Abstract:
The present invention relates to tracking and analyzing a trajectory of a moving object, like a sports equipment used in an exercise. The present invention to provides a solution for tracking and analyzing a trajectory of a moving object in such a way, that the trajectories can be analyzed and compared to reference data created for the purpose, in order to evaluate and score the movement of the object—including a performance of a person using the object.

Description:
FIELD OF THE INVENTION 
     The present invention relates to tracking and analyzing a trajectory of a moving object, like a sports equipment used in an exercise. Especially in action sports like skateboarding and snowboarding, the overall performance is depending on the execution of certain tricks and movements, where the performer has to take him and his board up in the air. These three-dimensional movements are difficult to track and record, in terms of evaluating and instructing athletes with regard to their performance. 
     DESCRIPTION OF RELATED ART 
     European patent application EP1846726 discloses a system for detecting, calculating, and displaying the time-of-flight or “hang-time” of a moving and jumping object such as a skier or snowboarder. Accelerometers are used to determine over a period of time, typically when doing a performance in a particular slope, how long the trajectories are and how much the total “hang-time” amounts to during the run. This time can then be evaluated out of different criteria, i.e. a snowboarder probably wants to be in the air as much as possible, while a skier most likely wants to minimize the same. 
     In the PCT application document WO9854581 a similar system is presented, where the jumps performed by a snowboarding or ski-boarding person are measured with regard to the duration and also the height of the jump. Acceleration sensors are used also here, and a variety of recording and displaying methods are devised. The recording of the length and height of individual jumps makes it possible to review and compare such data after the performance. However, each jump is measured only in 2 dimensions, time and height, so the use is limited to track each performer&#39;s personal improvements in this regard, and perhaps to compare the height of the jumps between friends, and is not suitable to establish a score indicating the quality of the performance as a whole, and to compare it with e.g. independent instructions for an “ideal” jump, or competition rules and standards. 
     SUMMARY OF THE INVENTION 
     It is an aim of the present invention to provide a solution for tracking and analyzing a trajectory of a moving object in such a way, that the trajectories can be analyzed and compared to reference data created for the purpose, in order to evaluate and score the movement of the object—including a performance of a person using the object. The invention is characterized by what is presented in the appending claims. Next, the invention will be examined more closely with the aid of a detailed description of preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described below in detail, with reference to the attached drawings, wherein: 
         FIG. 1  shows an embodiment of the invention integrated in a snowboard; 
         FIG. 2  shows another embodiment of the invention used on a skateboard; 
         FIG. 3  shows a simplified flowchart diagram of the inventive process; 
         FIG. 4  is a block diagram of a system according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a self-contained and standalone unit  3  integrated in a snowboard  1  with boot holders  2 . Attaching sensing elements to skateboards, snowboards and other sports equipment like boots, bicycles etc., are known from prior art. According to the present invention, tracking and registering the trajectory in three dimensions is however the key task of the sensors, so instead of complicated speed, height and time measuring sensor setups, the inventive solution is based on having on board sensors only to detect the movement of the object (here a snowboard) in three dimensions. Because the process of evaluating the trajectory is reduced to a comparative operation, the hardware and software setup needed is greatly simplified. The unit  3  incorporates three accelerometer sensors  5 , a display  6  and a user interface  4  that provides a user with buttons to select a mode of operation, e.g. between normal performance tracking or new-trick-recording, pre-selection of the trick to be performed, etc. It is also possible to use a single 3D-acceleration sensor in a sensor unit. 
     Instead of accelerometers, or in combination with them, gyroscopes may be used. Solid-state and low-cost MEMS gyroscopes are nowadays available. Especially in trajectories involving much rotational motion it may become unfeasible to track the movement with only accelerometers. The unit can be stand-alone as in  FIG. 1 , or have an interface to a computer for later data downloading, or it can be provided with wireless communication with external devices, as shown in  FIG. 2 . 
       FIG. 2  shows an inventive system consisting of a skateboard  7  with an integrated sensing element  8 . The sensor element may locate e.g. at the board surface or hidden at wheel trucks. There may be one sensor unit in one of the trucks, or there may be two sensor units, one in each truck. A central unit  9  carried by the user on his waist, or alternatively wrist. Unit  9  has a wireless communication interface with the sensing element  8 . The communication channel used between the sensor unit and the central unit can be e.g. a Bluetooth link, WIFI, NFC or any other low power radio system with a continuous data transfer capability. In a system like the one in  FIG. 2 , the measuring results may be stored either in the sensing element  8  or the central unit  9 , while the score is calculated and presented in a display of the central unit  9 . A central unit may also be a mobile phone. As handheld devices like smartphones are getting very sophisticated, such a device (not shown) may also contain a software application for receiving the measurement data and with a scoring algorithm according to the present invention. The score is then visible to the user on his own smartphone right after the performance. 
     In a further embodiment, as some smartphones also contain built-in accelerometers and gyroscopes, the smartphone device itself can be used as a standalone unit. In such a case no unit integrated in the board or any other equipment is needed. Of course the movements of the human body, and its temporary parting from the sports equipment like in skateboarding, determines if, where and how such a device may be attached to the body, in order to fulfill the requirement of reliable data for the system according to the present invention. 
     In one further embodiment the sensor unit has a wireless connection with a cellular data transfer system, such as a GSM system. This way the sensor data can be transmitted directly through the network without a central unit for the data transfer. 
     It is clear to one skilled in the art that the data received and stored in such a device can easily be shared e.g. through social media channels to the peers of the users, to facilitate score tables of live tricks on a website, or to send it forward onto a cloud computing service to induce micropayments related to participation in a competition or a game over the internet. A user can also record and introduce his own tricks. When several users generate trick data and store it in a common network, a commensurable trick data archive with time, location etc. identifiers can be created. 
     As a non-exclusive example, an algorithm that identifies the trajectories of say the top 20 skateboarding tricks is developed. The recognition is based on data through machine-learning methods, having different users repeating the tricks using a skateboard. Successful performances are recorded by measuring the acceleration rate and direction of the boards as a function of time in 3 dimensions through selected sensors according to the invention. 
     With reference now to  FIG. 3 , the algorithm can identifies the start and the end of a performance by recognizing when there is no acceleration (constant speed or standstill). When a user performance is to be evaluated, the system according to the present invention captures the acceleration data of the board between two standstill or constant-speed events, and compares it with the pre-stored trajectories in its memory. According to one embodiment of the invention, the length of the actual performance is scaled in turn to the length of each of the pre-recorded tricks, and the data sets of the actual and pre-recorded trick is compared by calculating the correlation between the two sets of data. The decision on which trick was in question is made based on the highest correlation. For each of the pre-recorded tricks, a score table is defined, e.g:
     0 . . . 0.4 poor   0.5 . . . 0.6 passable   0.6 . . . 0.7 satisfactory   0.7 . . . 0.8 good   0.9-1.0 excellent   

     The score is then presented to the user as shown in  FIG. 3 . 
     In another embodiment of the invention, the user selects the trick first before trying to do it, whereby the algorithm only performs the correlation calculation on the set of pre-recorded data that corresponds to the selected trick. The selection process to find the highest correlation can then be omitted. 
     The time scaling of the trajectory, to match a pre-recorded model or target trajectory, plays an important role in the present invention, as it conditions the signals from the sensors and contributes to circumvent the need of difficult timing, speed and distance measurements. 
     In  FIG. 4  is presented a block diagram of a system according to the present invention. A system according to the invention consists of various sensors, here accelerometers  10  for the x,y and z axes in a 3-D Cartesian coordinate system, as well as a gyroscope  11 . The sensor signals are fed, by wire or by wireless communication, to the central unit  12  that extracts the acceleration, speed and distance data from the signals. From acceleration and time data, the speed and distance of the object in all three directions can be easily calculated. With one or more gyroscopes  11 , the sensors may provide a full  6  component motion sensing; 
     acceleration for X, Y and Z movement, and the extent and rate of rotation in space (roll, pitch and yaw). Such sensing systems adapted to handheld and end-user appliances are known from modern smartphones and gaming gear. The number and configuration of sensors fixed on sport equipment, obviously depend on the various motions that reasonably can be expected from such equipment in normal use. 
     The central unit produces a trajectory curve of the movement of the object where the sensors reside, and also calculates the score, as explained above. A RF, e.g. a Bluetooth interface  13   a  provides a wireless link to a corresponding interface  13   b  of a user device  14 , such as a smartphone or a laptop computer with internet connection. 
     The tricks are recognized and evaluated by calculation and comparison to target reference data of certain known tricks. The storage of the reference data as well as the calculation and comparison can be implemented in the central unit or in the network or distributed in both central unit and network. It is also possible that the user trick data is stored in the network and used for recognizing new tricks which can be further used as new target reference trick data. The users can thus teach new tricks to the system. 
     It is clear to one skilled in the art that the invention is not restricted to the examples and embodiments presented above, but may vary within the scope of the appended claims.