| CPC A61B 34/35 (2016.02) [A61B 17/2909 (2013.01); A61B 17/3201 (2013.01); A61B 18/1445 (2013.01); A61B 34/37 (2016.02); A61B 34/71 (2016.02); A61B 90/06 (2016.02); B25J 9/104 (2013.01); B25J 9/1633 (2013.01); B25J 9/1641 (2013.01); B25J 13/085 (2013.01); A61B 17/3421 (2013.01); A61B 2018/00595 (2013.01); A61B 2034/301 (2016.02); A61B 2090/064 (2016.02); A61B 2090/066 (2016.02)] | 20 Claims | 

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               1. A computer-assisted device comprising: 
            a first engagement member coupled to a first actuator; 
                a second engagement member coupled to a second actuator; and 
                a control unit coupled to the first actuator and the second actuator; 
                wherein the control unit is configured to: 
              engage the first engagement member with a third engagement member of an instrument, where movement of the third engagement member causes a movement of a degree of freedom of an end effector of the instrument in a first direction; 
                  engage the second engagement member with a fourth engagement member of the instrument, where movement of the fourth engagement member causes a movement of the degree of freedom in a second direction opposite the first direction; 
                  in response to engagement between the first engagement member and the third engagement member reaching a pre-tension level and engagement between the second engagement member and the fourth engagement member reaching the pre-tension level: 
                actuate the degree of freedom in the first direction to a first detectable position that corresponds to a collision between the end effector and a first side of a cannula in the first direction; 
                    actuate the degree of freedom in the second direction to a second detectable position that corresponds to a collision between the end effector and a second side of the cannula in the second direction; and 
                    actuate the degree of freedom to a third position between the first detectable position and the second detectable position. 
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