Bionic quadruped robots received considerable worldwide research attention. For a quadruped robot walking with steady paces on a flat terrain, using a cam drive control mechanism instead of servomotors provides theoretical and practical benefits as it reduces the system weight, cost, and control complexities; thus it may be more cost beneficial for some recreational or household applications. This study explores the robot step mechanism including the leg and cam drive control systems based on studying the bone structure and the kinematic step sequences of dog. The design requirements for the cam drive robot legs have been raised, and the mechanical principles of the leg operating mechanism as well as the control parameters have been analyzed. A cam drive control system was constructed using three cams to control each leg. Finally, a four-leg demo robot was manufactured for experiments and it showed stable walking patterns on a flat floor. 1. Introduction Quadruped robots have been extensively studied as the most important branch of bionic robot applications. In 1968, General Electrics and the US Army Mobility Systems Laboratory constructed a quadruped walking machine, which used hydraulic server motors to drive [1]. It was later suggested that a large number of controllable degrees of freedom require highly efficient drives properly arranged, special design of feet to dissipate the energy of the strike, and so forth, and the problem of the control seems to be the main problem of the walking robot [2]. The first comprehensive quadruped robot, KUMO-I, was developed in 1976 by Japan’s Tokyo Institute of Technology, which subsequently also produced TITAN series quadruped robots based on this study [3–6]. Currently quadruped robots are widely studied in many universities and laboratories around the world [7–13]. The most advanced quadruped robot so far is BigDog, jointly developed by Boston Dynamics and M.I.T. in 2005 for the US Army. BigDog is able to be operated in unstructured environment, with multiple capabilities such as independent walking, running, jumping, and climbing obstacles. An upgraded version, LS3, is currently in intense development [13]. Considered in a constructed environment with flat terrain, the robot performs steady walking, and it is possible to use a mechanical transmission system to replace the servomotors at the leg joints. This reduces the system weight, cost, and control complexities; thus it may be more cost beneficial for some recreational or household applications. For this reason, this study utilizes some previous research
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