Force And Haptic Reappearance System Of Remote Palpation Robots

Force and haptic reappearance technology is considered to be one of the top ten technologies that can change human life in the future,with broad application prospects and market demand.Most of the existing medical robots,especially the remote diagnosis and treatment robots,lack tactile feedback,or the feedback force is insufficiently calculated.The force haptic reappearance technology is an effective method to solve the shortage of tactile presence of the medical robots and improve the practicality of the medical robots.Starting with the key technology of the force haptic reappearance system,the soft tissue model,haptic rendering and the construction of the system are studied in this thesis.The current situation of soft tissue modeling research has a contradiction between real-time and accuracy.This thesis considers the special biomechanical properties such as viscoelasticity and nonlinearity of soft tissue,and combines the finite element method with the mass-spring model.Ignoring the damping coefficient,the finite element method is used to estimate the parameters of the mass-spring model,then the relationship between the elastic coefficient and the Young's modulus and Poisson's ratio is obtained.Then according to the data of real soft tissue measurement and stress-strain curve in the literature,the values of each parameter are determined.Which avoids the randomness and experience of spring parameter selection to some extent and improves the accuracy of the model while ensuring the real-time performance of the system.Collision detection is a prerequisite for haptic rendering and deformation rendering in force haptic reappearance systems.Generally,an external force is only applied to the collision point.In this thesis,the external force application method is optimized.After the collision detection,the external force is applied to the collision point and a circle of the surrounding points.Meanwhile,the damping coefficient that is ignored in the parameter estimation is reintroduced to improve the numerical integration.Deformation rendering is more realistic and smooth,balancing computational efficiency and computational overhead.The construction of the force haptic reappearance system was completed based on the Geomagic Touch haptic device.The soft tissue surface model was drawn with OpenGL,and the human hand model was drawn with 3Ds Max.The hapticreappearance and visual feedback of the human hand palpation soft tissue model are realized.And the quality of the feedback was evaluated,the haptic reappearance is stable and realistic,while the visual feedback is smooth.The accuracy of the model and the real-time performance of the system are verified.In the interaction process,the data of force-displacement,stress relaxation,creep,etc.of the soft tissue model were compared with the in vivo,ex vivo real soft tissue measurement and empirical mass-spring model data.The data of this model is basically within the range of actual measured values.The model has certain accuracy and effectiveness,which is better than the empirical mass-spring model.At the same time,the frame rate in the interaction process is calculated and recorded.The frame rate of this thesis is much higher than the frame rate required by real-time,which verifies the real-time performance of the system.