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.

To solve the problems of large landing impact, vibration, and poor adaptability to complex ground surfaces in the motion of a foot-type robot, a two-degree-of-freedom flexible foot-end structure was proposed and designed in this study. The effects of flexible materials, flexible parameters, and structural forms on the performance of the foot end have been discussed. Through simulation and experimentation, the parameter analysis and mechanical calibration of the foot end were completed, and a motion experiment of the flexible foot robot was designed. The simulation and experimental results showed that the flexible foot-end structure has uniform and reliable force and can effectively reduce the foot impact. Compared with the rigid foot, the foot-end force of the flexible foot was only 1/3 of the contact force, the peak foot pressure decreased by 59%, the motion stability increased by 37.4%, and the error of force perception was controlled at 11%. The flexible foot structure improved the stability of the robot motion process, reduced the vibration, provided the robot with good terrain adaptability, and achieved omnidirectional motion of the robot. contact with the ground, the deformation of the claw pad adapts to the complex terrain, and the impact force of the claw in contact with the ground is slowed down; and (2) by the flexible membrane between the connecting claw and the tarsus, a contraction of the sacral joint is made to open all the claws, and the knuckles and the claws are completely in contact with the ground, thereby increasing the contact area. The flexible membrane serves to attenuate the impact force and protect the joints of the legs [19]. Many attempts have been made by experts at home and abroad to use flexible materials to absorb the impact force [20,21]. It was shown in Reference [22] that a new structure was proposed to absorb the impact force with a combination of wheel, intermediate, and stabilizer. Sun, Ling et al. [23,24] show that by compensating the flexible structure with a control algorithm, the errors caused to the robot system by the flexible structure were reduced. The structure designed in Reference [25] can well realize mechanical information perception. It was shown in Reference [26,27] that carried out research on the acquisition method and signal transmission mode of force signals that has great innovative significance and provided us with a good idea.Therefore, this study drew on the bionics analysis results to design and manufacture a flexible, two-degrees-of-freedom foot unit. When the foot strikes the ground, the flexible sole deforms to adapt to complex terrain while reducing the impact force, and the force is then transmitted to the compression spring through the push-pull rod to achieve secondary absorption of the impact force. The flexible sole was made by 3D printing mold-casted silicone, and the other modules of the flexible foot were 3D printed using photosensitive resin. The effects of the flexible materials, flexible parameters, and structural forms on the performance...

No abstract

By studying the relation of the robot’s postures and its energy consumption, a static analysis-based method to obtain the low-energy postures of the robot is proposed. This method decreases the energy consumption and increases the battery life by adjusting the postures in the horizontal environment. The method takes the low-speed hexapod bionic robot as the research object. First, we obtain the output torque of each joint of the leg through static analysis and establish the energy consumption model of the robot. Considering the flexibility of the robot, we then introduce the performance index of the maximum step length and establish an equilibrium solution based on energy consumption and maximum step size. Finally, we derive the low-energy postures of the robot using MATLAB (MATLAB 2014a, The MathWorks, Natick, Massachusetts State, USA, 2014) simulations. An energy consumption experiment is carried out with a physical prototype to verify the validity of the method.