Ripple counter with dynamic bandpass filter for DC motor
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Solution Overview
Problem
Traditional methods for tracking motor rotations in brushed DC motors, such as Hall effect sensors and optical sensors, add complexity and cost due to the need for PCB mounting, connectors, and cables.
Innovation Solution
A ripple counter with a dynamic bandpass filter that uses a current sense amplifier, analog-to-digital converter, digital filter, digital comparator circuit, and clock generator to detect and filter commutation spikes in the rotor windings, providing a pulsed signal for motor speed and position measurement without external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensors (Hall effect or optical sensors) are used to track motor rotations, then measurement precision is improved, but device complexity increases due to PCB mounting, connectors, and cables
Solution Approach 1:
The patent extracts the rotation detection function from external sensors and relocates it to the existing motor controller by utilizing the ripple current signal already present in the motor's power electronics. This eliminates the need for separate sensor assemblies, PCB mounting structures, connectors, and cables, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The motor controller is given multiple functions: it simultaneously performs motor drive control and rotation detection by analyzing ripple current signals. This multi-functionality eliminates the need for dedicated sensor hardware, reducing overall system complexity while maintaining precise rotation tracking capability.
2Measurement precision
If traditional sensors are used to track motor rotations, then measurement precision is improved, but manufacturing cost increases due to additional components
Solution Approach 1:
The patent extracts the rotation detection function from expensive external sensor assemblies and implements it within the existing motor controller using digital signal processing of ripple current. This eliminates the need to manufacture and assemble separate sensor modules, connectors, and mounting hardware, thereby reducing manufacturing cost while maintaining measurement precision.
Solution Approach 2:
Instead of using physical sensors to detect rotation, the system creates a digital copy of the rotation information by analyzing the characteristics of ripple current signals that naturally occur during motor operation. This virtual sensing approach eliminates the need for physical sensor components, reducing manufacturing cost.
3Measurement precision
If a dynamic bandpass filter is used to filter ripple current signals, then measurement precision is improved by removing noise, but device complexity increases due to additional signal processing components
Solution Approach 1:
The motor controller's digital signal processing unit performs multiple functions: it drives the motor, monitors current, and filters ripple signals to extract rotation information. By making the controller multi-functional, the patent avoids adding separate filter hardware, thereby improving measurement precision without significantly increasing device complexity.
Solution Approach 2:
The patent replaces potential analog filter hardware with digital filtering algorithms implemented in the controller's processor. This substitution uses software-based signal processing to achieve noise removal and signal enhancement, maintaining measurement precision while avoiding additional physical 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
This solution simplifies motor control by eliminating the need for external sensors, reducing complexity and cost, while accurately measuring motor speed and position through commutation spikes, thereby enabling precise motion control.
Implementation Method 1
a current sense amplifier configured to provide an analog voltage responsive to the inline current
Implementation Method 2
an analog-to-digital converter (ADC) configured to provide a digital signal responsive to the analog voltage
Implementation Method 3
a digital filter configured to receive the digital signal and a clock signal and is configured to vary a frequency response to allow the ripple current to escape
Implementation Method 4
a digital comparator circuit configured to receive the filtered ripple current and is configured to provide a pulsed output
Implementation Method 5
a clock generator configured to detect the frequency of the pulsed output and to provide the clock signal responsive to the detected frequency
Implementation Method 6
the rotor windings are coupled to commutator segments which are electrically coupled via brushes to a DC voltage supply, wherein commutation spikes are generated from contacts by the brushes with the commutator segments
Data Source
AI summary
Disclosed is a ripple counter with a dynamic bandpass filter for a DC motor. The ripple counter includes a current sense amplifier configured to provide an analog voltage responsive to an inline current in rotor windings of the DC motor. The ripple counter also includes an analog-to-digital converter configured to provide a digital signal responsive to the analog voltage. The ripple counter also includes a digital filter configured to receive the digital signal and a clock signal and configured to vary a frequency response to provide a filtered ripple current. The ripple counter also includes a digital comparator circuit configured to receive the filtered ripple current and to provide a pulsed output. The ripple counter also includes a clock generator configured to detect the frequency of the pulsed output and to provide the clock signal responsive to the detected frequency.