Ultrasonic Motor Control via Variable Waveform Drive Signals
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Solution Overview
Problem
Ultrasonic motors in surveying instruments face challenges in controlling rotation speed across different operation modes, particularly experiencing noise issues during low-speed intermittent driving, which affects smoothness and noise levels.
Innovation Solution
A method for controlling ultrasonic motors using variable frequency drive signals, with specific waveform adjustments based on rotation speed and operation mode, including square, triangular, and continuous signal patterns to manage noise and smoothness across different speed ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If intermittent driving is performed to achieve low-speed rotation, then rotation speed control is improved, but abnormal noise occurs at rises and falls of the drive signal
Solution Approach 1:
The drive signal waveform is dynamically changed based on the current rotation speed. When rotation speed is low, a triangular waveform is used to reduce noise. When rotation speed is high, a square waveform is used for efficient driving. This dynamic adaptation resolves the contradiction between achieving low-speed control and minimizing noise.
Solution Approach 2:
The waveform parameter of the drive signal is changed according to rotation speed conditions. By switching between triangular and square waveforms based on speed thresholds, the system optimizes both noise reduction at low speeds and driving efficiency at high speeds, resolving the technical contradiction.
2Stability of the object's composition
If signal waveform is made larger to improve rotation smoothness, then rotation smoothness is improved, but noise increases
Solution Approach 1:
The drive signal waveform is dynamically selected based on rotation speed. At low speeds where smoothness is critical, a triangular waveform is used. At high speeds where noise is less problematic, a square waveform is used. This resolves the contradiction between smoothness and noise by adapting to operating conditions.
Solution Approach 2:
The waveform parameter (triangular vs square) is changed based on rotation speed conditions. This parameter change allows the system to achieve smooth rotation when needed while minimizing noise when possible, resolving the trade-off between these two characteristics.
3Speed
If ultrasonic motor rotates at low speed during continuous driving, then low-speed rotation is achieved, but it becomes difficult to maintain continuous operation
Solution Approach 1:
The system uses intermittent periodic driving with on/off cycles to achieve low-speed rotation. By controlling the duty cycle and timing of drive signal application, the motor can operate at low speeds while maintaining continuous functional operation through repeated activation cycles.
Solution Approach 2:
The drive mode is dynamically switched between continuous and intermittent based on required rotation speed. At low speeds, intermittent driving is employed to maintain continuous operational capability. At higher speeds, continuous driving is used for sustained operation, resolving the contradiction between low-speed achievement and continuous 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
The method effectively meets rotation speed requirements and operation mode demands by reducing noise and ensuring smooth operation across various speed ranges, enhancing performance in manual, automatic collimation, and tracking modes.
Implementation Method 1
an ultrasonic motor (5, 12) that rotates a rotary shaft (6, 11)
Data Source
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AI summary
Provided is a method for controlling an ultrasonic motor (5, 12) driving a rotary shaft (6, 11) in a surveying instrument (1), featuring a plurality of operation modes by setting an AC voltage amplitude modulated drive signal according to the rotation speed. In a speed range from zero (V0) to a first speed (V1), a first drive signal (S1) with square wave modulation is applied. In a speed range from the first speed (V1) to a second speed (V2), a second drive signal (S2) with sloped rising or falling edges (FT) is applied. In a speed range from the second speed (V2) to a third speed (V3), a third drive signal (S3) with sloped rising and falling edges (RT, FT) is applied. In a speed range higher than the third speed (V3), a fourth drive signal (S4) is continuously applied.