Two-Stage Pneumatic Accumulators for Rapid Multi-Actuator Pressurization
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Solution Overview
Problem
Existing pneumatic actuation systems for robotic devices are often bulky, complex, and unable to achieve rapid and simultaneous pressurization of multiple actuators with different pressure requirements, making them unsuitable for lightweight and untethered applications in wearable assistive robots.
Innovation Solution
A two-stage accumulator-based pneumatic supply architecture using Polyethylene Terephthalate (PET) bottles as accumulators and Pulse Width Modulation (PWM) controlled solenoid valves, with a data-driven system performance model and Proportional Derivative (PD) control for rapid actuation and pressure maintenance, eliminating the need for feedback control between actuators and accumulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single accumulator system is used for pneumatic actuation, then the hardware is simplified, but the ability to achieve targeted pressure in multiple actuators rapidly within targeted time durations is compromised
Solution Approach 1:
The single accumulator system is segmented into multiple accumulators, with each accumulator dedicated to supplying pressurized air to a specific actuator. This segmentation allows each actuator to be pressurized independently and simultaneously, achieving targeted pressures within specified time durations without requiring complex centralized control hardware.
Solution Approach 2:
The accumulators are pre-charged to specific pressure levels before actuation is required. This preliminary action ensures that when actuation is needed, the pressurized air is already available in the accumulators, enabling rapid actuation without waiting for compression during the actuation cycle itself.
2Reliability
If traditional pneumatic supply systems are used, then pressure supply is maintained, but the system becomes bulky and unsuitable for wearable devices
Solution Approach 1:
The system uses small, lightweight accumulators that can be periodically recharged rather than requiring a large, permanent compressed air tank. These miniaturized accumulators sacrifice the longevity of traditional systems but gain in weight reduction, making them suitable for wearable applications where total system mass is critical.
Solution Approach 2:
The patent transitions from a single large-volume compressed air storage approach to multiple small-volume accumulators distributed throughout the system. This dimensional change from centralized bulk storage to distributed micro-storage reduces the weight and size burden on wearable devices while maintaining pressure supply reliability.
3Measurement precision
If complex control algorithms are used for pressure control, then pressure precision is improved, but the control system becomes too complex for rapid actuation
Solution Approach 1:
Instead of using complex real-time control algorithms to adjust pressure during actuation, the system pre-charges accumulators to the exact pressure levels needed for each actuator. This preliminary pressure setting eliminates the need for complex ongoing control calculations, enabling rapid actuation with simple control logic.
Solution Approach 2:
The accumulators self-regulate pressure supply to their associated actuators based on pre-determined pressure levels. Each accumulator acts as an autonomous pressure source, eliminating the need for complex centralized control algorithms to manage pressure distribution across multiple actuators.
4Reliability
If tethered pneumatic systems are used, then pressure supply is reliable, but mobility of the wearer is restricted
Solution Approach 1:
The centralized pneumatic supply system is segmented into distributed accumulators placed near each actuator. This segmentation eliminates the need for long pneumatic supply lines connecting a central compressor to multiple actuators, removing physical tethers and enabling unrestricted wearer mobility while maintaining reliable local pressure supply.
Solution Approach 2:
The accumulators serve as intermediary pressure storage devices between the external pressurization source and the actuators. They decouple the actuators from direct connection to the main air supply, allowing the wearer to move freely while the accumulators maintain reliable pressure supply to each actuator independently.
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 rapid and simultaneous pressurization of multiple actuators with individual targeted pressures within specified time durations, enhancing the mobility and comfort of wearable robotic devices by creating a lightweight and untethered pneumatic actuation system.
Implementation Method 1
A two-stage accumulator-based pneumatic supply architecture... consisting of two accumulators connected in series, where a primary reservoir supplies pressurized air to multiple secondary accumulators
Implementation Method 2
Pulse Width Modulation (PWM) controlled solenoid valves... supplying pressurized air from the one or more secondary accumulators
Implementation Method 3
Rejuvenation of pressure in the one or more secondary accumulators occurs through a pressure feedback based PD control scheme executed in between consecutive actuation cycles
Data Source
AI summary
A two-stage accumulator based pneumatic supply architecture (TAPSA) is provided for rapid actuation of multiple compliant pneumatic actuators simultaneously for their potential applications in wearable robotic assistive and rehabilitative devices, serving as light-weight and untethered actuation systems. The TAPSA comprises Polyethylene Terephthalate (PET) bottles serving as primary accumulators and secondary accumulators connected in series. Individual targeted levels of pneumatic pressures are achieved in actuators of the TAPSA within targeted durations of time for the rapid actuation of the actuators by the action of Pulse Width Modulation (PWM) controlled solenoid valves supplying pressurized air from the secondary accumulators which are in turn pressurized in prior to predetermined levels based on system performance model developed by a data driven approach utilized in the TAPSA. Rejuvenation of pressure in the secondary accumulators occurs through a pressure feedback based PD control scheme executed in between consecutive actuation cycles.