Fourier Transform Spectrophotometer Mirror Speed Control
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Solution Overview
Problem
The speed of the moving mirror in Fourier transform type spectrophotometers can fluctuate due to foreign objects, leading to instability in feedback control and potential divergence, especially when the moving mirror operates at low speeds, causing inaccuracies in spectral data acquisition.
Innovation Solution
A Fourier transform type spectrophotometer configuration that includes a movable unit with an external force-applying means, such as gravity or an elastic member, to ensure a consistent driving force, combined with a speed measurement unit and a driving force control unit to maintain a predetermined movement of the moving mirror, thereby stabilizing its speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is used to adjust the driving voltage of the driving motor, then the speed of the moving mirror can be controlled, but the control becomes unstable and may diverge when foreign objects enter the sliding portion
Solution Approach 1:
The patent applies preliminary action by pre-loading the movable unit with a constant force (via spring or gravity) before measurement begins. This constant force ensures that the movable unit maintains steady motion even when foreign objects temporarily increase friction, preventing the feedback control from diverging due to sudden speed changes.
Solution Approach 2:
The patent converts the harmful effect of friction and foreign objects into a benefit by using a constant driving force that is always greater than maximum expected friction. This ensures that even when foreign objects increase resistance, the movable unit continues moving smoothly, and the feedback control remains stable rather than diverging.
2Measurement precision
If the moving mirror operates at low speed to increase accumulation time, then spectral data quality improves, but speed fluctuations have a larger relative impact on control stability
Solution Approach 1:
The patent applies preliminary action by pre-loading the movable unit with a constant force (via spring or gravity) before measurement begins. This constant force ensures that the movable unit maintains steady motion even when foreign objects temporarily increase friction, preventing the feedback control from diverging due to sudden speed changes.
Solution Approach 2:
The patent uses a spring to store elastic energy beforehand, which provides a constant driving force that cushions against sudden increases in friction from foreign objects. This prior cushioning ensures smooth continuous motion at low speeds without abrupt stoppages that would disrupt spectral data acquisition.
3Speed
If the driving voltage is increased to compensate for friction and maintain speed, then the moving mirror can overcome foreign objects, but the relative change in voltage becomes larger and control becomes less stable
Solution Approach 1:
The patent applies preliminary action by pre-loading the movable unit with a constant force (via spring or gravity) before measurement begins. This constant force ensures that the movable unit maintains steady motion even when foreign objects temporarily increase friction, preventing the feedback control from diverging due to sudden speed changes.
Solution Approach 2:
The patent changes the parameter of driving force from variable voltage control to constant force application. By using a spring or gravity to provide constant force rather than adjusting voltage in response to speed changes, the system avoids the instability caused by large relative voltage changes when compensating for friction from foreign objects.
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 configuration enhances the stability of feedback control, reduces speed fluctuations, and maintains constant speed, improving the accuracy of spectral data acquisition and prolonging device lifetime by minimizing abrupt speed changes.
Implementation Method 1
an elastic member, to ensure a consistent driving force
Implementation Method 2
a laser light source and a laser light detector for the control interference system
Implementation Method 3
infrared light from an infrared light source is split into two by a beam splitter... these reflected light is guided to the same optical path again to be interfered
Data Source
AI summary
A Fourier transform type spectrophotometer capable of stably controlling a speed of a moving mirror comprises a movable unit to which a moving mirror is fixed, outside-force-applying means configured to apply external force larger than movement resistance of the movable unit to the movable unit, a driving source configured to apply positive or negative driving force along the moving direction of the movable unit to the movable unit, a speed measurement unit configured to measure the speed of the movable unit, and a driving force control unit configured to control the driving force of the driving source so that the movable unit is moved in a predetermined manner based on the speed, wherein a rate of fluctuation of the driving force is suppressed by operating in a state in which the driving force of the driving source is high due to the external force to thereby stabilize the control.