Linear Actuator Power Limiting Based on Spindle Nut Position
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Solution Overview
Problem
Existing linear electric actuator systems fail to adequately protect both the actuator and the mechanical application from overload, as the current protection methods do not account for the varying geometry and dynamic movement, leading to potential hazardous situations where the actuator can exceed permissible loads without triggering overload protection.
Innovation Solution
A linear electric actuator system with a power limiting circuit that adjusts its power limit values based on the position of the spindle nut on the spindle, using programmed values stored in a controller to ensure safe operation by dynamically changing power limits in response to the spindle nut's position, thereby safeguarding both the actuator and mechanical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a calibration cycle is performed to determine maximum current draw, then overload protection is improved, but the protection only safeguards the linear actuator and not the mechanics of the application
Solution Approach 1:
The patent applies dynamics by transitioning from a static calibration-based power limit to a dynamic power limit that varies with position. Instead of relying on a single calibration value obtained during manufacturing, the system continuously adjusts the power limit based on real-time position feedback. This ensures that the protection extends to the mechanical application by accounting for the varying mechanical conditions throughout the actuator's stroke, not just the actuator itself.
Solution Approach 2:
The patent implements feedback by using position feedback to continuously adjust the power limit during operation. Rather than relying solely on pre-calibration data, the system uses real-time position information to modify the power limit, ensuring that the mechanical application is protected from overload conditions that may occur at different positions in the actuator's stroke.
Data Source
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AI summary
A linear electric actuator system, preferably for patient lifters, comprising at least one linear electric actuator and a controller having a power limiting circuit for limiting the power to the at least one linear electric actuator. The actuator system is arranged such that the threshold value of the maximum permissible power in the power limiting circuit may be changed, and that this change may be performed via reference to the position of the spindle nut on the spindle as a look up in a table showing a corresponding value for the power limit.