Gait Planning and Analysis for Stair Climbing of Snake Robot

This research developed a stair-climbing algorithm for a 3D snake robot. According to the limitation of structure, the analysis of torque and the consideration of spaces, the research finds 6 rules to systematically plan the gaits of stair climbing, and develops a six-stage climbing algorithm. The six stages can be described as below. Stage 1：Lifting the first some units of snake robot and hooking stair n+1. For stability and safety during lifting, we have to take the position of center of gravity into consideration. Dividing the gaits into several steps control the position of center of gravity to prevent the snake from falling during lifting and helps lower the maximal torque of lifting units. Stage 2 & 3：Use the rear some units to raise up the body. The stable torque of units on the stair n+1 must be greater than that of units to be lifted with no risk of falling downwards. Stage 4：Shifting the center of gravity of snake robot to stair n+1. Stage 5：The rear some units lift up to stair n+1. The stable torque of units on the stair n+1 must also be greater than that of units to be lifted with no risk of falling downwards. Stage 6：In order to climb next stair, snake robot has to return to initial position. In the six-stage processes, we consider three essentials. 1. Shifting the center of gravity of snake robot from stair n to stair n+1. 2. Rotating directions (pitch and yaw) have to be taken into account during climbing. 3. Considering the spatial limitation while climbing. The six-stage algorithm generates gaits that assure stability and safety during climbing and offer substitutions for step-by-step manual control. Besides the simplification of climbing processes, it also provides the order of units and angles to be rotated in every stage. The result of experiment indicates that snake robot successfully climbs different stairs with the systematic gaits calculation methods where the snake robot can consist of from 8 units to 12 units. The snake can accomplish one-stair climbing in 11 seconds. What's more, the research provides the information for determining the least number of units needed so as to simplify the mechanism and reduce the cost.