Claims
- 1. A walking stick navigator (WSN) apparatus and process comprising:
a staff assembly having a lower end and a top end, the staff assembly being carried by a surveyor moving along a path to be surveyed, the surveyor positioning the lower end of the staff assembly at a stationary point on the ground at the start of a stride, and pivoting the staff assembly around the stationary point substantially in the direction of surveyor movement, the surveyor lifting the staff assembly and repositioning the lower end of the staff assembly to a further stationary point in the direction of surveyor movement at the conclusion of the stride, the sequence being repeated with each successive stride interval, an Aided Inertial Navigation System (AINS), coupled to and aligned on the staff assembly, the AINS system providing output signals comprising position, velocity and platform angle signals, a switch means coupled to the lower end of the staff assembly for providing a stationary interval signals characterizing each successive stationary interval, and an input process coupled to be responsive to AINS output signals and to the stationary interval signals for providing at least one aiding input to the AINS for each successive stationary interval.
- 2. The WSN of claim 1 wherein the switch means further comprises:
a micro-switch switch means coupled to the lower end of the staff assembly and characterized to transfer providing the stationary interval signal during the period that the lower end is in contact with the ground.
- 3. The WSN of claim 1 further wherein the switch means further comprises:
a spring restored plunger switch having a frame coupled to the lower end of the staff assembly, the frame having a cylindrical hole, and a spring restored plunger residing therein, the plunger being transferred further into the cylindrical hole by contact with the ground, the motion of the plunger transferring an electrical contact to provide the stationary interval signal.
- 4. The WSN of claim 1 further wherein the input process further comprises:
a position measurement process responsive to the AINS output signals for providing a position increment measurement vector during a portion of each step for each respective stationary interval, to the AINS for controlling position error drift.
- 5. The WSN of claim 4 wherein the AINS further comprises a Kalman filter designed be responsive to a position increment measurement vector {right arrow over (z)}SNV-PP for each stationary period for estimating and regulating position and velocity vector errors to obtain a low position error drift.
- 6. The WSN of claim 5 wherein the Kalman filter computes a position increment measurement vector {right arrow over (z)}SNV-PP for each stationary interval by the following four process steps:
Step 1: The Kalman filter computes the relative inertial measurement unit (IMU) position vectors {right arrow over (ρ)}1n and {right arrow over (ρ)}2n at times t1 and t2 as follows: {right arrow over (ρ)}1n=Cbn(t1){right arrow over (l)}IMU-GRb {right arrow over (ρ)}2n=Cbn(t2){right arrow over (l)}IMU-GRb Step 2: The Kalman filter computes the relative IMU displacement as the measured difference vector after time t2 as follows: Δ{right arrow over (ρ)}1-2n={right arrow over (ρ)}2n−{right arrow over (ρ)}1n Step 3: The Kalman filter computes the inertial navigation solution displacement vector Δ{right arrow over (r)}SNV1-2n for the interval from t1 to t2 as follows: 9Δ r →SNV1-2n=∫t1t2v →SNVn ⅆtwhere {right arrow over (v)}SNVn is the inertial navigator velocity vector resolved in the INS navigation frame, and Step 4: The Kalman filter computes the position increment measurement vector {right arrow over (z)}SNV-PP by taking the difference between the relative IMU displacement vector and the corresponding inertial navigation vector as: {right arrow over (z)}SNV-PP=Δ{right arrow over (r)}SNV1-2n−Δ{right arrow over (ρ)}1-2n whereby the Kalman filter uses the position increment measurement vector {right arrow over (z)}SNV-PP to estimate and regulate position and velocity errors to be nearly zero and to obtain a low position error drift.
- 7. The WSN of claim 1 further wherein the input process further comprises:
a velocity measurement process responsive to the AINS output signals for providing a relative IMU velocity measurement vector to the AINS during a portion of each step for each respective stationary interval to control the position error drift.
- 8. The WSN of claim 7 wherein the AINS further comprises a Kalman filter designed be responsive to the velocity measurement vector {right arrow over (z)}SNV-ZV for each stationary interval for estimating and regulating position and velocity vector errors to obtain a low position error drift.
- 9. The WSN of claim 8 wherein the Kalman filter computes the velocity measurement vector {right arrow over (z)}SNV-ZV for each stationary interval by the following process two steps:
Step 1: The Kalman filter computes the relative IMU velocity with respect to the stationary ground reference point at each Kalman filter cycle time between times t1 and t2 via the following equation: {right arrow over (v)}GR-IMUn=Cbn({right arrow over (ω)}IMUb×{right arrow over (l)}GR-IMUb)=−Cbn({right arrow over (ω)}IMUb×{right arrow over (l)}IMU-GRb) where {right arrow over (ω)}IMUb is the angular rate of the IMU as measured by the gyros and corrected for Earth rate. Step 2: The Kalman filter computes the velocity measurement vector by taking the difference between the relative IMU velocity from Step 1 and the inertial velocity vector {right arrow over (v)}SNVn from the AINS as follows: {right arrow over (z)}SNV-ZV={right arrow over (v)}SNVn−{right arrow over (v)}GR-IMUn whereby the Kalman filter uses the velocity measurement vector {right arrow over (z)}SNV-ZV to estimate and regulate position and velocity errors to be nearly zero and to obtain a low position error drift.
- 10. The WSN of claim 9 wherein the Kalman filter is characterized to performe the velocity measurement vector {right arrow over (z)}SNV-ZV process at an iteration rate of at least 10 iterations per second during the stationary interval between the time t1 when the surveyor plants the WSN and the ground switch closes and the time t2 when the surveyor lifts the WSN and the ground switch opens.
- 11. A walking stick navigator (WSN) formed on a staff assembly having a lower end terminating in a spike, and a top end, a surveyor supporting the staff assembly while walking, the surveyor positions the staff assembly lower end to be in contact with the ground at a fixed point in front of the surveyor at the beginning of a step marking the start of a stationary interval, the surveyor pivoting the staff assembly about the fixed point in the direction of his movement, and raising the staff assembly to interrupt the shaft lower end contact with the ground at the fixed point at the conclusion of each step marking the end of the stationary interval, the WSN comprising:
an AINS having an IMU providing output signals developed at least partially from the outputs of a plurality of inertial sensors, a position measurement process responsive to the AINS output signals for providing a position increment measurement vector to the AINS during a portion of each step for each respective stationary interval to control position error drift.
- 12 The WSN of claim 11 further comprising:
a switch means for providing a stationary interval signal to the AINS characterizing the interval during which the shaft lower end is in contact with the ground.
- 13. The WSN of claim 12 wherein the AINS further comprises a Kalman filter designed be responsive to the position increment measurement vector {right arrow over (z)}SNV-PP for each stationary period for estimating and regulating position and velocity vector errors to obtain a low position error drift.
- 14. The WSN of claim 13 wherein the Kalman filter computes a position increment measurement vector {right arrow over (z)}SNV-PP for each stationary interval by the following four process steps:
Step 1: The Kalman filter computes the relative IMU position vectors {right arrow over (ρ)}1n and {right arrow over (ρ)}2n at times t1 and t2 as follows: {right arrow over (ρ)}1n=Cbn(t1){right arrow over (l)}IMU-GRb {right arrow over (ρ)}2n=Cbn(t2){right arrow over (l)}IMU-GRb Step 2: The Kalman filter computes the relative IMU displacement as the measured difference vector after time t2 as follows: Δ{right arrow over (ρ)}1-2n={right arrow over (ρ)}2n−{right arrow over (ρ)}1n Step 3: The Kalman filter computes the inertial navigation solution displacement vector Δ{right arrow over (r)}SNV1-2n for the interval from t1 to t2 as follows: 10Δ r →SNV1-2 n=∫t1t2v →SNVn ⅆtwhere {right arrow over (v)}SNVn is the inertial navigator velocity vector resolved in the INS navigation frame. Step 4: The Kalman filter computes the position increment measurement vector {right arrow over (z)}SNV-PP by taking the difference between the relative IMU displacement vector and the corresponding inertial navigation vector as: {right arrow over (z)}SNV-PP=Δ{right arrow over (r)}SNV1-2n−Δ{right arrow over (ρ)}1-2n whereby the Kalman filter uses the position increment measurement vector {right arrow over (z)}SNV-PP to estimate and regulate position and velocity errors to be nearly zero and to obtain a low position error drift.
- 15. A walking stick navigator (WSN) method comprising the steps of:
forming a WSN staff assembly having a lower end, a hand hold mid region and a top end, positioning an AINS having a Kalman filter on the staff assembly, positioning a switch means for signaling when the lower end of the staff assembly is stationary and in contact with the ground and for sending a contact signal to the AINS, the contact signal defining each interval during which the lower end of the staff assembly is in contact with the ground, supporting the staff assembly by holding the hand hold mid region, while walking, positioning the staff assembly lower end to be in contact with the ground at a fixed point in front of the surveyor at the beginning of a step marking the start of a stationary interval, the surveyor rotating the staff assembly about the fixed point in the direction of his movement, and raising the staff assembly to interrupt the staff assembly lower end contact with the ground at the fixed point at the conclusion of each step marking the end of the stationary interval, coupling the contact signal to the AINS to define the term of each respective stationary interval to the AINS, calculating aiding information for the AINS during and for the contact signal interval in response to contemporaneous IMU inertial measurements and the position of the AINS on the staff assembly.
- 16. The WSN method of claim 15 wherein the AINS further comprises:
a velocity measurement process responsive to the AINS output signals and the contact signal for providing a relative IMU velocity vector to the AINS during a portion of each step for each respective stationary interval to control the position error drift.
- 17. The WSN method of claim 16 wherein the AINS further comprises a Kalman filter designed be responsive to a velocity measurement vector {right arrow over (z)}SNV-ZV for each stationary interval for estimating and regulating position and velocity vector errors to obtain a low position error drift.
- 18. The WSN of claim 16 wherein the Kalman filter computes the velocity measurement vector {right arrow over (z)}SNV-ZV for each stationary interval by the following process steps:
Step 1: The Kalman filter the relative IMU velocity with respect to the stationary ground reference point at each Kalman filter cycle time between times t1 and t2 as follows: {right arrow over (v)}GR-IMU=Cbn({right arrow over (ω)}IMUb×{right arrow over (l)}GR-IMUb)=−Cbn({right arrow over (ω)}IMU-GRb) where {right arrow over (ω)}IMUb is the angular rate of the IMU as measured by the gyros and corrected for Earth rate. Step 2: The Kalman filter the velocity measurement vector by taking the difference between the relative IMU velocity from Step 1 and the inertial velocity vector {right arrow over (v)}SNVn from the AINS as follows: {right arrow over (z)}SNV-ZV={right arrow over (v)}SNVn−{right arrow over (v)}GR-IMUn whereby the Kalman filter uses the ZUPD measurement vector {right arrow over (z)}SNV-ZV to estimate and regulate position and velocity errors to be nearly zero and to obtain a low position error drift.
- 19. The WSN of claim 17 wherein the Kalman filter is characterized to perform the ZUPD measurement vector {right arrow over (z)}SNV-ZV process at an iteration rate of at least 10 iterations per second during the stationary interval between the time t1 when the surveyor plants the WSN and the ground switch closes and the time t2 when the surveyor lifts the WSN and the ground switch opens.
- 20 A walking stick navigator (WSN) formed on a staff assembly having a lower end, the staff assembly being carried by a surveyor, the WSN comprising
an AINS coupled to the staff a switch coupled to the lower end to provide a contact signal indicating when the lower end of the staff assembly is stationary, the contact signal defining the duration of a stationary interval, a position measurement process using a computer running a program solving a position aiding algorithm responsive to the contact signal, the position measurement process providing an aiding signal to an AINS coupled to the staff assembly.
- 21. The WSN of claim 20 wherein the position measurement process further comprises:
an algorithm for calculating a position increment measurement by calculating a first relative IMU displacement at the beginning of the contact signal and a second relative IMU displacement at the conclusion of the contact signal and calculating a time synchronised relative IMU displacement vector from the difference between the second relative IMU displacement and the first relative IMU displacement vectors, the algorithm obtaining the inertial navigation solution for the contact signal interval from the inertial navigation system and calculating a position increment measurement from the difference between the inertial navigation solution and the time synchronised relative IMU displacement.
- 22. The WSN of claim 20 wherein the position measurement process further comprises:
an algorithm for calculating a ZUPD measurement having an IGRLA vector input defining the location of an IMU on the shaft assembly with respect to the lower end of the shaft assembly, the algorithm calculating a the relative IMU velocity with respect to stationary ground at each Kalman filter cycle time from the beginning of the contact signal until the end of the contact signal by taking the cross product of the angular rate of the IMU with the IGRLA vector while in contact with the ground, and multiplying each respective cross product by the direction cosine matrix for a body to navigational reference system, the process then constructing the ZPUD measurement by subtracting the relative IMU velocity from the equivalent inertial velocity.
- 23. The WSN of claim 20 further comprising:
a GPS receiver providing acceptable GPS position aiding signals to the AINS, the surveyor moving along a path to be surveyed, the surveyor carrying the staff assembly with the lower end above the ground during intervals in which acceptable GPS position aiding signal to the AINS are available, the staff assembly having the look and feel of a GPS survey instrument during intervals in which acceptable GPS position aiding signals are being transferred to the AINS.
- 24. The WSN of claim 20 further comprising:
a GPS receiver providing acceptable GPS position aiding signals to the AINS, the surveyor moving along a path to be surveyed, the surveyor carrying the staff assembly lower end above the ground during intervals in which an acceptable GPS position aiding signal to the AINS is available, the surveyor manipulating the staff assembly like a standard GPS survey instrument, the staff assembly being characterised as having the “look and feel” of a GPS survey instrument during intervals in which acceptable GPS position aiding signals are being transferred to the AINS.
- 25. The WSN of claim 20 further comprising a GPS receiver coupled to provide a GPS aiding signal to the AINS as the surveyor moves along a path to be surveyed, the surveyor carrying the staff without contact with the ground during intervals when an acceptable GPS signal are available, the AINS being aided by GPS data, the surveyor manipulating the staff assembly like a standard GPS survey instrument during intervals in which an acceptable GPS receiver is available, and when GPS is not available, due to signal obstruction, the surveyor manipulating the staff assembly as a walking stick while the surveyor is walking, the surveyor bringing the lower end of the shaft assembly into contact with the ground, the switch providing the contact signal, the input process being responsive to the contact signal and coupled to the AINS output signals to provide at least one aiding input signal to the AINS for each successive stationary interval.
Parent Case Info
[0001] This application claims priority from U.S. provisional patent application No. 60/337,256 filed Dec. 03, 2001 for “A WALKING STICK NAVIGATOR FOR POSITION DETERMINATION BACKGROUND OF THE INVENTION” and having a common inventor and assignee.
Provisional Applications (1)
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Number |
Date |
Country |
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60337256 |
Dec 2001 |
US |