Medical Manipulator Vibration Actuator Torque Control
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Solution Overview
Problem
The vibration-type actuator in medical manipulators experiences holding torque issues, leading to unbalanced loads and potential damage due to autonomous movements of biological organs, making precise positioning and operation challenging.
Innovation Solution
A medical manipulator with a driving unit including a vibration-type actuator, a moving unit, a pressure application unit, and a torque control unit that allows for controlled holding torque adjustment, enabling high-precision driving and manual operation by varying the applied pressure between the vibrating and moving units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the vibration-type actuator is used to provide holding torque for precise positioning, then position controllability is improved, but the manipulator becomes vulnerable to damage from unbalanced loads caused by autonomous organ movements
Solution Approach 1:
The patent applies dynamics by making the holding torque adjustable rather than fixed. The control unit dynamically changes the holding torque based on operational needs - maintaining high holding torque during positioning operations for precision, and reducing it during manual operations or when organs move autonomously to prevent damage from unbalanced loads.
Solution Approach 2:
The patent changes the parameter of holding torque from a constant value to a variable value. By controlling the vibration amplitude and frequency of the vibrating unit, the system can adjust the holding torque between high and low states, enabling adaptation to different operational conditions and resolving the contradiction between precision positioning and damage resistance.
2Stability of the object's composition
If the holding torque is maintained at high levels for precise positioning, then position stability is improved, but manual operation becomes difficult due to inability to selectively move the manipulator unit
Solution Approach 1:
The system dynamically adjusts the holding torque based on operational mode. During manual operations, the control unit reduces the holding torque to allow the operator to selectively move the manipulator unit, while during automated positioning operations, it increases the holding torque to maintain position stability.
Solution Approach 2:
The vibration-type actuator inherently operates with periodic vibration to generate holding torque. By modulating the amplitude and frequency of this periodic vibration, the system can switch between high holding torque states (for stability) and low holding torque states (for manual operation), enabling both functions to coexist.
3Reliability
If the vibration-type actuator provides continuous holding torque, then the manipulator maintains its attitude without power loss, but stress and strain occur in various parts due to unbalanced loads from organ movements
Solution Approach 1:
The system changes the holding torque parameter from constant to variable. When organs move autonomously causing unbalanced loads, the control unit reduces the holding torque to minimize stress and strain on manipulator parts, while still maintaining sufficient attitude maintenance capability when needed.
Solution Approach 2:
The system proactively adjusts the holding torque before damage can occur. The control unit monitors operational conditions and preemptively reduces holding torque when autonomous organ movements are detected or anticipated, preventing excessive stress and strain accumulation in manipulator components.
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
This solution allows for precise control of the holding torque, preventing damage from organ movements and enhancing operability by enabling both high-precision driving and manual adjustment of the manipulator's position.
Implementation Method 1
a piezoelectric element 31 bonded to the ring-shape vibrator 32. The piezoelectric element 31 generates a vibration in response to being excited by an applied electric signal
Implementation Method 2
The vibration of the vibrator 32 is transmitted to the moving unit 2 by a frictional force
Data Source
AI summary
A medical manipulator is improved in terms of invasiveness into a body tissue and an emergency avoidance difficulty. The medical manipulator includes a driving unit including a vibration-type actuator including a vibrating unit that generates a vibration wave, a moving unit movable relative to the vibrating unit in response to receiving the vibration wave, and a pressure application unit configured to apply a pressure between the vibrating unit and the moving unit. The medical manipulator further includes a manipulator unit connected to the driving unit and configured to be movable by being driven by the driving unit, a supporting unit that supports the driving unit and the manipulator unit, a driving circuit connected to the vibrating unit and configured to apply an AC voltage to the vibrating unit, and a torque control unit configured to control a holding torque with which the moving unit is held by the vibrating unit.