Aircraft Wiper Motor Control With Four-Quadrant Braking
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Solution Overview
Problem
Aircraft windshield wiper systems face inaccuracies in wiper position due to varying system friction and external aerodynamic loads, and reversing motor direction can induce transient high current, reducing the operational life of motors and motor drives.
Innovation Solution
A four-quadrant motor control system that directly drives the windshield wiper, using discrete speed profiles tailored to the aircraft windshield's curvature and aerodynamic loads, with a braking circuit to dissipate back EMF and maintain stable voltage, preventing noise injection and extending motor life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-direction motor control system is used, then the motor drive structure is simpler, but the wiper position accuracy deteriorates due to varying friction and aerodynamic loads
Solution Approach 1:
The patent applies four-quadrant motor control that enables the motor to operate dynamically in all four quadrants (forward motoring, forward braking, reverse motoring, reverse braking), allowing the system to adapt to varying aerodynamic loads and friction conditions throughout the wiper's reciprocating motion cycle, thereby maintaining position accuracy without requiring a mechanically complex bidirectional drive system
2Productivity
If motor direction is reversed to achieve reciprocating motion, then the wiper can clean both sides of the windshield, but transient high current is induced that reduces motor and motor drive operational life
Solution Approach 1:
The patent converts the harmful effect of back-EMF generated during motor deceleration and direction reversal into a useful braking torque by implementing regenerative braking control. The motor acts as a generator during deceleration, converting kinetic energy back into electrical energy that is fed back to the DC bus, thereby eliminating the need for high current transient spikes while maintaining reciprocating motion capability
3Device complexity
If friction and aerodynamic loads are used to reduce wiper speed, then the system requires fewer control components, but wiper position accuracy deteriorates
Solution Approach 1:
The patent implements a closed-loop control system that continuously monitors motor current, position, and velocity, and adjusts the motor drive signals in real-time to compensate for varying friction and aerodynamic loads. This feedback mechanism enables precise position control without requiring additional mechanical speed-reduction components
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 system accurately controls wiper speed and position, reducing position inaccuracies and extending the operational life of motors and motor drives by managing frictional and aerodynamic loads, while preventing voltage fluctuations and noise injection.
Implementation Method 1
A braking circuit connected between positive and negative direct current buses dissipates back emf produced during forward braking and reverse braking of the motor
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A windshield wiper system includes a three-phase motor (14), the three-phase inverter (34), a brake circuit (36), and a controller (18). The controller transmits commutation signals to the three-phase inverter to drive the motor according to an inboard-to-outboard speed profile and to drive the motor according to an outboard-to-inboard speed profile. The controller activates the brake circuit based on the inboard-to outboard speed profile, or the outboard-to-inboard speed profile, and a direct current bus voltage.