Servomotor Control System for High-Speed Oscillating Motion
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Solution Overview
Problem
Conventional servomotor control systems for jig grinders face challenges in achieving precise high-speed oscillating motion due to limitations in learning control methods, particularly with dynamic changes in commanded repetitive cycles and lack of reference angles, leading to instability and divergence.
Innovation Solution
A novel servomotor control system that incorporates a control unit with a reference angle calculating means, oscillation command calculating means, and learning control means to perform angle synchronization-based learning control, correcting positional differences and adjusting for overshoot and phase advancements, enabling precise control during high-speed oscillating motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If learning control based on time synchronization method is used, then tracking precision is improved, but the system cannot adapt when commanded repetitive cycle dynamically changes
Solution Approach 1:
The patent transitions from a static time-synchronization learning control to a dynamic angle-synchronization learning control. The reference angle is calculated based on instantaneous angular velocity that adapts to dynamic machining conditions, allowing the system to maintain precision while accommodating changing oscillation cycles. The learning control unit uses angle-based indexing rather than time-based indexing, enabling real-time adaptation.
Solution Approach 2:
The patent changes the fundamental parameter for learning control from time to angle. By calculating reference angles based on angular velocity and using angle-synchronized positional difference accumulation, the system can adapt to dynamic cycle changes while maintaining tracking precision. The oscillation command calculating unit dynamically adjusts commands based on angle position rather than fixed time intervals.
2Adaptability or versatility
If learning control based on angle synchronization method is used, then adaptability to dynamic changes is improved, but the system requires a reference angle that monotonously increases which is not available in oscillating motion
Solution Approach 1:
The patent creates a dynamic reference angle calculation system that adapts to oscillating motion. Instead of requiring a pre-existing monotonically increasing reference angle, the system calculates the reference angle dynamically based on instantaneous angular velocity and accumulated angle. This allows angle-synchronization learning control to work with bidirectional oscillating motion without requiring external reference angle input.
Solution Approach 2:
The patent introduces an angle accumulation mechanism as an intermediary between the oscillation command and the learning control unit. The reference angle calculating unit acts as a mediator that converts instantaneous angular velocity into a monotonically increasing reference angle, enabling the learning control system to function without direct access to external reference angle signals.
3Manufacturing precision
If commanded amplitude is gradually increased to improve precision, then upper and lower dead center precision is improved, but a long tracking time is required
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing positional differences at each angle position during the learning process. The learning control unit accumulates positional differences angle-by-angle, allowing the system to quickly converge to precise tracking without requiring gradual amplitude increases over extended periods. The angle-based learning enables faster adaptation to the oscillation pattern.
Solution Approach 2:
The patent changes the control parameter from amplitude-based gradual adjustment to angle-based immediate correction. By using angle-synchronization learning control, the system can achieve precise dead center positioning through direct angle-position correction rather than gradual amplitude modulation, significantly reducing the tracking time required to achieve desired precision.
4Device complexity
If conventional servo control is used, then system simplicity is maintained, but precision during high-speed oscillating motion deteriorates
Solution Approach 1:
The patent implements angle-synchronized feedback through the learning control unit that accumulates positional differences at each angle position. The feedback mechanism uses the calculated reference angle to synchronize the learning process with the oscillation cycle, providing precise correction for high-speed oscillating motion while maintaining relatively simple system architecture. The feedback is angle-based rather than time-based, enabling better synchronization with the mechanical oscillation.
Data Source
AI summary
A servomotor control system that includes a numerical control unit and servo control unit enables the use of learning control based on an angle synchronization method in high-speed oscillating motion performed by, for example, a jig grinder. The numerical control unit calculates a reference angle θ(=ωt), and also calculates a cyclic oscillation command F(t) according to the reference angle θ and a machining condition (angular velocity ω). The servo control unit calculates a difference between the value in the oscillation command F(t) and the position of the servomotor (positional difference ε) at intervals of a predetermined cycle, and performs learning control according to the reference angle θ, oscillation command F(t), and positional difference ε.