Open-Loop Rotary Actuator With Damped Travel Stops
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Solution Overview
Problem
Existing direct drive electric actuators for limited angular travel, such as those controlling a camshaft in internal combustion engines, experience violent shocks and erratic positioning due to stiff stops, leading to potential breakage and increased complexity with the use of closed-loop position sensors for feedback control.
Innovation Solution
A brushless rotary actuator with open-loop control using unfilled thermoplastic materials for the stroke limiting part and mechanical beams with high breaking stress and viscoelastic damping properties to minimize impact velocity and extend lifespan, featuring symmetrical beams and a position sensor for all-or-nothing actuation feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed-loop control with position sensor is used to slow down rotor movement and protect stops, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent removes the position sensor and closed-loop control system from the actuator, extracting the feedback mechanism entirely. The solution relies on open-loop control where the rotor position is determined by the control signal alone, eliminating the need for continuous position feedback and significantly simplifying the device structure while maintaining reliability through proper mechanical design
Solution Approach 2:
The patent implements beforehand cushioning by designing the stop mechanism with energy absorption capabilities. The stop is designed to absorb the kinetic energy of the rotor at the end of stroke through controlled deformation or damping mechanisms, preventing violent shocks and protecting both the rotor and stop from damage without requiring complex feedback control
2Manufacturing precision
If stiff stops are used to limit rotor travel, then manufacturing precision is improved, but object-generated harmful factors increase due to violent shocks
Solution Approach 1:
The patent changes the mechanical parameters of the stop mechanism, transitioning from a rigid, non-compliant stop to one with controlled compliance or energy absorption characteristics. This allows the stop to maintain precise travel limitation while absorbing impact energy, preventing violent shocks and bounces that occur with overly stiff stops
Solution Approach 2:
The patent converts the harmful kinetic energy of the impacting rotor into beneficial energy absorption through the stop mechanism. The stop is designed to dissipate or absorb the impact energy through controlled deformation, friction, or damping, transforming the harmful shock into a protective mechanism that prevents damage while maintaining positioning accuracy
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 solution effectively reduces shocks and ensures high reliability, robust operation, and increased lifespan by minimizing impact velocity and using open-loop control without continuous position feedback, while maintaining precise positioning.
Implementation Method 1
beams with high breaking stress and viscoelastic damping properties to minimize impact velocity
Implementation Method 2
the position sensor has a magnetic field transmitter secured to the yoke and a receiver of said magnetic field fixed relative to the stator structure
Implementation Method 3
at least one excitation coil, said stator structure being made of a material of high magnetic permeability
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention concerns a brushless rotary actuator with travel limited by two stops, comprising a wound stator (14, 15) and a magnetic cylindrical rotor (21) rigidly attached to a shaft (7) having a first end rigidly attached to a control member (9), characterised in that the second end of said shaft is rigidly attached to a travel limiting part (23) acting as stops, in that said travel limiting part (23) has bending, resilient beam shapes (50, 51, 52, 53), and in that the actuator is electrically controlled in an open-loop. The invention also concerns a control system for controlling the lift value of the valves of an internal combustion engine by a lever driven by such an actuator.