Surgical Robot Arm Joint-Limit Control Without Losing Motion Freedom
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Solution Overview
Problem
Conventional surgical robotic systems face issues with joint limits being unpredictably exceeded, leading to loss of degrees of freedom and potential collision risks, which can result in tracking errors and the need for system resets.
Innovation Solution
A control system that generates control signals to restrict movement of a first set of joints while allowing movement of a second set, ensuring the surgical robot arm maintains its primary function by dynamically defining keep-out regions and joint limits based on system mode and pose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the surgical robot arm is controlled to avoid exceeding joint limits, then tracking precision is improved, but the system loses degrees of freedom and requires resets when limits are exceeded
Solution Approach 1:
The patent implements dynamic joint limit adjustment based on the robot's current pose and system mode. Instead of using fixed joint limits, the control system continuously adapts the keep-out regions and joint limits according to the surgical robot arm's configuration and operational context, allowing the system to maintain tracking precision while preserving necessary degrees of freedom for safe operation
Solution Approach 2:
The control system changes the parameters of joint limits and keep-out regions dynamically based on the surgical robot arm's pose and system mode. By adjusting these parameters in real-time, the system resolves the contradiction between maintaining tracking precision and preserving adaptability, as the limits are optimized for each specific operational state rather than being statically constrained
2Reliability
If the control system restricts movement to prevent collision, then safety is improved, but system functionality is reduced
Solution Approach 1:
The patent applies local quality by implementing mode-specific control strategies where different sets of joints are restricted based on the current system mode and pose. Rather than uniformly restricting all joints, the control system selectively applies safety constraints only to the specific joints that pose collision risks in the current operational context, thereby maintaining safety while preserving overall system functionality
Solution Approach 2:
The control system dynamically adjusts which joints are restricted and by how much, based on real-time assessment of the surgical robot arm's pose and operational mode. This dynamic approach allows the system to maintain safety by preventing collisions while minimizing the impact on system functionality, as restrictions are applied adaptively rather than statically
3Reliability
If joint limits are set conservatively to prevent exceeding, then reliability is improved, but tracking precision deteriorates due to tracking errors
Solution Approach 1:
The patent employs parameter changes by continuously adjusting joint limits and keep-out region parameters based on the surgical robot arm's current pose and system mode. This allows the control system to maintain reliability by preventing unsafe movements while minimizing tracking errors, as the parameters are optimized for each specific operational state rather than being conservatively fixed
Solution Approach 2:
The control system uses feedback from the surgical robot arm's pose sensors and system mode information to continuously adjust joint limits and keep-out regions. This feedback mechanism ensures that reliability is maintained by preventing unsafe movements while tracking precision is preserved, as the limits are continuously optimized based on real-time system state rather than being statically conservative
Data Source
AI summary
A control system and a method for controlling a surgical robotic system are provided. The surgical robotic system comprises a surgical robot arm. The surgical robot arm comprises a plurality of joints by which its configuration can be altered. An input is received which indicates a desired motion of the surgical robot arm when the surgical robotic system is operating in a mode in which the surgical robot arm is controlled in accordance with an objective. The objective is to control a particular part of the surgical robot arm to have a desired position and/or orientation. The control system determines that the desired motion of the surgical robot arm would cause a limit to be exceeded. In response to determining that the desired motion of the surgical robot arm would cause the limit to be exceeded, a control signal is generated for controlling the surgical robot arm, and the generated control signal is sent to the surgical robot arm in order to control the surgical robot arm. The control signal is generated, in response to determining that the desired motion of the surgical robot arm would cause the limit to be exceeded, such that: (i) movement of a first set of one or more of the joints of the surgical robot arm is restricted, and (ii) movement of a second set of one or more of the joints of the surgical robot arm is not restricted.