Preparation method of spline tooth surface film sensor, pressure testing system and method

Abstract

This application provides a method for fabricating a spline tooth surface thin-film sensor, a pressure testing system, and a method, relating to the field of pressure testing technology. The method includes: pre-treating the target tooth surface of the spline; depositing an insulating layer on the pre-treated tooth surface; forming a sensor functional layer on the insulating layer using a patterning process, wherein the patterned sensor functional layer has a Wheatstone bridge circuit and leads for signal acquisition; depositing a protective layer on the tooth surface where the sensor functional layer is formed; and polishing the tooth surface with the deposited protective layer to obtain the spline tooth surface thin-film sensor. This application can improve the accuracy of pressure detection results for spline meshing structures.

Description

Technical Field

[0001] This application relates to the field of pressure testing technology, and in particular to a method for preparing a spline tooth surface thin film sensor, a pressure testing system and method. Background Technology

[0002] A spline is a transmission component in mechanical engineering, consisting of a shaft or hole with multiple longitudinal teeth (keys). These teeth mesh with corresponding grooves (keyways) on mating parts, primarily used for transmitting torque and motion.

[0003] The narrow spline tooth surface makes traditional sensors (such as strain gauges) too large and difficult to install, and it also significantly alters the contact state. Existing thin-film sensor technology faces difficulties in achieving uniform fabrication and circuit integration of sensors on the tiny arc surface of the spline structure. This is manifested in the thick coating film, which alters the tooth meshing characteristics and causes the measurement results to deviate from the true value. In addition, traditional thin-film sensors cannot achieve real-time and reliable acquisition of signals from rotating components.

[0004] The aforementioned issues result in low accuracy of pressure testing results for spline meshing structures.

[0005] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0006] In view of this, the purpose of this application is to propose a method for preparing a thin spline tooth surface thin film sensor, a pressure testing system and method, which can specifically solve the problem of low accuracy of pressure detection results in existing spline meshing structures.

[0007] Based on the above objectives, in a first aspect, this application proposes a method for fabricating a spline tooth surface thin-film sensor, comprising: pre-treating a target tooth surface of a spline; depositing an insulating layer on the pre-treated tooth surface; forming a sensor functional layer on the insulating layer by a patterning process, wherein the patterned sensor functional layer has a Wheatstone bridge circuit and leads for acquiring signals; depositing a protective layer on the tooth surface on which the sensor functional layer is formed; and polishing the tooth surface on which the protective layer is deposited to obtain the spline tooth surface thin-film sensor.

[0008] In some embodiments, the pretreatment of the target tooth surface of the spline includes: grinding the tooth surface until the roughness Ra of the target tooth surface is ≤0.1μm; and cleaning and drying the target tooth surface.

[0009] In some embodiments, the insulating layer is any one of Al2O3 insulating layer, SiO2 insulating layer, and HfO2 insulating layer, and the thickness of the insulating layer ranges from 300 to 800 nm.

[0010] In some embodiments, a sensor functional layer is formed on the insulating layer by a patterning process, including: spraying photoresist on the insulating layer; exposing the photoresist to ultraviolet light using a mask to form a sensor pattern; depositing a Cu–Mn–Ni alloy thin film in the toothed area where the sensor pattern has been formed using DC or RF magnetron sputtering to form the Wheatstone bridge circuit; and sputtering a highly conductive metal in the lead area to form the leads.

[0011] In some embodiments, the thickness of the Cu–Mn–Ni alloy film ranges from 4 to 6 μm.

[0012] In some embodiments, the thickness of the protective layer ranges from 1 to 3 μm.

[0013] Secondly, a spline tooth surface pressure testing system is also provided, comprising: a thin-film sensor, wherein the thin-film sensor is integrated into the external spline tooth surface using the preparation method described in any one of the first aspects, for converting spline tooth surface pressure into an electrical signal; a signal transmission unit, comprising a wire connected to the lead wire of the thin-film sensor, and a wireless transmitter connected to the wire, wherein the wireless transmitter is fixed to the end of the external spline shaft and rotates with it; and a signal receiving unit, comprising a wireless receiver, wherein the wireless receiver is used to receive the signal emitted by the wireless transmitter and process the signal to obtain pressure data.

[0014] In some embodiments, the signal receiving unit further includes a bracket fixed to the end of an internal spline shaft, wherein the internal spline and the external spline cooperate, and the wireless receiver and the wireless transmitter maintain a non-contact relationship to receive wireless signals.

[0015] Thirdly, a method for testing spline tooth surface pressure is also provided, applied to the system described in the second aspect, characterized by comprising the following steps: assembling and engaging an external spline integrating the thin-film sensor with an internal spline; establishing a signal transmission link, the link including the spline tooth surface thin-film sensor, a wireless transmitter, and a wireless receiver; driving the external spline to rotate; acquiring, in real time, the electrical signal generated by the thin-film sensor due to changes in tooth surface contact pressure through the signal transmission link; and processing the electrical signal to obtain dynamic distribution data of spline tooth surface pressure.

[0016] In some embodiments, static calibration of the thin-film sensor is further included prior to the step of driving the spline pair to rotate and transmit torque.

[0017] In summary, this application has at least the following beneficial effects: The method for fabricating a thin-film sensor on a spline tooth surface provided in this embodiment offers a standardized and feasible fabrication process for thin-film sensors. This ensures that a thin-film sensor integrating a complete measurement circuit can be fabricated on a spline tooth surface with extremely limited space. It enables stable film formation and measurement at a very small interface in the spline meshing space, while ensuring the integration and flatness of the sensor and the tooth surface, minimizing interference with the meshing state, achieving high-precision in-situ measurement, and improving the accuracy of pressure detection results for spline meshing structures.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0019] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application. Furthermore, the same reference numerals denote the same parts throughout all the drawings.

[0020] Figure 1 A flowchart illustrating the fabrication method of the spline tooth surface thin film sensor provided in an embodiment of this application is shown. Figure 2 A schematic diagram of the structure of a thin-film sensor according to an embodiment of this application is shown; Figure 3 This diagram shows the structure of the spline tooth surface pressure testing system provided in this embodiment; Figure 4 A flowchart of a spline tooth surface pressure testing method according to an embodiment of this application is shown.

[0021] Figure description: 1. External spline, 2. Thin film sensor, 3. Internal spline, 4. Wire, 5. Wireless transmitter, 6. Wireless receiver, 7. Bracket. Detailed Implementation

[0022] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0024] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0025] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This document shows a flowchart illustrating the fabrication method of the spline-tooth surface thin-film sensor provided in an embodiment of this application. Figure 1 As shown, the preparation method includes the following steps: S11. Preprocess the target tooth surface of the spline; S12. Deposit an insulating layer on the pretreated tooth surface; S13. On the insulating layer, a sensor functional layer is formed by a patterning process. After patterning, the sensor functional layer has a Wheatstone bridge circuit and leads for acquiring signals. S14. Deposit a protective layer on the tooth surface where the sensor functional layer is formed; S15. Polish the tooth surface with the deposited protective layer to obtain the spline tooth surface thin film sensor.

[0029] The spline tooth surface is a machined surface with fine tool marks, oil stains, and oxide layers. If a sensor is directly fabricated on it, the fit will not be good. Therefore, in this embodiment, pretreatment is required before fabricating the sensor on the spline tooth surface. For example, the tooth surface is ground and cleaned to provide a smooth and clean base for sensor fabrication and prevent the sensor from falling off during use.

[0030] The spline tooth surface is metallic and conductive, which can affect the sensor circuit. Therefore, an insulating layer is deposited on the pre-treated tooth surface to prevent the circuit in the thin-film sensor from directly contacting the tooth surface.

[0031] Thin-film sensors need to acquire and transmit pressure signals. Therefore, an acquisition circuit needs to be set inside the thin-film sensor. On the insulating layer, a sensor functional layer is formed through a patterning process. After patterning, the sensor functional layer has a Wheatstone bridge circuit and leads for acquiring signals. The Wheatstone bridge circuit changes its resistance value by sensing pressure changes, and then transmits the pressure signal through the leads.

[0032] Because the thin-film sensor is very thin, the patterned circuit is very fragile. In order to protect the stability of the circuit, this embodiment also deposits a protective layer on the tooth surface where the sensor functional layer is formed.

[0033] The above steps allow for the fabrication of a fully functional thin-film sensor. However, the surface of the thin-film sensor may be uneven, which can affect the pressure transmission path during spline engagement and thus the pressure detection results. Therefore, the tooth surface with the protective layer deposited is polished to ensure that the surface of the thin-film sensor and the spline tooth surface have the same flatness; in other words, the surface of the thin-film sensor and the spline tooth surface are parallel.

[0034] The structure of the fabricated thin-film sensor is as follows: Figure 2 As shown, the fabrication method of the spline tooth surface thin film sensor provided in the above embodiments provides a standardized and implementable fabrication process for thin film sensors. This ensures that a thin film sensor integrating a complete measurement circuit can be fabricated on the spline tooth surface where space is extremely limited. It enables stable film formation measurement at the interface with minimal spline meshing space, and ensures the integration and flatness of the sensor and the tooth surface, minimizing interference with the meshing state and laying the foundation for high-precision in-situ measurement.

[0035] In this embodiment, the target tooth surface of the spline is pretreated, including: grinding the tooth surface until the roughness Ra of the target tooth surface is ≤0.1μm; and cleaning and drying the target tooth surface.

[0036] If the spline tooth surface has a high roughness, the uneven surface will cause stress concentration in the film, resulting in poor adhesion and easy peeling and flaking during subsequent use.

[0037] Precision grinding is performed on the selected tooth surface to remove approximately 5 μm of surface material, thereby reducing the surface roughness. The surface roughness is controlled to Ra≤0.1 μm, providing a qualified substrate for the subsequent uniform and dense deposition of micron-scale thin films, ensuring film adhesion and sensor performance.

[0038] Cleaning and drying, for example, using anhydrous ethanol or acetone for multi-stage cleaning, followed by rinsing with deionized water and drying with nitrogen, remove oil, particles and surface-active contaminants, which helps improve the adhesion between the thin-film sensor and the spline tooth surface.

[0039] In this embodiment, the insulating layer is any one of Al2O3 insulating layer, SiO2 insulating layer, and HfO2 insulating layer, and the thickness of the insulating layer ranges from 300 to 800 nm.

[0040] Radio frequency magnetron sputtering technology can be used to deposit an insulating layer with a thickness of 300–800 nm on the spline tooth surface. This prevents measurement inaccuracies caused by the insulating layer being too thin or too thick.

[0041] Al2O3, SiO2, and HfO2 insulating layers all possess high resistivity and density, as well as good chemical stability, which can improve the performance of thin-film sensors.

[0042] The above embodiments clarify the implementation method and thickness boundary of the insulation layer, achieving an optimal balance between ensuring electrical insulation reliability and minimizing changes to the tooth surface geometry.

[0043] In this embodiment, a sensor functional layer is formed on an insulating layer using a patterning process, including: spraying photoresist onto the insulating layer; exposing the photoresist to ultraviolet light using a mask to form a sensor pattern; depositing a Cu–Mn–Ni alloy thin film on the toothed area where the sensor pattern has been formed using DC or RF magnetron sputtering to form the Wheatstone bridge circuit; and sputtering highly conductive metal in the lead area to form leads.

[0044] Spraying photoresist onto an insulating layer allows the photoresist to cover the curved and grooved spline tooth surface, making it suitable for complex curved surfaces and enabling it to uniformly cover the narrow spline tooth surface.

[0045] Using a photomask to expose the photoresist to ultraviolet light, the chemical properties of the photoresist exposed to ultraviolet light will change, while the unexposed areas will remain unchanged. Thus, some areas on the tooth surface are exposed and cured photoresist, while others are unexposed and soluble photoresist. Removing the unexposed and soluble photoresist exposes the clean insulating layer underneath, creating a three-dimensional mold on the tooth surface. The shape of the exposed insulating layer forms the sensor pattern, i.e., the pattern of the Wheatstone bridge circuit.

[0046] In the toothed area where the sensor pattern has been formed, a Cu–Mn–Ni alloy thin film is deposited using DC or RF magnetron sputtering. This allows the use of the characteristic that the resistance of Cu–Mn–Ni alloy changes sensitively and linearly with the pressure applied, thus forming a Wheatstone bridge circuit.

[0047] In this process, highly conductive metals (such as gold or aluminum) can be sputtered into the lead area to form leads, thereby reducing signal loss during transmission.

[0048] Finally, a stripping process is used to remove the photoresist, yielding the sensor functional layer.

[0049] In this embodiment, the thickness of the Cu–Mn–Ni alloy film ranges from 4 to 6 μm. This optimizes the sensor's performance, as this thickness range ensures sufficient piezoresistive effect (sensitivity) while maintaining sufficient mechanical strength to withstand meshing pressure without easily being damaged, and the overall thickness is still controlled at the micrometer level, minimizing interference with spline meshing.

[0050] After obtaining the functional layer, a protective layer is deposited on the tooth surface where the sensor functional layer is formed. The thickness of the protective layer ranges from 1 to 3 μm, which balances protection and impact.

[0051] A 1-3μm protective layer is sufficient to effectively protect the sensor circuit from wear and corrosion in the meshing environment. At the same time, its thickness, combined with the final polishing process, can make the sensor surface highly consistent with the original tooth surface, achieving a seamless and flat integrated surface.

[0052] The above embodiments enable stable film formation and pressure measurement of thin-film sensors at interfaces with minimal spline meshing space. Furthermore, after depositing the protective layer, the protective layer is polished, such as by performing a 0.5–1 μm fine polishing process, to make the protective film and tooth surface integrated and flat without changing the contact parameters of the external and internal splines, thereby improving the pressure detection effect.

[0053] This embodiment provides a spline tooth surface pressure testing system, such as Figure 3 As shown, the spline tooth surface pressure testing system includes: a thin film sensor 2, a signal transmission unit, and a signal receiving unit.

[0054] The thin-film sensor 2 is integrated onto the tooth surface of the external spline 1 using the above-described fabrication method, and is used to convert the pressure on the tooth surface of the spline 1 into an electrical signal; The signal transmission unit includes a wire 4 connected to the lead wire of the thin film sensor 2, and a wireless transmitter 5 connected to the wire 4. The wireless transmitter 5 is fixed to the shaft end of the external spline 1 and rotates with it. The signal receiving unit includes a wireless receiver 6, which receives signals emitted by the wireless transmitter 5 and processes the signals to obtain pressure data.

[0055] When the thin-film sensor 2 is subjected to the squeezing force between the outer spline 1 and the inner spline 3, its internal resistance will change. This change in internal resistance can then be transmitted to the wireless transmitter via a wire. The wireless transmitter 5 transmits the signal wirelessly to the wireless receiver 6. The wireless receiver 6 processes the signal sent by the transmitter to obtain pressure data.

[0056] In this embodiment, the wireless transmitter is fixed to the end of the external spline shaft and rotates with it. In this embodiment, the external spline shaft end refers to the end closest to the external spline tooth surface. Figure 3 As shown, after the external spline and internal spline are assembled, the wireless transmitter is located in the shaft cavity of the internal spline. This shortens the distance between the wireless transmitter and the thin-film sensor, thereby reducing the length of the wire and preventing the wire from tangling during rotation. In this embodiment, the wire is a miniature wire, which can be placed in the groove of the spline shaft and extend along the groove to the shaft end to further prevent tangling during rotation.

[0057] In this embodiment, the signal receiving unit further includes a bracket 7, which is fixed to the shaft end of the inner spline 3. The inner spline 3 and the outer spline 1 are coupled. The wireless receiver 6 and the wireless transmitter 5 are kept in non-contact relative to each other to receive wireless signals. This embodiment uses a wireless transmitter and a wireless receiver. Since the wireless transmitter and the wireless receiver do not contact each other, pressure detection during rotation can be achieved, solving the problem that the prior art is not suitable for high-speed rotating parts.

[0058] This embodiment also provides a spline tooth surface pressure testing method, applied to the above-mentioned spline tooth surface pressure testing system, such as... Figure 4 As shown, it includes the following steps: S21. The external spline and internal spline, which integrate the thin-film sensor, are assembled and engaged. S22. Establish a signal transmission link, which includes a spline-tooth thin-film sensor, a wireless transmitter, and a wireless receiver; S23, drive the external spline to rotate; S24. The electrical signal generated by the thin film sensor due to the change in tooth surface contact pressure is acquired in real time through the signal transmission link; S25. Process the electrical signal to obtain dynamic distribution data of the pressure on the spline tooth surface.

[0059] The external spline integrating the thin-film sensor is engaged with the internal spline to form a structure like... Figure 3 The system shown activates the wireless transmitter and receiver, enabling the thin-film sensor to transmit the collected pressure information to the wireless receiver. Driving the external spline to rotate changes the pressure between it and the internal spline. The thin-film sensor generates an electrical signal due to this change in tooth surface contact pressure. This signal is then transmitted to the signal receiver via a signal transmission link. The signal receiver processes the signal to obtain dynamic distribution data of the spline tooth surface pressure.

[0060] The above embodiments, based on the high sensitivity of the thin-film sensor and its fit with the spline tooth surface, can improve the accuracy of pressure detection of the spline meshing structure and realize pressure detection during spline rotation.

[0061] In this embodiment, static calibration of the thin-film sensor is included before the step of driving the spline pair to rotate and transmitting torque.

[0062] Static calibration includes checking whether the resistance of the Wheatstone bridge in the thin-film sensor meets the design requirements, and performing static testing on the thin-film pressure sensor. Multiple measurements are taken, and the measurement results are compared with the preset pressure to check the quality of the thin-film pressure sensor, thereby improving the accuracy and reliability of the final measurement data.

[0063] It should be noted that: In the foregoing text, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0064] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0065] The embodiments of this application have been described above with reference to the accompanying drawings. These are merely specific implementations of this application, but this application is not limited to the specific implementations described above. The specific implementations described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method of producing a splined surface thin film sensor, characterized by, include: Preprocess the target tooth surface of the spline; An insulating layer is deposited on the pretreated tooth surface; A sensor functional layer is formed on the insulating layer by a patterning process. After patterning, the sensor functional layer has a Wheatstone bridge circuit and leads for acquiring signals. A protective layer is deposited on the tooth surface where the sensor functional layer is formed; The tooth surface with the protective layer deposited is polished to obtain the spline tooth surface thin film sensor.

2. The method of claim 1, wherein, The preprocessing of the target tooth surface of the spline includes: Grind the tooth surface until the roughness Ra of the target tooth surface is ≤0.1μm; The target tooth surface is cleaned and dried.

3. The method of claim 1, wherein, The insulating layer is any one of Al2O3 insulating layer, SiO2 insulating layer, and HfO2 insulating layer, and the thickness of the insulating layer ranges from 300 to 800 nm.

4. The method of claim 1, wherein, A sensor functional layer is formed on the insulating layer using a patterning process, including: Photoresist is sprayed onto the insulating layer; A photoresist is exposed to ultraviolet light using a mask to form a sensor pattern; In the toothed area where the sensor pattern has been formed, a Cu–Mn–Ni alloy thin film is deposited using DC or RF magnetron sputtering to form the Wheatstone bridge circuit, and a highly conductive metal is sputtered in the lead area to form the leads.

5. The method according to claim 4, characterized in that, The thickness of the Cu–Mn–Ni alloy film ranges from 4 to 6 μm.

6. The method according to claim 1, characterized in that, The thickness of the protective layer ranges from 1 to 3 μm.

7. A spline tooth surface pressure testing system, characterized in that, include: A thin-film sensor, wherein the thin-film sensor is integrated on the external spline tooth surface using the preparation method described in any one of claims 1-6, for converting spline tooth surface pressure into an electrical signal; The signal transmission unit includes a wire connected to the lead wire of the thin-film sensor and a wireless transmitter connected to the wire, the wireless transmitter being fixed to the end of the external spline shaft and rotating therewith; The signal receiving unit includes a wireless receiver, which is used to receive signals emitted by a wireless transmitter and process the signals to obtain pressure data.

8. The spline tooth surface pressure testing system according to claim 7, characterized in that, The signal receiving unit also includes a bracket, which is fixed to the end of the internal spline shaft. The internal spline and the external spline are engaged. The wireless receiver and the wireless transmitter are kept in a non-contact relationship to receive wireless signals.

9. A method for testing the pressure on the spline tooth surface, applied to the system described in claim 7 or 8, characterized in that, Includes the following steps: The external spline and internal spline of the integrated thin-film sensor are engaged; A signal transmission link is established, the link including the spline tooth surface thin film sensor, the wireless transmitter, and the wireless receiver; Drive the external spline to rotate; The electrical signal generated by the thin-film sensor due to the change in tooth surface contact pressure is acquired in real time through the signal transmission link. The electrical signal is processed to obtain dynamic distribution data of the pressure on the spline tooth surface.

10. The method for testing the pressure on the spline tooth surface according to claim 9, characterized in that, Prior to the step of driving the spline pair to rotate and transmitting torque, static calibration of the thin-film sensor is also included.

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