DC Motor Rotor Speed Control via Adaptive Pulse Timing
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Solution Overview
Problem
Existing control methods for continuous rotation DC electric motors in horological applications suffer from speed instability, leading to fluctuations in rotor speed, which can result in inaccurate time display and susceptibility to direction changes due to external shocks.
Innovation Solution
A control method that adjusts the speed of the rotor by varying the duration and energy of drive voltage pulses, using a digital control unit to monitor and adjust the rotational speed through a series of phases, including start-up, measurement, and speed control, with thresholds set to maintain optimal rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple control method with fixed duration drive voltage pulses is used, then the device complexity is reduced, but the rotor speed stability deteriorates
Solution Approach 1:
The patent applies periodic action by using a start-up phase followed by periodic measurement phases and speed control phases. The control unit periodically measures the rotational speed and adjusts drive voltage pulses accordingly, creating a rhythmic control pattern that stabilizes rotor speed while maintaining relatively simple device architecture.
Solution Approach 2:
The patent implements feedback control by measuring the actual rotational speed of the rotor and using this information to adjust subsequent drive voltage pulses. The control unit continuously monitors speed and modifies pulse duration based on whether the rotor is accelerating or decelerating, creating a closed-loop system that stabilizes speed without requiring complex hardware.
2Device complexity
If fixed duration drive voltage pulses are applied periodically, then the device complexity is minimized, but the rotor speed varies periodically causing time display inaccuracy
Solution Approach 1:
The patent applies dynamics by transitioning from static fixed-duration pulses to dynamic adaptive pulses. The control unit adjusts pulse duration in real-time based on measured rotor speed, allowing the system to adapt to changing conditions and maintain accurate time display while keeping the control system relatively simple.
Solution Approach 2:
The patent implements parameter changes by modifying the duration of drive voltage pulses based on measured rotor speed. The control unit varies pulse duration as a controllable parameter to compensate for speed variations, thereby maintaining accurate time display without requiring complex control hardware.
3Device complexity
If fixed duration drive voltage pulses are used, then the control method remains simple, but the rotor may stop or change direction due to small shocks
Solution Approach 1:
The patent applies preliminary action by implementing a start-up phase that accelerates the rotor to operational speed before normal operation begins. This preliminary acceleration builds momentum that helps the rotor resist external shocks and maintain continuous rotation, improving reliability without complicating the control method.
Solution Approach 2:
The patent uses feedback control to monitor rotor speed continuously and provide compensatory drive voltage pulses when deceleration is detected. This feedback mechanism ensures the rotor maintains sufficient speed to overcome external disturbances, enhancing reliability while keeping the control approach relatively simple.
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 method ensures smooth and stable rotor speed control, minimizing power consumption and complexity, while maintaining precise timekeeping and reducing the risk of motor stoppage or direction change due to external shocks.
Implementation Method 1
DC electric motors convert electrical energy into mechanical energy
Implementation Method 2
The stator comprises coils, which typically do not move. This kind of electric motor allows for smaller design and results in reduced power consumption.
Implementation Method 3
The drive units are typically arranged to alternate the current that travels in the stator coils and thus the direction of the magnetic flux lines which are coupled to the magnet(s) of the rotor.
Data Source
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Figure 3
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AI summary
The present invention concerns a method of controlling a rotational speed of a rotor (3) of a direct current electric motor (1) comprising an inductor circuit (A, B) for rotating the rotor, which is configured to rotate continuously and is equipped with permanent magnets. The method comprises: measuring the rotational speed of the rotor ; determining a time drift in the rotor rotation compared to a reference signal; defining N speed thresholds with at least one being a variable speed threshold depending on the determined time drift, the N speed thresholds defining N+1 rotational speed ranges for the rotor ; determining in which one of the N+1 rotational speed ranges the determined rotational speed of the rotor is ; and finally selecting an action relative to the control of the inductor circuit, based on the determined rotational speed range, for controlling the rotational speed of the rotor.