Epicyclic Gear Actuator With Direct Output Angle Sensing
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Solution Overview
Problem
Existing actuators for land motor vehicles face challenges in achieving high torque transmission with compact designs and accurate angular position measurement, particularly due to complex rotational guidance and misalignments in epicyclic gear stages, leading to parasitic forces and measurement errors.
Innovation Solution
The actuator design incorporates an internal mechanical transmission with a high step-up ratio using epicyclic gear stages, guided by a connecting rod with positive diametrical clearance, and integrates an angular position sensor behind the planet gear wheels to measure the output member's position accurately, reducing complexity and parasitic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ball bearing guidance is used for rotational support of the epicyclic gear stage, then rotational support is provided, but device complexity increases and parasitic forces occur due to misalignments
Solution Approach 1:
The patent removes the ball bearing guidance system from the epicyclic gear stage, eliminating the complex rotational support mechanism that caused misalignment issues and parasitic forces. The guidance function is extracted and replaced with a simpler mounting approach where the epicyclic gear stage is directly supported without intermediate bearing elements.
Solution Approach 2:
The patent segments the functional requirements by separating the rotational support function from the epicyclic gear stage itself, allowing the gear stage to be mounted independently without complex guidance constraints, thereby reducing overall system complexity while maintaining reliability.
2Ease of manufacture
If the angular position sensor measures the input component position, then the sensor can be integrated into the actuator, but measurement error is multiplied by the high reduction ratio
Solution Approach 1:
The patent introduces an intermediary element - a magnetic target attached to the output component of the epicyclic gear stage - that serves as a mediator between the output shaft and the angular position sensor. This allows the sensor to measure output position directly without being affected by the reduction ratio, eliminating error multiplication while maintaining integration benefits.
3Force
If a high step-up reduction ratio is used in the mechanical transmission, then high torque is achieved on the output shaft, but measurement error is amplified by the reduction ratio
Solution Approach 1:
The magnetic target on the output component acts as an intermediary that enables direct measurement of the output shaft position. This intermediary approach allows the system to maintain high torque multiplication through the epicyclic gear stage while independently measuring output position without error amplification, as the sensor reads the actual output position rather than inferring it from input position.
Data Source
AI summary
The invention relates to an actuator comprising at least one epicyclic gear stage (28, 28.1, 28.2), and including an angular position sensor (42) comprising a target (46) mounted in a secured manner on a connecting rod (52) which is secured in rotation to a output mechanical connector (24) of the actuator (10),characterized in that the input component of the epicyclic gear stage is guided in rotation on the connecting rod (52) with a first positive diametrical guide clearance (“jg1”) relative to the main axis (A2),in that the output component of the epicyclic gear stage is rigidly connected to the connecting rod (52),and in that a rotatable assembly of the epicyclic gear stage (28) is positioned relative to the actuator casing (12) with a diametrical displacement clearance (“jd”) which is at least 3 times greater than the first diametrical guide clearance (“jg1”).