Joystick Speed Control for Ophthalmologic Apparatus
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Solution Overview
Problem
Conventional ophthalmologic apparatuses face a limitation in vertical movement speed of the optical system when the joystick is rotated quickly, leading to a decrease in moving amount due to an upper limit in motor rotation speed, resulting in a large and expensive apparatus.
Innovation Solution
The rotation speed of the joystick is detected at predetermined intervals, and when the current speed is lower than the previous speed, a predetermined value is subtracted from the previous speed to set a new current speed, allowing the head part to move at a speed corresponding to this new speed, enabling improved operability even with inexpensive and small-size motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor rotation speed upper limit is increased to track the joystick rotation speed, then the moving speed of the optical system is improved, but the apparatus becomes large and expensive
Solution Approach 1:
The patent applies dynamics by making the motor rotation speed limit variable rather than fixed. The control device dynamically adjusts the upper limit of motor rotation speed based on the detected rotation speed of the joystick, allowing the system to adapt its performance characteristics to the operator's input intensity without requiring a permanently high-performance (and thus large and expensive) motor.
Solution Approach 2:
The patent changes the parameter of motor rotation speed upper limit based on the joystick rotation speed. When the joystick is rotated quickly, the control device increases the motor's upper rotation speed limit accordingly, allowing the system to achieve high moving speeds only when needed, rather than maintaining a constantly high-performance configuration that would increase size and cost.
2Loss of time
If the joystick is rotated quickly to increase moving speed, then the response time is improved, but the moving amount decreases due to motor speed saturation
Solution Approach 1:
The patent implements feedback by detecting the rotation speed of the joystick and using this information to control the motor's upper rotation speed limit. The control device continuously monitors the joystick's rotation speed and adjusts the motor performance in real-time, creating a closed-loop system where the output (motor speed) is regulated based on input (joystick rotation speed) to achieve both fast response and adequate moving amount.
Data Source
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Figure 6~6A
AI summary
In an ophthalmologic apparatus in which a head part is moved at a speed according to a rotation speed of a rotational part of a joystick, in order to enable a moving amount of the head part to correspond to a rotation amount even when the rotation speed becomes higher, the rotation speed of the joystick is detected at predetermined intervals, and when a current rotation speed (count of an encoder during a predetermined period) is lower than a previous rotation speed, a speed obtained by subtracting a predetermined value from the previous rotation speed is compared to the current rotation speed. Then, a higher speed is set as the current rotation speed, and the head part is moved at the speed corresponding to the current rotation speed.