Hydraulic Actuator Layout for Variable-Stiffness Robot Arms
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Solution Overview
Problem
Existing hydraulic actuators for robot arms and hands require large installation space and are cost-intensive, limiting their flexibility and applicability in 'Industry 4.0' scenarios where variable stiffness and low mass are necessary for collaborative robotics.
Innovation Solution
A hydraulic actuator design featuring a drive cylinder, a first output cylinder, a pressure limiting valve, and a second output cylinder with a pressure relief valve, allowing for adjustable rigidity and reduced installation space by sharing roles via a multi-way valve, and utilizing preloaded check valves and throttles for efficient pressure management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional hydraulic actuators are used for active control of robot arms or hands, then active actuation capability is achieved, but installation space increases and cost increases
Solution Approach 1:
The patent combines two opposite actuators into a single hydraulic actuator unit. The first output cylinder and second output cylinder are integrated into one actuator, sharing common components including the drive cylinder, pressure limiting valve, and reservoir. This merging allows the actuator to cover two opposite directions of movement while reducing installation space and component count compared to using two separate actuators.
Solution Approach 2:
The pressure limiting valve serves multiple functions: it limits pressure in the first output cylinder to provide controlled stiffness, and it relieves pressure in the second output cylinder to enable movement in the opposite direction. The reservoir also serves dual purposes by balancing fluid flow for both output cylinders. This multi-functionality reduces the number of components needed and simplifies the overall system.
2Adaptability or versatility
If conventional hydraulic actuators are used for active control of robot arms or hands, then active actuation capability is achieved, but cost increases
Solution Approach 1:
The patent combines two opposite actuators into a single hydraulic actuator unit. The first output cylinder and second output cylinder are integrated into one actuator, sharing common components including the drive cylinder, pressure limiting valve, and reservoir. This merging allows the actuator to cover two opposite directions of movement while reducing installation space and component count compared to using two separate actuators.
Solution Approach 2:
The pressure limiting valve serves multiple functions: it limits pressure in the first output cylinder to provide controlled stiffness, and it relieves pressure in the second output cylinder to enable movement in the opposite direction. The reservoir also serves dual purposes by balancing fluid flow for both output cylinders. This multi-functionality reduces the number of components needed and simplifies the overall system.
3Strength
If pressure is limited in the first output cylinder to adjust stiffness, then rigidity control is achieved, but pressure management complexity increases
Solution Approach 1:
The pressure limiting valve automatically regulates pressure in the first output cylinder based on the duration of force applied to the drive piston. When the drive piston is actuated for a longer duration, the valve limits pressure buildup, allowing the system to self-adjust stiffness without external control intervention. This self-regulating mechanism simplifies the control system while achieving variable rigidity.
Solution Approach 2:
The pressure limiting valve responds to the duration of force applied to the drive piston and automatically adjusts pressure limitation accordingly. This feedback mechanism allows the system to maintain appropriate stiffness levels based on operational conditions, with the valve sensing and responding to pressure and time parameters to achieve variable rigidity control.
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 active actuation of robot arms and hands with reduced space and cost, simulating human muscle functionality by adjusting rigidity based on force duration and direction, thus enhancing flexibility and efficiency in robotic applications.
Implementation Method 1
a pressure limiting valve which, depending on the duration of a force acting on the drive cylinder and/or the drive piston, limits the pressure in the first output cylinder, wherein the pressure limiting valve is arranged to limit pressure in relation to and/or to relieve pressure in a second output cylinder
Implementation Method 2
the first output cylinder is coupled to the drive cylinder via a first pre-tensioned check valve and the second output cylinder is coupled to the drive cylinder via a second pre-tensioned check valve
Implementation Method 3
a hydraulic drive cylinder, in particular with a drive piston, a first hydraulic output cylinder which is hydraulically coupled to the drive cylinder
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
The hydraulic actuator comprises a hydraulic drive cylinder, a first hydraulic output cylinder which is hydraulically coupled to the drive cylinder, and a pressure limiting valve which limits the pressure on the output cylinder depending on an action time of a force on the drive cylinder and/or output piston, wherein the pressure limiting valve is arranged opposite a second output cylinder for limiting pressure and/or in a second output cylinder for relieving pressure, and wherein the second output cylinder is hydraulically coupled to the drive cylinder. The method is a method for operating such a hydraulic actuator, wherein the drive actuator is deflected with deflections having a deflection duration at a deflection frequency for the duration of an acting or a non-acting phase of the hydraulic actuator, wherein the deflection duration defines a movement stiffness of the hydraulic actuator and the deflection frequency defines the resulting deflection speed of the hydraulic actuator.