Shear Force Actuator Structure for High-Stress Safe Pneumatics
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Solution Overview
Problem
Existing soft pneumatic actuators face limitations in generating mechanical advantage and are prone to bursting when over-pressurized, which restricts their use in applications requiring high stress and confined spaces.
Innovation Solution
The development of shear force actuators, inspired by pennate muscles, which convert horizontal compressive force to vertical shear force through a network of obliquely positioned elastomeric beams, allowing for high actuation stress without being limited by input differential pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional soft pneumatic actuators are used, then they can contact delicate objects with compliant materials, but they are prone to bursting when over-pressurized and cannot generate high stress
Solution Approach 1:
The actuator is divided into multiple sealed chambers separated by shared walls. Each chamber can be independently pressurized to a safe level, but the cumulative effect across multiple chambers generates high actuation stress. This segmentation prevents bursting because failure in one chamber does not compromise the entire actuator, while still achieving the required high stress through combined chamber pressure.
Solution Approach 2:
The actuator employs composite construction with rigid structural elements (such as 3D-printed components) combined with flexible sealing elements. This composite approach allows the actuator to withstand high pressures without bursting while maintaining the compliance needed for delicate object contact. The rigid components provide structural integrity against bursting, while flexible seals maintain soft robot compliance.
2Force
If high pressure is applied to achieve high actuation stress, then more force can be generated, but the actuator may burst or become dangerous
Solution Approach 1:
By dividing the actuator into multiple chambers, the system can generate high total force through cumulative pressure across chambers while keeping individual chamber pressures at safe levels. This eliminates the dangerous high-pressure single-chamber design while maintaining high force output capability.
Solution Approach 2:
The multi-chamber design inherently provides safety cushioning by distributing pressure risk across multiple independent chambers. If one chamber fails, the others continue to operate safely, preventing catastrophic failure and protecting operators from dangerous high-pressure releases.
3Ease of operation
If pneumatic actuators are used in confined spaces, then actuation can be achieved, but volume increase during pressurization is problematic
Solution Approach 1:
The multi-chamber design allows the actuator to maintain a compact overall volume by efficiently packing multiple chambers within a confined space. Each chamber contributes to the actuation function while sharing structural walls, maximizing space utilization and enabling deployment in confined areas where traditional single-chamber actuators would be too bulky.
4Adaptability or versatility
If McKibben actuators are used, then muscle-mimetic functionality is achieved, but hysteresis from dry friction and non-elastic mesh deformation prevents precise positional control
Solution Approach 1:
The invention extracts and eliminates the source of hysteresis by replacing the non-elastic mesh constraint with rigid structural elements and sealed chambers. This removes the dry friction and non-elastic deformation that cause hysteresis in McKibben actuators, enabling precise positional control while retaining muscle-mimetic contraction functionality through alternative means.
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
These actuators achieve high actuation stress with minimal strain, enabling them to lift heavier loads and operate safely in confined spaces, overcoming the limitations of traditional soft pneumatic actuators.
Implementation Method 1
shear force actuators, e.g., pennate-muscle inspired vacuum actuators ('PIVA'; also referred to as shear-VAM (shear-mode vacuum-actuated machine)), whose output stress generated by the actuator is not limited by the atmospheric pressure or the input differential pressure
Implementation Method 2
at least one of the joint sections, the first structural components, and the second structural components is elastic so that cell collapses upon removal of fluid from the cell to generate a linear force along the first axis
Implementation Method 3
pennate-muscle inspired vacuum actuators ('PIVA'; also referred to as shear-VAM (shear-mode vacuum-actuated machine))
Implementation Method 4
cell collapses upon removal of fluid from the cell to generate a linear force along the first axis
Data Source
AI summary
A shear force actuator is described, including: two substantially parallel first structural components disposed along a first axis; a plurality of substantially parallel second structural components disposed between and bridging the two first structural components; a plurality of joint sections each joining the second structural component with the first structural components at an oblique angle of between 0 and 90 degrees to define a plurality of cells, each capable of being connected with a fluid inflation or deflation source; an elastic surface covering the remaining surfaces of the cells in a fluid-tight manner, wherein at least one of the joint section, the first structural components, and the second structural components is elastic so that cell collapses upon removal of fluid from the cell to generate a linear force along the first axis.