Surgical Robot Prismatic Joint Control for Rapid Tool Withdrawal
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Solution Overview
Problem
Conventional surgical robots face challenges in providing a larger workspace around the surgical site and efficiently withdrawing tools from the body cavity, which can obstruct the work of assistants and complicate emergency situations.
Innovation Solution
The surgical robot is designed with a manipulator that supports the surgical instrument without holding a trocar, allowing for redundant degrees of freedom to avoid interference. The controller manages the motion of the manipulator to ensure the tool is withdrawn quickly and reliably by moving only the prismatic joint, reducing shaking and increasing speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If instrument holders are disposed to hold tubes (cannulas or trocar sleeves) at the surgical site, then the tubes are securely positioned, but the instrument holders crowd around the surgical site and obstruct the work of assistants
Solution Approach 1:
The patent removes the instrument holder from the surgical site by having the manipulator directly support the surgical instrument without holding the trocar. The manipulator arm extends through or alongside the trocar to reach the surgical site, extracting the intermediate instrument holder component that was causing crowding and obstruction while maintaining secure instrument positioning through direct manipulator support.
2Adaptability or versatility
If multiple joints of the manipulator are moved to withdraw the tool from the body cavity, then the manipulator has flexibility in positioning, but the withdrawal process becomes slower and causes shaking of the shaft
Solution Approach 1:
The patent segments the manipulator's degrees of freedom by isolating the withdrawal function to a single prismatic joint while assigning positioning functions to rotational joints. This segmentation allows the withdrawal operation to be performed by one joint moving linearly along the instrument axis, achieving fast, shake-free withdrawal, while other joints remain stationary or perform only positioning tasks.
Solution Approach 2:
The patent dynamically assigns different functions to different joints based on the operational phase. During normal surgery, multiple joints work together for flexible positioning. During emergency withdrawal, the system transitions to a dynamic mode where only the prismatic joint is activated for rapid linear retraction, while rotational joints are locked or held stationary to prevent shaking and maximize withdrawal speed.
3Adaptability or versatility
If the manipulator is designed with redundant degrees of freedom to avoid interference, then the manipulator can navigate complex surgical paths, but the control complexity increases when withdrawing the instrument
Solution Approach 1:
The patent segments the control functions by assigning navigation and positioning tasks to rotational joints while assigning the withdrawal task exclusively to the prismatic joint. This segmentation simplifies the control logic during withdrawal operations, as the controller only needs to command the prismatic joint to retract the instrument linearly, while the redundant rotational degrees of freedom remain stationary or are independently controlled for positioning without interfering with the withdrawal motion.
Data Source
AI summary
A surgical robot includes: a surgical instrument including a base disposed at a proximal end of the surgical instrument, a tool disposed at a distal end of the surgical instrument, and a shaft extending in an axial direction between the base and the tool; a manipulator configured to support the surgical instrument, the manipulator including an instrument interface to which the base of the surgical instrument is attached, an arm including rotational joints, and a prismatic joint coupling the instrument interface to a distal end of the arm; and a controller. including a memory that stores a remote center that is a center of motion of the surgical instrument. The controller is configured to control the motion of the manipulator such that with the shaft inserted through a trocar retained at a body wall of a patient and the tool located in a body cavity of the patient, a relationship (L−β)≥T1≥(L+α) is established in a case of L≤T0, wherein: L represents an intra-body cavity length of the surgical instrument, the intra-body cavity length L being a length from the remote center to the distal end of the surgical instrument; T0 represents a maximum possible linear movement amount of the prismatic joint, the maximum possible linear movement amount T0 being an amount of movement from an origin position to an end point position; T1 represents a first linear movement amount of the prismatic joint, the first linear movement amount T1 being an amount of movement from the origin position to a current position; α represents a distance from the remote center to an inlet of the trocar; and β represents a distance from the remote center to an outlet of the trocar.