Active Vibration Isolation System Using Intermediate Mass
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Solution Overview
Problem
Active vibration isolation systems face challenges in efficiently suppressing vibrations at low frequencies while minimizing the strain and wear on expensive piezoelectric actuators, as passive support elements can compromise vibration isolation performance by allowing ground vibrations to transfer through them.
Innovation Solution
An active vibration damping system that uses a stiff spring to support static forces and a soft actuator, such as a voice coil motor, to isolate dynamic forces, with an intermediate mass providing stability and a feedback compensation loop to maintain vibration isolation without relying on expensive piezoelectric actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric stack actuator is used to bear both static weight and provide vibration cancellation forces, then vibration isolation performance is improved, but actuator cost and complexity increase significantly
Solution Approach 1:
The system divides the actuator functions into two separate components: a passive support spring that bears the static weight, and an active piezoelectric actuator that provides only dynamic vibration cancellation forces. This segmentation allows each component to be optimized for its specific function, reducing the complexity and cost of the active actuator while maintaining overall vibration isolation performance.
2Duration of action of moving object
If an offload spring is used to bear portion of static weight, then actuator strain and wear are reduced, but vibration isolation efficiency is compromised
Solution Approach 1:
The support spring is designed with specific local properties (stiffness, damping characteristics) that allow it to bear static weight while minimizing its impact on dynamic vibration isolation. The spring's mechanical properties are carefully selected to provide static support without creating resonance issues or compromising the active actuator's ability to cancel vibrations in the critical frequency range.
3Force
If support springs extend from the ground, then static weight support is provided, but ground vibrations transfer through springs at frequencies below resonance frequency
Solution Approach 1:
The passive support spring acts as an intermediary element between the ground and the payload, providing static force support while its mechanical properties (stiffness, damping) are designed to filter out low-frequency ground vibrations. The spring's natural frequency is tuned to be below the critical vibration frequencies, allowing it to support static weight while the active piezoelectric actuator compensates for any vibrations that do transfer through the spring.
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
This configuration allows for effective vibration isolation across multiple axes, reducing the burden on actuators and maintaining performance by using less expensive actuators that only compensate for dynamic forces, while passive support elements ensure stability and decouple the payload from vibrations.
Implementation Method 1
The vibrations sensed by these dynamic systems are provided to a processor which activates an actuator that applies the cancellation forces. This type of actuator can be quite expensive; therefore, to reduce the strain and wear on the actuator, some systems combine the actuator with other passive support elements
Implementation Method 2
an offload or support spring, to bear a portion of the static weight. However, as disclosed in U.S. Patent Application Publication No. 2010/0030384, it is generally accepted that the extent to which an offload spring may reduce the burden on the actuator by bearing a portion of the static weight is limited because of the risk that the offload spring would compromise the efficiency of the vibration isolation system
Implementation Method 3
Active isolation systems have been developed to suppress vibrations acting on a structure or payload at low frequencies. Generally, active isolation systems measure vibrations at specific locations on a platform bearing a payload and dynamically apply cancellation forces in an equal and opposite direction to suppress the effect of the vibration
Data Source
AI summary
An active damping system for use in connection with a vibration isolation system includes an intermediate mass between a base and an isolated payload. The intermediate mass is supported by at least one support element which also supports at least substantially all of the static forces of the isolated payload. An actuator dampens and isolates dynamic forces acting on the intermediate mass from the isolated payload. The active damping system also includes a payload support element and a passive damping element, both of which are coupled at one end to the payload platform and at an opposite end to the intermediate mass. A sensor is affixed to the intermediate mass to generate a feedback signal to a processor coupled to the actuator.