We proposed a new force sensing technique for estimation of gripping force, that detects extension of a driving component with two encoders and estimates applied force based on differences of two displacements. The technique fulfills three requirements for surgical robot; (i) high tolerance for noise, (ii) sterilizability and (iii) compactness in size. A method to compensate backrush and various effects of power transfer elements was proposed and verified by simulation and experiments. We could estimate gripping force with average errors of 0.32[N] for a surgical tool with one degree of freedom. We also developed gripping force control method based on the estimate force value, and implemented it on a master-slave surgical system. In the future, we will apply the technique to other joints of surgical tool.
