Software Remote Center of Motion for Robotic Systems
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Solution Overview
Problem
Existing computer-assisted systems face limitations in flexibility and dexterity due to fixed hardware remote centers of motion (RCM), which restrict the range of motion and can cause undesirable motion or collisions, especially when the RCM is relocated away from its fixed position.
Innovation Solution
Implementing a software remote center of motion (RCM) that is dynamically set and maintained by a processing system, allowing the repositionable structure to move while keeping the software RCM fixed, using a combination of joint sets to manage the hardware RCM's position and enable more intuitive and collision-free instrument movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a hardware RCM is used to constrain joint motions, then the repositionable structure maintains a fixed RCM position, but the range of motion and flexibility are limited
Solution Approach 1:
The patent replaces the hardware-based mechanical constraint system with a software-based constraint system. Instead of physically designing joints to maintain a fixed RCM through mechanical linkages, the system uses software to calculate and enforce RCM constraints on joint motions. This allows the repositionable structure to achieve a virtual RCM that can be dynamically adjusted without changing the physical hardware architecture, thereby increasing range of motion while avoiding the complexity of hardware modifications.
Solution Approach 2:
The patent implements a dynamic RCM system where the RCM position can be changed during operation. The processing system dynamically calculates commanded joint motions that maintain the desired RCM position based on real-time structural configuration. This dynamic adaptability allows the system to adjust the RCM to optimize performance for different tasks and workspace regions, transforming a static hardware constraint into a flexible software-controlled constraint.
2Ease of operation
If the RCM is relocated away from its fixed position, then the repositionable structure gains flexibility, but undesirable motion and collisions occur
Solution Approach 1:
The patent implements a feedback mechanism where the processing system continuously monitors the actual position and orientation of the repositionable structure, along with the commanded joint motions. The system calculates whether the desired RCM position can be maintained given the current structural configuration and adjusts the commanded motions accordingly. This feedback control prevents undesirable motions and collisions by ensuring that joint motions always result in the RCM remaining at the desired location, while still allowing flexible repositioning when safe.
Solution Approach 2:
The patent changes the parameter of RCM position from a fixed hardware constraint to a dynamically adjustable software parameter. The processing system calculates optimal RCM positions based on the current configuration of the repositionable structure and selects appropriate RCM locations that avoid collisions and undesirable motions. By dynamically adjusting this parameter rather than using a fixed hardware constraint, the system achieves flexibility while preventing harmful effects.
3Adaptability or versatility
If a software RCM is implemented, then the flexibility and dexterity are enhanced, but the device complexity increases
Solution Approach 1:
The patent makes the processing system multi-functional by having it perform multiple tasks: it controls the actuators to drive joints, calculates the RCM position based on structural configuration, determines commanded joint motions to maintain the desired RCM, and prevents undesirable motions. By consolidating these functions into a single processing system with integrated algorithms, the patent avoids the need for separate dedicated hardware systems for each function, thereby managing overall system complexity while achieving enhanced flexibility and dexterity.
Data Source
AI summary
Setting and using a software remote center of motion (RCM) for a computer-assisted system including an input control, a repositionable structure comprising a plurality of joints, and a processing system. The processing system is configured to: receive a proposed position for a software RCM of the repositionable structure; determine whether to accept the proposed position based on a geometric relationship between a position of a hardware RCM and the proposed position; in response to determining to accept the proposed position, set a current position of the software RCM based on the proposed position; after setting the current position and in response to an indication to move the repositionable structure with a desired motion, determine a commanded motion of the joints to move the repositionable structure in accordance with the desired motion while maintaining the current position of the software RCM; and drive the joints in accordance with the commanded motion.