Hydraulic Forceps Control Using Proximal Piston Position Estimation
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Solution Overview
Problem
The challenge in controlling the opening and closing of robotic forceps grippers at the distal end is exacerbated by the difficulty in installing position sensors due to the thin nature of the distal end portions, which is a limitation in pneumatic actuator systems.
Innovation Solution
A hydraulic forceps system utilizing a motor-driven second piston with a linear motion mechanism, a position sensor for the second piston, and a control device that includes an observer to estimate the position of the first piston, allowing for precise control of the gripper without the need for a position sensor at the distal end, using incompressible hydraulic fluid and feedback from pressure and position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor is installed at the distal end of robotic forceps to detect gripper position, then control precision is improved, but device complexity and difficulty of installation increase due to the thin structure of distal end portions
Solution Approach 1:
The patent introduces a second piston as an intermediary component located at the proximal end (thicker portion) of the forceps. This second piston is coupled to the first piston (at distal end) through incompressible hydraulic fluid in a communication passage. By measuring the position of the second piston instead of the first piston, the system achieves position detection without installing sensors at the thin distal end, thus resolving the contradiction between measurement precision and device complexity.
2Ease of operation
If a displacement sensor is used in pneumatic actuators to detect piston position, then gripper control is enabled, but the system requires installation at distal end portions which are too thin for sensor mounting
Solution Approach 1:
The patent divides the actuator system into two separate piston-cylinder assemblies: a first piston-cylinder at the distal end and a second piston-cylinder at the proximal end. These are connected through hydraulic fluid in a communication passage. This segmentation allows the position sensor to be installed on the second piston at the proximal end where space is available, while the first piston at the distal end remains simple and sensor-free, thus resolving the manufacturing and installation difficulty.
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
Enables the control of the gripper's opening and closing without installing a position sensor at the distal end of the robotic forceps, improving precision and reliability by using hydraulic fluid dynamics and sensor feedback.
Implementation Method 1
a first pressure chamber filled with a hydraulic fluid, a second pressure chamber filled with the hydraulic fluid
Implementation Method 2
since the incompressible hydraulic fluid is used, the moving amount of the first piston coupled to the gripper, i.e., the moving amount of the first piston disposed at the distal end side of the robotic forceps, is proportional to the moving amount of the second piston
Data Source
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AI summary
A hydraulic forceps system includes: robotic forceps including a gripper, a first piston coupled to the gripper, a first cylinder forming a first pressure chamber together with the first piston, the first pressure chamber being filled with a hydraulic fluid, a second piston, a second cylinder forming a second pressure chamber together with the second piston, the second pressure chamber being filled with the hydraulic fluid, a communication passage through which the first pressure chamber and the second pressure chamber communicate with each other, and a motor that drives the second piston via a linear motion mechanism; a control device that controls the motor based on a command position for the first piston; and a position sensor used for detecting a position of the second piston. The control device includes: an observer that derives an estimated position of the first piston based on the position of the second piston detected by using the position sensor; and a position controller that derives a target rotational speed of the motor based on a deviation between the estimated position of the first piston and the command position.