Analysis of Stability and Horizontal Motion of a Single Leg Hopping Robot

The structure of the hopping robot is such that the robot, relying on a single leg, must make consecutive jumps and be able to maintain its balance with hand tools. For this purpose, changing the angle of the robot's hands on the upper body is responsible for maintaining the robot's balance. If the upper body function is optimal, the leg mechanism can jump from the momentum caused by the robot mass. In this research, a semi-active mechanism is used for jumping, and the active actuator only performs the task of compensating for wasted energy. The new content of this research is based on the use of a simple four-link mechanism to compress the passive element rather than the ball-screw mechanism or any complete active mechanisms for jumping actions, and two moving arms to get balanced and do horizontal motion like acrobats by leading forward and changing orientation based on a unicycle model. Robot control method and how to implement PD controllers to move on a plane in a 3D space are presented; also, this paper presents the total modeling and motion control based on jump movement, balance, and robot orientation. The control concept of jumping is obtained as an open-loop multi-phases controller with no feedback from spatial position and orientation, just the internal joints of the robot, as well as the balancing control that used feedbacks of position and velocity states for observing different phases. Although, the rotating motion is a feedforward control. Finally, by implementing the control method and the robot model in a virtual environment (Simscape/Matlab), the robot's pursuit of some paths simulated. So the control motions act independently to guide the robot at a maximum speed of 3.1 cm per second. The simulations included the following online and offline trajectories, and the robot's performance is validated for movements in the range of 7–16 m per 260–600 s, as the robot is able to jump as high as 28 cm at the duration of 0.6 s in each stage hop.