Computation Of Contact Force And The Design Of The Haptic Device In Virtual Surgery

Virtual surgery is the research direction of virtual reality technology that integrates computer graphics,biomechanics,clinical medicine,computational mathematics,and robotics.One of the most important applications of virtual surgery is surgical training.In virtual surgical training systems,sensory perception is crucial.Contact collision is the most basic form of interaction in virtual surgery training.How to simulate the contact force in real surgery has a decisive effect on the real sense of virtual surgery training.In the calculation of the virtual surgery contact force,it is necessary to consider the type of the collision object and the contact force.In this paper,the virtual knee arthroscopic surgery training was used as the object to study the contact force during the removal of free body and to calculate the higher precision contact force.A six-degree-of-freedom knee arthroscopic surgery hardware device with force feedback was designed and processed for experimentation.The main research content includes:(1)Establish a mechanical model in virtual surgery.Analyze forces in virtual surgery through relevant physics engine knowledge;use particle systems to represent rigid and deformable bodies in virtual surgery that can be applied to numerical calculations of physical laws;Lagrange dynamics can add correct Physical constitutive law and dynamics constraints;and the finite element method is used to deform the primitive object.Based on this,the establishment of virtual surgery exerts force on the model object,creating a force interaction.(2)Calculation of contact force with friction.By setting up the most commonly used particle systems in computer graphics physics simulations,deformable and rigid body objects in virtual surgery can be approximated.After establishing the force-aware model,through the collision detection analysis,the potential collision points were found out,and the mathematical models of the collision-constraints and friction-constraints online were established;finally,the real-time frictional contact force was solved by a Gauss-Seidel-like algorithm.(3)Design of force feedback device.A 6-DOF minimally invasive surgical training device with force feedback was designed.This design was based on the actual knee arthroscopic surgical procedure.The pros and cons of the series-parallel mechanism were taken into consideration in the design.The design has submitted a patent application for invention,entered the stage of substantive examination,and processed a sample of the device.The operation was in good condition during the experiment.(4)Contact force and force feedback device association.After the contact force is calculated in the developed virtual surgery training software system,the force is output to the designed force feedback hardware device and delivered to the human hand to achieve force perception.By adding a force sensor and a closed-loop control system to the force feedback device,it can compensate for the errors caused by gravity,inertia,and friction of the device itself.Because software and hardware are updated at different frequencies,virtual coupling technology is used.The connection between hardware and software is asynchronous data transmission.Combining biomechanics,computer graphics and physics simulation techniques,this paper proposes a contact force calculation method.In combination with actual surgical operations,robotic technology is used to design a force feedback device that matches this.After repeated testing,the operation effect is good,and the output and size control of the real-time force can be satisfied.