Applied Mathematics & Information Sciences

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For a quadruped robot with 12 active joints driven by linear hydraulic actuators, some important parameters, such as the oil flow of the hydraulic system and the needed maximum output force of each actuator, are hard to calculate precisely with kinematics and dynamics equations. The oil flow is mainly determined by the walking speed of the quadruped robot, but also influenced by the stride frequency, gait type and the foot trajectory. This paper planned the foot trajectory with cubic polynomial firstly. Then selected optimal stride frequency referred to that of four-legged mammals and stride length according to the required walking speed of the quadruped robot. Furthermore, displacement curves and velocity curves with respect to time for all linear hydraulic actuators can be obtained easily with inverse kinematics equations in MATLAB. The needed maximum output force of each actuator can be obtained from dynamic simulation with MSC.ADAMS. Then the effective area of the hydraulic actuator can be calculated according to the output force of actuator and oil pressure of the hydraulic system. Lastly, the oil flow can be calculated precisely by summing all the products of the velocity and the effective area of each actuator.

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