JP4911356B2 - Small animal positioning system - Google Patents

Description

  The present invention relates to a position measurement system for collecting position information of small animals such as mice in a breeding case by measuring several loads.

  Conventionally, as a method of collecting not only the position information of small animals but also the movement and position of an object, a method of capturing an image using a video camera or the like and acquiring the movement and position by human eyes is generally used. ing.

  A method for measuring the position of a small animal using a large number (64) of infrared sensors has been proposed. (KUROBOX made by Phenotype Analyzing)

  In addition, a method of providing a plurality of load sensors in the periphery of the plate to which a load is applied and measuring the load, such as a centroid shaker, and deriving the center of gravity, that is, the position of the small animal from the result can be considered. (See Patent Document 1)

JP-A-48-17784

  The technique using a video camera or the like is expensive and requires specialized knowledge when performing image processing. Furthermore, in order to observe about 10 animals at the same time, a large number of video cameras are required, which increases the initial investment. In addition, if it is necessary to observe in a dark place, an expensive infrared video camera is required.

  The method using an infrared sensor requires a large number of infrared sensors in order to increase the spatial resolution, which also results in an expensive system.

  The method of deriving the center of gravity and weight using a structure such as a center-of-gravity sway meter has multiple load cells installed, so the cost of the load cell affects the overall cost.

  Here, it is considered to observe an experimental mouse in a breeding case by the same technique as that of the center of gravity shake meter. The experimental mouse has a very light weight of about 10 g to 30 g, and a load meter is required to have high sensitivity in order to accurately grasp a load change of about several tens mg due to the movement.

  On the other hand, a general breeding case is about 1 kg when food and water are set, and the load meter needs a measurement range that can measure this weight.

  In order to observe minute changes due to the movement of small animals that are light and heavy in the overall weight, a load meter with a wide dynamic range is required to some extent. A system using such a load meter is still expensive. It becomes a system.

  An object of the present invention is to provide a small animal position measurement system at low cost without using expensive equipment as described above.

  In a method for obtaining the center of gravity using a mechanism such as a center of gravity shaker, a fulcrum that mainly supports weight is added to estimate the position information of small animals, apart from a load meter that measures minute load changes due to changes in the center of gravity. It is assumed that the system is added with a function of acquiring reference data necessary for this.

  Specifically, using a device that obtains the center of gravity by providing a plurality of load meters around the plate where the load is applied, such as a center of gravity shake meter, position information of small animals such as mice present in the breeding case placed on it In a system having a plate for placing a breeding case, four load meters for holding the plate in the periphery of the plate, and an inner side of a quadrangle whose apex is the power point of the four load meters It has a load measuring unit characterized by having one support column supporting the load, and has a reference data collection function and a calculation function for converting the information obtained from the load meter into the position information of the small animal. A position measurement system for a small animal having a function of outputting position information and a function of accumulating.

  Further, the position measuring system of a small animal may be characterized by having three load cells and one support column for supporting a load inside a triangle having a vertex of the force point of the three load cells.

  In addition, the present invention is a small animal position measuring system characterized in that it has two load cells, has one support column that supports the load applied to the plate, and can form a triangle with two load points and one support column. Also good.

  Further, the position measuring device for a small animal may be characterized in that a sensor is added only to two adjacent load meters among the four load meters or only to three load meters.

  Further, as a method for measuring the load, a small animal position measuring device may be used, in which a cantilever leaf spring is formed and the displacement is obtained by a strain gauge.

  The position information of the small animal is information indicating where on the xy plane (bottom surface) the small animal such as a mouse to be measured exists.

  The force point of the load cell is a portion where a load is applied to the load cell, specifically, a contact point between the load cell and the plate on which the breeding case is installed. If the plate on which the breeding case is installed is equipped with a load meter, it refers to the contact point between the load meter and the ground, or between the load meter and the lower plate.

  The reference data is a value indicating the relationship between the actual position of the small animal in the breeding case and information obtained from the load meter at that position.

  The information obtained from the load cell may be an actual weight (gram) or a change in resistance value due to displacement of the load cell.

  When there are four load cells, for example, the arrangement is as shown in FIG. FIG. 1 is a top view. The support column 2 that supports the load exists inside the quadrangle 111 having the force points 132, 142, 152, and 162 of the load cell as apexes. Although the support column 2 is expressed in the central portion, it may not be the central portion.

  When there are three load cells, for example, the arrangement is as shown in FIG. A support column 2 that supports a load exists inside a triangle 211 having apexes at the force points 232, 242 and 272 of the load cell. Although the support column 2 is expressed in the central portion, it may not be the central portion.

  When there are two load cells, for example, the arrangement is as shown in FIG. The force points 332 and 342 of the load cell and the support column 2 that supports the load constitute a triangle 311. The meaning of forming a triangle is to make a plane. If the three points are aligned, a problem arises because a plane cannot be formed.

  The sensor is added only to the two adjacent load cells among the four load cells. The remaining two load cells do not have a sensor. In other words, the load is displaced but there is no output. That's what it means. This corresponds to the case where four load meters are made of cantilever leaf springs, and sensors such as strain gauges are added to only two of them. Similarly, sensors are added to only three load cells.

  The two adjacent load meters are, for example, load meter 132 and load meter 142, load meter 142 and load meter 152, load meter 152 and load meter 162, or load meter 162 and load meter 132 in FIG. It is.

  There is a technique for measuring the unbalance of an automobile tire as a thing that is very similar to the idea of providing a fulcrum that mainly supports the load and measuring the load at other places (see Patent Document 2). A position where the center of gravity is thought to be supported is supported, a plurality of load cells are installed in the periphery, and an unbalance amount and a position for correcting the unbalance are calculated from the output of the load cell.

JP-A-57-146125

  The technique of Patent Document 2 can only obtain an unbalance amount and a position for correcting the unbalance, and cannot obtain position information of a small animal as it is.

  The present invention adds a function of collecting reference data in order to obtain position information of a small animal, thereby enabling information obtained from a load cell to be converted into a position of a small animal in real time. .

  By providing a fulcrum that mainly supports weight, the load meter that measures the load change does not require a large load, and as a result, a system can be constructed with an inexpensive load meter that does not require a wide dynamic range.

  In addition, animal behavior studies that collect position information of small animals such as experimental mice and analyze their behavior are effective means of evaluating their effects and functions in the field of drug development and functional food development. ing.

  However, the position information of small animals cannot be collected as easily as expected. To achieve this, a system must be constructed using expensive equipment. Also, in experiments that are judged by significant differences, experiments are usually performed with about 10 mice at the same time. Therefore, a large amount of money is required for system construction, which is a high hurdle for research and development.

  If an inexpensive system can be provided, it will be introduced even in research and development institutions that have not been easily evaluated so far, and it will be possible to establish a system in which more researchers can actively conduct research. Therefore, it can contribute to the improvement of academic level in research and development of pharmaceuticals and functional foods.

  First, the case where there are four load cells will be described with reference to FIGS. 4 and 5. FIG. 4 is a configuration diagram of the load measuring unit viewed from the top surface, and FIG. 5 is a configuration diagram viewed from the side surface. As a method for measuring the load, a cantilever leaf spring is formed and the displacement is obtained by a strain gauge. It is assumed that a mouse rearing case 8 is placed on the plate 1 of the position measuring device, and the mouse is in the inside.

  A column 2 for supporting the weight is installed in the central portion of the plate 1. The column does not have to be particularly at the center of the plate, but is preferably near the center in order to sufficiently support the weight. Hereinafter, the column 2 will be referred to as the center column 2 for convenience.

  In the periphery of the plate 1, cantilever leaf springs 31, 41, 51, 61 having the same shape are formed so that a rectangular vertex having the central column 2 as an intersection of diagonal lines becomes a force point to which a force is applied. Supports 32, 42, 52 and 62 are installed at each power point. Hereinafter, columns other than the central column 2 will be referred to as peripheral columns for convenience.

  The central support column 2 may not exist at the intersection of the rectangular diagonal lines formed by the peripheral support columns, but the intersection is desirable in consideration of the ease of calculation.

  The peripheral columns 32, 42, 52, 62 and the central column 2 are basically fixed to the lower plate 9, but need not be particularly fixed. Further, the lower plate 9 is not particularly required. In this case, the load measuring unit is directly installed on the table or the ground.

  The peripheral struts 32, 42, 52, 62 and the central strut 2 have the same length when fixed to the lower plate 9. If not fixed, the length is adjusted so that the four peripheral struts do not leave the lower plate 9 or the ground even when the plate 1 is tilted as the load changes during use.

  The stoppers 33, 43, 53, and 63 protect the cantilever leaf spring when an unintended load is applied. The length is adjusted to a length that does not hinder the inclination of the plate 1.

  Strain gauges 34, 44, 54, 64 (front side), 35, 45, 55, 65 (back side) are affixed to the roots of the cantilever leaf springs 31, 41, 51, 61. Sensitivity can be increased by attaching eight strain gauges.

  The number of strain gauges does not have to be 8 in particular, and in the case of the smallest number, it is only necessary to attach a total of 2 strain gauges to 2 adjacent cantilever springs. In many cases, it can be installed as long as space permits.

Since the load measuring unit moves like a 360-degree seesaw with the central support column 2 as a fulcrum, the amount of change in the strain gauge due to the change in the center of gravity is basically in the relationship of Equation 1 and Equation 2.

  For this reason, the balanced bridge for converting the resistance value of the strain gauge into a voltage value can be assembled as shown in FIG. As a result, the resistance value of the strain gauge is combined into two outputs, output A and output B, and the number of channels for A / D conversion for taking data into a personal computer or the like is two. Outputs A and B may be amplified and A / D converted as necessary.

When the x-axis and y-axis are set parallel to each side of the breeding case, the output A and output B are as shown in FIG. The output A is a vector in the direction from the central column 2 to the column 42 or the column 62, and the output B is a vector in the direction from the center column 2 to the column 32 or the column 52. Although depending on how the voltage of the parallel bridge is applied, the direction of the column 42 and the direction of the column 32 are positive for convenience. Equation 3 is used to convert this into values in the x-axis and y-axis directions.

  Here, since the values in the x-axis and y-axis directions do not directly indicate the position in the breeding case, conversion corresponding to the coordinates of the breeding case is required.

  The coordinate conversion will be described with reference to FIG.

  Coordinates A1, A2, A3, and A4 are obtained by directly plotting the values in the x-axis and y-axis directions obtained from the outputs A and B obtained when the mouse is in the corner of the breeding case on the xy plane. When the small animal moves in the breeding case, the obtained data is generally within the range of a quadrilateral (A1, A2, A3, A4) with these four points as vertices. The reason why this square is distorted is due to individual differences in strain gauges, variations in strain gauge application, variations in the length, thickness, and width of the leaf spring, deviation of the initial center of gravity from the central support column 2, and the like.

  Coordinates B1, B2, B3, and B4 are obtained by plotting the coordinates of the four corners of the breeding case. By calculating A1 to B1, A2 to B2, A3 to B3, and A4 to B4, and calculating so that the internal points are equally distributed, it can be approximated to the actual position.

  First, consider converting A1 to B1. D1 represents a vector (size and direction) of conversion in A1. Converting A1 to B1 means that the quadrangle (A1, A2, A3, A4) becomes a quadrangle (B1, A2, A3, A4).

  By this conversion, arbitrary coordinates C1 inside the rectangle (A1, A2, A3, A4) are converted into coordinates C2. D2 is a vector of conversion in C1, and its direction is the same as D1.

  Here, since the line segment (A3, A4) and the line segment (A3, A2) do not change after conversion, if C1 is on the line segment (A3, A4) or on the line segment (A3, A2) It is not transformed and stays at the same coordinates. That is, the closer the coordinates are to the line segment (A3, A4) or the line segments (A3, A2), the smaller the conversion size, and conversely, the closer the coordinates are to the coordinate A1, the closer the conversion size is to the size of D2. .

  In order to obtain the ratio, E1, E2, E3, and E4 are determined. Here, the straight line 1 is a straight line passing through A3 and A4. Similarly, the straight line 2 is A1 and A2, the straight line 3 is A1 and A4, and the straight line 4 is a straight line passing through A3 and A2.

  The straight line 5 is a straight line passing through the intersection of the straight line 3 and the straight line 4 and C1. When the straight line 3 and the straight line 4 are parallel, the straight line passing through C1 with the same inclination as the straight line 3 is used. The intersection of the straight line 5 and the straight line 1 is E4, and the intersection of the straight line 5 and the straight line 2 is E2.

  The straight line 6 is a straight line passing through the intersection of the straight line 1 and the straight line 2 and C1. When the straight line 1 and the straight line 2 are parallel, the straight line passing through C1 with the same inclination as the straight line 1 is used. Assume that the intersection of the straight line 6 and the straight line 3 is E1, and the intersection of the straight line 6 and the straight line 4 is E3.

By dividing each of the line segment (E4, E2) and the line segment (E3, E1) by C1, the magnitude of the conversion at C1 can be expressed by the ratio of the line segment. The size of the vector D2 is obtained by the following equation (4).

  By performing the same conversion at A2, A3, and A4, the coordinates inside the rectangle (A1, A2, A3, A4) can be converted into the coordinates inside the rectangle (B1, B2, B3, B4).

  In this conversion, if the coordinates A1, A2, A3, and A4 when the mouse is in the four corners of the breeding case can be grasped, the conversion amount of the arbitrary coordinates C1 can be derived. Therefore, A1, A2, A3, and A4 are obtained at the initial stage of the experiment. A function to grasp as reference data is added to the program.

  Specifically, a square imitating the bottom of the breeding case is displayed on the personal computer screen. When the experimental mouse approaches each of the four corners of the breeding case, the position of the experimental mouse is visually confirmed, and the corresponding position of the rectangle on the personal computer screen is clicked with the cursor. Since the xy coordinates on the clicked personal computer screen are obtained inside the program, this can be realized by replacing it with the coordinates of the breeding case.

  In this method, even when the experimental mouse does not move to exactly four corners, it can be specified easily and accurately in the vicinity thereof, so that the labor of collecting reference data can be greatly reduced.

  This calculation can be performed by collecting all the data and then picking up the coordinates A1, A2, A3, and A4 from the collected data.

  Next, the case where there are three load cells will be described with reference to FIGS. The structure of cantilever leaf springs, struts, stoppers, etc. is the same as when there are four load cells. The straight line formed by the column 72 and the center column 2 is arranged so as to be parallel to the x-axis, but may not be particularly parallel.

  A total of six strain gauges are affixed on both sides of all three leaf springs. It is also possible to affix only on one side of each.

  The affixed strain gauge forms a balanced bridge for each leaf spring. As a result, there are three strain gauge values, output A, output B, and output C, and the number of A / D conversion channels is three.

When the x-axis and y-axis are set parallel to each side of the breeding case, outputs A, B, and C are as shown in FIG. The output A is a vector in the direction from the central column 2 to the column 42, or the direction opposite to 180 degrees, the output B is a vector in the direction from the central column 2 to the column 32, or the direction opposite to 180 degrees, and the output C is the vector in the direction opposite to the center column 2. It becomes a vector in the direction from 72 to the direction of the column 72 or the opposite direction. Although depending on how the voltage of the parallel bridge is applied, the direction of the column 42, the direction of the column 32, and the direction of the column 72 are positive for convenience. Equation 5 is used to convert this into values in the x-axis and y-axis directions.

  Here, when the straight line formed by the column 72 and the central column 2 is not parallel to the x-axis, a value obtained by multiplying the coefficient in the output C is added to or subtracted from the value in the y-axis direction of Equation 5.

  The conversion to the coordinates of the breeding case is the same as when there are four load cells.

  Next, the case where there are two load cells will be described with reference to FIGS. This is a configuration in which there are no two adjacent load cells when there are four load cells. The structure of the cantilever leaf spring, the support column, the stopper, and the like is the same as that when there are four load cells, but in this configuration, it is essential to fix the support columns 32 and 42 to the lower plate 9. The central support column 2 is desirably installed near the center of the plate 1 so that the center of gravity of the rearing case can be almost directly above.

  A total of four strain gauges are attached to both sides of two leaf springs. It is also possible to affix only on one side of each.

  The affixed strain gauge forms a balanced bridge for each leaf spring. As a result, the strain gauge values are output A and output B, and the number of channels for A / D conversion is two.

  If the x-axis and y-axis are set parallel to each side of the breeding case, outputs A and B are as shown in FIG. The output A is a vector in the direction from the central column 2 to the column 42 or 180 degrees opposite thereto, and the output B is a vector in the direction from the center column 2 to the column 32 or 180 degrees opposite thereto. Although depending on how the voltage of the parallel bridge is applied, the direction of the column 42 and the direction of the column 32 are positive for convenience. Equation 3 is used to convert this into values in the x-axis and y-axis directions.

  Conversion to the coordinates of the rearing case is the same as when there are four load cells.

  We explained load measurement using a cantilever leaf spring and strain gauge, but you can use a load cell or pressure sensor that can directly measure the load. Conversion to the position of a small animal is the same as when using a strain gauge. This method can be realized.

  The load cell shown in FIG. 4 was implemented in a configuration in which four load gauges were formed, a leaf spring was formed, and a strain gauge was attached.

  As the plate 1, a normal iron plate having a thickness of 1 mm was used. The size was 30 cm × 22 cm. The rectangle made by the peripheral struts was 27 cm × 19 cm. The width of the leaf spring was 1 cm, and the length was 8 cm from the root to the position where the support was attached. Eight strain gauges were used which were 120 ohms of general foil gauges, and affixed so that the tips of the gauges came to the bases of the leaf springs. The length of each column was 1.5 cm and was fixed to the lower plate 9. The length of the stopper was 0.8 cm.

  The strain gauge was connected to a strain measuring instrument (UCAM-70A manufactured by Kyowa Denki Co., Ltd .: performing A / D conversion) so as to be connected as shown in FIG. The strain measuring instrument is connected to a personal computer and sends the strain amount to the personal computer at any time.

  A breeding case having a bottom surface of about 19 cm × 13 cm was placed on the plate 1 in a state where a mouse was placed.

  When the experimental mouse moves inside the case and approaches the corner of the breeding case, click on the position corresponding to the point where the experimental mouse is located in the rectangle imitating the bottom of the breeding case on the PC screen and click the reference I got the data. Reference data was obtained at all four corners, and the coefficients for conversion to actual positions were grasped.

  Thereafter, the data from the strain measuring device was collected on a personal computer at regular intervals, the actual position of the mouse was obtained by arithmetic processing, and the positional information was displayed and stored on the personal computer screen. A personal computer screen showing the position of the experimental mouse during monitoring is shown in FIG. The black portion indicates the locus of the last 10 pieces of position information, and the white portion indicates the locus of the position information before that.

  As shown in FIG. 6, a system was constructed in the same manner as in Example 1 except that the load meter had three configurations, and the same results were obtained.

  As shown in FIG. 8, a system was constructed in the same manner as in Example 1 except that the load cell had two configurations, and the same results were obtained.

  As shown in FIG. 4, the system was constructed in the same manner as in Example 1 except that only two strain gauges 44 and 34 were attached, with the configuration of four load cells, and similar results were obtained. .

  As shown in FIG. 8, the system was constructed in the same manner as in Example 1 except that only two strain gauges 44 and 34 were attached, with the configuration of two load cells, and similar results were obtained. .

  As shown in FIG. 1, except that a leaf spring is not formed, four peripheral struts are directly attached to the plate 1, a pressure sensor is installed at the contact point with the ground, and the output is amplified and collected by an OP amplifier. A system was constructed in the same manner as in Example 1, and similar results were obtained.

  As shown in FIG. 2, except that the leaf springs are not formed, three peripheral struts are directly attached to the plate 1, a pressure sensor is installed at the contact point with the ground, and the output is amplified and collected by an OP amplifier. A system was constructed in the same manner as in Example 1, and similar results were obtained.

It is a block diagram explaining the positional relationship of four load cells and one center support | pillar. It is the block diagram explaining the positional relationship of three load cells and one center support | pillar. It is the block diagram explaining the positional relationship of two load cells and one center support | pillar. It is the block diagram seen from the upper surface of the load measurement part which has four load cells. It is the block diagram seen from the side of the load measurement part which has four load cells. It is the block diagram seen from the upper surface of the load measurement part which has three load cells. It is the block diagram seen from the side of the load measurement part which has three load cells. It is the block diagram seen from the upper surface of the load measurement part which has two load cells. It is the block diagram seen from the side of the load measurement part which has two load cells. It is a parallel bridge circuit diagram at the time of having four load cells and attaching eight strain gauges. It is an image figure which converts the output result of a load cell into position information. It is a personal computer screen during the monitoring of the position information of the experimental mouse.

Explanation of symbols

1 Plate 2 Center column 31, 41, 51, 61, 71 Cantilever leaf spring 32, 42, 52, 62, 72 Peripheral column 33, 43, 53, 63, 73 Stopper 34, 44, 55, 65, 74 Surface distortion Gauge 35, 45, 55, 65, 75 Back strain gauge 8 Rearing case 9 Lower plate 132, 142, 152, 162 Load point position 232, 242, 272, 332, 342 Load point position 111 4 A quadrangle with the point of force of two load cells 211 A triangle with the point of force of three load cells as a vertex 311 A triangle with the point of force of two load cells and the center column

Claims (5)

  A system that obtains position information of small animals such as mice in a breeding case placed on a device that uses a device that obtains the center of gravity by providing a plurality of load meters around the plate where the load is applied, such as a center of gravity shaker The support column has a plate for placing a breeding case, has four load meters for holding the plate in the periphery of the plate, and supports the load inside a quadrangle whose vertex is the force point of the four load meters It has a load measuring unit characterized by having one, has a reference data collection function and a calculation function for converting information obtained from a load cell into position information of a small animal, and outputs the obtained position information A small animal position measuring system characterized by having a function and a function of accumulating.   The position measuring system for a small animal according to claim 1, comprising three load cells, and one support column for supporting a load inside a triangle having a vertex of a force point of the three load cells.   The position measuring system for a small animal according to claim 1, comprising two load cells, one column for supporting a load applied to the plate, and a triangle formed by two force points and one column. .   2. The position measuring apparatus for small animals according to claim 1, wherein a sensor is added only to two adjacent load meters among the four load meters, or only to three load meters.   5. The small animal position measuring apparatus according to claim 1, wherein a cantilever leaf spring is formed as a load measuring method, and a displacement is obtained by a strain gauge.