Surgical Robot Arm Torque Control for Staff Interaction
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Solution Overview
Problem
Existing surgical robotic systems pose challenges in safely and easily allowing operating room staff to interact with the robot arm before, during, and after invasive procedures, as they require complex setup and control mechanisms that are not intuitive for staff other than the surgeon.
Innovation Solution
A control system for a surgical robot arm that utilizes torque sensors to alter its configuration in response to externally applied forces or torques, allowing for intuitive interaction by mapping sensed torque states to selected states and sending command signals to adjust the arm's configuration, incorporating a Jacobian matrix for force determination and noise-weighted sensory data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a surgical robotic system is designed to allow operating room staff to interact with the robot arm before, during, and after procedures, then the ease of operation is improved, but the device complexity increases due to the need for multiple control modes and safety mechanisms
Solution Approach 1:
The control system dynamically switches between three distinct operational modes (compliant mode, surgical mode, and instrument retract mode) based on the current task requirements. In compliant mode, the robot arm is highly interactive for setup and teardown. In surgical mode, it becomes rigid and precise for the actual procedure. In instrument retract mode, it provides controlled resistance for safe instrument removal. This dynamic adaptation allows the system to maintain ease of operation when interaction is needed while ensuring precision and safety when interaction should be limited.
Solution Approach 2:
The system changes key control parameters including stiffness, damping coefficients, and force thresholds depending on the operational mode. During compliant mode, lower stiffness values allow easy manipulation by staff. During surgical mode, higher stiffness values ensure precise positioning. The Jacobian matrix and torque sensors are used to continuously adjust these parameters based on the current state, enabling the system to transition smoothly between different levels of interaction and control.
2Reliability
If torque sensors are used to sense externally applied forces and alter the robot arm configuration, then the safety is improved by preventing unintended movements, but the device complexity increases due to additional sensors and control mechanisms
Solution Approach 1:
The control system continuously receives feedback from torque sensors mounted on the robot arm joints. These sensors measure the external forces applied by operating room staff in real-time. The control system processes this feedback information and adjusts the motor torques accordingly to maintain the desired operational mode. This closed-loop feedback mechanism ensures that unintended movements are prevented while providing appropriate resistance or compliance based on the current task, thereby enhancing safety without requiring overly complex external monitoring systems.
Solution Approach 2:
The robot arm uses its own torque sensors and control system to automatically detect and respond to external forces applied by staff. Instead of requiring external safety monitoring equipment or manual intervention, the system self-regulates by sensing the applied torques and adjusting its configuration through its built-in actuators. This self-service approach to safety enhances reliability while minimizing additional device complexity.
3Ease of operation
If the robot arm is made compliant to allow easy manipulation by staff, then the ease of operation is improved, but the manufacturing precision deteriorates as it becomes difficult to maintain precise positioning
Solution Approach 1:
The system dynamically adjusts its mechanical and control characteristics between compliant and rigid states based on the operational phase. During setup and teardown operations, the robot arm operates in compliant mode with reduced stiffness, allowing staff to easily reposition and manipulate the arm. During the surgical procedure, the system transitions to a rigid, precision-controlled state where positioning accuracy is maintained through active control. This temporal separation of compliance and precision requirements resolves the contradiction.
Solution Approach 2:
The control system modifies key parameters including gain values, stiffness coefficients, and damping ratios depending on the operational mode. In compliant mode, lower gain values and stiffness coefficients facilitate easy manipulation. In precision surgical mode, these parameters are increased to maintain stable, accurate positioning. The Jacobian matrix is used to transform forces between task space and joint space, enabling precise control even when compliance is activated, thus maintaining positioning precision across different operational states.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the safety and ease of interaction for operating room staff by allowing compliant, surgical, and instrument retract modes, enabling staff to manipulate the robot arm without affecting the surgical instrument's position or orientation, thus improving procedural efficiency and safety.
Implementation Method 1
one or more torque sensors, each torque sensor configured to sense a torque at a joint of the series of joints
Data Source
AI summary
A control system of a surgical robot arm, the surgical robot arm comprising a series of joints by which the configuration of that surgical robot arm can be altered and one or more torque sensors, each torque sensor configured to sense a torque at a joint of the series of joints, the control system being configured to control the configuration of the surgical robot arm to be altered in response to an externally applied force or torque by: receiving sensory data from the one or more torque sensors indicative of a sensed torque state of the surgical robot arm resulting from the externally applied force or torque; mapping the sensed torque state to a selected torque state of a set of candidate torque states; and sending a command signal to the surgical robot arm to drive the robot arm such that the configuration of the robot arm is altered so as to comply with the selected torque state.