Synchronous measurement system and method for surface pressure of rotary tilting component and fixed component

Abstract

The invention discloses a synchronous measurement system and method for surface pressure of a rotary tilting component and a fixed component. The system comprises a computer, a synchronizer, a first electric control rotary table, a second electric control rotary table, a first camera and a second camera. The synchronizer is formed by cascading an arbitrary function signal generator and a signal delayer, and is used for receiving a rotation or tilting trigger signal and generating a plurality of paths of high-precision synchronous control signals. The first camera shoots the fixed part, and the second camera is installed on the second electric control rotary table and tracks and shoots the rotary tilting part. The method comprises the steps of pre-calibrating a motion coordinate sequence of the second electric control rotary table, setting synchronization parameters, controlling the camera to carry out image acquisition at a specific rotation or tilting phase based on a phase locking trigger or frequency doubling trigger mode, and simultaneously driving the second electric control rotary table to drive the camera to track a target to move. According to the invention, automatic visual angle tracking and multi-device high-precision synchronous image acquisition of a composite motion part are realized, the problems that a target is easy to deviate from a visual field and synchronous control is complex in traditional optical measurement are effectively solved, and the efficiency and safety of a wind tunnel test are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of pneumatic testing, specifically to a system and method for synchronously measuring the surface pressure of rotating and tilting components and stationary components. Background Technology

[0002] Pressure-sensitive paint (PSP) technology is a global, non-contact optical measurement method that uses a camera to measure the change in luminescence intensity of a sensitive paint coating on a model surface under oxygen conditions, thereby inferring the pressure distribution on the model surface. This technology has been widely used in wind tunnel testing, especially demonstrating significant advantages in measuring complex curved surfaces and dynamic flow phenomena.

[0003] With the rapid development of the "low-altitude economy," new low-altitude aircraft such as electric vertical takeoff and landing (eVTOL) aircraft and compound-wing UAVs have become research hotspots. To achieve the transition between vertical takeoff and landing and high-speed forward flight modes, the aerodynamic layout of these aircraft often involves a wide range of attitude changes in movable components (such as rotors, propellers, and deflectable wings). In wind tunnel aerodynamic characteristic studies, it is crucial to accurately measure the dynamic pressure distribution of these movable and fixed components under different flight modes to analyze their complex aerodynamic interference mechanisms and load characteristics.

[0004] However, existing fixed PSP measurement systems exhibit serious technical bottlenecks when faced with measurement requirements involving such dynamic and large-scale attitude changes:

[0005] Unable to adaptively track field of view: When the movable parts of the model (such as the rotor system) change attitude, the fixed camera angle cannot be adjusted accordingly, causing the measurement target to easily move out of the camera's field of view or deviate from the optimal imaging area, resulting in the loss of key data or a decrease in image quality.

[0006] The complexity of synchronous control increases dramatically: the measurement process requires the synchronous control of multiple cameras to capture the instantaneous pressure field on the surface of fixed and moving parts from different perspectives. Simultaneously, the motion mechanism used to adjust the camera perspective must be coordinated, and its triggering logic must be strictly synchronized with the motion phase of the model. Existing synchronization devices have limited interfaces and insufficient control precision, making it difficult to handle such complex multi-device, high-precision timing coordination requirements.

[0007] Low testing efficiency and safety: To obtain data under different attitudes, the wind tunnel needs to be frequently started and stopped, and the attitude of the high-altitude camera needs to be manually adjusted by the experimenters. This process is not only time-consuming and costly, but also poses significant safety risks for high-altitude operations, failing to meet the needs of modern efficient research and development.

[0008] Therefore, there is an urgent need in this field for an intelligent image acquisition system capable of automatically tracking moving targets and achieving high-precision synchronous and coordinated control of multiple devices to overcome the aforementioned technical bottlenecks and meet the high-standard aerodynamic testing requirements brought about by the rapid development of new aircraft in the low-altitude economic sector. This invention is proposed precisely to effectively solve these technical challenges.

[0009] Chinese invention patent CN115615589A proposes a rotating model global pressure measurement system and method. This method accumulates multiple brief luminescence events of PSP coating within a long-exposure image from a single camera, thereby acquiring a high signal-to-noise ratio (SNR) image while maintaining a low SNR. However, this method cannot track the camera's field of view based on component tilt.

[0010] Chinese invention patent CN118836920A proposes a method for synchronous measurement of pressure-deformation (PSP) on the surface of a rotating model. This method utilizes binocular vision technology and phase-locked loop (PLL) to achieve high signal-to-noise ratio and high resolution images of the rotating model, facilitating high-precision binocular feature recognition and effective extraction of PSP signals. However, this method cannot acquire PSP images of multiple phases within a single rotation cycle. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a synchronous measurement system and method for the surface pressure of a rotating and tilting component and a fixed component, mainly solving the following technical problems:

[0012] How to achieve automatic tracking and optimal viewing angle of a camera on a target with components exhibiting complex motion (high-speed rotation + large-angle tilt) to prevent the target from moving out of the field of view.

[0013] How to achieve high-precision synchronous control of multiple devices (two cameras and an electronically controlled turntable) under complex triggering logic, and ensure that image acquisition is accurately triggered at the preset component rotation and tilt phases.

[0014] One aspect of the present invention provides a synchronous measurement system for the surface pressure of a rotating and tilting component and a fixed component, the scheme of which is as follows:

[0015] (1) A synchronous measurement system for surface pressure of a rotating tilting component and a fixed component, comprising a computer, a synchronizer, a first electrically controlled turntable, a second electrically controlled turntable, a first camera and a second camera.

[0016] (2) The computer serves as the control center and is equipped with equipment control and image acquisition software.

[0017] (3) The synchronizer is connected to a computer for receiving external trigger signals that characterize the rotation or tilt phase of the component, and generating multiple synchronous control signals with precise timing. The synchronizer is composed of an arbitrary function signal generator and a signal delay unit cascaded and coupled together, thereby expanding the input / output interface and improving control accuracy and flexibility.

[0018] (4) Both the first and second electrically controlled turntables are connected to the computer and the synchronizer. The electrically controlled turntable has quantitative adjustment functions for two degrees of freedom: pitch and yaw, and its controller is equipped with an external trigger interface, which can receive TTL pulse signals from the synchronizer and trigger preset quantitative rotation.

[0019] (5) The first camera is fixedly mounted on the first electrically controlled turntable and is used to acquire PSP images of the surface of static components; the second camera is fixedly mounted on the second electrically controlled turntable and is used to acquire PSP images of the surface of dynamic components. The external trigger interfaces of both cameras are connected to the output of the synchronizer.

[0020] One aspect of the present invention provides a method for synchronously measuring the surface pressure of a rotating tilting component and a fixed component, the scheme of which is as follows:

[0021] (1) Pre-calibration steps: Before the test, the pitch and yaw motion coordinate sequence required by the second electronically controlled turntable to keep the dynamic component always in the center of the camera's field of view under different tilt phases of the dynamic component is pre-calibrated and uploaded to the computer.

[0022] (2) System construction and parameter setting steps: Build the system according to the above connection relationship. According to the test requirements (component rotation speed, tilt speed, exposure time, number of acquisition phases), set the synchronization trigger parameters in the synchronizer software, including pulse frequency, delay time, number of pulses and working mode.

[0023] (3) Synchronous acquisition and tracking steps:

[0024] The rotating component begins to move and outputs a rotation or tilt trigger signal.

[0025] After receiving the trigger signal, the synchronizer generates a synchronization control signal according to a preset mode:

[0026] Phase-locked trigger mode: Used for continuous tilting of components. The synchronizer generates a pulse at a fixed azimuth angle in each rotation cycle, synchronously triggering the two cameras to acquire images; and after the camera exposure ends, another pulse is generated after a predetermined delay, triggering the second electronically controlled turntable to step to the next pre-calibrated tilt angle position.

[0027] Frequency doubling trigger mode: Used when the rotating component is fixed at a certain tilt angle. The synchronizer generates M equally spaced pulses in each rotation cycle, triggering two cameras to acquire M frames of images with different rotation phases within that cycle.

[0028] The loop execution steps are repeated until all preset tilt phase or rotation phase image acquisition tasks are completed. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the synchronous measurement system for surface pressure of rotating and tilting components and fixed components proposed in this invention;

[0030] The components include: 1. Computer; 2. Signal delay unit; 3. Arbitrary function signal generator; 4. First electronically controlled turntable controller; 5. Second electronically controlled turntable controller; 6. First electronically controlled turntable; 7. Second electronically controlled turntable; 8. First camera; 9. Second camera; Detailed Implementation

[0031] 1. System hardware composition and connection

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0033] The external trigger interface (Trig in) of the arbitrary function signal generator receives speed sensor signals from the wind tunnel test section.

[0034] The CH2 output channel of the arbitrary function signal generator is connected to the external trigger interface of the second electronically controlled turntable controller via a BNC line.

[0035] The enable port (Enin) of the signal delayer receives the enable signal from the CH1 channel of the arbitrary function signal generator via the BNC line.

[0036] The CH3 output channel of the signal delayer is connected to the external trigger interfaces of both the first and second cameras via a BNC cable.

[0037] Electrically controlled turntable and camera:

[0038] The first electrically controlled turntable is used to mount the first camera to photograph stationary components; the second electrically controlled turntable is used to mount the second camera to track and photograph rotating components. Both turntables are connected to the computer via a USB-to-DB9 cable to receive motion commands. Both cameras are high-speed industrial cameras, connected to the computer's data acquisition card via a CAT6 network cable. The cameras are equipped with a Nikon 50mm f / 1.8D lens and a 650nm bandpass filter.

[0039] 2. Implementation Steps

[0040] 2.1 Implementation method of "phase-locked triggering" mode

[0041] Step 1: Pre-calibration

[0042] The second electronically controlled turntable and the second camera were installed near the wind tunnel test section. It was assumed that this test required phase-locked data acquisition at three tilt phases (e.g., -20°, 0°, +20°) during continuous tilting. At each phase, the pitch and yaw angles of the second electronically controlled turntable were manually adjusted to ensure the rotor hub center remained at the center of the second camera's field of view, and the corresponding turntable coordinate sequence was recorded.

[0043] Step 2: Parameter Calculation and System Settings

[0044] Assuming rotation frequency F = 50Hz, tilt period T = 4s, and camera exposure time: t e =100μs.

[0045] Based on the pre-calibrated coordinate sequence, the maximum rotation angle required by the electrically controlled turntable in the pitch and yaw directions is approximately 0.8°, and its maximum movement speed is set to 10° / s. Calculate the time t required for the electrically controlled turntable to achieve a single maximum rotation angle. r ≈80ms.

[0046] Set both CH1 and CH2 channels of the arbitrary function signal generator to external trigger (Burst) mode, and set the number of output pulses to 3 (N+1). Set the output frequency to f = N / T = 2 / 4 = 0.5Hz (i.e., the pulse period is 2s).

[0047] The delay time t of the CH2 channel d Set to t e +t r =100μs+80ms=80.1ms.

[0048] The parameters of the CH3 channel (connected to the camera) of the signal delay unit are set according to the rotation speed signal.

[0049] Step 3: Operation and Data Acquisition

[0050] Start the wind tunnel to bring the rotating components to the predetermined speed and begin to tilt slowly.

[0051] When the tilting mechanism reaches the starting angle, it sends a TTL rising edge signal to the synchronizer.

[0052] Synchronizer (2) is triggered and begins to work:

[0053] Image acquisition: The CH1 channel immediately emits a pulse sequence, synchronously triggering the two cameras to perform the first exposure acquisition of the stationary and rotating parts.

[0054] Turntable tracking: After a delay of 80.1ms, the CH2 channel emits a pulse sequence. Upon receiving the rising edge of the first pulse, the controller of the second electronically controlled turntable immediately drives the turntable, carrying the second camera, to move from the initial position to the first pre-calibrated position and stop, waiting for the next pulse.

[0055] The pulse sequence is emitted repeatedly with a period of 2 seconds. Whenever the second camera completes an exposure, the second electronically controlled turntable moves to the next pre-calibrated position when the next pulse arrives.

[0056] The entire process is automated and requires no manual intervention. The computer automatically stores all timestamp-aligned image data.

[0057] 2.2 Implementation method of "frequency multiplication triggering" mode

[0058] The "frequency doubling trigger" mode is suitable for the condition where the rotor tilts to a certain fixed phase. Its purpose is to acquire a series of images of different rotation phases within the same rotation cycle under the same tilt phase.

[0059] Step 1: Pre-calibration

[0060] In this mode, the tilt phase is fixed, eliminating the need for multi-tilt phase calibration. Simply adjust the second electrically controlled turntable to the optimal viewing angle coordinates corresponding to this fixed phase and then fix it.

[0061] Step 2: Parameter Calculation and System Settings

[0062] Assume that during the test, the rotor rotation frequency F = 50 Hz and there is no tilting motion.

[0063] Camera exposure time t e Set to 100μs. Set the frequency multiplication factor M=3, which means that 3 frames of images are required to be acquired within one rotation cycle.

[0064] Trigger frequency: f trigger =M*F=3*50=150Hz.

[0065] Set the CH1 channel of the arbitrary function signal generator to Burst mode, with the signal source being externally triggered.

[0066] Connect the rotor's rotation phase-locked signal (frequency 50Hz) to the external trigger input port of the arbitrary function signal generator.

[0067] Parameter configuration: Set the trigger frequency of channel CH1 to 150Hz and the number of output pulse train cycles to M=3.

[0068] Step 3: Operation and Data Acquisition

[0069] Start the system. Each rising edge of the rotating phase-locked signal triggers the CH1 channel of the arbitrary function signal generator to generate a sequence of 3 pulses with a frequency of 150Hz.

[0070] The pulse sequence is simultaneously sent to the external trigger inputs of both the first and second cameras. Within one rotation cycle, the two cameras are triggered three times at equal time intervals, acquiring three images with different rotation phases.

[0071] During this process, the second electrically controlled turntable remains stationary because its viewing angle has been fixed in the pre-calibration.

[0072] 3. Effects of the Example

[0073] Through the above implementation methods, this invention successfully enables the electrically controlled turntable and camera to achieve optical path tracking and image acquisition under a preset phase of rotation and tilt model via preset signals, ensuring that the subject is always in the optimal viewing angle and phase-locked phase. During the shooting process, the system operates automatically without manual intervention.

Claims

1. A system and method for synchronously measuring surface pressure between a rotating / tilting component and a stationary component, characterized in that, include: computer; A synchronizer, which is communicatively connected to the computer, is used to receive external trigger signals and generate multiple synchronization control signals. The first and second electronically controlled turntables are both communicatively connected to the computer and the synchronizer. Both the first and second electronically controlled turntables have quantitative adjustment functions in two dimensions: pitch and yaw, and are equipped with external trigger interfaces. The first camera and the second camera are fixedly mounted on the first electronically controlled turntable and the second electronically controlled turntable, respectively. The external trigger interfaces of the first camera and the second camera are communicatively connected to the output of the synchronizer. The synchronizer receives an external trigger signal that characterizes the rotation or tilt phase of a component, and sends a synchronization control signal with a specific timing relationship to the first camera, the second camera, and the second electronically controlled turntable accordingly, so as to realize the synchronous time-division image acquisition of stationary and rotating components, and enable the second electronically controlled turntable to drive the second camera to track the tilt motion.

2. The system according to claim 1, characterized in that, The synchronizer is composed of an arbitrary function signal generator and a signal delay unit cascaded and coupled together. The arbitrary function signal generator has multiple signal output channels and external trigger signal input channels; The signal delayer has multiple independent signal output channels, each with an independently adjustable delay time and level width, and an enable signal input port.

3. The system according to claim 1, characterized in that, The controller of the second electronically controlled turntable is equipped with an external trigger interface, which can receive TTL pulse signals from the synchronizer and perform quantitative rotation according to the motion coordinate sequence preset in the computer after being triggered by the rising edge of the pulse.

4. A synchronous image acquisition control method based on the system according to any one of claims 1-3, characterized in that, Includes the following steps: Pre-calibration step: Pre-calibrate the motion coordinate sequence required by the second electronically controlled turntable to maintain the best shooting angle under the tilt phase of different rotating components; System construction steps: Connect the components as described in claim 1, and load the motion coordinate sequence into the control software of the computer; Synchronization triggering step: The rotating component begins to move and sends an external trigger signal to the synchronizer; Image acquisition steps: After receiving the external trigger signal, the synchronizer sends a synchronization pulse signal to the first camera and the second camera, triggering them to acquire images of the fixed component and the rotating component respectively; Turntable tracking step: After the image acquisition step is completed, the synchronizer sends a synchronization pulse signal with a specific delay to the second electronically controlled turntable, triggering it to rotate to the next pre-calibrated phase position; The cyclic execution steps are repeated: the image acquisition steps and the turntable tracking steps are executed repeatedly until all pre-calibrated phase images are acquired.

5. The method according to claim 4, characterized in that, The synchronization triggering step specifically supports two working modes: Phase-locked trigger mode: used for continuous tilting of rotating components, the synchronizer triggers the first camera and the second camera to perform an image acquisition at a fixed azimuth angle in each rotation cycle, and triggers the second electronically controlled turntable to step to the next tilt phase after the acquisition is completed; Frequency doubling trigger mode: used when the rotating component is fixed at a certain tilt phase, the synchronizer performs M equal azimuth interval triggers in each rotation cycle, so that the first camera and the second camera can acquire M frames of images with different rotation phases in one rotation cycle.

6. The method according to claim 5, characterized in that, In the phase-locked trigger mode, the signal delay unit in the synchronizer is controlled by its enable port and only responds to the rotation signal and generates the camera trigger signal when it receives the enable pulse from the arbitrary function signal generator.

7. The method according to claim 4, characterized in that, The specific delay time in the turntable tracking step is set to be greater than or equal to the camera's exposure time to ensure that the electronically controlled turntable only starts moving after the camera exposure is complete.

8. A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method as claimed in any one of claims 4 to 7.

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