Piano tuning auxiliary positioning system

Abstract

The invention discloses a piano tuning auxiliary positioning system, belongs to the technical field of musical instrument tuning, and aims to solve the problem of positioning deviation caused by neglecting string tension dynamic evolution and environmental disturbance in the prior art. The system comprises a tuning peg state sensing module, a string tension evolution monitoring module, a central cooperative controller, a man-machine interaction guide module and an audio feedback verification module. Through fusion of triple information of tuning peg angular displacement, tension steady state discrimination and acoustic frequency feedback, staged accurate guidance and dynamic decision are realized. The system rapidly approaches the target in the coarse tuning stage, premature termination is avoided in the fine tuning stage according to the tension steady state, the tuning accuracy is ensured through audio closed-loop verification, and the tuning precision, efficiency and robustness are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of musical instrument tuning technology, and more specifically, relates to a piano tuning auxiliary positioning system. Background Technology

[0002] As a precision stringed instrument, the piano's intonation and stability directly affect the quality of performance and auditory experience, thus holding a central position in music education, professional performance, and instrument manufacturing. Tuning, a crucial maintenance step in preserving the piano's acoustic performance, requires not only keen auditory discernment from the operator but also a precise grasp of the complex coupling relationship between tuning pin torque, string tension, and pitch frequency. Traditional tuning relies heavily on the tuner's subjective experience, involving repeated fine-tuning of the tuning pins to approximate the target frequency by comparing the sound with a standard sound source or feedback from an electronic tuner. This process is time-consuming and demands a high level of skill from the operator. To reduce human error and improve tuning efficiency, the industry has gradually introduced various auxiliary positioning devices in recent years, attempting to provide a visual or mechanical reference standard for tuning pin adjustment at a physical level.

[0003] Against this backdrop, typical solutions in existing technologies include optically marked tuning pin position recognition systems, intelligent tuning wrenches integrating angle sensors, and semi-automatic tuning platforms combining audio analysis and motor drive. Optical marking systems typically set high-contrast markings on the tuning pin plate surface, using a camera to capture the tuning pin rotation angle in real time, and converting it into frequency offset using image processing algorithms. Intelligent tuning wrenches, on the other hand, incorporate miniature angle encoders or gyroscopes to directly measure the amount of rotation applied to the tuning pin by the wrench, and wirelessly transmit the data to a terminal device for display. These solutions, to a certain extent, quantify and visualize the tuning process, demonstrating superior repeatability and consistency compared to purely manual operations, especially in batch tuning or teaching scenarios. Their design aims to transform abstract pitch deviations into intuitive physical displacement or angle parameters, thereby reducing absolute reliance on auditory experience and enabling even novice practitioners to complete basic tuning tasks.

[0004] However, as piano manufacturing processes become more refined and users' demands for pitch stability become increasingly stringent, the inherent limitations of the aforementioned technical solutions at the principle level are gradually becoming apparent. Fundamentally, this lies in simplifying the non-linear, time-varying mapping relationship of "pitch-string pin position," which is affected by multiple environmental factors, into a static, unidirectional geometric correspondence model. Specifically, string tension is not solely determined by the rotation angle of the string pin; its actual state is also significantly influenced by the friction coefficient of the string pin hole, the hammer striking history, wood deformation caused by temperature and humidity, and the tension coupling effect between adjacent strings. This means that even in the same register of the same piano model, the amount of string pin angular displacement required to reach the same target frequency in two independent tuning processes may have observable differences. If existing auxiliary systems rely solely on preset calibration curves or initial calibration data for positioning guidance, they are highly susceptible to positioning errors due to ignoring the aforementioned dynamic disturbance factors, leading to the secondary problem of "visually accurate but inaccurate pitch." Furthermore, such systems often lack the ability to perceive the real-time tension relaxation characteristics of the strings during tuning. After the tuning pin is rotated, the string tension needs to undergo stress redistribution for several seconds or even tens of seconds to reach a new equilibrium state. However, most existing solutions lock the position reading the moment the wrench stops rotating, failing to effectively distinguish between transient response and steady-state result, thus misleading the operator to terminate the adjustment prematurely. Correspondingly, in pursuit of higher positioning accuracy, some solutions attempt to introduce closed-loop feedback mechanisms to dynamically correct the tuning pin position by continuously monitoring the audio signal. However, this inevitably prolongs the single-note tuning cycle, sacrificing operational efficiency, and is susceptible to background noise interference in noisy environments, leading to feedback distortion. Thus, existing technologies are deeply entangled in the inherent contradiction of being unable to simultaneously achieve "accuracy, efficiency, and robustness": over-reliance on static models sacrifices environmental adaptability, while introducing dynamic feedback weakens real-time performance and anti-interference capabilities.

[0005] Therefore, how to construct an auxiliary system that can dynamically sense the evolution of string tension, adaptively compensate for the effects of environmental disturbances, and provide tuners with high-precision and high-reliability string pin positioning guidance without significantly increasing operational complexity has become a key challenge and an urgent technical problem for those skilled in the art. Summary of the Invention

[0006] This invention provides a piano tuning auxiliary positioning system, aiming to solve the positioning deviation problem caused by neglecting the dynamic evolution characteristics of string tension and environmental disturbances in existing technologies, while taking into account the accuracy, efficiency, and robustness of tuning operations. To achieve the above-mentioned objectives, the piano tuning auxiliary positioning system of this invention includes a tuning pin state sensing module, a string tension evolution monitoring module, a central collaborative controller, a human-computer interaction guidance module, and an audio feedback verification module. These modules are connected via hardwired connections to a high-speed serial communication bus, forming a closed-loop collaborative architecture.

[0007] The tuning shaft state sensing module is fixedly installed inside the tuning wrench body. Its core component is a high-resolution absolute angle encoder. The rotating shaft of the encoder is coaxially fixed to the force application end of the tuning wrench, ensuring that the rotational motion of the tuning shaft is directly converted into an angle signal. The output end of the angle encoder is connected to the digital input interface of the central coordinating controller through a shielded twisted pair cable. Its real-time sampling frequency is no less than one thousand times per second to fully capture any angular displacement change of the tuning shaft during the fine-tuning process.

[0008] The string tension evolution monitoring module consists of a micro-strain-sensitive element array and a temperature compensation unit. The strain-sensitive element array is embedded in a preset stress concentration area on the inner side of the tuning pin plate, corresponding to the circumferential position of each tuning pin hole. Each strain-sensitive element is rigidly coupled to the wood substrate through an epoxy resin encapsulation process, ensuring that the micro-strain caused by changes in string tension can be effectively transmitted. The temperature compensation unit is integrated in the central area of ​​the back side of the tuning pin plate. It uses a thermistor network to collect the local ambient temperature in real time and transmits the temperature data synchronously to the central co-controller to correct the thermal drift error of the strain signal. The output signals of the strain-sensitive element array and the temperature compensation unit are converted from analog to digital and then connected to the analog signal processing unit of the central co-controller via the SPI bus.

[0009] The central collaborative controller, serving as the core computing and scheduling unit of the system, incorporates a multi-channel synchronous sampling circuit, a tension state discrimination engine, an adaptive calibration database, and a collaborative decision-making logic unit. The multi-channel synchronous sampling circuit timestamps the angle signal from the string axis state sensing module and the strain signal from the string tension evolution monitoring module, ensuring that the two physical quantities are correlated under a unified time reference. The tension state discrimination engine, based on a preset stress relaxation time window model, continuously monitors the attenuation rate of the strain signal. When the strain change is less than a preset threshold within three consecutive sampling periods, it determines that the string tension has entered a steady-state phase. The adaptive calibration database stores data for different piano models, registers, and historical tuning records. The system records a dynamic mapping relationship table, which takes the angular displacement of the string axis, the initial tension value, the ambient temperature, and the tension state of adjacent strings as input dimensions, and the steady-state position of the string axis corresponding to the target frequency as the output dimension. After receiving the tuning command, the collaborative decision-making logic unit first reads the target frequency parameter of the current note, and then combines the real-time collected initial tension value, ambient temperature, and adjacent string state to retrieve the optimal mapping path from the adaptive calibration database and generate a preliminary target position of the string axis. During the tuning process, the collaborative decision-making logic unit continuously receives the steady-state judgment result from the tension state discrimination engine. Only when the state is determined to be steady will the actual position of the current string axis be compared with the target position, and the instruction action of the human-computer interaction guidance module be triggered.

[0010] The human-computer interaction guidance module is integrated into the outer surface of the tuning wrench handle and consists of a ring-shaped LED array and a tactile feedback vibration motor. The ring-shaped LED array has red, yellow, and green light-emitting units evenly distributed along the circumference of the handle. Its lighting mode is dynamically controlled by the central coordinating controller based on the direction and amplitude of the deviation between the current position of the tuning shaft and the target position: when the deviation is greater than a first preset range, the red LED is constantly lit and points to the direction to be rotated; when the deviation is within a second preset range, the yellow LED flashes to indicate fine-tuning; when the deviation is less than a third preset range and the tension state discrimination engine confirms that a steady state has been achieved, the green LED is constantly lit to indicate that the positioning is complete. The tactile feedback vibration motor is embedded inside the handle, and its vibration intensity and frequency are adjusted by the central coordinating controller according to the deviation convergence rate, providing progressive tactile cues as it approaches the target position to assist the operator in perceiving the adjustment process.

[0011] The audio feedback verification module consists of a high-sensitivity electret microphone, a bandpass filter circuit, and a frequency demodulation unit. The electret microphone is installed at the front end of the tuning wrench near the string striking point to pick up single-note vibration signals. The center frequency of the bandpass filter circuit covers the fundamental frequency range of the entire piano range, effectively suppressing non-harmonic noise. The frequency demodulation unit performs zero-crossing detection and time-domain periodic analysis on the filtered signal, and outputs the actual frequency value of the current note in real time. This actual frequency value is sent to the central coordinating controller and compared with the target frequency. If the deviation exceeds the allowable tolerance, the central coordinating controller reactivates the tuning pin state sensing module and the string tension evolution monitoring module, initiating a secondary fine-tuning process until the audio feedback verification module confirms that the frequency deviation meets the requirements.

[0012] Furthermore, the central coordinating controller is equipped with a non-volatile memory for recording the initial tension, target position, steady-state achievement time, and final frequency deviation data of each note in each tuning operation, and updating the dataset to the adaptive calibration database to enable the system to continuously learn and optimize the model for specific individual piano characteristics.

[0013] In a preferred embodiment of the present invention, the strain-sensitive element array is a semiconductor piezoresistive strain gauge with a nominal resistance of 1,200 ohms, a sensitivity coefficient of not less than 150, and a package thickness of not more than 0.5 mm, so as to minimize the impact on the structural strength of the chord plate.

[0014] As another preferred embodiment of the present invention, the absolute angle encoder adopts the magnetic induction principle, with a resolution of 4,096 counting units per revolution, a repeatability better than ±0.01 degree, and has a mechanical shock resistant and dustproof sealing structure, making it suitable for complex working conditions at the tuning site.

[0015] A hardware debouncing circuit is installed between the tuning shaft state sensing module and the central co-controller to eliminate signal glitches caused by mechanical vibrations generated by the tuning wrench during rapid rotation or pauses, ensuring the continuity and authenticity of angle data.

[0016] The strain signal sampling period of the string tension evolution monitoring module is strictly synchronized with the frequency demodulation period of the audio feedback verification module. The synchronization mechanism is uniformly triggered by the timer unit inside the central coordinating controller to ensure that the tension state and acoustic response are evaluated in association at the same physical moment.

[0017] The LED lighting logic and tactile feedback strategy of the human-computer interaction guidance module are dynamically switched by the central coordinating controller according to the current tuning stage: in the coarse tuning stage, only the direction indication function is enabled; in the fine tuning stage, the fine tuning flashing prompt is activated; and in the steady-state confirmation stage, both the green completion indication and high-frequency short vibration are enabled, forming a multi-modal guidance system.

[0018] The audio feedback verification module starts after a delay each time the string axis stops rotating. The delay time is dynamically set by the tension state discrimination engine based on the current strain attenuation trend, ensuring that the collected audio signal reflects the true vibration frequency of the string under steady-state tension, rather than the distorted harmonics during the transient transition process.

[0019] The system described in this invention performs an initial calibration process before the tuning operation begins: the operator selects several reference notes for manual tuning, and the system simultaneously records the string axis position, tension value and environmental parameters of each reference note in steady state, and uses this to construct an initial adaptive calibration database; subsequent tuning of non-reference notes is based on this database for interpolation deduction and dynamic correction.

[0020] The central coordinating controller is powered by an isolated power supply module, which has a built-in voltage regulation circuit and an electromagnetic interference filter to ensure the stability of the system operation and signal integrity under different power supply environments.

[0021] The tuning wrench body is made of non-magnetic alloy material to avoid interference with the magnetic field induction of the angle encoder. At the same time, its shape and size are consistent with traditional tuning wrenches, ensuring that the operator does not need to change his original grip and force application habits.

[0022] The beneficial effects of this invention are:

[0023] This invention deeply integrates three pieces of information: the geometric position of the tuning pin, the dynamic evolution of string tension, and acoustic frequency feedback. Under the unified scheduling of a central coordinating controller, it achieves precise, phased guidance of the tuning process: in the coarse tuning phase, it relies on high-response angle perception to quickly approach the target area; in the fine tuning phase, it uses tension steady-state judgment to avoid premature termination; and in the final verification phase, it introduces an audio closed loop to ensure acoustic accuracy. This system abandons the inherent defects of the static mapping model in traditional solutions, instead adopting a dynamic decision-making mechanism based on real-time physical states. This fundamentally solves the technical problem of "visual accuracy but inaccurate pitch." Furthermore, through multimodal human-computer interaction design, it significantly improves tuning accuracy and reliability without increasing operational complexity. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of a piano tuning auxiliary positioning system according to the present invention.

[0025] Figure 2 This is a schematic diagram showing the partial installation and signal connection relationship between the string axis state sensing module and the string tension evolution monitoring module in this invention.

[0026] Figure 3 This is a schematic diagram of the data interaction and control logic flow between the central collaborative controller and each functional module of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0028] like Figure 1-3 As shown, this invention provides a piano tuning auxiliary positioning system. Its overall architecture comprises a tuning pin state sensing module, a string tension evolution monitoring module, a central collaborative controller, a human-computer interaction guidance module, and an audio feedback verification module. These modules are connected via hardwired connections to a high-speed serial communication bus, forming a closed-loop collaborative working system. The following will describe in detail the various components of this invention and their interaction mechanisms, in conjunction with the accompanying drawings and practical engineering implementation details.

[0029] The tuning shaft status sensing module is integrated inside the tuning wrench body, and its core sensing element is a high-resolution absolute angle encoder. This angle encoder is designed based on the principle of magnetic induction, achieving a resolution of 4,096 counting units per revolution, a repeatability better than ±0.01 degrees, and features a shock-resistant and dustproof sealed structure to adapt to complex working conditions such as vibration, dust, and temperature and humidity fluctuations that may occur during tuning. The rotating shaft of the angle encoder is coaxially fixed to the force-applying end of the tuning wrench, ensuring that any angular displacement generated by the tuning shaft during rotation can be directly and without hysteresis converted into a digital angle signal. This signal is transmitted to the digital input interface of the central co-controller via shielded twisted-pair cable, with a sampling frequency of no less than 1,000 times per second, thus completely capturing the instantaneous motion characteristics of the tuning shaft during the fine-tuning stage. To further improve signal quality, a hardware debouncing circuit is installed between the tuning shaft status sensing module and the central co-controller to filter out signal glitches caused by mechanical vibrations resulting from rapid rotation or sudden stops of the wrench, ensuring the continuity and accuracy of the angle data.

[0030] The string tension evolution monitoring module consists of a micro-strain-sensitive element array and a temperature compensation unit. The strain-sensitive element array uses semiconductor piezoresistive strain gauges with a nominal resistance of 1200 ohms, a sensitivity coefficient of not less than 150, and a package thickness of no more than 0.5 mm to minimize the impact on the strength of the wooden structure of the tuning pin plate. These strain gauges are precisely embedded in preset stress concentration areas on the inner side of the tuning pin plate corresponding to the circumferential positions of each tuning pin hole, and rigidly coupled to the wooden substrate through an epoxy resin encapsulation process, ensuring that the micro-strain caused by changes in string tension is effectively transmitted to the surface of the sensing element. The temperature compensation unit is integrated in the central area of ​​the back side of the tuning pin plate, consisting of a thermistor network, used to collect local ambient temperature in real time and synchronously transmit the temperature data to the central co-controller as a key parameter for correcting thermal drift errors in the strain signal. The analog signals output by the strain-sensitive element array and the temperature compensation unit are converted from analog to digital and then connected to the analog signal processing unit of the central co-controller via an SPI bus. The sampling period of the strain signal is strictly synchronized with the frequency demodulation period of the audio feedback verification module. The synchronization mechanism is triggered uniformly by the timer unit inside the central coordinating controller to ensure that the tension state and acoustic response are evaluated in association at the same physical moment.

[0031] The central collaborative controller, serving as the core computing and scheduling unit of the system, integrates a multi-channel synchronous sampling circuit, a tension state discrimination engine, an adaptive calibration database, and a collaborative decision-making logic unit. The multi-channel synchronous sampling circuit is responsible for timestamping the angle signal received from the string axis state sensing module and the strain signal from the string tension evolution monitoring module, enabling correlation analysis between these two heterogeneous physical quantities under a unified time reference. The tension state discrimination engine, based on a preset stress relaxation time window model, continuously monitors the attenuation rate of the strain signal; when the strain change is less than a preset threshold within three consecutive sampling periods, it determines that the string tension has entered a steady-state phase. The adaptive calibration database stores a dynamic mapping table for different piano models, registers, and historical tuning records. This mapping table uses string axis angular displacement, initial tension value, ambient temperature, and adjacent string tension states as input dimensions, and the steady-state string axis position corresponding to the target frequency as the output dimension. Upon receiving a tuning command, the collaborative decision-making logic unit first reads the target frequency parameters of the current note. Then, combining this with real-time collected initial tension values, ambient temperature, and the state of adjacent strings, it retrieves the optimal mapping path from the adaptive calibration database and generates a preliminary target position for the string axis. During tuning, the collaborative decision-making logic unit continuously receives the steady-state determination results from the tension state discrimination engine. Only when a steady-state condition is determined does it compare the actual position of the current string axis with the target position and trigger the instruction action of the human-computer interaction guidance module. Furthermore, the central collaborative controller is equipped with non-volatile memory to record the initial tension, target position, steady-state achievement time, and final frequency deviation data for each note in each tuning operation. This dataset is then updated to the adaptive calibration database, enabling the system to continuously learn and optimize the model based on the specific characteristics of each piano.

[0032] The human-computer interaction guidance module is integrated into the outer surface of the tuning wrench handle, consisting of a ring-shaped LED array and a tactile feedback vibration motor. The ring-shaped LED array evenly distributes red, yellow, and green light-emitting units along the circumference of the handle. Its illumination mode is dynamically controlled by the central coordinating controller based on the direction and amplitude of the deviation between the current position of the tuning shaft and the target position: when the deviation exceeds a first preset range, the red LED remains constantly lit and points in the direction to be rotated; when the deviation is within a second preset range, the yellow LED flashes to indicate fine-tuning; when the deviation is less than a third preset range and the tension state judgment engine confirms steady-state achievement, the green LED remains constantly lit to indicate positioning completion. The tactile feedback vibration motor is embedded inside the handle. Its vibration intensity and frequency are adjusted by the central coordinating controller based on the deviation convergence rate, providing progressive tactile cues as it approaches the target position to assist the operator in perceiving the adjustment process. The LED lighting logic and tactile feedback strategy are dynamically switched by the central coordinating controller according to the current tuning stage: in the coarse-tuning stage, only the direction indicator function is activated; in the fine-tuning stage, the fine-tuning flashing cue is activated; and in the steady-state confirmation stage, both the green completion indicator and high-frequency short vibrations are activated simultaneously, forming a multi-modal guidance system.

[0033] The audio feedback verification module consists of a high-sensitivity electret microphone, a bandpass filter circuit, and a frequency demodulation unit. The electret microphone is mounted on the front of the tuning wrench near the string striking point to pick up single-note vibration signals. The bandpass filter circuit's center frequency covers the fundamental frequency range of the entire piano's range, effectively suppressing non-harmonic noise. The frequency demodulation unit performs zero-crossing detection and time-domain periodic analysis on the filtered signal, outputting the actual frequency value of the current note in real time. This actual frequency value is sent to the central coordinating controller for comparison with the target frequency. If the deviation exceeds the allowable tolerance, the central coordinating controller reactivates the tuning pin state sensing module and the string tension evolution monitoring module, initiating a secondary fine-tuning process until the audio feedback verification module confirms that the frequency deviation meets the requirements. It is worth noting that the audio feedback verification module starts with a delay after each tuning pin stops rotating. The delay time is dynamically set by the tension state discrimination engine based on the current strain attenuation trend, ensuring that the acquired audio signal reflects the true vibration frequency of the string under steady-state tension, rather than distorted harmonics during transient transitions.

[0034] Before the system is officially put into tuning, an initial calibration process must be performed. The operator selects several reference notes (usually including middle C, A440, and other key octave nodes) for manual tuning. The system simultaneously records the string pin position, tension value, and environmental parameters of each reference note in a steady state, and uses this to construct an initial adaptive calibration database. Subsequent tuning of non-reference notes is based on this database for interpolation and dynamic correction, thereby achieving efficient and accurate tuning of the entire piano.

[0035] The central coordinating controller is powered by an isolated power supply module, which incorporates a voltage regulator circuit and an electromagnetic interference filter to ensure system stability and signal integrity under different power supply environments. The tuning wrench body is made of a non-magnetic alloy material to avoid interference with the magnetic field induction of the angle encoder. At the same time, its dimensions are consistent with traditional tuning wrenches, ensuring that operators do not need to change their original grip and force application habits.

[0036] To further illustrate the technical effects of the present invention, a set of comparative experimental data from embodiments and comparative examples are provided below:

[0037] In one specific embodiment, an upright piano was selected as the test object, and the piano tuning auxiliary positioning system described in this invention was used for full-range tuning. During the initialization phase, the system manually calibrated three reference notes: A4 (440Hz), C4 (261.63Hz), and E5 (659.25Hz), and established an initial adaptive calibration database accordingly. Subsequently, the remaining 78 notes were automatically guided for tuning sequentially. Throughout the process, the system recorded the initial tension, target tuning pin position, steady-state achievement time, and final frequency deviation for each note in real time. The results showed that the frequency deviation of all notes was controlled within ±0.5 cents, the average steady-state achievement time was 3.2 seconds, and there were no instances of "visually in tune but out of tune" caused by premature termination of adjustment before tension stabilization.

[0038] As a comparison, a traditional electronic tuner was used with a standard tuning wrench to tune the same piano under identical conditions. The operator manually adjusted the tuning pins based on the frequency deviation displayed on the electronic tuner until the screen indicated the green zone. Due to a lack of awareness of the dynamic evolution of string tension, the operator often read the frequency value immediately after the tuning pins stopped rotating, at which point the strings were still in a transitional phase of stress relaxation. Experimental data showed that although most notes showed a frequency deviation within ±1 cent after the initial adjustment, when retested after 10 minutes of rest, approximately 35% of the notes showed a frequency deviation exceeding ±2 cents, requiring two or even three rework attempts.

[0039] The table below summarizes the key performance indicators of the above embodiments and comparative examples:

[0040] Indicator Item Example (System of the Invention) Comparative Example (Traditional Method) Average frequency deviation (initial) ±0.3 cents ±0.8 cents Frequency drift after 10 minutes ≤±0.2 cents Maximum ±2.1 cents Average tuning time per note 4.1 seconds 5.7 seconds Secondary fine-tuning of the ratio is required. 0％ 35％ Steady-state judgment mechanism Based on strain decay model none

[0041] The above data demonstrates that this invention, by integrating three pieces of information—the geometric position of the tuning pin, the dynamic evolution of string tension, and acoustic frequency feedback—and under the unified scheduling of a central coordinating controller, achieves precise, phased guidance of the tuning process. In the coarse tuning phase, it relies on high-response angle perception to quickly approach the target area; in the fine tuning phase, it uses tension steady-state judgment to avoid premature termination; and in the final verification phase, it introduces an audio closed loop to ensure acoustic accuracy. This system abandons the inherent defects of the static mapping model in traditional solutions, instead adopting a dynamic decision-making mechanism based on real-time physical states. This fundamentally solves the technical problem of "visual accuracy but inaccurate pitch." Furthermore, through multimodal human-computer interaction design, it significantly improves tuning accuracy and reliability without increasing operational complexity.

[0042] Furthermore, the adaptive calibration database of this invention supports cross-piano transfer learning. After completing the full tuning of a piano, the system can abstract the individual characteristic parameters of the piano (such as the coefficient of friction of the tuning pins, the tension distribution of the strings, and the elastic modulus of the wood) into feature vectors and store them in a cloud-based knowledge base. When faced with a new piano of the same brand and model, the system can call similar feature vectors for pre-loading, significantly shortening the time required for initial calibration. This mechanism has been verified on multiple high-end upright and grand piano models, reducing the average calibration time from 8 minutes to 2.5 minutes.

[0043] At the hardware implementation level, the central co-controller uses an embedded microcontroller based on the ARM Cortex-M7 core with a main frequency of 480MHz, equipped with 512KB SRAM and 2MB Flash storage space, which is sufficient to accommodate complex tension state discrimination algorithms and large-scale adaptive calibration databases. The SPI bus operating frequency is set to 20MHz to ensure high-speed transmission of strain signals and temperature data; the digital input interface adopts the LVDS level standard to improve anti-interference capability; the audio signal processing unit integrates a dedicated DSP coprocessor, supporting real-time FFT and zero-crossing detection dual frequency demodulation algorithms to improve the robustness of frequency identification.

[0044] In terms of software architecture, the system adopts an event-driven real-time operating system (RTOS), with each functional module running as an independent task, and synchronization and communication achieved through message queues and semaphores. The tension state discrimination engine uses the exponentially weighted moving average (EWMA) algorithm to smooth the raw strain data, and its mathematical expression is:

[0045] S t =αx t +(1-α)S t-1

[0046] Where S t Let x represent the smooth strain value at time t. t The original sample value is represented by α, which is a smoothing factor ranging from 0.1 to 0.3 and dynamically adjusted according to the current tuning stage. When three consecutive sample points satisfy |S... t -S t-1 When | < δ (δ is a preset threshold, typically 0.005% strain), it is determined that the state has entered a steady state.

[0047] The mapping table in the collaborative decision-making logic unit is queried using a four-dimensional interpolation algorithm. Let the input vector be X = [θ, T0, T]. env ,P adj ], where θ is the angular displacement of the chord axis, T0 is the initial tension, and T env For ambient temperature, P adjAs a comprehensive index of the tension state of adjacent strings, the target string axis position θ target It can be represented as:

[0048]

[0049] in The target location is defined by the N nearest reference samples in the database, with weight w. i The result is obtained by normalizing the inverse of the Euclidean distance:

[0050]

[0051] This interpolation mechanism ensures that the system can still output a reasonable target location estimate even in parameter space regions not fully covered by the database.

[0052] In summary, the piano tuning assistance positioning system described in this invention constructs a highly integrated, adaptive, and robust tuning assistance platform through a sophisticated sensing architecture, rigorous signal processing logic, dynamic decision-making mechanism, and user-friendly interactive design. Its technical solution is not only fully disclosed but also possesses clear engineering feasibility. Those skilled in the art can reproduce all the functions of this invention based on the above description and by combining conventional electronic, mechanical, and software engineering methods.

[0053] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A piano tuning auxiliary positioning system, characterized in that, The system includes a tuning pin state sensing module, a string tension evolution monitoring module, a central coordinating controller, a human-computer interaction guidance module, and an audio feedback verification module. The tuning pin state sensing module is fixed inside the tuning wrench body and includes an absolute angle encoder coaxially connected to the force application end of the tuning wrench for real-time output of the tuning pin angular displacement signal. The string tension evolution monitoring module includes a strain-sensitive element array embedded in the stress concentration area inside the tuning pin plate and a temperature compensation unit located on the back side of the tuning pin plate for synchronous output of strain and ambient temperature signals. The central coordinating controller receives the angular displacement signal, strain signal, and ambient temperature signal, determines whether the string tension has entered a steady state based on a preset stress relaxation time window model, and generates the target position of the tuning pin using an adaptive calibration database. The human-computer interaction guidance module is located on the outer surface of the tuning wrench handle and dynamically controls the indication mode based on the deviation between the current position and the target position of the tuning pin. The audio feedback verification module collects the string vibration signal and demodulates the actual frequency value, feeding it back to the central coordinating controller to verify the tuning accuracy.

2. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The absolute angle encoder uses the magnetic induction principle, has a resolution of 4096 counting units per revolution, a repeatability better than ±0.1 degrees, and is connected to the central coordinating controller via shielded twisted pair cable, with a sampling frequency of not less than 1kHz.

3. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The strain-sensitive element array is a semiconductor piezoresistive strain gauge with a nominal resistance of 1200 ohms, a sensitivity coefficient of not less than 150, an encapsulation thickness of not more than 0.5 mm, and a rigid coupling with the wooden substrate of the chord plate through epoxy resin.

4. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The central collaborative controller has a built-in multi-channel synchronous sampling circuit that performs timestamp alignment processing on the angular displacement signal and the strain signal. Only after determining that the string tension has entered a steady state will the actual position of the tuning peg be compared with the target position to trigger the human-computer interaction guidance action.

5. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The adaptive calibration database stores a dynamic mapping table with string axis angular displacement, initial tension value, ambient temperature and adjacent string tension state as input dimensions and steady-state string axis position corresponding to the target frequency as output dimension. The database records the data of each tuning operation through non-volatile memory and is continuously updated.

6. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The human-computer interaction guidance module includes a red, yellow, and green LED array evenly distributed along the circumference of the handle and a tactile feedback vibration motor embedded inside the handle. When the deviation is greater than the first preset range, the red LED is constantly lit to indicate the rotation direction. When the deviation is within the second preset range, the yellow LED flashes to indicate fine-tuning. When the deviation is less than the third preset range and the tension steady state is achieved, the green LED is constantly lit to indicate completion. At the same time, the vibration motor adjusts the vibration intensity and frequency according to the deviation convergence rate.

7. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The audio feedback verification module includes an electret microphone installed at the front end of the tuning wrench, a bandpass filter circuit covering the fundamental frequency range of the entire piano, and a frequency demodulation unit. The frequency demodulation unit outputs the actual frequency value through zero-crossing detection and time-domain periodic analysis.

8. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The audio feedback verification module starts after the string axis stops rotating. The delay time is dynamically set by the central coordinating controller according to the strain attenuation trend to ensure that the collected audio signal reflects the true vibration frequency of the string under steady-state tension.

9. The piano tuning auxiliary positioning system according to claim 1, characterized in that, The strain signal sampling period of the string tension evolution monitoring module and the frequency demodulation period of the audio feedback verification module are uniformly triggered by the internal timer of the central coordinating controller, so as to realize the synchronous correlation evaluation of tension state and acoustic response.

10. The piano tuning auxiliary positioning system according to claim 1, characterized in that, Before tuning, the system performs an initial calibration process: the operator manually tunes several reference notes, and the central coordinating controller synchronously records the string axis position, tension value and environmental parameters of each reference note in steady state, and uses this to build an initial adaptive calibration database for subsequent interpolation derivation and dynamic correction of non-reference notes.

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