Vibration Actuator Phase Control for Low-Speed Stability
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Solution Overview
Problem
Vibration type actuators face reduced controllability due to the dead zone in phase difference control, which affects low-speed driving and is influenced by individual differences in the relationship between phase difference and speed, making it difficult to achieve stable and precise control.
Innovation Solution
A control apparatus and program that adjust the phase difference of a two-phase drive signal for a vibration type actuator by determining an initial phase difference based on a phase difference shift, allowing the actuator to move from a stopped state while minimizing the impact of the dead zone and individual differences, thereby improving controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase difference control is used for low-speed driving, then low-speed control capability is improved, but dead zone causes unstable drive state and reduced controllability
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between phase differences and actuator speeds in a lookup table before actual operation. During low-speed driving, the control unit directly retrieves pre-computed phase difference values from the table, avoiding real-time calculations and ensuring stable control without entering the dead zone. This pre-computation approach allows the system to maintain reliable controllability while achieving precise low-speed control.
2Measurement precision
If individual phase difference characteristics are fitted for each actuator, then measurement precision is improved, but device complexity and calibration time increase
Solution Approach 1:
The patent applies parameter changes by allowing the control system to adaptively adjust the lookup table data based on individual actuator characteristics. During an initial calibration phase, the actual phase difference to speed relationship for each specific actuator is measured and stored in the lookup table. This enables precise control tailored to each actuator's unique characteristics without requiring complex real-time calculations or ongoing adjustments, balancing measurement precision with system simplicity.
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
The solution enhances the controllability of vibration type actuators by reducing the influence of the dead zone and individual differences, allowing for more precise and stable low-speed driving and reducing driving start lag and noise.
Implementation Method 1
a vibration is excited when a two-phase drive signal having a phase difference is applied to the piezoelectric element
Data Source
AI summary
A vibration type actuator control apparatus is configured to control driving of a vibration type actuator configured to move a moving body that is one of the vibrator and a contact body that contacts a vibrator. The vibration type actuator includes the vibrator in which a vibration is excited when a two-phase drive signal having a phase difference is applied to an electro-mechanical energy conversion element. The vibration type actuator control apparatus includes a drive signal generator configured to generate the two-phase drive signal. The drive signal generator changes a phase difference of the two-phase drive signal from an initial phase difference when the moving body is moved from a stopped state. The initial phase difference is determined based on a phase difference shift indicative of a shift from a phase difference set so as to stop the moving body.