Embedded Jamming Soft Actuator for Variable Stiffness and Damping
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Solution Overview
Problem
Existing robotic actuators lack an all-soft actuator with controllable variable stiffness and damping, which is essential for enhancing embodied intelligence and safe, robust interactions with the environment.
Innovation Solution
A soft jamming brake and artificial muscle (SJBAM) actuator is designed with an embedded jamming brake inside a pneumatic artificial muscle, allowing independent control of stiffness and damping through positive pressure layer jamming, without the need for a vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional robotic actuators are used, then they can be programmed to alter interaction impedances, but they suffer from stability and bandwidth limitations inherent to active control
Solution Approach 1:
The actuator uses variable stiffness elements that can dynamically change their mechanical properties in real-time. The stiffness of the actuator can be adjusted during operation to match task requirements, enabling adaptive impedance control through passive mechanical means rather than active control loops, thus improving stability and bandwidth.
Solution Approach 2:
The actuator changes its physical parameters (stiffness and damping) by varying the pre-tension in spring elements and the compression in foam elements. This allows continuous adjustment of impedance characteristics without relying on active control, resolving the contradiction between adaptability and stability.
2Reliability
If variable stiffness actuators are used, then intrinsic safety is improved, but underdamped dynamics and instability are introduced
Solution Approach 1:
The actuator combines multiple material types with complementary properties: spring elements provide variable stiffness and energy storage, while foam elements provide variable damping and energy dissipation. This composite structure allows simultaneous achievement of intrinsic safety through compliance and stable dynamics through controlled damping.
Solution Approach 2:
The actuator integrates multiple functions within a single device: it can store elastic energy like a spring, dissipate energy like a damper, and vary both stiffness and damping independently. This multi-functionality allows it to provide intrinsic safety while maintaining stable, well-damped dynamics.
3Reliability
If compliance is built into actuators using springs, then safety is improved, but energy storage can make collisions more dangerous in pre-tensioned state
Solution Approach 1:
The actuator converts the potential harm of energy storage into a benefit by using the spring elements to store energy during normal operation and then dissipating it through the foam elements during collisions. The foam acts as a controlled energy dissipation mechanism that prevents dangerous rebound while maintaining safety during normal operation.
Solution Approach 2:
The actuator recovers energy through spring elements during normal operation and discards (dissipates) it through foam elements during collisions or when safety is concerned. This selective energy management allows the system to maintain safety while avoiding the dangers of uncontrolled energy release.
4Measurement precision
If variable damping actuators are used, then energy dissipation and position accuracy are improved, but they have received comparatively less attention and lack integrated solutions
Solution Approach 1:
The actuator merges variable stiffness and variable damping functionalities into a single integrated device. The spring and foam elements work together in parallel, allowing independent control of both stiffness and damping characteristics without requiring separate actuators or complex mechanisms, thus reducing overall system complexity.
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 SJBAM achieves synergistic benefits of improved muscle static and dynamic response, expanded brake bandwidth, and new functionalities such as energy storage and dissipation, while maintaining a soft profile suitable for various applications including industrial robots and exoskeletons.
Implementation Method 1
The SJBAM can store elastic energy like a PAM
Implementation Method 2
the layer jamming brake can be used to dissipate energy
Implementation Method 3
By independently controlling the muscle and brake pressures, one can vary the SJBAM's stiffness and damping
Implementation Method 4
positive pressure layer jamming
Data Source
AI summary
A variable impedance actuator is provided with a bladder-style actuator having a first end and a second end, and a jamming brake located inside the bladder-style actuator and connected to the first end and the second end of the bladder-style actuator. The bladder-style actuator and the jamming brake are independently controlled.