Dithering Actuator Control for Consistent Surgical Grasp Force
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Solution Overview
Problem
In computer-assisted devices with repositionable arms, maintaining consistent grasp force while preventing excessive force generation is challenging, especially in minimally invasive surgical procedures where instruments must fit through small openings and operate with limited access, leading to uncertainty in grasp force and potential wear and tear.
Innovation Solution
Implementing a dithering mechanism in the actuators of the instrument's jaws, controlled by a controller that modulates the force or torque applied, converting static friction to dynamic friction to maintain a suitable grasp without excessive force spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dithering is applied to actuator control signals, then grasp force consistency is improved and excessive force is prevented, but device complexity increases
Solution Approach 1:
The patent applies dithering by adding a small periodic oscillation to the actuator control signal. This periodic action prevents the actuator from settling into static friction states that cause force inconsistencies, thereby improving grasp force reliability while using a relatively simple control mechanism.
Solution Approach 2:
The dithering technique introduces high-frequency low-amplitude vibrations to the actuator operation. This mechanical vibration approach converts static friction to dynamic friction, ensuring consistent force application without requiring complex control algorithms.
2Volume of moving object
If instrument size is reduced to fit through small openings, then minimally invasive capability is improved, but grasp force control precision deteriorates
Solution Approach 1:
The patent replaces complex mechanical force control mechanisms with a control signal processing approach. By applying dithering to the control signals rather than using complex mechanical feedback systems, the patent achieves precise grasp force control in miniaturized instruments without adding mechanical complexity.
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
The dithering mechanism ensures consistent grasp force on the material, reducing wear and tear on the instrument while preventing excessive force application, thereby enhancing the reliability and longevity of the device.
Implementation Method 1
dither one or more control signals to the one or more actuators so as to cause variations in a force or torque applied by the one or more actuators
Data Source
AI summary
Systems and methods of dithering to maintain grasp force include a computer-assisted device. The computer-assisted device includes an instrument having a first jaw and a second jaw configured to grasp a material, one or more actuators configured to actuate the first and second jaws to apply force to the grasped material, and a controller coupled to the one or more actuators. The controller is configured to determine that actuation of the one or more actuators should be dithered and in response to the determination, dither one or more control signals to the one or more actuators so as to cause variations in a force or torque applied by the one or more actuators. In some embodiments, the one or more control signals correspond to a force setpoint, a torque setpoint, a current setpoint, or a position setpoint for the one or more actuators.