Nested Hydraulic Joint Locking for Compact Exoskeleton Joints
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Solution Overview
Problem
Existing hydraulic locking devices for exoskeleton joints are bulky, heavy, and prone to damage when laterally arranged, interfering with the user and introducing rotational moments, while also taking up significant space and being cumbersome during movement.
Innovation Solution
A hydraulic locking device featuring a plunger cylinder housed within a compact design, utilizing a plunger cylinder with a plunger piston and a rotary shaft mechanism, which allows for efficient mechanical operation and reduced weight, along with a check valve for extended movement in the blocking position and a pressure relief valve for safety, minimizing space and weight while protecting against damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lateral arrangement of hydraulic cylinders is used, then the exoskeleton joint can be locked during stance phase, but the device becomes bulky, heavy, and prone to damage
Solution Approach 1:
The hydraulic cylinder is nested inside the housing of the exoskeleton joint, with the cylinder rod extending axially from the joint center. This nested arrangement eliminates the need for lateral mounting, reducing the device footprint and weight while maintaining locking functionality during stance phase.
Solution Approach 2:
The hydraulic cylinder is reoriented to extend in the axial direction of the joint rather than laterally. This dimensional change in cylinder orientation allows the locking mechanism to be integrated within the joint's existing structural envelope, reducing overall device weight and protecting against lateral damage.
2Reliability
If a lateral arrangement of hydraulic cylinders is used, then the exoskeleton joint can be locked during stance phase, but the device takes up significant space and interferes with user movement
Solution Approach 1:
The hydraulic cylinder is nested inside the housing of the exoskeleton joint, with the cylinder rod extending axially from the joint center. This nested arrangement eliminates the need for lateral mounting, reducing the device footprint and weight while maintaining locking functionality during stance phase.
Solution Approach 2:
The hydraulic cylinder is reoriented to extend in the axial direction of the joint rather than laterally. This dimensional change in cylinder orientation allows the locking mechanism to be integrated within the joint's existing structural envelope, reducing overall device weight and protecting against lateral damage.
3Reliability
If a differential cylinder with switching valve is used, then the joint can be locked during stance phase, but the device becomes complex and heavy
Solution Approach 1:
The switching valve and differential cylinder components are removed from the system. Instead, a simple check valve is integrated directly into the hydraulic cylinder, eliminating the need for complex valve mechanisms while maintaining the ability to lock the joint during stance phase through passive hydraulic blocking.
Solution Approach 2:
The check valve automatically blocks hydraulic flow in the retraction direction during stance phase without requiring external control signals. This self-activating mechanism eliminates the need for switching valves, control systems, and associated complexity, while reliably maintaining joint position.
4Ease of operation
If acceleration sensors or contact sensors are used to detect stance phase, then the locking can be automated, but the device complexity increases
Solution Approach 1:
The check valve automatically blocks hydraulic flow in the retraction direction during stance phase without requiring external control signals. This self-activating mechanism eliminates the need for switching valves, control systems, and associated complexity, while reliably maintaining joint position.
Solution Approach 2:
The hydraulic system itself provides the sensing and actuation function through the check valve mechanism. The hydraulic pressure and flow conditions naturally indicate stance phase, eliminating the need for separate sensors and electronic control systems.
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 solution results in a lightweight, space-efficient hydraulic locking device that effectively supports the user without interfering with their movement, providing reliable locking during stance phases and allowing for further extension of joints while preventing damage from leakage.
Implementation Method 1
A spring-loaded check valve 124 is disposed in the short-circuit line 122, which opens in the direction of flow from the rod chamber 114 to the piston chamber 112
Implementation Method 2
the hydraulic cylinder is hydraulically blocked
Implementation Method 3
a pressure relief valve for safety, minimizing space and weight while protecting against damage
Data Source
AI summary
A hydraulic locking device for an exoskeleton joint with an extendable and retractable hydraulic cylinder, a tank and a switching valve. The hydraulic cylinder is connected to the tank via a line arrangement and the switching valve is disposed in the line arrangement. The switching valve is switchable between a release position and a blocking position. The hydraulic cylinder is freely movable in the release position of the switching valve, and the switching valve prevents retraction of the hydraulic cylinder in the blocking position. The hydraulic locking device further comprises a housing, and the hydraulic cylinder is a plunger cylinder with a plunger cylinder housing and a plunger piston movably arranged in the plunger cylinder housing, the plunger cylinder being arranged within the housing. Further, an exoskeleton joint having such a hydraulic locking device is disclosed.