| Due to the combination of optical navigation systems and robots,information medical technologies such as preoperative image planning,intraoperative real-time navigation,and precise positioning of target areas have emerged,which effectively contributes to the increase of the success rate of puncture operations and shorten the operation time.However,the current fact is that the robot-assisted needle puncture technology have little feedback information and low degree of automation.When facing the actual work,doctors are still required to perform a large degree of participation in order to complete an operation.In addition,there are still harsh problems to be solved,such as the shaking of the operating arm,deformation of the puncture needle during the puncture process and the target area movement caused by respiratory movement and other factors.Based on this context,the robot force feedback related technology is further explored on the basis of the previous research on the optical positioning robot control technology to make the robot-assisted puncture achieve a higher level of automation,deal with various complex puncture environments,and further free the doctor’s hands.After the force of the puncture needle in different puncture scenarios is taken into consideration,a feedback control system with software and hardware is designed exclusively,and the fixture self-weight filtering algorithm and admittance control algorithm are analyzed to adapt and solve abnormal force of the puncture needle in actual puncture operation,and realize the zero-force follow-up control of the puncture needle.The specific research contents are presented as follows:(1)Establishment and design of the optical power control platform of the mechanical armFor the purpose of realizing a robot-assisted needle puncture system with a high level of automation and hand-eye simulation,this paper further introduces the force-sensing servo control based on the previous research of visual servo control manipulator.The research content which is related to the technical direction includes the following items:The mechanical structure design of the end puncture needle holder is applied to complete the control and fixation of the puncture needle and the puncture guidance;The control circuit of the end manipulator is used to complete the collection and communication of the puncture needle force signal and control the movement of the needle advancement module;The upper computer software is adopted to coordinate the communication,control and deployment between the mechanical arm and the end holder.The software and hardware modules of this platform can work normally through validation.(2)Sensor load gravity bias filteringFor the reason that heavy objects,such as clamps and puncture needles mounted on the force sensor at the end of the holder will exert strong impacts on the stress data collection of the puncture needle,it is a key point to focus on the interference of the self-weight of the clamp loaded by the sensor on the contact force.First,the forward and inverse kinematics of the mechanical arm is used for analysis of the acceleration of gravity in the sensor coordinate system at the end of the robot arm at any posture.Then,the actual self-weight mass parameters are accurately identified.The advantages and disadvantages of various algorithms are compared.Finally,the least square method is employed and the objective function is made to identify the quality of the fixture.The result is shown that the average reading of the sensor in all directions can be maintained at 0.08 under the situation that the puncture needle is not subject to any contact force.(3)Research on zero-force following control algorithmThe sensor can collect a more realistic contact force between the needle and the tissue by following the filtering of self-weight bias.Because of the complete position control function of selected mechanical arm,the motion planning in the Cartesian coordinate system space at the end of the robot arm can be carried out.Thus,the system space dynamics modeling can be implemented in the Cartesian coordinate system at the end of the robot arm.The contact force signal collected by the sensor is used as the input of the system after the bias is eliminated.In addition,the numerical method of the differential equation is utilized to solve the zero force compensation pose of the mechanical arm at each moment.As a consequence,the mechanical arm can compensate for a new pose based on the contact force of the puncture needle.After the manipulator moves to this position,the collected value can restore to below 0.1N,which has achieved zero force following and confirmed the effectiveness of the solution.In this paper,the force feedback control system is perfectly constructed,including mechanical structure,control circuit,upper and lower computer control software,gravity bias algorithm and compliance control algorithm,which establishes a good foundation for the subsequent development of light force fusion control and live animal experiments. |
