Motor Control Circuit Preventing Overrunning in Electronic Timepieces
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Solution Overview
Problem
Existing motor control technologies for electronic timepieces, such as those described in JP-T-2009-542186, often result in the motor turning an excess number of steps instead of stopping at the desired position when driven at high speeds, leading to inaccuracies in timekeeping.
Innovation Solution
The electronic timepiece incorporates a motor control circuit with a driver, current detector, polarity changer, remaining drive step count detector, and drive period adjuster to precisely control the motor's polarity and brake force, ensuring accurate step counting and preventing overrunning by adjusting the no-drive period and brake force based on the remaining drive steps and elapsed time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor is driven at high speed using conventional control technology, then the productivity is improved, but the manufacturing precision deteriorates as the motor turns an excess number of steps instead of stopping at the desired position
Solution Approach 1:
The control circuit performs preliminary actions by detecting the motor's deceleration state in advance and activating the brake force before the motor completes its final steps. This prevents overrunning by applying braking force proactively when deceleration is detected, ensuring accurate positioning even at high speeds
Solution Approach 2:
The control circuit continuously monitors the motor's operating state and uses this feedback to dynamically adjust the brake force. By detecting current flow patterns and deceleration characteristics, the system responds in real-time to prevent the motor from turning excess steps, thereby maintaining positioning accuracy during high-speed operation
2Manufacturing precision
If the brake force is continuously applied to prevent overrunning, then the manufacturing precision is improved, but the use of energy increases due to prolonged brake activation
Solution Approach 1:
The brake force is applied periodically rather than continuously - specifically, it is activated only during the deceleration phase when the motor approaches the target position. This periodic application maintains positioning accuracy while minimizing energy consumption by keeping the brake inactive during constant-speed operation
Solution Approach 2:
The brake force is dynamically adjusted based on the motor's real-time operating state. The control circuit monitors deceleration characteristics and activates the brake only when needed, transitioning from a static braking approach to a dynamic one that adapts to the motor's speed and position, thereby optimizing energy usage
3Productivity
If the polarity changes immediately when the specific condition is met, then the productivity is improved, but the manufacturing precision deteriorates due to insufficient deceleration time causing the motor to overshoot
Solution Approach 1:
The control circuit performs preliminary deceleration by applying brake force before the polarity change is executed. This preliminary braking action reduces the motor's momentum in advance, allowing the subsequent polarity change to occur without causing overshoot, thereby maintaining positioning accuracy while preserving drive speed
Solution Approach 2:
The brake force serves as a preliminary counter-action to the motor's inertia before the polarity reversal. By opposing the motor's motion temporarily through braking, the system prevents the momentum from carrying the motor past the target position, ensuring accurate positioning during high-speed operation
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 enables the motor to quickly decelerate and accurately stop at specific positions, preventing overrunning and ensuring precise timekeeping, while also reducing power consumption and optimizing brake force application.
Implementation Method 1
a current detector configured to detect a current value flowing through the coil
Implementation Method 2
a driver that has a terminal through which drive current is supplied to the coil, and which is controlled to an on state supplying the drive current to the coil, and an off state not supplying the drive current
Data Source
AI summary
An electronic timepiece can prevent overrunning when driving a motor at a high speed. The electronic timepiece has a controller that controls a driver to an on state or an off state according to the current value detected by the current detector; a polarity changer that determines driving one step of the motor ended and changes the polarity of the drive current when the on time or off time is detected to meet a specific condition; and a drive period adjuster that sets the terminal supplying the drive current to the coil to a first state if the remaining drive step count is greater than the remaining count evaluation number, and if the remaining drive step count is less than or equal to the remaining count evaluation number, sets the terminal to a second state in which the brake force applied to the rotor is greater than in the first state.