Description:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to the position update method based on the inertial measurements, and more specifically, relates to a system and method for position update correction for a stationary vehicle.

BACKGROUND
[0002] Real-time position estimation based on inertial measurements of a vehicle is of strategic importance. In the absence of a global positioning system (GPS), the inertial parameters measured by an inertial measurement unit (IMU) are used to update the position estimate. The measurements used are three-axis accelerometer readings and three rotation rate measurements along the three-axes along with odometer count.
[0003] The algorithm consists of a position update algorithm using these measurements, using the starting point latitude, longitude, heading roll and pitch. In the stationary case, the position estimate gets disturbed as sensor outputs other than the odometer give nonzero measurements due to inherent noise and Earth rotation. Further, the vehicles generally stop with the engine on which leads to a large error in the position estimate of the vehicle. Ideally, under vehicle stationary conditions all sensor outputs must be zero if the Earth rotation effect is eliminated.
[0004] An example of such a navigation system is recited in a patent EP1760431A1, which describes an inertial navigation system consisting of a plurality of Kalman filters. The system consists of at least one inertial sensor. A processing unit and plurality of Kalman filters are implemented in the processing unit. The plurality of Kalman filters process zero velocity updates on the last cycle. The plurality of Kalman filters is used to optimize the performance during periods of intermittent motion.
[0005] Yet another example is recited in a patent US6029111A, entitled “Vehicle navigation system and method using GPS velocities”. The patent relates to a low-cost sensor i.e., micro-machined and piezoelectric sensors that are used, which partially overcomes the low dynamics and line of sight limitations of GPS. The low-cost sensors introduce system-level errors due to their inherent DC offset and drift rates. In a vehicle navigation system, minimizing both the sensor-induced errors and GPS low dynamic limitations is done by using a zero-motion detection system.
[0006] The basic method adopted for navigation requires the estimation of the position of a vehicle in real-time. This is performed by the following steps:
• Start from a position of known latitude and longitude
• Initialize the attitude and quaternion parameters.
• As the vehicle moves update the attitude parameters
• Use the attitude parameters and the distance movement information from the odometer to update the latitude and longitude.
[0007] The basic drawback of the existing methods is that even if the vehicle gets stationary, once the movement has started the engine may disturb the heading, pitch and roll values as the quaternion gets updated. This leads to wrong position estimates once the movement starts.
[0008] Therefore, it is desired to overcome the drawbacks, shortcomings, and limitations associated with existing solutions, and develop a cost-effective system that removes errors due to positional updates occurring during stationary situations of vehicles during navigation and avoids any computationally intensive methods.

OBJECTS OF THE PRESENT DISCLOSURE
[0009] An object of the present disclosure relates, to the position update method based on the inertial measurements, and more specifically, relates to a system and method for position update correction for a stationary vehicle.
[0010] Another object of the present disclosure is to provide a system that removes errors due to positional updates occurring during the stationary situations of the vehicle during navigation.
[0011] Another object of the present disclosure is to provide a system that detects the stationarity of the vehicle and restores the quaternion to the previous value.
[0012] Another object of the present disclosure is to provide a system that does not require any computationally intensive methods such as Kalman filters or any kind of complex algorithms.
[0013] Yet another object of the present disclosure is to provide a cost-effective system.

SUMMARY
[0014] The present disclosure relates to the position update method based on the inertial measurements, and more specifically, relates to a system and method for position update correction for a stationary vehicle. The main objective of the present disclosure is to overcome the drawback, limitations, and shortcomings of the existing system and solution, by providing a system for detecting the stationarity of a vehicle and restoring the navigation parameters such as quaternion, and direction cosines to previous values.
[0015] The present disclosure includes an inertial measurement unit (IMU) sensor that provides inertial measurement data from an accelerometer and gyroscope. The inertial measurement data pertaining to acceleration and angular velocity components for the vehicle. An attitude computer is coupled to the IMU sensor, the attitude computer is adapted to receive the inertial measurement data from the IMU sensor to compute altitude parameters. The altitude parameters pertaining to heading, roll and pitch values. An odometer is coupled to the attitude computer, the odometer is adapted to monitor the distance travelled by the vehicle to generate count values of a set of pulses at a pre-designed distance. A navigation processing unit coupled to the attitude computer, the navigation processing unit is configured to receive the attitude parameters and odometer count values and analyse the received attitude parameters and odometer count values to compute and display a set of output parameters pertaining to velocity, attitude, and position, thereby facilitating the detection of the stationarity of the vehicle. Further, the navigation processing unit is configured to restore the navigation parameters to previous values when there is no change in the odometer count value and a change in the attitude parameters is less than a pre-defined threshold. The navigation parameters pertaining to quaternion and direction cosines. Accordingly, the system removes errors due to positional updates occurring during the stationary situations of the vehicle during navigation.
[0016] The navigation processing unit is adapted to update quaternion values, the navigation processing unit is configured to store navigation parameters and start a counter, detect changes in the attitude parameters, detect changes in the odometer count value and restore quaternion values based on the counter. The change in the attitude parameters is detected by calculating the difference between the current heading, pitch and roll values and the previous heading, pitch and roll value stored before a certain pre-defined time instant. The vehicle is detected as stationary if the differences in heading, pitch and roll values are less than a pre-defined threshold.
[0017] Besides, the change detection in odometer count value is performed by obtaining a difference between the current odometer count value and the odometer count value stored before a certain pre-defined time instant and the vehicle is detected as stationary if there is no change in the odometer count value. The change in the odometer count value is determined before the change in the attitude parameters. Those skilled in the art would appreciate that as the conventional computationally intensive methods such as Kalman filters or any kind of complex algorithms is avoided in the present invention, the additional material usage and additional assembly operation may not be required, thereby reducing cost.
[0018] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0020] FIG. 1 illustrates an exemplary representation of the inertial navigation system, in accordance with an embodiment of the present disclosure.
[0021] FIG. 2 illustrates an exemplary flow chart of the navigation algorithm, in accordance with an embodiment of the present disclosure.
[0022] FIG. 3 illustrates an exemplary flow chart of quaternion restoration based on stationarity detection, in accordance with an embodiment of the present disclosure.
[0023] FIG. 4 illustrates an exemplary flow chart of the method for providing a position estimate of a vehicle, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0024] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0025] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0026] The present disclosure relates, in general, to the position update method based on the inertial measurements, and more specifically, relates to a system and method for position update correction for a stationary vehicle. The proposed system disclosed in the present disclosure overcomes the drawbacks, shortcomings, and limitations associated with the conventional system by providing a system that enables quaternion restoration based on stationarity detection of the vehicle. In traditional navigation, the initial position parameters are found using the initialization algorithms based on acceleration and rotation rate measurements while the vehicle is stationary. The initial state can be represented in terms of quaternion/direction cosine/heading, roll, and pitch. Then as the vehicle moves the quaternion parameters are updated. The present invention mainly relates to a position update method based on the inertial measurements and more particularly correction of the position based on the detection of stationarity of the vehicle after movement has started. Furthermore, the present invention can be used for the position estimation of land vehicles. The present disclosure can be described in enabling detail in the following examples, which may represent more than one embodiment of the present disclosure.
[0027] The present disclosure describes a system and method to detect if a vehicle is stationary and restore the quaternion to the previous value. The method requires the detection of vehicle stationarity based on changes in the heading, roll and pitch values and changes in the odometer count value. The main code for quaternion update based on inertial measurements runs freely. Whenever the stationarity is detected, the quaternion is restored and the method for quaternion restoration can be used for any type of navigation system.
[0028] In an aspect, the present disclosure relates to a system for detecting the stationarity of a vehicle, the system includes an inertial measurement unit (IMU) sensor that provides inertial measurement data from an accelerometer and gyroscope, the inertial measurement data pertaining to acceleration and angular velocity components for a vehicle. An attitude computer is coupled to the IMU sensor, the attitude computer is adapted to receive the inertial measurement data from the IMU sensor to compute altitude parameters. The altitude parameters pertaining to heading, roll and pitch values. An odometer is coupled to the attitude computer, the odometer monitors the distance travelled by the vehicle to generate count values of a set of pulses at a pre-designed distance, and the odometer is coupled to the attitude computer. A navigation processing unit coupled to the attitude computer, the navigation processing unit is configured to receive the attitude parameters and odometer count values and analyse the received attitude parameters and odometer count values to compute a set of output parameters to be displayed, the set of output parameters pertaining to velocity, attitude, and position facilitating the detection of the stationarity of the vehicle. The navigation processing unit is configured to restore the navigation parameters to previous values, the navigation parameters pertaining to quaternion values and direction cosines. when the counter value is equal to a predefined value and if there is no change in the odometer count value and change in the attitude parameters is less than a pre-defined threshold.
[0029] Further, the attitude computer computes the direction cosine matrix using the inertial measurement data of the gyroscope and subsequently updates the attitude parameters. The navigation processing unit is configured to restore the navigation parameters to previous values, the navigation parameters pertaining to quaternion values and direction cosines. Moreover, the change in the odometer count value is determined before the change in the attitude parameters.
[0030] The advantages achieved by the system of the present disclosure can be clear from the embodiments provided herein. The proposed system removes errors due to positional updates occurring during the vehicle stationary situations during navigation, where the system detects the stationarity of a vehicle and restores the quaternion to the previous value. The system does not require any computationally intensive methods such as Kalman filters or any kind of complex algorithms, thereby facilitating a cost-effective system. The description of terms and features related to the present disclosure shall be clear from the embodiments that are illustrated and described; however, the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents of the embodiments are possible within the scope of the present disclosure. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect to the following description.
[0031] FIG. 1 illustrates an exemplary representation of the inertial navigation system, in accordance with an embodiment of the present disclosure.
[0032] Referring to FIG. 1, the inertial navigation system 100 (also referred to as system 100, herein) is configured to detect the stationarity of a vehicle and restore the navigation parameters to the previous value. The navigation parameters pertaining to quaternion values and direction cosines. The system 100 can include IMU sensors 102, attitude computer 104, odometer 106, navigation processing unit 108 and display unit (not shown). The proposed system 100 is configured for the removal of errors due to positional updates occurring during the stationary situations of vehicles during navigation. The proposed system 100 can be used for the position estimation of land vehicles.
[0033] In an embodiment, the IMU sensors 102 can include three-axis accelerometers 110 and three-axis gyroscopes 112. The IMU sensor 102 can provide inertial measurement data from the accelerometer 110 and gyroscope 112. The inertial measurement data pertains to acceleration and angular velocity components. The attitude computer 104 is coupled to the IMU sensor 102 and adapted to receive the acceleration and angular velocity components from the IMU sensor 102 to compute attitude parameters pertaining to heading, roll and pitch values. The attitude computer 104 computes the direction cosine matrix using the current gyroscope outputs and subsequently updates the attitude parameters.
[0034] The odometer 106 is coupled to the attitude computer 104, to monitor the distance travelled by the vehicle to generate count values of a set of pulses at a pre-designed distance, the odometer 106 is coupled to the attitude computer. The velocity components can be obtained from the odometer 106 obtained from the rate at which it gives the count. The navigation processing unit 108 is coupled to the attitude computer 104 and adapted to receive the attitude parameters and odometer count values of the odometer as input and computes velocity, attitude, and position. A display unit for displaying the attitude, velocity, and position of the vehicle. The odometer 106 from which velocity components can be obtained from the rate at which it gives the count. The present disclosure requires the detection of vehicle stationarity based on changes in the attitude parameters and the odometer count value.
[0035] The present disclosure discloses the removal of errors due to positional updates occurring during the stationary situations of the vehicle during navigation. When the vehicle moves on terrain, the set of pulses obtained from odometer 106 can be converted into distance travelled. The distance is subsequently dissolved into north and east components. The dissolved components can be accumulated and can be added to the initial position as the vehicle moves. The vehicle generally stops with the engine on and in such a stationary case, the position estimate is disturbed as sensor outputs give nonzero measurements due to inertial sensor errors.
[0036] Further, if the navigation algorithm is not halted during vehicle stationarity, the engine-on noise is measured by the accelerometer sensors and the gyroscope can disturb the quaternion, which quantifies the orientation of the vehicle. This further leads to a large error in the position estimate of the vehicle. To overcome the above limitation, the present disclosure detects the stationarity of the vehicle based on the odometer value and the attitude parameters. The navigation processing unit 108 is configured for running navigation equations. The stationarity detection is as follows:
• Storage of the navigation parameters and starting of the counter. The navigation parameters pertain to a quaternion, Direction Cosines.
• Detecting the changes in the attitude parameters such as heading, roll and pitch.
• Detecting the changes in the odometer count value.
• Quaternion restoration based on the counter.
• Once the counter value is equal to a pre-defined value, the quaternion is restored to the previous value if there is no change in the odometer count value and change in the attitude parameters is less than a pre-defined threshold.
[0037] The change detection process in the attitude parameters further can include the following steps:
• Difference between the current heading and the previous heading value stored before a certain pre-defined time instant is calculated.
• Difference between the current pitch and the previous pitch value stored before a certain pre-defined time instant is calculated.
• Difference between the current roll and the previous roll value stored before a certain pre-defined time instant is calculated.
• The vehicle is detected as stationary if the differences in heading, pitch and roll values are less than a pre-defined threshold.
[0038] Besides, the odometer count change detection can include the following steps:
• Difference between the current odometer count and the odometer count value stored before a certain pre-defined time instant is obtained.
• The vehicle is detected as stationary if there is no change in the odometer count value.
[0039] The change in the odometer count value is checked before the change in the attitude parameters. Once the counter value is equal to a predefined value, the quaternion is restored to the previous value. If there is no change in the odometer count value and the change in the attitude parameters is less than a pre-defined threshold.
[0040] Thus, the present disclosure overcomes the drawbacks, shortcomings, and limitations associated with existing solutions, and provides a system that removes errors due to positional updates occurring during the stationary situations of the vehicle during navigation. The proposed system for quaternion restoration can be used for any type of navigation system. The system detects the stationarity of the vehicle and restores the quaternion to the previous value and does not require any computationally intensive methods such as Kalman filters or any kind of complex algorithms, thereby facilitating a cost-effective system.
[0041] FIG. 2 illustrates an exemplary flow chart of the navigation algorithm 200, in accordance with an embodiment of the present disclosure.
[0042] At block 202, processing block 202 shows the sensor measurement interface coupled to the processing unit. The IMU sensor 102 can be adapted to measure the acceleration and angular velocity components.
[0043] At block 204, the sensor outputs are used to find the initial orientation of the vehicle. This initial orientation can either be represented as heading, pitch and roll or quaternion vector. At block 206, once the vehicle starts moving the sensor outputs are used to update the quaternion vector, which in turn gives the heading, pitch, and roll values.
[0044] FIG. 3 illustrates an exemplary flow chart of quaternion restoration 300 based on stationarity detection, in accordance with an embodiment of the present disclosure.
[0045] Referring to FIG. 3, at block 302, the present quaternion values are stored at the start of the stationarity detection algorithm. At block 304, the present attitude values and odometer count value is also stored at the start of the stationarity detection algorithm. At block 306, the motion counter is incremented until it reaches a pre-defined count value “C” at block 308. At block 310, once the count value is reached, a check is made to whether the present odometer count value is equal to the odometer count value stored at the start of the stationarity detection algorithm. If the values are not equal, the motion counter is reset and quaternion values at the present instant of time are stored.
[0046] At block 312, if the odometer count values are equal, the difference between the present heading value and the heading stored at the start of the algorithm, the difference between the present pitch and the pitch stored at the start of the algorithm, and the difference between the present roll and the roll stored at the start of the algorithm are computed. At block 314, if the differences in the heading, roll and pitch values are less than a pre-defined threshold, quaternions are restored with the previous values stored at the start of the algorithm at block 316.
[0047] FIG. 4 illustrates an exemplary flow chart of the method for providing a position estimate of a vehicle, in accordance with an embodiment of the present disclosure.
[0048] Referring to FIG. 4, method 400 includes block 402, the inertial measurement unit (IMU) sensor can provide inertial measurement data from an accelerometer and gyroscope. The inertial measurement data pertaining to acceleration and angular velocity components for a vehicle. At block 404, the attitude computer can receive the inertial measurement data from the IMU sensor to compute altitude parameters, the attitude computer is coupled to the IMU sensor.
[0049] At block 406, the odometer can monitor the distance travelled by the vehicle to generate count values of a set of pulses at a pre-designed distance, the odometer is coupled to the attitude computer. At block 408, the navigation processing unit coupled to the attitude computer can receive the attitude parameters and odometer count value. At block 410, the navigation processing unit can analyse the received attitude parameters and odometer count values to compute a set of output parameters to be displayed, the set of output parameters pertaining to velocity, attitude, and position facilitating the detection of the stationarity of the vehicle and restoring the navigation parameters.
[0050] It will be apparent to those skilled in the art that the system 100 of the disclosure may be provided using some or all of the mentioned features and components without departing from the scope of the present disclosure. While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.

ADVANTAGES OF THE PRESENT INVENTION
[0051] The present disclosure provides a system that removes errors due to positional updates occurring during the stationary situations of the vehicle during navigation.
[0052] The present disclosure provides a system that detects the stationarity of the vehicle and restores the quaternion to the previous value.
[0053] The present disclosure provides a system that does not require any computationally intensive methods such as Kalman filters or any kind of complex algorithms.
[0054] The present disclosure provides a cost-effective system.
, Claims:1. A system (100) for providing position estimate of a vehicle, the system comprising:
an inertial measurement unit (IMU) sensor (102) that provides inertial measurement data from an accelerometer and gyroscope, the inertial measurement data pertaining to acceleration and angular velocity components for a vehicle;
an attitude computer (104) is coupled to the IMU sensor, the attitude computer is adapted to receive the inertial measurement data from the IMU sensor to compute altitude parameters;
an odometer (106) is coupled to the attitude computer, the odometer is adapted to monitor the distance travelled by the vehicle to generate count values of a set of pulses at a pre-designed distance; and
a navigation processing unit (108) coupled to the attitude computer, the navigation processing unit configured to:
receive the attitude parameters and odometer count values; and
analyse the received attitude parameters and odometer count values to compute and display a set of output parameters pertaining to velocity, attitude, and position facilitating the detection of the stationarity of the vehicle and restoring the navigation parameters.
2. The system as claimed in claim 1, wherein the altitude parameters pertaining to heading, roll and pitch values.
3. The system as claimed in claim 1, wherein the navigation processing unit (108) is configured to restore the navigation parameters to previous values, the navigation parameters pertaining to quaternion values and direction cosines.
4. The system as claimed in claim 1, wherein the navigation processing unit (108) adapted to update the quaternion values, the navigation processing unit configured to:
store navigation parameters and start a counter;
detect changes in the attitude parameters;
detect changes in the odometer count value; and
restore the quaternion values based on the counter.
5. The system as claimed in claim 1, wherein the detection of change in the attitude
parameters configured to:
calculate the difference between the current heading value and the previous heading value stored before a certain pre-defined time instant;
calculate the difference between the current pitch value and the previous pitch value stored before a certain pre-defined time instant;
calculate the difference between the current roll value and the previous roll value stored before a certain pre-defined time instant; and
detect the vehicle as stationary if the differences in heading, pitch and roll values are less than a pre-defined threshold.
6. The system as claimed in claim 1, wherein the odometer count change detection
configured to:
obtain a difference between the current odometer count value and the odometer count value stored before a certain pre-defined time instant; and
detect the vehicle as stationary if there is no change in the odometer
count value.
7. The system as claimed in claim 1, wherein the change in the odometer count value is determined before the change in the attitude parameters.
8. The system as claimed in claim 1, wherein the quaternion values are restored to the previous value when the counter value is equal to a predefined value and if there is no change in the odometer count value and change in the attitude parameters is less than a pre-defined threshold.
9. The system as claimed in claim 1, wherein the attitude computer (104) computes the direction cosine matrix using the inertial measurement data of the gyroscope and subsequently updates the attitude parameters.
10. A method (400) for providing a position estimate of a vehicle, the method comprising:
providing (402), by an inertial measurement unit (IMU) sensor, inertial measurement data from an accelerometer and gyroscope, the inertial measurement data pertaining to acceleration and angular velocity components for a vehicle;
receiving (404), by an attitude computer, the inertial measurement data from the IMU sensor to compute altitude parameters, the attitude computer is coupled to the IMU sensor;
monitoring (406), by an odometer, the distance travelled by the vehicle to generate count values of a set of pulses at a pre-designed distance, the odometer is coupled to the attitude computer;
receiving (408), at a navigation processing unit coupled to the attitude computer, the attitude parameters and odometer count values; and
analysing (410), at the navigation processing unit, the received attitude parameters and odometer count values to compute a set of output parameters to be displayed, the set of output parameters pertaining to velocity, attitude, and position facilitating the detection of the stationarity of the vehicle and restoring the navigation parameters.