Robotic Surgical Control Arm Friction Compensation
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Solution Overview
Problem
Robotic surgical systems face challenges with frictional forces in their transmission components, which can make the input handles feel 'heavy' to clinicians, affecting the precision and ease of control during surgical procedures.
Innovation Solution
The implementation of a control arm system with a drive motor, joint encoders, and a controller that calculates and compensates for transmission friction by generating control signals to overcome it, ensuring smoother movement and reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transmission component is used to couple the drive motor to the control arm, then mechanical advantage and force amplification are achieved, but frictional forces increase making the input handle feel heavy
Solution Approach 1:
The system uses joint encoders to detect the actual position of the control arm and feeds this information back to the controller. The controller compares the commanded position with the actual position and adjusts the motor output accordingly to compensate for friction forces in the transmission, making the input handle feel responsive despite the presence of friction
Solution Approach 2:
The controller dynamically adjusts motor torque and velocity parameters based on encoder feedback to compensate for transmission friction. By changing these control parameters in real-time, the system maintains smooth operation despite the fixed frictional characteristics of the transmission component
2Ease of operation
If additional forces are applied to overcome transmission friction, then the control arm can be moved smoothly, but the input handle becomes heavy for the clinician
Solution Approach 1:
The joint encoder provides real-time feedback on the control arm position, allowing the controller to detect when friction is resisting movement. The controller then applies just enough additional motor force to overcome the friction while keeping the input handle movement smooth and natural for the clinician
Solution Approach 2:
The system replaces direct mechanical coupling with an electronically controlled system using encoders and feedback control. This substitution allows the motor to compensate for transmission friction electronically rather than requiring the clinician to physically overcome mechanical friction
3Ease of operation
If friction compensation control signals are generated, then transmission friction is overcome improving responsiveness, but control system complexity increases
Solution Approach 1:
The friction compensation system uses joint encoders to provide position feedback and a controller to generate compensating control signals. This feedback mechanism improves responsiveness by dynamically adjusting for friction while maintaining a relatively simple implementation using standard encoder and controller components
Data Source
AI summary
A control arm of a robotic surgical system includes a member, a drive motor, a first joint encoder, and a controller. The member is supported about a first joint. The drive motor is operably coupled to the member and configured to rotate the member about the first joint. The first joint encoder is disposed about the first joint and configured to transmit position signals indicative of the position of the member about the first joint. The controller is configured to transmit control signals in response to receiving position signals from the first joint encoder, the control signals causing the drive motor to overcome friction associated with the motion of the member about the first joint.