Sliding Perturbation Observer Based Reaction Force Estimation Method in Surgical Robot Instrument

Abstract

Previous research applied SMCSPO (sliding mode control with sliding perturbation observer) algorithm as robust controller to control the instrument and found that the value of SPO (sliding perturbation observer) followed force disturbance, reaction force loaded on the tip very similarly. However, in fact, some factors like friction which are not easy to find model parameters beforehand can make an effect on reaction force estimation because the factors are included in any perturbation. This paper addresses the SPO based reaction force estimation method to extract a reaction force on the surgical robot instrument in case of including Coulomb friction due to operation of cable-pulley structure. The Coulomb friction can be estimated by experiment and compensated from the estimated perturbation. To prove the suggested estimation method, experimental evaluation is performed. The results show that it is possible to substitute SPO for sensors to measure the reaction force. This estimated reaction force will be used to realize haptic function by sending the reaction force to a master device for a surgeon. The results will contribute to create surgical benefit such as shortening the practice time of a surgeon and giving haptic information to surgeon by using it as haptic signal to protect an organ by making force boundary.