DC Motor Rotor Positioning via Brush Voltage Measurement
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Solution Overview
Problem
Existing direct current electric motors in wiper systems of motor vehicles lack precision in determining the position of wiper arms, leading to inefficiencies in spraying cleaning liquids, especially in varying conditions like water, frost, or dirtiness, due to reliance on imprecise speed estimation methods.
Innovation Solution
A direct current electric motor with a rotor and stator configuration including three connection brushes and a processing unit that measures voltage variations to determine the rotor position, utilizing a Schmitt trigger and filter to create pulses from overvoltages, allowing precise determination of wiper arm positions without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated sensor is used to determine the position of the wiper arms, then the position precision is improved, but the cost increases significantly
Solution Approach 1:
The motor system determines its own rotor position using voltage measurements from its existing connection brushes and commutator, without requiring external sensors. The processing unit analyzes voltage variations naturally occurring during brush-commutator interaction to calculate rotor position and control wiper arm positioning.
Solution Approach 2:
The connection brushes serve as intermediaries that both power the motor and provide position information. By measuring voltage between the brushes and commutator segments, the system extracts position data from the existing electrical connection path, eliminating the need for separate sensing elements.
2Device complexity
If a counter or incrementer is used to estimate the position of the rotor, then the device complexity is reduced, but the measurement precision deteriorates
Solution Approach 1:
The system continuously measures voltage between connection brushes and commutator segments to obtain real-time rotor position feedback. This feedback is processed to determine precise rotor position and update the control system, enabling accurate position tracking without relying on imprecise speed-based estimation methods.
Solution Approach 2:
The patent replaces mechanical position sensing methods (like park fingers or encoders) with an electrical measurement approach. By analyzing voltage variations in the existing brush-commutator electrical connection, the system derives position information without adding mechanical sensing components.
3Device complexity
If the speed of the wiper arms is used to determine position, then the device complexity is reduced, but the measurement precision deteriorates due to varying friction conditions
Solution Approach 1:
The connection brushes serve as intermediaries that both power the motor and provide position information. By measuring voltage between the brushes and commutator segments, the system extracts position data from the existing electrical connection path, eliminating the need for separate sensing elements.
Solution Approach 2:
The motor system determines its own rotor position using voltage measurements from its existing connection brushes and commutator, without requiring external sensors. The processing unit analyzes voltage variations naturally occurring during brush-commutator interaction to calculate rotor position and control wiper arm positioning.
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
Enables precise positioning of wiper arms with an error of 0.43°, allowing for accurate activation of the wash pump only when necessary, thereby optimizing cleaning liquid application and reducing costs by eliminating the need for additional sensors.
Implementation Method 1
the connection brushes being configured to come into contact with the commutator of the rotor
Implementation Method 2
a measurement unit configured to measure the voltage between the third bonding brush and ground when the second bonding brush is energized and to measuring the voltage between the second bond brush and ground when the third bond brush is energized
Implementation Method 3
the processing unit is configured to determine the position of the rotor according to the detection of overvoltages produced by the passage of the connection brush on which the voltage is measured, from one conductive track of the collector to another
Implementation Method 4
the processing unit comprises a Schmitt trigger configured to create a series of pulses from overvoltages of the measured voltage associated with passages of the connection brush from a conductive track to another and a filter arranged upstream of the Schmitt trigger and configured to shape the signal of the measured voltage to be exploitable by the Schmitt trigger
Data Source
Figure 1~2
Figure 3~5
Figure 6a~6d
AI summary
The present invention relates to a DC-current electric motor (1) for a geared motor, in particular for a wiping system of a motor vehicle, comprising: - a rotor (3) comprising a collector (5), - a stator (9) comprising: - a first connection brush (B1) intended to be connected to ground (4), - a second connection brush (B2) intended to be connected to a voltage source (6) and associated with a first rotational speed of the electric motor (1), - a third connection brush (B3) intended to be connected to a voltage source (6) and associated with a second rotational speed of the electric motor (1) different from the first speed, the connection brushes (B1, B2, B3) being configured so as to come into contact with the collector (5) of the rotor (3), - a switching unit (8) for selectively supplying power to the second (B2) or the third (B3) connection brush depending on a command from a user, the electric motor (1) also comprising - a measurement unit (17) configured so as to measure the voltage between the third connection brush (B3) and ground (4) when the second connection brush (B2) is supplied with power or so as to measure the voltage between the second connection brush (B2) and ground (4) when the third connection brush (B3) is supplied with power, - a processing unit (19) configured so as to determine the position of the rotor (3) from the variations in the measured voltage.