Methods for analyzing horse movement

Abstract

A method for analyzing horse movement, wherein a contact point (6) of a horse's hoof (3) with the ground (7) is determined during the horse's movement, characterized in that a first spatial orientation of the hoof (3) is determined at a first measurement time (11), that a second spatial orientation of the hoof (3) is determined at a second measurement time (12a, b), and that based on the first spatial orientation and the second spatial orientation, the contact point (6) of the hoof (3) with the ground (7) is determined.

Description

[0001] The invention relates to a method for analyzing horse movement with the features of the preamble of claim 1.

[0002] When keeping horses, observing their gait is an important way to ensure their well-being. An irregular gait can be a symptom of an underlying health problem. For horses participating in any kind of sport, such gait analysis is particularly important.

[0003] Several approaches exist for analyzing a horse's gait using electronic and computer tools. These typically involve attaching accelerometers near the horse's hooves and recording its movement. A specific aspect of gait analysis concerns the point of contact between the hoof and the ground. This contact occurs regularly along the hoof wall, which is essentially circular. This contact can occur both during the landing phase of the stride—where the contact is an impact—and during the lift-off phase. Identifying this point of contact is therefore an important aspect of evaluating the horse's gait.

[0004] It is known from the prior art to identify this contact point by arranging a sensor on the hoof wall itself, thus directly recording the contact. The article “Motion analysis and its use in equine practice and research” by Hobbs et al. [Wien. Tierärztl. Mschr. - Vet. Med. Austria 97 (2010), 55-64], from which the present invention is based, describes the use of force plates or horseshoes equipped with instruments for such measurements.

[0005] On the one hand, this approach allows for a direct measurement of the contact point. On the other hand, the sensor's placement is such that it could lead to a distorted result regarding what the contact point would be if the sensor were not attached to the hoof. Furthermore, due to the strong forces involved, the sensor is subject to considerable stress and therefore must either be very robust or will deteriorate rapidly.

[0006] Therefore, the object of the invention is to provide a method for analyzing horse movement that can determine the contact point of a hoof with the ground, which is less intrusive with respect to the movement of the hoof and avoids a direct impact on the sensors.

[0007] With regard to a method for analyzing horse movement with the features of the preamble of claim 1, this problem is solved with the features of the characterizing part of claim 1.

[0008] The invention is based on the insight that the contact point can be indirectly determined by comparing the respective orientation of the hoof at two points in time. Based on these two orientations, the corresponding rotational movement of the hoof during the time between can be determined. Since the contact point can be assumed to be located on the circumference of the hoof, i.e., on the hoof wall, identifying this rotational movement, in turn, allows for the precise determination of the contact point on the hoof wall. Such an approach, based on the determination of a rotational movement, does not require absorbing the actual impact with a sensor and is therefore less intrusive on the gait and less damaging to the sensor.

[0009] The method according to the invention is used for analyzing the movement of horses. In this method, a contact point of a horse's hoof with the ground is determined during the horse's movement. This contact point is either the initial contact point of the hoof when it lands on the ground, or the final contact point of the hoof when it lifts off the ground. In both cases, the contact point can be assumed to be a single point. It can also be assumed that the contact point has a specific contact area that is larger than a single point.

[0010] The method according to the invention is characterized in that a first spatial orientation of the hoof is determined at a first measurement time, a second spatial orientation of the hoof is determined at a second measurement time, and the contact point of the hoof with the ground is determined based on the first and second spatial orientations. Determining the contact point of the hoof with the ground can include calculating an orientation difference between the first and second spatial orientations. Based on this orientation difference, a rotational movement of the hoof before or after contact occurs at the contact point can be determined, which in turn allows the contact point itself to be determined.Within the scope of the present invention, in principle any orientation, in particular spatial orientation, of the hoof or any other structure can be determined relative to any base orientation. When considering the relative change between two different orientations, the arbitrary base orientation underlying the two different orientations is generally irrelevant. In a preferred case, for any spatial orientation, the base orientation can be chosen such that it corresponds to a hoof lying flat on a substrate with a level surface, with the direction of gravity normal to the surface of the substrate. Since spatial orientation can be expressed in terms of pitch, roll, and yaw, these quantities can also be expressed relative to any base orientation.For these, it is also preferred that the basic orientation corresponds to the hoof, which lies flat on a surface with a level base.

[0011] In a preferred embodiment of the method, the first measurement point is a static event, when the hoof is flat on the ground. Such a hoof position represents a natural starting position in which complete contact along the hoof wall with the ground can be assumed. It is further preferred that the second measurement point occurs when the hoof has point contact with the ground. It can be assumed that the rotational movement of the hoof between these two measurement points defines the direction corresponding to the point of contact on the circumference of the hoof, or in other words, on the hoof wall. It is preferably assumed that the hoof is at rest with respect to rotation during the static event. This assumption can also aid in calculating hoof movement based on measurements. To uniquely define a static event, a further condition for a static event can be added.The preferred outcome is when the hoof is flat on the ground and no longer moving in a linear direction in line with the horse's movement. In other words, the hoof has stopped slipping. This additional condition can be useful because the hoof can typically continue to slide for some distance after reaching this flat position.

[0012] In principle, the first and second measurement points can occur in any temporal sequence. In a further preferred embodiment of the method, the second measurement point occurs after the first. Preferably, the first and second measurement points occur during a hoof lift-off movement. In particular, the second measurement point can be a hoof lift-off event, i.e., the moment just before the hoof loses contact with the ground.

[0013] Alternatively, it is preferred that the second measurement time occurs before the first measurement time. Preferably, the first and second measurement times then take place during a landing movement of the hoof. In particular, the second measurement time can be a hoof impact event. This is the moment at which the hoof has just made point contact with the ground.

[0014] A preferred embodiment of the method is characterized in that the first and second spatial orientations are determined based on measurements by a sensor arrangement for measuring linear acceleration and rotational velocity. Such a sensor arrangement, which may be an inertial sensor, is particularly suitable for performing measurements of the aforementioned quantities from which spatial orientations can be indirectly derived. Preferably, the sensor arrangement is located at a distal end of a horse's limb, particularly substantially near the hoof. In particular, the sensor arrangement may be located substantially on the front of the limb, which in turn corresponds to the front of the hoof.This placement of the sensor array ensures that the sensor array is sufficiently close to the horse's hoof to participate in essentially all of the hoof's movement during the horse's movement, and that the rotation of the hoof around a transverse axis can be effectively measured by the sensor array.

[0015] It is preferred that the sensor arrangement comprises a three-axis accelerometer for measuring linear acceleration in three directions and a three-axis gyroscope for measuring rotational speed about three axes. Furthermore, the three-axis accelerometer may be a lower acceleration sensor for measuring lower accelerations, and the sensor arrangement may include another three-axis accelerometer, a higher acceleration sensor, for measuring higher linear accelerations in three directions. Thus, the lower acceleration sensor and the higher acceleration sensor may have lower and higher measuring ranges, respectively. In this context, the lower and higher accelerations are relative to each other, i.e., in the sense that the lower acceleration is smaller than the higher acceleration.

[0016] When placing or attaching the sensor array to the horse's limb, a relative orientation between the sensor array and the hoof can be determined with sufficient precision before determining the first and second spatial orientations. Accordingly, a further embodiment of the method is characterized in that determining the first and second spatial orientations is based on specific roll, pitch, and yaw movements between the sensor array and the hoof. Thus, determining these parameters by measuring and calibrating the sensor array in this way can be a preliminary step in determining the first and second spatial orientations.Since the sensor arrangement is fixed with respect to the hoof, the rolling, pitching and yawing between the sensor arrangement and the hoof are preferably essentially constant over time.

[0017] It is preferred that the rolling and pitching motions between the accelerometer and the hoof are determined during the hoof's standing event. In particular, the standing event can be identified based on the fact that rotational velocities about three axes are below a standing event threshold. This identification is based on the assumption that the hoof is essentially stationary during the standing event, at least for a short period, and therefore exhibits no rotational velocity.

[0018] In a preferred embodiment of the method, the yaw rate between the accelerometer and the hoof is determined based on the direction of the maximum rotational speed, which is assumed to be a transverse axis of the hoof. In other words, the rotational speed is measured over time, and based on this measurement, the axis about which the rotational speed is maximum is determined, which is also referred to here as the direction of the maximum rotational speed. Based on knowledge of the dynamics of hoof movement, this direction corresponds to a transverse axis of the hoof. The rotational speed about this axis corresponds to the pitching speed, i.e., the rate at which the pitching of the hoof changes.

[0019] In a further preferred embodiment of the method, the first and second spatial orientations are determined from a series of linear acceleration and rotational velocity measurements taken over a measurement period covering several steps of the horse. The individual steps of a horse's stride are known and can therefore be identified without great difficulty. Analyzing multiple such steps provides a larger data set, thus enabling the reduction of noise and other artifacts. Preferably, the measurement period is divided into a series of individual steps based on detected tilting events of the hoof movement. A tilting event begins when the heel of the hoof leaves the ground, and the hoof begins to rotate around the toe, which is still in contact with the ground.The tipping event is therefore a specific, but in principle arbitrary, event during the tipping process. In particular, the tipping event is detected based on a pitching velocity threshold. Thus, the detection of the tipping event can be based on the pitching velocity exceeding the pitching velocity threshold. This pitching velocity threshold can be constant and / or predefined. It can also be variable.

[0020] A preferred embodiment of the method is characterized in that each step is subdivided into a landing period, a stance period encompassing the stance event, and a tipping period encompassing the tipping event. Furthermore, a vibration period and the determination of the first and second measurement times are preferably based on the subdivision of each step. Such a subdivision into characteristic time periods facilitates the identification of specific events during the step. The landing period can begin when the hoof makes point contact with the ground upon landing, i.e., starting with the hoof impact event during the landing movement.

[0021] Each of the time periods into which a step is divided can, in turn, be further subdivided into any number of sub-periods, which can be called phases. For example, the landing period can be divided into a first phase, beginning from the hoof impact event until the first time the hoof is flat on the ground. This first phase can be called the landing phase. The second phase can then follow. Thus, the second phase begins at the first time the hoof is flat on the ground and continues until the time the hoof stops any remaining sliding motion. Based on the preferred definition of the stance event described above, the second phase of the landing period can therefore continue until the stance event. The second phase can be called the sliding phase.

[0022] In general, the relevant physical quantities, such as position and speed, cannot be measured directly by a sensor, but can only be determined through further calculations based on sensor measurements. Accordingly, another embodiment of the method is characterized in that an orientation sequence of the hoof is determined based on an integration, preferably a quaternion integration, of the measured rotational velocities. The orientation sequence is a sequence or progression of values ​​that describes the orientation of the hoof and thus represents its orientation over time.

[0023] The above approach to determining orientation is based on the observation that, in principle, the angular position can be determined by integrating the rotational velocity, where the rotational velocity equals the angular velocity. It is further preferred that the orientation sequence of the hoof be determined based on an integration of the measured rotational velocities during a single step. With integration, small offsets or measurement errors can lead to large errors in the result. By performing this integration step by step and, for example, making certain assumptions about the orientation for specific events during the step, such errors can be avoided or reduced. In particular, the orientation sequence of the hoof can be determined by combining a forward integration of the measured rotational velocities with a backward integration of the measured rotational velocities.This two-part approach can similarly reduce the effect of measurement errors.

[0024] Quaternion integration, as described above, means that the rotation of the hoof is expressed in quaternions. Quaternions are well-known in mathematics. It is also known that rotations in three-dimensional space can be expressed using quaternions, with combinations of rotations corresponding to operations on the quaternions. In this way, the integration of rotations is expressed more efficiently when expressed using quaternions.

[0025] The above approach of combining forward and backward integration can also be extended to linear velocity. In a preferred embodiment of the method, a velocity sequence of the hoof is determined based on an integration of the measured linear accelerations, which are adapted by a specific orientation sequence. This adaptation by the orientation sequence takes into account that changes in the orientation of the hoof—and thus of the sensor arrangement—also affect the direction of the measured linear accelerations. Analogous to the orientation sequence, the velocity sequence is a sequence or progression of values ​​that describes the linear velocity and thus represents the velocity over time. Preferably, the velocity of the hoof is a three-dimensional quantity.Similarly to the orientation sequence, the velocity sequence of the hoof is preferably determined by combining a forward integration of the measured linear accelerations and a backward integration of the measured linear accelerations.

[0026] The above considerations regarding orientation and velocity can be further extended to position. In another preferred embodiment of the method, a position sequence of the hoof is thus determined based on an integration of the velocity sequence. It is further preferred that the position sequence of the hoof be determined by combining a forward integration of the velocity sequence and a backward integration of the velocity sequence.

[0027] In principle, the calculations described above and any other calculations can be performed by computing hardware integrated into the sensor arrangement. However, since the calculations can be relatively resource-intensive and a low weight for the sensor arrangement is generally desirable, in a preferred embodiment of the method, a wireless transmitter of the sensor arrangement transmits the measured linear acceleration and the measured rotational velocity to a computing device, which may be, in particular, a personal computer, a smartphone, or the like. It is further preferred that the computing device performs a calculation to determine the first spatial orientation and the second spatial orientation based on the transmitted linear acceleration and rotational velocity.In particular, the computer device can also perform calculations to determine the roll, pitch, and yaw between the sensor array and the hoof, to identify the stand event, to divide the measurement period into a series of individual steps, to detect tipping events, and / or to divide each step into the landing period, the stand center period, the tipping period, and the vibration period. Furthermore, the computer device can perform calculations for integrating the measured rotational velocities and / or for combining the forward integration and backward integration of the measured rotational velocities. The computer device can also perform calculations for any other determination, directly or indirectly, based on the measured linear acceleration and the measured rotational velocity.

[0028] When processing the measured linear acceleration and the measured rotational velocities, as well as in all further calculations, filters, averaging and other numerical operations can be applied to reduce noise and reduce the effect of measurement errors.

[0029] A preferred embodiment of the method is characterized in that a hoof lift-off event is determined based on a hoof lift-off acceleration threshold for the acceleration in an upward vertical direction. The hoof lift-off event is the time or interval at which the hoof has completed its tilting and completely leaves contact with the ground. The hoof lift-off event can therefore be considered the time at which there is essentially only a single point of contact between the hoof and the ground. Accordingly, it is preferred that the determined hoof lift-off event be the second measurement time. It has been found that the hoof lift-off event can be equated with, or at least approximated with, the time at which the linear acceleration in an upward vertical direction exceeds a threshold with substantial accuracy.Here, the upward-pointing vertical direction refers to the horizontal plane of the substrate.

[0030] In a preferred embodiment of the method, the start of the tipping event is determined based on a tipping threshold for a change in pitching relative to the standing event. This is based on the understanding that the pitching is zero in the standing event, as the hoof is assumed to be lying flat on the ground. Thus, the start of the tipping occurs when the pitching of the hoof exceeds a specific threshold, namely the tipping threshold.

[0031] Another preferred embodiment of the method is characterized in that a hoof impact event is determined based on an impact acceleration threshold for acceleration in an upward vertical direction. In particular, the hoof impact event is further determined based on the fact that it occurs after the start of the tipping event. This is similar in principle to the detection of the hoof lift-off event, whereby the hoof impact event is distinguished from the hoof lift-off event in particular by the fact that the start of the tipping event precedes the hoof impact event. Preferably, the determined hoof impact event is the first measurement point.

[0032] In another preferred embodiment of the method, an angular position for the contact point of the hoof is determined. This angular position is a value that indicates the angle, relative to any initial position with an angle of zero, of the contact point from a center point of the hoof within the plane defined by the hoof wall. Based on the knowledge that the wall of the hoof is essentially circular, such an angular position would be sufficient to indicate the contact point. In this context, it is assumed that the bottom surface of the hoof wall lies essentially in a plane.

[0033] Preferably, the nodding angle of the hoof is determined at the moment when the hoof's point of contact with the ground is in contact. This introduces a third spatial dimension in addition to the angular position within the plane of the hoof wall. This additional information, which goes beyond simply identifying the point of contact, is also valuable for assessing the horse's gait. This nodding angle can also be referred to as the hoof angle. Additionally or alternatively, a roll angle of the hoof is determined at the moment when the hoof's point of contact with the ground is in contact.

[0034] Further advantageous and preferred features are discussed with reference to the figures in the following description of the method according to the invention. The following shows Fig. 1 a schematic representation of the orientation of the hoof of a horse whose movement is to be analyzed by the method according to the invention, during the movement of the horse, Fig. 2 a schematic representation of the position of a sensor arrangement with respect to the hoof, and Fig. 3 A schematic representation of the hoof wall.

[0035] Before carrying out the method according to the invention, a sensor arrangement 1 is attached to a distal end of a body part 2, i.e., a leg, of a horse at or near the hoof 3. Such placement is described in Fig. 2 shown. The sensor arrangement 1 of the Fig. 2, also referred to here as the inertial motion unit, comprises an arrangement of micromechanical systems. Specifically, sensor arrangement 1 includes a first three-axis accelerometer for measuring higher linear accelerations and a second three-axis accelerometer for measuring lower linear accelerations. The respective axes of the accelerometers are aligned. Both accelerometers are designed to measure linear accelerations within different ranges. Based on this, the respective measurements from each accelerometer can be combined into a single value. Sensor arrangement 1 also includes a three-axis gyroscope for measuring rotational velocities about three axes.The sensor arrangement 1 further comprises computer processing equipment and a memory for storing measurements, as well as wireless communication equipment for transmitting the measured values ​​to a computing device, such as a desktop computer, a laptop, or a smartphone. The sensor arrangement 1 can be part of a larger system comprising several such sensor arrangements 1, e.g., a system of four sensor arrangements 1, each attached to a respective limb 2 of the same horse and all in wireless communication with the computing device.

[0036] As from Fig. As can be seen in Figure 2, the placement of the sensor arrangement 1 on the horse's limb 2 results in a relative orientation between the sensor arrangement 1 and the hoof 3, which relative orientation is represented here by a sensor normal axis 4 and a hoof normal axis 5. Since this relative orientation is variable for each attachment and unknown beforehand, it is determined in the process of the inventive method, as described below.

[0037] The measurement process by the sensor arrangement 1 and the analysis of the corresponding measured values ​​begins while the horse is moving, either at a walk or a trot. These two gaits can be divided into individual steps, with each step involving a specific hoof 3 going through the phases of landing – which begins with a hoof impact event 8 – standing, tipping, and swinging. The tipping phase ends with a hoof lift-off event 9. A standing event 10 occurs during the standing phase. The position of the hoof 3 relative to the ground 7 during the hoof impact event 8, which is the point in time when the hoof 3 makes contact with the ground 7 at contact point 6, the standing event 10, in which the hoof 3 is at rest with respect to rotational speed, and the hoof lift-off event 9, which is the point in time when the hoof 3 has contact with the ground 7 only at contact point 6, is described in Fig. Figure 1 illustrates this. If there is an extended period during the stance phase in which the hoof 3 is at rest with respect to its rotational speed, then the stance event 10 can, in principle, be determined at any point in time within this period. The respective contact points 6 of the hoof impact event 8 and the hoof lift-off event 9 can differ from each other.

[0038] The method according to the invention is for determining the contact point 6 – either during the hoof impact event 8 or the hoof lift-off event 9, or for both – of the hoof 3 with the ground 7 during movement, where contact point 6 can be understood as a point in the mathematical sense or a surface that is small in relation to the entire hoof 3 or the hoof wall. This determination can be made for a single step only. Alternatively, each contact point 6 can be determined for a plurality of steps or even all steps, in which case it would also be possible to determine an average of the determined contact points 6.

[0039] The determination of the contact point 6 for the hoof impact event 8 is based on a comparison between the spatial orientation of the hoof 3 during the standing event 10 and a further point in time when the contact between the hoof 3 and the ground 7 is only a single contact point 6. Based on the above considerations, this further point in time is either the hoof impact event 8 or the hoof lift-off event 9. According to a first embodiment of the method according to the invention, the first measurement time 11 is thus the standing event 10, and the second measurement time 12a is the hoof impact event 8. In a second embodiment of the method according to the invention, the first measurement time 11 is again the standing event 10, and the second measurement time 12b is the hoof lift-off event 9. The attributes "first" and "second" measurement time do not imply a temporal sequence; that is, the second measurement time 12a,b can occur before the first measurement time 11.

[0040] The underlying idea is that the change in the spatial orientation of the hoof 3 between one of these further time points and the standing event 10 maps an angular position of the contact point 6 on the hoof wall, which hoof wall essentially forms the circumference of the hoof 3, at least for the part of the hoof 3 where the contact point 6 can be expected. Furthermore, it is assumed that the hoof 3 pivots essentially between these time points in a rotational movement that corresponds to the change in spatial orientation. The hoof wall is also in Fig. Figure 3 shows that contact point 6 can be determined without any sensor at contact point 6 itself.

[0041] In a first step, the relative orientation 13 - which is symbolically in Fig. 2 is displayed – determined between the sensor arrangement 1 and the hoof 3 and preferably expressed in terms of roll, pitch, and yaw. For this purpose, a standstill event 10 is first identified. Based on the consideration that at standstill event 10 the hoof 3 will be essentially stationary with respect to rotation, standstill event 10 is identified when the rotational speed about all three axes, as determined by the three-axis gyroscope of the sensor arrangement 1, is below a standstill event threshold, i.e., sufficiently low. This standstill event threshold can either be predefined and constant or determined dynamically during the measurement.

[0042] It is assumed that during the standing event 10, the only acceleration measured by the accelerometers is gravity. It is further assumed that during the standing event 10, the hoof lies flat on the ground 7. Thus, the orientation of the hoof 3, as defined by the hoof normal axis 5, corresponds to the direction of gravity. Based on these considerations, the rolling and pitching of the relative orientation 13 can be determined based on the linear accelerations measured by the sensor array 1.

[0043] The determination of the yaw of the relative orientation 13 can be carried out based on the assumption that the greatest rotational speed—in any direction—will occur during the movement of the hoof 3 about a transverse axis 14 of the hoof 3, i.e., an axis parallel to the ground 7 and normal to the average translational direction of the movement of the hoof 3 during a single step or a number of steps. Thus, the transverse axis 14 is considered the direction of the maximum rotational speed. If this transverse axis 14 is now corrected for the roll and pitch of the relative orientation 13 determined above, the resulting vector can be projected onto the ground 7. Based on this projection, the yaw of the relative orientation 13 can be determined.

[0044] Assuming that the yaw angle is small enough, the pitch angle of hoof 3 can be determined from the measurements of sensor arrangement 1.

[0045] By thus determining the relative orientation 13, which is defined by roll, pitch and yaw, the accelerations and rotational velocities measured by the sensor arrangement 1 can be rotated into the reference frame of the hoof 3.

[0046] The motion data measured by sensor array 1 during the horse's movement are initially divided into individual steps. To identify individual steps, tipping events are detected among the measured data. A tipping event is detected when the pitching velocity—which is the rotational velocity about the transverse axis 14 of the hoof 3—exceeds a pitching velocity threshold. This threshold is, in principle, variable and can be determined dynamically based on the consideration that tipping events occur over a period that is essentially constant or at least slowly changing, and that at each step the pitching velocity will be at or near its maximum at the tipping event.Based on the tipping event, the standing event 10, which immediately precedes the tipping event, is detected based on the observation that the rotational speed of the hoof 3 during standing event 10 will be essentially zero or very small. Each step then consists of the time from one standing event 10 to the subsequent standing event 10.

[0047] For each step, the progression or sequence of the orientation and velocities of hoof 3 over time is determined by integrating the measured rotational velocities and accelerations, specifically using quaternion integration. For integrating the orientation, the starting point is the stance event 10, at which hoof 3 is assumed to be in a flat position on the ground. From this starting point, the integration proceeds in both a forward and a backward direction. The result of the backward integration is combined with the result of the forward integration from the previous stance event 10. The same combination is performed analogously with the result of the forward integration. This determines a sequence or progression of hoof 3 orientations over time for the entire step.

[0048] Based on the orientations thus determined, the accelerations are integrated into a sequence of linear velocities over time. For this, the integration again starts from the stationary event 10 in the forward and backward directions, and a union takes place as described for the orientation. It is assumed that the velocity of hoof 3 is zero at stationary event 10. Then the velocities can be integrated in the same way to obtain a position sequence over time.

[0049] Phase transitions in the gait can now be determined in the following manner. The hoof lift-off event 9 is detected by comparing an acceleration in an upward vertical direction 15, i.e., in the direction normal to the ground 7, with a hoof lift-off acceleration threshold, which is also variable in the same way as described for the pitching velocity threshold. The onset of the tipping, which precedes the tipping event, can be identified when the pitching angle of the hoof 3 exceeds a tipping threshold.

[0050] The hoof impact event 8 is also determined by comparing the acceleration in the upward vertical direction 15 with a variable impact acceleration threshold. It should be noted that after a standing event 10, the hoof lifting event 9 occurs first, and only then the hoof impact event 8.

[0051] As in Fig.As shown in Figure 3, based on the difference between the first and second spatial orientations, the contact point 6, and thus also an angular position 16, are determined that defines the contact point 6 on the circumference of the hoof 3, which is represented by the hoof wall. Furthermore, the pitch angle and the roll angle of the hoof 3 can be determined at this time.

Claims

[1] A method for analyzing horse movement, wherein a contact point (6) of a hoof (3) of a horse with the ground (7) is determined during the movement of the horse, characterized by , that a first spatial orientation of the hoof (3) is determined at a first measurement time (11), that a second spatial orientation of the hoof (3) is determined at a second measurement time (12a, b), and that based on the first spatial orientation and the second spatial orientation the contact point (6) of the hoof (3) with the ground (7) is determined. [2] The method according to claim 1, characterized by , that the first measurement time (11) is a standing event (10) when the hoof (3) is flat on the ground (7), preferably that the second measurement time (12b) takes place when the hoof (3) has point contact with the ground (6). [3] The method according to claim 2, characterized by, that the second measurement time (12a, b) takes place after the first measurement time (11), preferably that the first measurement time (11) and the second measurement time (12a, b) take place during a lifting movement of the hoof (3). [4] The method according to claim 2, characterized by , that the second measurement time (12a, b) takes place before the first measurement time (11), preferably that the first measurement time (11) and the second measurement time (12a, b) take place during a landing movement of the hoof (3). [5] The method according to any one of claims 1 to 4, characterized by, that the first spatial orientation and the second spatial orientation are determined based on a measurement by a sensor arrangement (1) for measuring linear acceleration and rotational velocity, which sensor arrangement (1) is preferably arranged at a distal end of a body part (2) of the horse, in particular substantially in the vicinity of the hoof (3), further preferably that the sensor arrangement (1) comprises a three-axis accelerometer for measuring linear acceleration in three directions and a three-axis gyroscope for measuring rotational velocity about three axes. [6] The method according to claim 5, characterized by, that the determination of the first spatial orientation and the second spatial orientation is based on a specific roll, a specific pitch and a specific yaw between the sensor arrangement (1) and the hoof (3), preferably that the roll and pitch between the sensor arrangement (1) and the hoof (3) is determined during the stand event (10) of the hoof (3), in particular that the stand event (10) is identified based on the fact that rotational velocities about three axes are below a stand event threshold. [7] The method according to claim 6, characterized by , that the yaw between the accelerometer (1) and the hoof (3) is determined based on a direction of the maximum rotational speed, of which direction of the maximum rotational speed is assumed to be a transverse axis (14) of the hoof (3). [8] The method according to claim 6 or 7, characterized by, that the first spatial orientation and the second spatial orientation are determined from a series of linear acceleration and rotational velocity measurements taken over a measurement period covering several steps of the horse, preferably dividing the measurement period into a series of individual steps based on detected tipping events of the hoof movement, in particular detecting a tipping event based on a pitching velocity threshold. [9] The method according to claim 8, characterized by , that each step is subdivided into a landing period, a stand mid-period including the stand event (10), a tipping period including the tipping event, and an oscillation period, and that the determination of the first measurement time and the second measurement time is based on the subdivision of each step. [10] The method according to any one of claims 6 to 9, characterized by, that an orientation sequence of the hoof (3) is determined based on an integration, preferably a quaternion integration, of the measured rotational velocities, wherein further preferably an orientation sequence of the hoof (3) is determined based on an integration of the measured rotational velocities during a single step, wherein in particular the orientation sequence of the hoof (3) is determined by combining a forward integration of the measured rotational velocities and a backward integration of the measured rotational velocities. [11] The method according to claim 10, characterized by, that a velocity sequence of the hoof (3) is determined based on an integration of the measured linear accelerations which are fitted by the determined orientation sequence, wherein preferably the velocity sequence of the hoof (3) is determined by combining a forward integration of the measured linear accelerations and a backward integration of the measured linear accelerations. [12] The method according to claim 11, characterized by , that a position sequence of the hoof (3) is determined based on an integration of the velocity sequence, wherein the position sequence of the hoof (3) is determined by combining a forward integration of the velocity sequence and a backward integration of the velocity sequence. [13] The method according to any one of claims 6 to 12, characterized by, that a hoof lifting event (9) is determined based on a hoof lifting acceleration threshold for the acceleration in an upward vertical direction (15), preferably that the determined hoof lifting event (9) is the second measurement time point (12a, 12b). [14] The method according to any one of claims 6 to 13, characterized by , that a hoof impact event (8) is determined based on an impact acceleration threshold for the acceleration in an upward vertical direction (15), preferably that the determined hoof impact event is the first measurement time. [15] The method according to any one of claims 1 to 14, characterized by , that for the specified contact point (6) of the hoof (3) an angular position (16) for the contact point (6) is determined, preferably that a nodding angle of the hoof (6) is determined at the time when the contact point (6) of the hoof (3) is in contact with the ground (7).

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