Research On Multi-Mode Locomotion For Inertia Driving Force Actuating Soft Spherical Robot

Soft robots are robots whose actuators are made of soft materials providing large-scale deformation. Due to the soft components, soft robots’ locomotion is much more flexible when compared with traditional robots consisting of rigid parts. Soft robots are flexible, safe and adaptive, showing a huge potential in the application of service business, education and food industry etc. However, soft robots show weakness in the enhancement of actuation and low efficiency of locomotion. Spherical robots mainly move in the way of rolling, which is quite efficient, but rolling locomotion requires that the moving terrain must be plane when the robots can hardly adapt to the environment otherwise. In this case, combining soft robots and spherical robots is a win-win solution, solving both the low efficiency in locomotion of soft robots and the low adaptability to the environment.Based on the idea of soft spherical robot, a new kind of actuation method called inertia driving force actuating is proposed in this paper. It drives a robot by the inertia force provided by a rotating mass load. According to the safety and high adaptability of soft robots, multi-mode locomotion including rolling and jumping of the soft spherical robots can be achieved. Analyze the global mechanic situation of the robot under different locomotion mode, along with studying the phase difference between the inertia driving force and the locomotion. This helps set up the dynamic model of the robot. The positon, velocity and acceleration of the locomotion in the first motion cycle is studied with analyzing the mathematics functions. Continuous locomotion is studied with simulation to find out how the locomotion changes with the inertia driving force.Stable locomotion needs planning and controlling. A planning method based on the expecting locomotion is proposed. A ideal spring oscillator model is proposed to provide expecting robot locomotion. Based on this, the locomotion of actuators is calculated. The simulation of a planned locomotion is studied to show the validity of the planning method. Besides this, a control algorithm based on position error is proposed to control the motor speed.In this paper, a prototype of the soft spherical robot is designed when mechanism and softness should both be considered. Motors are used to drive mass loads to generate inertia driving force. A soft spherical shell is used to provide the robot’s softness and spherical shell. A servo motor control system is established to achieve the position and velocity control of the motors. An acceleration sensor is used to get feedback signal establishing the closed-loop locomotion control system. Experiment is accomplished with the prototype to study its multi-mode locomotion. Both the rolling and jumping locomotion is achieved and optimized to prove that the inertia driving method is valid.