Dual Redundant EMA Driveline Torque Spike Dissipation
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Solution Overview
Problem
Designing small, high power density electro-mechanical actuators (EMAs) is challenging due to the rotational inertia of electric motors, which can cause damage when the actuator hits a stop, leading to increased size, weight, and complexity in addressing torque spikes through overbuilding or adding components like slip clutches.
Innovation Solution
A dual motor and brake system with a differential gear train that uses an engaged brake to dissipate torque spikes by overcoming stiction, allowing the stored energy to be absorbed by friction material, thereby reducing the need for oversized components and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the gear train and EMA stops are overbuilt to handle torque spikes from rapid motor deceleration, then the actuator can handle the torque spike, but the actuator becomes significantly larger and heavier
Solution Approach 1:
The patent extracts the torque spike dissipation function from the motor and gear train structure and relocates it to a dedicated brake component. The brake is specifically designed to absorb the kinetic energy of the motor rotor when the actuator hits a stop, separating the shock absorption function from the load-bearing structure, thereby allowing the gear train and stops to be sized for normal operation rather than peak shock loads.
Solution Approach 2:
The brake acts as an intermediary component between the motor and the load. When the actuator encounters a stop, the brake engages to dissipate the motor's kinetic energy through friction, preventing this energy from being transmitted to the gear train and stops. This intermediary mechanism protects the primary structural components from excessive stress without requiring them to be overbuilt.
2Strength
If a slip clutch is incorporated in the driveline to allow the output to stop instantly while the motor decelerates, then the torque spike is absorbed by friction material, but components are added that increase size, cost, weight, and reduce reliability
Solution Approach 1:
The patent integrates the brake into the existing actuator architecture, where it serves multiple functions: providing controlled stopping capability during normal operation and absorbing torque spikes during impact events. By making the brake a multi-functional component rather than a dedicated shock absorber, the design avoids adding separate slip clutch mechanisms while still achieving the desired torque spike dissipation.
Solution Approach 2:
The brake is merged with the motor mounting structure and gear train assembly, combining several functions into a single integrated component. The brake housing also serves as a motor mount, and the brake assembly is integrated with the gear train support structure, eliminating the need for separate shock absorption components and reducing overall system complexity.
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 solution enables a lightweight, mechanically simple mechanism to effectively dissipate rotational energy, preventing damage and improving reliability by using redundant motors and brakes to manage torque spikes without adding excessive size or weight.
Implementation Method 1
the torque spike overcomes stiction in the engaged brake so that the torque spike is dissipated in the engaged brake
Data Source
AI summary
An apparatus has a first motor for moving an actuator, a first brake for selectively braking the motor, a second brake that is engaged, the second brake dissipating torque spikes in the system, and a gear attaching the first motor to the actuator to cause the actuator to move and to the second brake whereby the torque spikes overcome stiction in the engaged brake so that the torque spike is dissipated in the engaged brake.