| Fracture is one of the common disease in orthopaedics.In recent years,the incidence rate has gradually increased,which seriously threatened people’s health and had a great impact on the quality of patients’ life.At present,the commonly used bone fracture treatment methods in clinical practice,such as manual reduction splint external fixation and open reduction plate internal fixation,can not take into account the reduction accuracy and the low trauma.With the continuous improvement of people’s requirements for the surgery quality,it has become an urgent need to develop a surgical method that can accurately reduce the fracture under the condition of low trauma.The robot system has been used more and more in clinical surgery because of its high accuracy and stability.However,there are few mature fracture reduction robot systems at present,especially in the field of human-machine collaborative fracture surgery robot that can exert advantages of doctors’ experience.Therefore,this paper takes the force feedback control based fracture reduction surgery robot as the research object,and develops a number of theories and technologies including human-machine cooperative control,robot-robot cooperation,collision detection and other algorithms through establishing relevant models and control architecture to promote the development of fracture reduction surgery robot technology.The position conversion and force feedback technology between the force feedback manipulator and the reduction robot are the basis of the fracture reduction robot studied in this paper.Based on the Euler angle rotation and quaternion transformation theory,the force vector and posture transformation relationship between the manipulator and the robot was obtained respectively.A human-machine cooperative control program that could realize position control and force feedback was developed.The single-factor experiments were carried out to respectively reveal the influence of the parameters such as the motion ratio and the list container volume on the position control accuracy and the delay time,and the influence of the parameters such as the force value,the ratio,the robot posture on the force feedback performance.The experimental results show that in the aspect of motion control,the motion trajectory of the robot can be consistent with the force feedback manipulator trajectory.The translation and rotating motion amplitude can change correspondingly when the motion ratio changes,and the two motion do not affect each other.The volume of list not only affects the delay time,but also the amplitude ratio of the motion.In the aspect of force feedback,the force feedback manipulator can correctly reflect the force at the robot end in any posture.The feedback force changes linearly as the force value and force ratio change.In order to deal with the weak load capacity of the serial-type robot in the process of fracture reduction,a cooperative control method of the stretching system was studied in this paper.Firstly,the coordinate transformation model of the stretching platform was established by the RPY rotation method,and then the force model of the robot end in the reduction process was established according to the three-element viscoelastic theory.In order to verify the effectiveness of the above two models,a control program were designed to conduct the single factor experiments.In the axis alignment experiment,the influence of the fracture axis position and the alignment length n on the alignment results was studied.The experimental results show that regardless of the posture of P1-P2,the robot 2 could move P4-P5 to the specified position.When the value of n increaces,the alignment effect can not be affected,but the distance between P4 and P1 increases linearly.The stretch cooperative control experiment results show that the algorithm can effectively reduce the load at the reduction robot end during the reduction process,and the effect is not affected by the reduction speed,which means that this method can adapt to the changing speed of the force feedback manipulator when fracture reduction.Although the increase of soft tissue stiffness will increase the load of the reduction robot,the load distribution between the stretching platform and the reduction robot can be optimized by properly selecting the filtering length of the force value and raising the force-position coefficient,thus ensuring that the load at the reduction robot end will not be too large.In order to realize the real-time detection of the broken bone collision state during the reduction process,this paper proposed a method of broken bone collision detection based on the slope ratio of the force curve.In this method,a fracture collision model based on the threeelement viscoelastic model was established to analyze the factors influencing the slope of the curve.According to this model,the effects of four factors,namely reduction speed,soft tissue mass,collision angle and collision area.on the slope and slope ratio of the force curve were studied.It is concluded that the increase of reduction speed and soft tissue mass can reduce the slope ratio,while the increase of collision angle can increase the slope ratio.Based on the force curve obtained from the single factor experiment,by drawing slope ratio curves under various experimental conditions,this paper proved the universality of the collision detection model;The difference of slope ratio curve before and after optimization was analyzed through comparative experiments,and it was proved that the optimized detection model could effectively filter out invalid waveforms and reduce the occurrence of false detection;At last,this paper analyzed the factors that affect the performance of the detection model.Under the experimental conditions in this paper,When a=5 and b=40,the stability of the system can be ensured while having a lower detection time delay.On the basis of the above collision detection research,this paper also studied a method of bone fracture collision detection based on vibration.By establishing a vibration response model based on viscoelastic theory,the factors affecting the amplitude of vibration response were revealed,including the clamping length of distal and proximal broken bone,soft tissue mass,soft tissue tension,excitation voltage,etc.The single-factor experimental results show that in the aspect of influence on amplitude,the increase of excitation voltage would make the vibration amplitude increase linearly,and the increase of soft tissue mass and tension would make the vibration transmission capacity of soft tissue increase in the frequency range of 500 Hz～1000 Hz;In terms of influence on peak frequency,the clamping length of the distal broken bone has the greatest influence,which makes peak frequency difference reach 74 Hz,followed by 45 Hz at the proximal end.While the influence of other factors is little.According to the single-factor experimental results,the excitation frequency in the verification experiment was determined to be 677 Hz.In verification experiment,under the vibration interference with acceleration amplitude of 1.2 G,the detection threshold was set to 0.3 G,and this method achieved correct detection under different conditions. |
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