Multi Gait Planning And Preliminary Maintenance Of Stability Controlling Based On Quadruped Robot With Force Sensor

Because of its special rod mechanism, bionic quadruped robot can work in the unstructuredenvironments. With its excellent characteristics of strong adaptability of the terrain, strong bearingcapacity, good stability, bionic quadruped robot is widely used in disaster relief, demining,exploring and other military fields, so it has broad application prospects. Studying the movementand stability control of bionic quadruped robot has important theoretical significance and practicalvalue in developing new biomimetic quadruped robot. In order to make the quadruped robot canperform a variety of gait movement more stable, and improve the motion stability by a submissivereaction of reaction supple legs when the foot end was suffered an external impact force. Thispaper has conducted a variety of gait planning, improving and researched on force feedbackcontrol.Firstly, this paper analyzed and calculated the normal&inverse solution of kinematics ofsingle leg for two kinds of quadruped robots. Then the movement space of single leg for two kindsof quadruped robots was calculated using the result of forward kinematics combined with theactual range of motion of the joints and the rod constraints. After comparing and analyzing themovement space of single leg of this two kinds of quadruped robots, it comes up with the resultthat bionic quadruped robot with four degrees of freedom of each leg has bigger movement space,moves more flexibly, and can be adapted to more kinds of moving surfaces.Secondly, designed the trotting gait based on elliptic curve and compound cycloid as the footend trajectory. The simulation and analysis validated that compound cycloid can guarantee thecontact between the foot end and the ground is vertical in the start and landing moment, whichreduced the contact force in the yaw direction effectively, maintained the stability of center ofgravity, and improved the stability of the gait from the foot end trajectory respect. For the twoquestions of hind legs’ mopping and body’s swaying, the paper raised two solutions that arechanging the initial position of the support foot and increasing four-leg support state to improvethe stability of the trotting gait. Designed and realized forward, backward, turning and a variety ofsports experiments with trotting gait based on two kinds of quadruped robots. Moreover, it issuccessful to complete the movement of upstairs and downstairs by bionic quadruped robot withfour degrees of freedom of each leg.Thirdly, after analyzing the traditional trotting gait it is found that the velocity of centroid hasmutation in the diagonal commutation instant which is not conducive to the body stability.Through analyzing and simulating the variable length pendulum theory, the paper verified the effectiveness and feasibility of increasing four-legged support state it the trotting gait, andeliminated the mutation of centroid. In addition, the variable step size and variable speed trottinggait were designed based on inverted pendulum model, and the two gaits were verified throughsimulations. So changing step size or speed during trotting gait motion without mutation ofcentroid was approached.Finally, the hybrid force/position control based on force sensor in foot end was designed, itused the classic PID control to achieve the position tracking control, and used the impedancecontrol to achieve compliance control. The single leg hybrid force/position control model basedon force sensor in foot end was built in the simulink environment, and adjusting the parametersthrough simulation experiments, then making the completion of the experimental verification forthe control system. Then made the semi-physical exercise test based on hybrid force/positioncontrol based on force sensor in foot end with quadruped robot, successfully achieved the positiontracking under unstressed conditions, as well as the compliance control in the cases of static,one-dimensional horizontal movement and two-dimensional planar motion. The experimentsproved the feasibility and effectiveness of the control method, and laid a solid foundation inimproving the stability of the walking robot.