Table 2.

Summary of different control methods.

Literature	Design principle	Actuation	Model based or free	Control method	Accuracy
[116]	Backbone	Tendon driven	Model based	Hybrid control based on the adaptive PID and NN model	<2.14 mm
[26]	Backbone	Tendon driven	Model free	Optimal control considering contacts	—
[110]	Backbone	Tendon driven	Model based	Closed control based on the mechanics model	<1.07 mm
[111]	Backbone	Magnetic driven	Model based	Closed control based on the mechanics model	0.42 mm
[117]	Backbone	Tendon driven	Model based	Open control based on the FEM model	<2.14 mm
[112]	Backbone	Fluid driven	Model based	Closed control based on the inverse kinematics	12.3 mm
[113]	Concentric tube	Motor driven	Model based	Closed control based on the Cosserat rod model	<1.67 mm
[118]	Backbone	Magnetic driven	Model based	Closed control based on the inverse kinematics	<5.41 mm
[93]	Backbone	Tendon driven	Model based	Closed control based on the reinforcement learning	<0.029 mm
[119]	Backbone	Fluid driven	Model based	Closed control based on the Koopman operator theory	<0.43 mm
[120]	Backbone	Fluid driven	Model based	Closed control based on the online learning kinematic	16.8 pixels