Design of a Tendon-Actuated Foldable Wheeled-Legged Hybrid Mobile Robot with high load-bearing capacity

Mobile robots that can carry heavy loads play an important role in transporting and exploring in unstructured environment. However, there are some problems existing in conventional motor direct-drive robots such as excessive joint torque and unfoldable legs when they are under heavy loads. This paper proposes a tendon-actuated foldable wheeled-legged robot with high load-bearing capacity. A spreader is attached to the knee joint so that the output torque of the motor can be amplified by pulling the end of the spreader with a cable. The single and double fixed pulleys are used to reduce the required cable tension and avoid the interference of different cables, which can better achieve the folding of legs. In addition, the statics and kinematics of the tendon-actuated leg and the formulas for calculating the required tension and motor torque, as well as the relationship between foot velocity, joint speed, and motor speed are given. Finally, Matlab is used for simulation analysis, and it is found that the joint torques required for the tendon actuation are lower than for the direct actuation at the same joint angles.