Medical Manipulator Joint Control for Wire Looseness Compensation
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Solution Overview
Problem
Medical manipulator systems face discrepancies in movement and curvature due to wire looseness and friction, which existing systems fail to accurately compensate for, leading to instability and inaccuracy in joint movement.
Innovation Solution
A medical manipulator system with a first sensor to detect joint rotational motion, a second sensor to detect actuator operation, and a controller that adjusts a transfer function's control gains based on detected differences between joint and actuator movements, allowing for precise feedback control and compensation for looseness and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor and encoder are used for feedback control to compensate for wire looseness and friction, then the accuracy of joint movement control is improved, but the device complexity increases
Solution Approach 1:
The patent combines the first sensor (detecting joint movement) and second sensor (detecting actuator operation) into a unified feedback control system that jointly compensates for wire looseness and friction. By merging these sensing functions into a coordinated control algorithm, the system achieves accurate joint movement control without proportionally increasing complexity, as the sensors work together within a single control loop rather than as separate independent systems.
Solution Approach 2:
The patent implements a feedback control mechanism where the controller continuously receives signals from both sensors, compares the actual joint movement with the commanded movement, and adjusts the actuator operation in real-time to compensate for wire looseness and friction. This closed-loop feedback system maintains high measurement precision while managing device complexity through efficient signal processing and control algorithms.
2Measurement precision
If high-resolution encoders are used to detect joint and actuator movements, then the control precision is improved, but the diameter of the distal end portion increases
Solution Approach 1:
The patent applies local quality by using a low-resolution encoder only at the distal end joint where space is constrained, while accepting that the proximal end actuator can accommodate larger components. The control algorithm compensates for the lower resolution at the distal end by using feedback from both sensors to calculate and correct movement discrepancies, thereby achieving adequate control precision without increasing the distal end diameter.
Solution Approach 2:
The patent changes the resolution parameter of the encoder at the distal end to be lower than what would traditionally be required, reducing the distal end diameter. The system compensates for this parameter change by implementing a control algorithm that uses feedback from both sensors to calculate movement discrepancies and adjust the actuator operation, thereby maintaining acceptable control precision despite the lower encoder resolution.
3Reliability
If feedback control is implemented to compensate for wire looseness and friction, then the operational stability is improved, but the control system complexity increases
Solution Approach 1:
The patent implements feedback control by continuously monitoring both joint movement (first sensor) and actuator operation (second sensor), comparing these measurements to detect discrepancies caused by wire looseness and friction, and automatically adjusting the actuator to compensate. This feedback mechanism improves operational stability while managing control system complexity through efficient algorithms that process sensor signals and generate correction commands within the existing control architecture.
Solution Approach 2:
The control system performs self-service by automatically detecting and compensating for wire looseness and friction through its own sensors and control algorithms, without requiring external calibration or manual adjustment. The system uses its built-in sensors to monitor its own performance and self-correct discrepancies, thereby improving operational stability while avoiding the added complexity of external calibration systems or manual intervention mechanisms.
Data Source
AI summary
A medical manipulator system that includes a joint, a first sensor that detects an amount of rotational motion of the joint, an actuator that drives the joint via a wire, a second sensor that detects an amount of operation of the actuator based on a rotation angle of the actuator, an input device, and a controller. The controller generates a control signal based on: an operation mode in which the control signal is generated by a transfer function that receives an input target value of the rotation angle of the joint and the amount of operation of the actuator, and a calibration mode in which the transfer function is adjusted based on comparing to a predetermined threshold value the amount of rotational motion of the joint and the amount of operation of the actuator. The controller then transmits the generated control signal to the actuator to drive the joint.