Balancing and Locomotion of a Hexapod Robot Traversing Uneven Terrain

Abstract: This master thesis project has developed a method for a six-legged robot to traverse uneven terrains. From a previous project, the robot already possessed basic locomotion which had to be extensively redesigned. Several new subsystems have been introduced, such as a continuous balancing system, a system estimating the slope of the ground the robot is walking on, and method for detecting when the robot’s legs hits the ground. This project designed a system that lets the robot balance its body as it moved using an inertial measurement unit. Several different controllers have been tested and compared. A lot of work has gone into gathering data and identifying how different controllers and sampling rates help the system. To move across uneven terrain it is important to estimate the tilt of the ground that the robot is moving on. This estimate has been made by integrating the angles from the inertial measurement unit. However, a superior solution using distance measuring sensors has been developed in a simulated environment. The distance measuring sensors also made it possible to control the height of the robot more accurately than before. A large part of the project has been spent on testing and comparing different methods of detecting when the legs of the robot hit the ground. No satisfactory solution was found using buttons or force sensitive resistors. Instead the legs’ movement deviations were used to detect when a leg touched the ground. This was then successfully implemented in simulation. Several new features, unrelated to the balancing but improving the movements of the hexapod, have been developed and implemented. Also, a mathematical model for the maximum speed of hexapod walking on sloping ground has been designed.