A Multi-module Controller for Walking Quadruped Robots

Motion control based on biologically inspired methods,such as Central Pattern Generator(CPG)models,offers a promising technique for robot control.However,for a quadruped robot which needs to maintain balance while performing flexible movements,this technique often requires a complicated nonlinear oscillator to build a controller,and it is difficult to achieve agility by merely modifying the predefined limit cycle in real time.In this study,we tried to solve this problem by constructing a multi-module controller based on CPG.The different parallel modules will ensure the dynamic stability and agility of walking.In the proposed controller,a specific control task is accomplished by adding basic and superposed motions.The basic motions decide the basic foot end trajectories,which are generated by the predefined limit cycle of the CPG model.According to conventional kinematics-based design,the superposed motions are generated through different modules alter the basic foot end trajectories to maintain balance and increase agility.As a considerable stability margin can be achieved,different modules are designed separately.The proposed CPG-based controller is capable of stabilizing a walking quadruped robot and performing start and stop movements,turning,lateral movement and reversal in real time.Experiments and simulations demonstrate the effectiveness of the method.

Untethered quadrupedal hopping and bounding on a trampoline

For quadruped robots with springy legs,a successful jump usually requires both suitable elastic parts and well-designed control algorithms.However,these two problems are mutually restricted and hard to solve at the same time.In this study,we attempt to solve the problem of controller design with the help of a robot without any elastic mounted parts,in which the untethered robot is made to jump on a trampoline.The differences between jumping on hard surfaces with springy legs and jumping on springy surfaces with rigid legs are briefly discussed.An intuitive control law is proposed to balance foot contact forces;in this manner,excessive pitch oscillation during hopping or bounding can be avoided.Hopping height is controlled by tuning the time delay of the leg stretch.Together with other motion generators based on kinematic law,the robot can perform translational and rotational movements while hopping or bounding on the trampoline.Experiments are conducted to validate the effectiveness of the proposed control framework.