Fluid Pressure Actuator Grip Force Estimation From Pressure and Length
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Solution Overview
Problem
Existing technologies struggle to estimate the gripping force acting in a direction orthogonal to the tube axis of fluid pressure actuators, particularly when the tube axis is curved due to deformation.
Innovation Solution
An actuator gripping force estimation apparatus and method that utilizes a pressure sensor, length acquisition unit, and gripping force estimation unit to estimate the gripping force using the equation F=ω1P(L−Lmin)+ω2, where L represents the length from one end to the other end of the most contracted side surface, P is the internal pressure, ω1 and ω2 are parameters based on the actuator's characteristics, and Lmin is a geometric constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a restraint member is provided in a rubber tube to enable curved deformation for gripping, then the actuator can achieve gripping function, but the measurement of gripping force becomes complex and difficult
Solution Approach 1:
A wire member is introduced as an intermediary element that conforms to the curved deformation of the actuator. The wire member translates the complex curved deformation into a measurable linear length change, enabling easy measurement of gripping force without directly measuring the complex curved state
Solution Approach 2:
The patent replaces direct mechanical measurement of gripping force with a mathematical model that uses pressure and length measurements. The gripping force is calculated using the equation F=ω1P(L−Lmin)+ω2, substituting complex mechanical measurement with simpler pressure and length sensing
2Force
If the tube axis is curved due to deformation during gripping, then the actuator can exert gripping force, but estimating the force acting orthogonal to the tube axis becomes difficult
Solution Approach 1:
The patent changes the measurement parameters from direct orthogonal force measurement to using pressure and length parameters. By measuring internal pressure P and length L, and applying the mathematical model F=ω1P(L−Lmin)+ω2, the orthogonal gripping force can be precisely estimated without directly measuring it
3Adaptability or versatility
If multiple fluid pressure actuators are combined to form gripping fingers, then the actuator system can perform gripping operations, but the complexity of force estimation increases
Solution Approach 1:
The patent creates a universal force estimation method that can be applied to multiple actuators using the same mathematical model F=ω1P(L−Lmin)+ω2. Each actuator uses identical measurement principles and calculation methods, making the system scalable and reducing overall complexity despite having multiple actuators
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 easy estimation of the gripping force acting orthogonal to the tube axis by measuring internal pressure and length changes, even in a curved state, with an accuracy of about 1 N error at peak gripping forces.
Implementation Method 1
a pressure sensor that acquires a tube internal pressure of the main body portion
Implementation Method 2
a middle portion which is disposed at a curved side of the main body portion and conforms to the curved deformation
Implementation Method 3
a measurement unit that applies tension to the wire member and measures a length change amount of the wire member
Data Source
AI summary
A method for estimating an actuator gripping force for estimating, as a gripping force of a fluid pressure actuator, a force acting in a direction orthogonal to a tube axis of the fluid pressure actuator when the tube axis is not curved due to curvature, in which the fluid pressure actuator includes a tubular main body portion having a tube circumference of which one side is shortened in a tube axis direction and curved due to increase in internal pressure in a tube, a proximal end side of the fluid pressure actuator along the tube axis is fixed to a base body, and a distal end of the fluid pressure actuator moves relative to the base body, the method including estimating the gripping force using Equation F=ω1P(L−Lmin)+ω2, where L represents a length from one end portion to the other end portion of the most contracted side surface of the main body portion, P represents the internal pressure in the tube, F represents the gripping force, ω1 and ω2 represent parameters set based on basic characteristics of the fluid pressure actuator, and Lmin represents a constant based on geometric characteristics of the fluid pressure actuator.