Snake robots are mostly designed based on single mode locomotion.However,single mode gait most likely could not work efectively when the robot is subject to an unstructured working environment with diferent measures of terrain complexity.As a solution,mixed mode locomotion is proposed in this paper by synchronizing two types of gaits known as serpentine and wriggler gaits used for non-constricted and narrow space environments,respectively,but for straight line locomotion only.A gait transition algorithm is developed to efciently change the gait from one to another.This study includes the investigation on kinematics analysis followed by dynamics analysis while considering related structural constraints for both gaits.The approach utilizes the speed of the serpentine gait for open area locomotion and exploits the narrow space access capability of the wriggler gait.Hence,it can increase motion flexibility in view of the fact that the robot is able to change its mode of locomotion according to the working environment. Snake robots are mostly designed based on single mode locomotion.However, single mode gait most likely could not work efectively when the robot is subject to an unstructured working environment with diferent measures of terrain complexity. As a solution, mixed mode locomotion is proposed in this paper by synchronizing two types of gaits known as serpentine and wriggler gaits used for non-constricted and narrow space environments, respectively, but for straight line locomotion only. A gait transition algorithm is developed to efciently change the gait from one to another.This study includes the investigation on kinematics analysis followed by dynamics analysis while considering related structural constraints for both gaits. the approach utilizes the speed of the serpentine gait for open area locomotion and exploits the narrow space access capability of the wriggler gait .ence, it can increase motion flexibility in view of the fact that the robot is able to change its mode of locomotion accordin g to the working environment.