In view of the lack of effective feedback function for the minimally invasive surgical robot at present, the design of force feedback device and verification of force feedback effect of the master manipulator are carried out, so that the operator of the master manipulator can obtain force feedback and improve the quality of surgery. A force feedback method based on the variable shear stress characteristics of magnetorheological fluid is proposed. The telecentric mechanism of the main manipulator end and the force feedback device are designed. And the relationship model of the output torque of the force feedback device, magnetic field intensity and angular velocity is established. The output characteristics of the device is analyzed by the experiment, and the linear relationship model between input current and output force of the force feedback device is obtained. The working performance of the force feedback device is tested by simulating the force conditions of surgical instruments in different cases of prostatectomy. The experimental results show that the delay of the force feedback device is 0.1-0.2 s, and the output performance of the force feedback device is related to the type and value of the applied force signal. When the input force signals are step signal, pulse signal and small range fluctuation signal, the average error of force feedback decreases with the increase of applied force. Analyzed from the experimental results, the overall force feedback effect of the force feedback device is well, which proves its feasibility and effectiveness in assisting doctors to carry out minimally invasive surgery.

Minimally invasive surgery（MIS）has the advantages of less trauma and quick recovery, so it is favored by patients. However, there are more requirements for surgeons’skill and experience in MIS. Combining robot-assisted technology with MIS can improve the quality of surgery and shorten the learning time for surgeons. Besides, with the help of robot-assisted technology, remote surgery can be achieved. Because of small incisions in MIS, the manipulator must pass through a fixed point during movement, which is the key point to develop the MIS robot and an obvious feature of the MIS robots. The ways whose classification is made into mechanisms with redundant degrees of freedom (DOF) and constrained by mechanisms to meet the requirement are summarized, and the principles, advantages, and drawbacks of each method are analyzed in this article. Based on summarizing the research results and analyzing the key technologies, the insight into future work is proposed.