Engagement and/or homing of a surgical tool in a surgical robotic system
Engaging and/or homing is provided for a motor control of a surgical tool in a surgical robotic system. Where two or more motors are to control the same motion, the motors may be used to detect engagement even where no physical stop is provided. The motors operate in opposition to each other or in a way that does not attempt the same motion, resulting in one of the motors acting as a stop for the other motor in engagement. A change in motor operation then indicates the engagement. The known angles of engaged motors and the transmission linking the motor drives to the surgical tool indicate the home or current position of the surgical tool.
1 . A surgical robotic system for engagement, the system comprising:
a surgical effector connected by a transmission to first and second rotary tool pads, the surgical effector connected by the transmission such that rotation of the first and second rotary tool pads moves the surgical effector in a single degree of freedom;
a tool drive having first and second rotary drives mateable with the first and second rotary tool pads, respectively; and
a processor configured to signal the first and second rotary drives to rotate in opposition to each other and while doing so detect mating of the first and second rotary tool pads with the first and second rotary drives, respectively, as a change in a signal representing a speed of the first rotary drive or a speed of the second rotary drive dropping below a speed threshold.
2 . The surgical robotic system of claim 1 wherein the surgical effector comprises an endoscope rotatable about a longitudinal axis.
3 . The surgical robotic system of claim 2 wherein the endoscope is rotatable about the longitudinal axis free of a hard stop.
4 . The surgical robotic system of claim 1 wherein the first rotary tool pad is driven by the first rotary drive to rotate in a first direction while the second rotatory tool pad is driven by the second rotary drive to rotate in a second direction that is opposite the first direction, resulting in the surgical effector rotating in only one of the first direction or the second direction.
5 . The surgical robotic system of claim 4 wherein the processor is configured to drive both the first and second rotary drives in position control mode.
6 . The surgical robotic system of claim 1 further comprising first and second encoders connected with the first and second rotary drives, and the speed threshold is within a threshold amount of zero.
7 . The surgical robotic system of claim 1 further comprising current sensors connected to detect currents to the first and second rotary drives, the processor configured to detect first and second currents for the first and second rotary drives spiking, and detect the mating further based on detecting non-existence of repeating spikes in the first and second currents.
8 . The surgical robotic system of claim 1 wherein the processor is configured to verify the mating by comparing a first rotational angle of the first rotary drive to a second rotational angle of the second rotary drive.
9 . The surgical robotic system of claim 1 wherein the processor is configured to determine a rotational angle of the surgical effector based on rotational angles of the first and second rotary drives as mated to the first and second rotary tool pads.
10 . The surgical robotic system of claim 1 further comprising a current source configured to apply a dithering current to a current ramp in current control mode to the first rotary drive, wherein the processor is configured to detect the mating from the change in the signal from the first rotary drive while in the current control mode.
11 . The surgical robotic system of claim 1 wherein the processor is further configured to, upon detecting the mating, check whether a first rotation angle of the first rotary tool pad is within a threshold amount with an opposite sign as a second rotation angle of the second rotary tool pad.
12 . A method for tool engagement in a surgical robotic system, the method comprising:
a) signaling a first rotary drive and a second rotary drive of a tool drive in a surgical robotic system to rotate in opposition to each other, wherein the first and second rotary drives are mateable with first and second rotary tool pads, respectively, wherein the first and second rotary tool pads are connected by a transmission to a surgical effector such that rotation of the first and second rotary tool pads moves the surgical effector in a single degree of freedom; and
b) while performing a), detecting a mating of the first and second rotary tool pads with the first and second rotary drives, respectively, as a change in a signal representing a speed of the first rotary drive or a speed of the second rotary drive dropping below a speed threshold.
13 . The method of claim 12 wherein the first rotary tool pad is driven by the first rotary drive to rotate in a first direction while the second rotatory tool pad is driven by the second rotary drive to rotate in a second direction that is opposite the first direction, resulting in the surgical effector rotating in only one of the first direction or the second direction.
14 . The method of claim 13 wherein signaling the first rotary drive and the second rotary drive to rotate in opposition to each comprises driving both the first and second rotary drives in position control mode.
15 . The method of claim 12 wherein detecting the mating comprises detecting non-existence of repeating spikes in currents to the first and second rotary drives.
16 . The method of claim 12 further comprising verifying the mating by comparing a first rotational angle of the first rotary drive to a second rotational angle of the second rotary drive.
17 . The method of claim 12 further comprising determining a rotational angle of the surgical effector based on rotational angles of the first and second rotary drives as mated to the first and second rotary tool pads.
18 . The method of claim 12 further comprising, while performing b), applying a dithering current to a current ramp in current control mode to the first rotary drive, wherein detecting the mating occurs while in the current control mode.