Sensor unit and motion measurement system using the same

The first buffer portion provides a first base portion and a first outer wall provided on a peripheral edge of the first base portion. The second buffer portion provides a second base portion which provides a mounting surface outside to a measurement target, and a second outer wall provided on a peripheral edge of the second base portion. The buffer body provides the first base portion and a top surface of the second outer wall abutting against each other. A housing portion for the sensor portion is provided inside. A holding portion which holds the sensor portion is provided at least at a part of the top surface of at least one of the first buffer portion and the second buffer portion. The sensor portion is held by the holding portion.

BACKGROUND

1. Technical Field

The present invention relates to a sensor unit and a motion measurement system or the like using the sensor unit.

2. Related Art

According to the related art, when a measurement device such as a motion sensor which detects acceleration, angular velocity and the like is mounted on a measurement target such as sporting equipment, a shock and vibration absorber is arranged between the measurement device and the measurement target. As the shock and vibration absorber damps a shock and vibration from the measurement target, the measurement device carries out accurate measurement without being affected by the shock and vibration.

According to JP-A-1-302169, a buffer is mounted on an outer surface of an exterior package of an acceleration sensor, thus preventing the sensor from being damaged by a fall when the sensor is carried around. The literature discloses the acceleration sensor can be mounted on a vehicle via the buffer.

According to JP-A-3-170065, on a first member with high mechanical strength which supports a substrate of an acceleration sensor, a buffer is provided parallel to a connector unit. As the connector is connected to a main body unit, the buffer is laid between the acceleration sensor and the main body unit.

According to JP-UM-A-7-008775, an elastic cover body with high shock absorptivity covers a housing of an acceleration sensor. According to JP-A-9-145738, a buffer is provided between an acceleration sensor and a substrate.

However, JP-A-1-302169 to JP-A-9-145738 do not disclose a structure to install a sensor portion such as an acceleration sensor onto sporting equipment.

FIG. 1shows a comparative example in which when a sensor portion2is mounted on sporting equipment, for example, on a mounting surface1bprovided at a grip end1aof a tennis racket1, a shock and vibration absorber3is provided as in-between, as in JP-A-1-302169 to JP-A-9-145738. In the case where a motion of the tennis racket1is measured by the sensor portion2, the shock and vibration absorber3can be provided as in-between as in the comparative example ofFIG. 1in order to prevent direct transmission of a shock and vibration generated when the tennis racket1strikes a ball to the sensor portion2.

Here, in order for the shock and vibration absorber3to absorb a strong shock and vibration at the time of striking, it is necessary to increase the volume of the shock and vibration absorber3or switch to a material that can easily absorb a shock and vibration.

However, if the volume of the shock and vibration absorber3is increased, for example, as shown inFIG. 2, the shock and vibration absorber3becomes heavier, making the whole racket1heavier and also changing weight balance of the tennis racket1. The shock and vibration absorber3protruding as shown inFIG. 2becomes an obstruction when a user holds the grip of the tennis racket1.

Meanwhile, if the material of the shock and vibration absorber3is softened so that the material can easily absorb a shock and vibration, as shown inFIG. 3, the sensor portion2itself swings, for example, in the direction of arrows shown inFIG. 3and cannot measure the motion of the tennis racket1accurately.

SUMMARY

An advantage of some aspects of the invention is to solve at least apart of the problems described above, and some aspects of the invention can be implemented as the following forms or application examples.

Application Example 1

This application example of the invention is directed to a sensor unit including: a buffer body having a first buffer portion and a second buffer portion that abuts against the first buffer portion and is softer than the first buffer portion; and a sensor portion arranged inside the buffer body. The first buffer portion provides a first base portion and a first outer wall provided on a peripheral edge of the first base portion. The second buffer portion provides a second base portion which provides a mounting surface outside to a measurement target, and a second outer wall provided on a peripheral edge of the second base portion. The buffer body provides the first base portion and the second base portion facing each other and also provides a top surface of the first outer wall and a top surface of the second outer wall abutting against each other. A housing portion for the sensor portion is provided inside. A holding portion which holds the sensor portion is provided at least at a part of the top surface of at least one of the first buffer portion and the second buffer portion. The sensor portion is held by the holding portion.

According to such a sensor unit, the first buffer portion and the second buffer portion that is softer than the first buffer portion are provided in the buffer body. The sensor portion is held by the holding portion provided at least a part of the top surface of at least one of the first buffer portion and the second buffer portion. In the sensor unit, since the first buffer portion is provided in such a way as to hold the second buffer portion down, the second buffer portion can be deformed easily, thus restraining transmission of a shock and vibration to the sensor portion. The first buffer portion absorbs an excess shock and vibration that cannot be absorbed by the second buffer portion.

Application Example 2

In the sensor unit according to the above application example, it is preferable that the housing portion is filled with a filler.

According to such a sensor unit, since the void is filled with the filler, the filler can hold the sensor portion. The filler absorbs deformation of the second buffer portion and can reduce transmission of the deformation to the sensor portion. Moreover, the filler can hold the sensor portion in a hollow state without making the sensor portion directly contact the second buffer portion. Therefore, transmission of a shock and vibration can be minimized.

Application Example 3

In the sensor unit according to the above application example, it is preferable that the sensor portion provides a sensor mounted on a substrate and that a peripheral edge portion of the substrate is held by the holding portion.

According to such a sensor unit, the substrate provided in the sensor portion is held by the holding portion with a gap to avoid abutting against the first buffer portion. Thus, transmission of a shock and vibration from the first buffer portion to the sensor portion held by the holding portion of the second buffer portion can be restrained. Also, since a shock and vibration applied to the second buffer portion is transmitted to the first outer wall abutting against the second outer wall, by providing a gap between the first buffer portion and the substrate, transmission of a shock and vibration transmitted to the first buffer portion to the sensor portion via the substrate held by the holding portion can be restrained.

Application Example 4

In the sensor unit according to the above application example, it is preferable that there is a gap between the substrate and the top surface.

According to such a sensor unit, a gap is provided between the substrate and the top surface, and the sensor portion is provided in the housing portion. In the sensor unit, a shock and vibration is absorbed mainly by the deformation of the second buffer portion and transmission of the shock and vibration to the sensor portion provided in the housing portion can be restrained. Also, in the case where a gap is provided between the substrate and the top surface, and the housing portion is a void, the sensor portion cannot abut against the buffer body except on the holding portion. Therefore, direct transmission of the shock and vibration to the sensor portion can be restrained.

Application Example 5

In the sensor unit according to the above application example, it is preferable that the first buffer portion and the second buffer portion are fitted with each other.

According to such a sensor unit, the top surface of the first buffer portion and the second buffer portion are fitted with each other. Therefore, a shock and vibration from a measurement target is absorbed by the deformation of the second buffer portion. Moreover, when an excess shock and vibration that cannot be absorbed by the second buffer portion is transmitted to the first buffer portion, a shift of the first buffer portion and the second buffer portion from each other can be restrained.

Application Example 6

In the sensor unit according to the above application example, it is preferable that the second buffer portion provides a smaller specific gravity than the first buffer portion.

According to such a sensor unit, since the second buffer portion provides a smaller specific gravity than the first buffer portion, the first buffer portion can have a greater weight than the second buffer portion and deformation of the second buffer portion by the weight of the first buffer portion can be restrained.

Application Example 7

This application example of the invention is directed to a motion measurement system including the above sensor unit.

According to such a motion measurement system, since the system includes the above sensor unit, the buffer body can absorb an excessive shock and vibration that is generated, for example, by a strike with a measuring target. Thus, an unwanted shock and vibration for measurement of a motion of the measuring target can be damped.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the invention will be described with reference to the drawings. In the drawings described below, each component is shown in a large enough size to be recognized in the drawings and therefore the dimension and proportion of each component may be different from the actual component according to need. Also, an XYZ orthogonal coordinate system is set and the positional relation of each portion is described with reference to this XYZ orthogonal coordinate system. A predetermined direction within a vertical plane is defined as an X-axis direction. A direction orthogonal to the X-axis direction within the vertical plane is defined as a Y-axis direction. A direction orthogonal to each of the X-axis direction and the Y-axis direction is defined as a Z-axis direction. Referring to the gravitational direction, the gravitational direction is defined as a downward direction and the opposite direction is defined as an upward direction.

First Embodiment

FIG. 4is a sectional view schematically showing a cross section of a sensor unit according to a first embodiment of the invention. A sensor unit10aaccording to the first embodiment shown inFIG. 4provides a sensor portion20and a buffer body30.

The sensor portion20provides a three-axis acceleration sensor and a three-axis angular velocity sensor, and a drive circuit and a signal processing circuit for the sensors, for example, installed on face and back sides of a substrate22a. The maximum acceleration that can be measured by the sensor portion20is, for example, 50 G.

The buffer body30provides a first buffer portion30aand a second buffer portion30b. The first buffer portion30aprovides a first base portion34aand a first outer wall32aextending from the first base portion34a. The second buffer portion30bprovides a second base portion34b, a second outer wall32bextending from the second base portion34b, and a holding portion36at one end opposite to the second base portion34b, of the second outer wall32b. In the sensor unit10aof this embodiment, plural first outer walls32aand second outer walls32bare extending from the first base portion34aand the second base portion34b. However, the number of these walls is not limited to this example and a set of a first outer wall32aand a second outer wall32bmay be provided. In this embodiment, a form in which two first outer walls32aand two second outer walls32bare extending is described.

In the buffer body30, the first base portion34aand the second base portion34bfact each other and the first outer walls32aand the second outer walls32babut against each other. The second base portion34bis bonded and fixed to the mounting surface1bof the tennis racket1(seeFIG. 1), for example, with a double-side adhesive tape or the like, using a surface opposite to the first base portion34aas a mounting surface34c. Also, the buffer body30provides a housing portion50that is surrounded by the first base portion34a, the second base portion34b, the first outer walls32a, and the second outer walls32b.

In the buffer body30, a shock and vibration transmitted from the mounting surface34cis absorbed by the second buffer portion30b. An excess shock and vibration that cannot be absorbed there is transmitted from the second outer walls32bto the first outer walls32aof the first buffer portion30aand is absorbed by the first buffer portion30a.

The sensor portion20is provided in the housing portion50. A peripheral edge portion22bthat is an edge portion of the substrate22ais held by the holding portions36provided on top surfaces37bof the second outer walls32bof the second buffer portion30b. The substrate22ais held by the holding portions36with a gap to avoid abutment against top surfaces37aprovided on the first outer walls32aof the first buffer portion30a. Therefore, when a shock and vibration is transmitted from the second outer walls32bto the first outer walls32a, transmission of the shock and vibration to the sensor portion20via the substrate22aheld there can be restrained.

While the holding portions36in this embodiment are provided on the top surfaces37b, the holding portions36may also be provided on the top surfaces37a. In such a case, the substrate22aheld by the holding portions36is provided in such a way as to avoid abutting against the top surfaces37b.

As the member used for the second buffer portion30b, a softer material than the member used for the first buffer portion30ais used. In other words, as the member used for the first buffer portion30a, a harder material than the member used for the second buffer portion30bis used. Also, the second buffer portion30buses a member with smaller specific gravity than the first buffer portion30a. In other words, the first buffer portion30auses a member with a greater specific gravity than the second buffer portion30b. In the buffer body30, for example, if rubber is used for the first buffer portion30a, urethane foam can be used for the second buffer portion30b. The member used for the first buffer portion30amay be silicone resin and the like as well as rubber. The member used for the second buffer portion30bmay be polyurethane and the like as well as urethane foam.

The buffer body30in the first embodiment of the invention provides a shock and vibration absorbing structure that is formed as a two-stage structure. The first buffer portion30ausing the harder material is superimposed on the second buffer portion30busing the softer material.

In the buffer body30, since the first buffer portion30amade of the harder material and with a greater specific gravity is superimposed on the second buffer portion30bmade of the softer material and with a smaller specific gravity, the second buffer portion30bcan be formed easily and can restrain a shock and vibration. The first buffer portion30acan absorb an excess shock and vibration that cannot be absorbed by the second buffer portion30b.

Thus, a shock and vibration that is generated when the tennis racket1shown inFIG. 1hits a ball or the like is absorbed by the first buffer portion30aand the second buffer portion30bof the sensor unit10aand cannot be easily transmitted to the sensor portion20, as shown inFIG. 5.

On the other hand, in the comparative example shown inFIGS. 1 to 3, a shock and vibration that is generated when the tennis racket1strikes an object or the like is absorbed by the shock and vibration absorber3and thus damped, as shown inFIG. 6. However, since the sensor portion2exists in the escape path of the shock and vibration that cannot be absorbed by the shock and vibration absorber3, an excessive shock and vibration is directly transmitted to the sensor portion2in a so-called rear-end collision state.

InFIG. 4, the housing portion50as an in-between can be further provided between the second buffer portion30band the sensor portion20. Thus, deformation of the second buffer portion30bcan be absorbed by the housing portion50and therefore transmission of a shock and vibration to the sensor portion20can be reduced further.

In the buffer body30, the housing portion50can allow (absorb) deformation generated in the second outer walls32band the second base portion34bby a shock and vibration. This housing portion50can be a void (air gap). By forming the housing portion50as a void, deformation of the second buffer portion30bis absorbed by the housing portion50and transmission of the deformation to the sensor portion20can be reduced.

FIGS. 7A to 9Cshow graphs illustrating the results of shock and vibration tests.

FIGS. 7A to 7Cshow graphs illustrating the results of measurement in which the sensor portion2is mounted via amounting jig onto the mounting surface1bof the tennis racket1shown inFIG. 1(without the shock and vibration absorber3).

FIGS. 8A to 8Cshow graphs illustrating the results of measurement in which the sensor portion2is mounted via the shock and vibration absorber3by the method of the comparative example shown inFIG. 1.

FIGS. 9A to 9Cshow graphs illustrating the results of measurement in which the sensor unit10aof this embodiment shown inFIG. 4is mounted on the mounting surface1bof the tennis racket1shown inFIG. 1.

FIGS. 7A to 9Cshow data as a result of measuring acceleration on three axes (X, Y and Z axes) when the tennis racket1is dropped in the Z-axis direction from the same height.

FIG. 7A,FIG. 8AandFIG. 9Aeach show acceleration in the Z-axis direction.FIG. 7B,FIG. 8BandFIG. 9Beach show acceleration in the Y-axis direction.FIG. 7C,FIG. 8CandFIG. 9Ceach show acceleration in the X-axis direction. A comparison between the graphs shown inFIGS. 7A to 7CandFIGS. 8A to 8Cshows that the time when a strong shock (acceleration) in the Z-axis direction is received is shorter in the graph ofFIG. 8A. This can be recognized as the effect of inserting the shock and vibration absorber3ofFIG. 1. Meanwhile, the graphs ofFIGS. 8B and 8Cshow greater changes in acceleration in the X and Y-axis directions than in the graphs shown inFIGS. 7B and 7C. It can be considered that this is because the swing of the sensor portion2itself becomes larger as the shock and vibration absorber3ofFIG. 1is inserted.

Meanwhile, in the graph shown inFIG. 9Aillustrating data as a result of measurement by the sensor unit10aof this embodiment, the time when a strong shock (acceleration) in the Z-axis direction is received is much shorter than in the graph shown inFIG. 8A, and the time when the influence of a shock and vibration is received is shorter also in the X-axis direction and the Y-axis direction, as shown in the graphs ofFIGS. 9B and 9C. Thus, high effects can be confirmed.

The sensor unit10aof the embodiment provides the following effects.

According to such a sensor unit10a, the sensor portion20which measures acceleration and the like of a measurement target is provided in the buffer body30with a structure in which the first buffer portion30aand the second buffer portion30bwhich are different in specific gravity and hardness are superimposed on each other. Thus, in the sensor unit10a, the second buffer portion30bis deformed to absorb a shock and vibration from a measurement target and the deformation of the second buffer portion30bis restrained by the first buffer portion30a. Therefore, transmission of the shock and vibration to the sensor portion20can be restrained.

Second Embodiment

A sensor unit10baccording to a second embodiment of the invention is shown inFIG. 10. The sensor unit10bshown inFIG. 10is different from the sensor unit10ashown inFIG. 4in that a part of the first outer wall32aand a part of the second outer wall32bof the buffer body30extend respectively and the first buffer portion30aand the second buffer portion30bare jointed together in a box-joint form. Hereinafter, different features from the sensor unit10aaccording to the first embodiment are described, whereas the same configurations are denoted by the same reference numerals and the description thereof is partly omitted.

The sensor unit10bprovides a sensor portion20and a buffer body30, similarly to the sensor unit10aaccording to the first embodiment. The buffer body30provides a first buffer portion30aand a second buffer portion30bmade of different materials from each other. The buffer body30also provides a housing portion50that is surrounded by the first buffer portion30aand the second buffer portion30b.

As shown inFIG. 10, in the buffer body30of the sensor unit10b, the first outer wall32aof the first buffer portion30aand the second outer wall32bof the second buffer portion30bare jointed together in a box-joint form. The first outer wall32aextends a portion substantially half its thickness so as to protrude as a box joint portion33atoward the second outer wall32b. The second outer wall32bextends a portion substantially half its thickness and different from the extended portion of the box joint portion33awhen joined with (fitted with) the first outer walls32a, so as to protrude as a box joint portion33btoward the first outer wall32a.

In the buffer body30, a holding portion36is provided between the box joint portion33bextending toward the second outer wall32band the second outer wall32b. The sensor portion20is provided in the housing portion50, as in the sensor unit10a. A peripheral edge portion22bthat is an edge portion of a substrate22ais held by the holding portion36provided on the second buffer portion30b.

The sensor unit10bof the embodiment provides the following effect.

The sensor unit10bprovides a structure such that when the sensor unit10breceives a shock and vibration, the shock and vibration is absorbed by the first buffer portion30aand the second buffer portion30band is not easily transmitted to the sensor portion20, as in the foregoing sensor unit10a. Also, in the buffer body30, since the first outer wall32aand the second outer wall32bare jointed together in a box-joint form, the area where the first outer wall32aand the second outer walls32babut against each other is greater than in the sensor unit10a. Thus, in the sensor unit10b, a shock and vibration transmitted from the mounting surface34cis absorbed by the second buffer portion30b, and when the shock and vibration is transmitted to the first buffer portion30a, the transmission to the first buffer portion30acan be made efficiently. Moreover, when the shock and vibration is transmitted from the second buffer portion30bto the first buffer portion30a, a “shift” of the first buffer portion30aand the second buffer portion30bfrom each other can be restrained.

Third Embodiment

A sensor unit10caccording to a third embodiment is shown inFIG. 11. The sensor unit10cshown inFIG. 11is different from the sensor unit10ashown inFIG. 4in that the housing portion50having a void is filled with a filler60. Different features from the sensor unit10aaccording to the first embodiment are described, whereas the same configurations are denoted by the same reference numerals and the description thereof is partly omitted.

The filler60fills the gap between a first outer wall32a, a second outer wall32b, a first base portion34aand a second base portion34b, and a sensor portion20. In other words, the filler60fills the void of the housing portion50in which the sensor portion20is provided. As the filler60, a member that solidifies after filling the void is used. In this embodiment, for example, a potting material such as trade name TSE3051 (TANAC Co., Ltd.) or trade name 1230G (ThreeBond Co., Ltd.) can be preferably used as the filler60.

While the sensor portion20is held by the holding portion36provided on the top surface37bof the second outer wall32bin the foregoing example as shown inFIG. 4, a substrate22aof the sensor unit10caccording to the third embodiment shown inFIG. 11need not be held since the filler60fills the housing portion50. This is because the sensor portion20can be held by the filler60within the housing portion50. Thus, the sensor portion20does not directly contact the second buffer portion30b(second outer wall32b), transmission of deformation of the second buffer portion30bto the sensor portion20can be restrained. Therefore, the swing of the sensor portion20due to a shock and vibration can be reduced.

As the sensor unit10c, a form in which the housing portion50of the sensor unit10ashown inFIG. 4is filled with the filler60is described. However, a form in which the housing portion50of the sensor unit10bshown inFIG. 10is filled with the filler60may also be employed.

The sensor unit10cof the embodiment provides the following effects.

According to the sensor unit10c, the sensor portion20can be fixed to the first base portion34aof the first buffer portion30avia the filler60filling the housing portion50. Thus, the sensor portion20is fixed via the filler60onto the first base portion34ahaving the least deformation in the buffer body30and therefore the swing of the sensor portion20can be reduced. Also, since the sensor portion20does not directly abut against the buffer body30, transmission of a shock and vibration to the sensor portion20from the buffer body30can be restrained.

Fourth Embodiment

FIG. 12shows the configuration of a motion measurement (analysis) system according to this embodiment. A motion measurement system100of this embodiment includes one of the above sensor units10a,10b,10c(hereinafter referred to as a “sensor unit10” where the unit is called by a general term) and a host terminal150, and measures and analyzes a motion of a measurement target (for example, the tennis racket1). The sensor portion20provided in the sensor unit10and the host terminal150may be connected wirelessly or wire-connected.

The sensor unit10is mounted on a measurement target of motion measurement (analysis), for example, on the tennis racket1shown inFIG. 1, and carries out processing to detect a predetermined physical quantity. In this embodiment, the sensor portion20includes, for example, plural sensors102xto102zand104xto104z, a data processing unit110, and a communication unit120, also as shown inFIG. 13.

Here, the sensors are sensors which detect a predetermined physical quantity and output a signal (data) corresponding to the magnitude of the detected physical quantity (for example, acceleration, angular velocity and the like). In this embodiment, a six-axis motion sensor including three-axis acceleration sensors102xto102zwhich detect acceleration in the X-axis direction, Y-axis direction and Z-axis direction (an example of an inertial sensor) and three-axis gyro sensors104xto104zwhich detect angular velocity in the X-axis direction, Y-axis direction and Z-axis direction (an example of an angular velocity sensor and inertial sensor) is provided.

The data processing unit110carries out processing to synchronize output data from the respective sensors102xto102zand104xto104z, combine the output data with time information and the like to form a packet, and output the packet to the communication unit120. The data processing unit110may also carry out processing of bias correction and temperature correction on the sensors102xto102zand104xto104z. The functions of bias correction and temperature correction may be incorporated in the sensors themselves.

The communication unit120carries out processing to transmit the packet data received from the data processing unit110, to the host terminal150.

The host terminal150shown inFIG. 12includes a processing unit (CPU)200, a communication unit210, an operation unit220, a ROM230, a RAM240, a non-volatile memory250, and a display unit260.

The communication unit210carries out processing to receive the data transmitted from the sensor portion20and send the data to the processing unit200. The operation unit220carries out processing to acquire operation data from a user and send the operation data to the processing unit200. The operation unit220is, for example, a touch panel display, button, key, microphone and the like.

The ROM230stores programs for the processing unit200to carry out various kinds of calculation and control processing, and various programs and data to realize application functions. The RAM240is a storage unit which is used as a work area for the processing unit200and which temporarily stores programs and data read out from the ROM230, data inputted from the operation unit220, and results of arithmetic operations executed by the processing unit200according to various programs. The non-volatile memory250is a storage unit which records data that needs to be saved for an extended period, of data generated in the processing by the processing unit200.

The display unit260is to display results of processing by the processing unit200, in the form of characters, graphs, or other images. The display unit260is, for example, a CRT, LCD, touch panel display, HDM (head-mounted display) and the like. Also, the functions of the operation unit220and the display unit260may be realized by a single touch panel display.

The processing unit200carries out various kinds of calculation processing with respect to data received from the sensor portion20via the communication unit210and various kinds of control processing (display control to the display unit260and the like) according to programs stored in the ROM230.

In this embodiment, the processing unit200includes a data acquisition unit202, an arithmetic operation unit204, a data correction unit206, and a motion measurement (analysis) information generation unit208. The data acquisition unit202carries out processing to acquire output data from the sensors102xto102zand the sensors104xto104z. The acquired data is stored, for example, in the RAM240. The arithmetic operation unit204carries out arithmetic operation to calculate m-order time integration of the output data from the sensor portion20. Thus, velocity data and position data are generated based on acceleration data. Alternatively, an angle is generated based on angular velocity data.

The data correction unit206corrects the result of the arithmetic operation by the arithmetic operation unit204, for example, based on known data of a standstill state. The motion measurement (analysis) information generation unit208carries out processing to generate information for measuring (analyzing) a motion of a measurement target (hereinafter referred to as “motion analysis information”), based on the corrected data from the data correction unit206. The generated motion analysis information may be displayed on the display unit260in the form of characters, graphs, diagrams and the like, or may be outputted outside the host terminal150. The arithmetic operation unit204, the data correction unit206, and the motion measurement (analysis) information generation unit208are an example of a motion measurement (analysis) unit.

The motion measurement system100of the embodiment provides the following effects.

According to the motion measurement system100, since the system includes the sensor unit10, an excessive shock and vibration that is generated, for example, by hitting an object with the measurement target, can be absorbed by the first buffer portion30aand the second buffer portion30b. Thus, measurement of an unwanted shock and vibration for motion measurement of the measurement target can be restrained and a predetermined physical quality of the measurement object can be measured accurately.

The invention is not limited to the above embodiments and various changes, improvements and the like can be added without departing from the scope of the invention. A modification is described hereinafter.

The sensor portion20in the sensor units10a,10b,10ccan be an inertial measurement unit20a. A sensor unit10dshown inFIG. 14includes the inertial measurement unit20aand a buffer body30, and the buffer body30includes a first buffer portion30aand a second buffer portion30b, as in the sensor units10a,10b,10c. The inertial measurement unit20ais provided in a housing portion50, and a mounting portion22cextending from the inertial measurement unit20ais held by a holding portion36provided on a second outer wall32bof the second buffer portion30b. Thus, in the sensor unit10d, a shock and vibration can be absorbed by the buffer body30, for example, when the sensor unit10dis mounted on the tennis racket1(seeFIGS. 1 to 3) and the like. Therefore, transmission of the shock and vibration to the inertial measurement unit20acan be restrained.

The entire disclosure of Japanese Patent Application No. 2012-127814, filed Jun. 5, 2012 is expressly incorporated by reference herein.