Boring Bar Electrodynamic Actuation for Low-Frequency Vibration Control
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Solution Overview
Problem
Existing boring bars face challenges in effectively counteracting low-frequency vibrations due to limitations in force generation by piezoelectric and electromagnetic actuators, particularly in constrained environments, where piezoelectric actuators struggle at high frequencies and electromagnetic actuators require complex control and high energy consumption.
Innovation Solution
A boring bar equipped with two electrodynamic actuators, each with windings and a moving mass surrounded by permanent magnets and springs, arranged to generate forces perpendicular to the longitudinal axis, allowing for significant force generation and easy control, suitable for constrained spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If piezoelectric actuators are used to counter vibrations, then high-frequency vibrations can be damped, but they cannot generate sufficient force for low-frequency vibrations
Solution Approach 1:
The patent replaces piezoelectric actuators with electrodynamic actuators that use electromagnetic fields to generate force. The electrodynamic actuator includes a coil, permanent magnet, and movable mass assembly that converts electrical energy to mechanical motion through electromagnetic induction, enabling high-force generation at low frequencies while maintaining high-frequency response capability
Solution Approach 2:
The patent changes the actuation mechanism from piezoelectric deformation (limited displacement) to electromagnetic force generation (high force output). The electrodynamic actuator uses a coil-wound around a permanent magnet assembly that can generate large forces through current control, with the force proportional to the product of current and magnetic field strength, enabling effective counter-vibration across the full frequency spectrum
2Force
If electromagnetic actuators are used to generate large forces, then low-frequency vibrations can be countered, but the control becomes complex and energy consumption increases
Solution Approach 1:
The patent implements a dynamic control system with sensors (accelerometers) that continuously measure boring bar vibrations and feed this data to a processor. The processor dynamically adjusts the electrodynamic actuator's coil current in real-time based on measured vibration characteristics, enabling adaptive counter-vibration control that optimizes force generation while minimizing energy consumption and simplifying the control algorithm
Solution Approach 2:
The patent employs a closed-loop feedback system where vibration sensors mounted on the boring bar continuously monitor vibration amplitude and frequency, and this feedback is processed to generate appropriate counter-vibration commands for the electrodynamic actuator. The feedback mechanism enables simple proportional control where the actuator force is directly proportional to the measured vibration, greatly simplifying control complexity
3Force
If the moving mass is positioned radially internal to electromagnets, then force generation is improved, but the air gap must be carefully controlled to avoid zero gap conditions
Solution Approach 1:
The patent positions springs between the movable mass and the electromagnet assembly to provide a mechanical cushion that prevents the air gap from closing to zero. The springs are pre-compressed or positioned to maintain a minimum safe air gap distance even when the movable mass is in its extreme position, thereby protecting the electromagnet from overheating and mechanical damage while allowing the mass to be positioned radially internal for maximum force generation
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 electrodynamic actuators provide linear behavior, generating substantial forces without increasing the air gap risk, effectively counteracting vibrations across a range of frequencies, including low frequencies, while maintaining efficient energy use and ease of control.
Implementation Method 1
a first electrodynamic actuator comprising windings surrounding a moving mass provided with at least one permanent magnet... a second electrodynamic actuator provided with windings surrounding a moving mass provided with at least one permanent magnet
Implementation Method 2
at least one spring mounted on the moving mass, the assembly being arranged to define a first actuation direction perpendicular to the longitudinal axis of the boring bar
Data Source
Figure 1
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Figure 4
AI summary
Boring bar with electrodynamic actuators for counteracting vibrations and machine tool provided with such a bar. The boring bar (BF) is provided with a wall (P), an internal recess (LI) and a longitudinal axis (Z), the boring bar (BF) comprising, in its internal recess (LI): • a first electrodynamic actuator (100) provided with coil windings (101, 102) associated with a moving mass (110) and a spring assembly (120, 121) that are arranged to define a first actuation direction (X) perpendicular to the longitudinal axis (Z) of the boring bar; • a second electrodynamic actuator (200) provided with coil windings (201, 202) associated with a moving mass (210) and a spring assembly (220, 221) that are arranged to define a second actuation direction (Y) perpendicular to both the first actuation direction (X) and the longitudinal axis (Z) of the boring bar. The actuators thus allow counteraction of the vibrations in the directions (X, Y) perpendicular to the longitudinal axis (Z) of the bar. The longitudinal axis also defines the boring direction.