Experimental Study on Motion Control of Rope-Driven Snake Manipulator Using Velocity Mapping Method

The rope-driven snake manipulator is a bionic mechanism with hyper redundant DOFs and can be applied in narrow and confined environments, such as surgery, spacecraft, nuclear plant, etc. The kinematic mapping expressed by the rope length, joint angle and end pose is highly nonlinear and difficult to be calculated. Moreover, the control methods with rope length as input are prone to redundant driving ropes getting stuck due to differences in model and actual mechanism. Therefore, the perfect kinematic mapping of the rope-driven snake manipulator is necessary for designing high-efficiency motion controllers. In this paper, an analytical mapping about the velocities of ropes, joints and end is established and verified. Firstly, a prototype inspired by the biological snake spine is designed. And then the Jacobian matrix representing the velocity mapping is derived and analyzed in detail. The joint and rope velocities are optimized by configuring the null space vector of the Jacobian matrix. Based on the velocity mapping and optimization, a motion control scheme for the snake manipulator is established to realize servo control of the joints and end. Finally, the trajectory tracking simulation and experiment are executed to verify the velocity mapping theory and control scheme. This research can provide solutions for the complex motion control problems of subsequent snake manipulators.