Oscillating Motor Control Using Dynamic Braking and Back-EMF Sensing
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Solution Overview
Problem
Existing motor control methods for oscillating motors require lengthy interruptions to measure back EMF, leading to reduced efficiency, or add additional components to measure motor speed, increasing costs.
Innovation Solution
A motor unit with a motor control unit that dynamically brakes the motor during a braking time interval to measure a physical variable indicative of current flow, compares this value with a target value, and adjusts the power level to maintain constant motor amplitude, using pulse-width modulation to shape the current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drive current is reduced to zero to measure back EMF, then the back EMF measurement is accurate, but the motor efficiency is reduced due to lengthy interruptions and energy dissipation
Solution Approach 1:
The patent applies dynamic braking during the measurement interval instead of completely stopping current flow. The motor is braked to a controlled state where measurement can occur without fully dissipating energy, allowing the system to transition between driving and measurement states more efficiently while maintaining measurement accuracy.
Solution Approach 2:
The patent implements periodic switching between driving mode and measurement mode, using short controlled intervals to measure back EMF while the motor is dynamically braked, then immediately resuming drive current. This periodic action minimizes the time energy is dissipated while still obtaining accurate measurements.
2Loss of energy
If a secondary measurement coil is used to determine motor velocity, then the measurement can occur without interrupting drive current, but additional components are required increasing device complexity and cost
Solution Approach 1:
The patent makes the existing motor coil serve dual functions: it acts as both the drive coil for motor operation and the measurement coil for back EMF detection. By using the same coil for both driving and measuring, the system eliminates the need for separate measurement coils while maintaining measurement capability during dynamic braking.
Solution Approach 2:
The motor's own coil and electromagnetic structure are used to provide the measurement function. The back EMF is measured directly from the motor coil itself during dynamic braking, allowing the motor to self-diagnose its state without external measurement devices.
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 approach enhances motor efficiency by avoiding the need to reduce motor current to zero for EMF measurement and reduces costs by eliminating the need for additional components, while maintaining consistent motor amplitude.
Implementation Method 1
measuring a value of a physical variable that is indicative of a current flow through the motor during a dynamic braking interval
Implementation Method 2
a supply circuit for providing a supply voltage at the motor to provide a set power level to the motor for driving the armature into motion
Implementation Method 3
the voltage induced in the motor coil by the relative motion between the motor coil and a permanent magnet
Data Source
AI summary
A motor unit having a motor having a stator and an armature, the armature being arranged for relative driven motion with respect to the stator. A motor control unit has a supply circuit for providing a supply voltage at the motor to provide a set power level to the motor for driving the armature into motion. A measurement circuit is measuring a value of a physical variable indicative of a current flow through the motor, The motor control unit is arranged to interrupt the provision of the supply voltage by the supply circuit and to dynamically brake the motor during a braking time interval and further to measure the value of the physical variable during the braking time interval. The motor control unit is further arranged to compare the measured value of the physical variable with a target value that depends on the supplied power level and on an intended motion amplitude of the armature, to determine a new set power level in dependence on the comparison result and to subsequently provide the new set power level to the motor.