DC Motor Deceleration Control via Voltage Threshold Feedback
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Solution Overview
Problem
Existing methods for regenerative braking of DC motors often result in energy waste due to prolonged short-circuiting or high impedance modes to prevent over-voltages, as they fail to accurately monitor and terminate the dangerous condition of motor-induced back currents.
Innovation Solution
A method and controller that apply a deceleration PWM signal to reduce motor-induced back currents by short-circuiting or setting windings into high impedance mode only when the power supply voltage exceeds a first threshold and returns to normal when it falls below a second threshold, ensuring the duration of energy reduction is minimized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the windings of the DC motor are short-circuited or set into high impedance mode for a predetermined time interval to prevent over-voltage, then the power supply output voltage is protected from dangerous over-voltages, but energy is wasted due to prolonged duration of the dangerous condition
Solution Approach 1:
The controller continuously monitors the power supply output voltage and uses this feedback to dynamically adjust the motor winding state. When voltage exceeds the first threshold, the controller activates short-circuit or high impedance mode. When voltage drops below the second threshold, the controller deactivates this mode, creating a closed-loop feedback system that responds to real-time voltage conditions rather than using fixed timing
Solution Approach 2:
The system transitions from a static, predetermined time interval approach to a dynamic, voltage-threshold-based approach. The duration of the protective mode (short-circuit or high impedance) is no longer fixed but varies dynamically based on when the voltage thresholds are crossed, allowing the system to adapt its response duration to the actual electrical conditions
2Reliability
If a predetermined time interval is used to ensure the dangerous condition will not occur again, then the power supply is protected from recurring over-voltages, but the time interval must be selected long enough which causes energy waste
Solution Approach 1:
The voltage monitoring provides continuous feedback that allows the controller to determine precisely when the dangerous condition has ended. By using the second voltage threshold as a termination criterion, the system extends the protective mode only as long as necessary, avoiding both premature termination and excessive duration
Solution Approach 2:
The system uses voltage threshold parameters (first threshold for activation, second threshold for deactivation) to control the timing of the protective mode. This parameter-based control replaces the fixed time interval approach, allowing the duration to be determined by electrical conditions rather than arbitrary time settings
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 effectively prevents energy waste by monitoring and terminating the reduction of motor-induced back currents as soon as the voltage drops below a second threshold, ensuring efficient energy recycling and reducing the duration of energy dissipation.
Implementation Method 1
Since during deceleration the motor also acts as a generator, braking regimes are possible where a net current is delivered back to the power supply. Mechanical energy present in the inertia of the rotor is recuperated to electrical energy for the supply battery or capacitor.
Implementation Method 2
applying a deceleration PWM signal to the bridge driver for decelerating the DC motor
Implementation Method 3
If the windings are short circuited, energy is dissipated because of friction and because the back-EMF of the motor results in current through the winding resistance.
Data Source
AI summary
Consistent with an example embodiment there is a method for controlling a deceleration process of a DC motor, wherein the DC motor is driven by a bridge driver coupled to a power supply intended to provide a supply voltage VDD at a power supply output. The method comprises applying a deceleration PWM signal to the bridge driver for decelerating the DC motor, and controlling the bridge driver such that a motor-induced back current is reduced, if the voltage at the power supply output exceeds a first voltage threshold which is higher than VDD. In accordance with the example embodiment, the method includes the following: if the voltage at the power supply output falls below a second voltage threshold which is lower than the first voltage threshold, control of the bridge driver is terminated such that the motor-induced back current is reduced.