be measured accurately and in real time. Therefore, when the position of the foot end of the support leg is unchanged, a unique set of joint angles can be obtained with the change of body posture at a certain moment. Based on the designed mapping model, the smooth adjustment of the posture can be achieved by the smooth adjustment of the support legs. Second, a constraint index that satisfies the requirements of the robot’s steady adjustment of the robot is given. The S-curve acceleration/deceleration method is used to plan the body’s attitude angle transformation curve, and then the mapping control relationship is used to obtain the control trajectory requirements of the joint to achieve smooth adjustment. In addition, this paper also gives a simple choice and motion control method for the redundancy problem caused by the number of support legs of a multi-footed robot when the attitude is changed. The simulation and prototype experiments verify and analyze the proposed method. The results of comparative experiments show that the posture adjustment method proposed in this paper has continuous acceleration without breakpoints, the speed changes gently during the start and stop phases of the attitude transformation, and there is no sudden change in the entire process, which improves the consistency of the actual values of the attitude planning curve with the target values. The physical prototype experiment shows that the maximum deviation between the actual value of the attitude angular velocity and the target value changes from 62.5% to 5.5%, and the degree of fit increases by 57.0%. Therefore, this study solves the problem of the instability of the fuselage when the robot changes its attitude, and it provides an important reference for the multi-footed robot to improve the terrain adaptability.

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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