Method for Teleoperating an Unmanned Ground Vehicle With a Pan Camera and Such a Ground Vehicle

• US 20100138079A1
• Filed: 02/12/2007
• Published: 06/03/2010
• Est. Priority Date: 02/17/2006
• Status: Active Grant

• Current Assignee: Totalforsvarets Forskningsinstitut (FOI)
• Original Assignee: Totalforsvarets Forskningsinstitut (FOI)
• Inventors: Ögren, Petter
• Granted Patent: US 8,386,089 B2
• Time in Patent Office: Days
• US Class Current: 701/2
• CPC Class Codes: G05D 1/0038 by providing the operator with simple or augmented images from one or more cameras located onboard the vehicle, e.g. tele-operation images analyzed by a computer and used for automatic navigation G05D1/0246

Abstract

The invention relates to a method of teleoperating an unmanned ground vehicle (10) comprising a first drive unit (1), a second drive unit (2) and a pan camera (4), arranged in front of or behind the nominal centre of rotation (z) of the vehicle. In the method, the operator (8) controls the translation and rotation of the camera, and thus his field of vision, relative to a camera-fixed coordinate system, and the movement of the vehicle is calculated to perform this camera movement. Consequently, the operator can in most cases ignore the vehicle dynamics and experience the feeling of controlling a floating camera. The invention also concerns an unmanned ground vehicle with a control unit which performs the method.

Claims

1. A method of teleoperating an unmanned ground vehicle (10) comprising a first drive unit (1), a second drive unit (2) and a pan camera (4), arranged in front of or behind the nominal centre of rotation (z) of the vehicle, characterised in that the operator (8) controls the rotation of the camera decoupled from the vehicle rotation and controls the motion of the vehicle in each time instant based upon the orientation of the camera, meaning that what is seen in the centre of the camera image is reached by a command to move the vehicle forward etc., and that the vehicle comprises a control unit (5) which based upon the command signal (20) for the movement of the vehicle calculates a first and a second control signal (21, 22) to the respective drive units (1, 2) that will move the vehicle in the desired way and a third control signal (24) to the camera (4) that counter-acts the movement of the vehicle so that the orientation of the camera is not affected by the movement of the vehicle.

2. A method as claimed in claim 1, characterised in that

the signal (20) comprises information on speed (s₁, s₂) and the angular velocity (s_ω

) of the camera (4) relative to a camera-fixed coordinate system;

the velocity of the first and the second drive unit (2) is calculated by the control unit (5) as follows;

$\left(\begin{array}{c}{v}_1\\ v_2\end{array}\right)={\left(\begin{array}{cc}1/2& 1/2\\ L/b& -L/b\end{array}\right)}^{-1}<br><br>\left(\begin{array}{cc}\cos <br><br><br><br>\mathrm{\phi <br><br>}& -\sin <br><br><br><br>\mathrm{\phi <br><br>}\\ \sin <br><br><br><br>\mathrm{\phi <br><br>}& \cos <br><br><br><br>\mathrm{\phi <br><br>}\end{array}\right)<br><br>\left(\begin{array}{c}{s}_1\\ s_2\end{array}\right)$

where b is the distance between the drive units, L is the distance from the nominal centre of rotation z to the camera (4) and θ

the angle of the camera relative to the vehicle;

the angular velocity of the camera relative to the vehicle is calculated by the control unit (5) as follows;

$k=s_{\mathrm{\omega <br><br>}}-\stackrel{.}{\mathrm{\theta <br><br>}}=s_{\mathrm{\omega <br><br>}}-\frac{v_1-v_2}{b}$

where θ

is the orientation of the vehicle relative to an earth-fixed coordinate system;

the first and the second control signal (21, 22) contain information on the velocity (v₁, v₂) of the respective drive units (1, 2);

the third control signal (24) contains information on the angular velocity (k) of the camera (4) relative to the vehicle.

3. A method as claimed in claim 1, characterised in that

the signal (20) contains information on acceleration (s₁, s₂) and the angular velocity (s_ω

) of the camera (4) relative to a camera-fixed coordinate system;

the force and the torque of the first and the second drive unit (1, 2) are calculated as follows;

$\left(\begin{array}{c}F/m\\ \mathrm{\tau <br><br>}<br><br><br><br>L/J\end{array}\right)=\left(\begin{array}{c}L<br><br><br><br>{\mathrm{\omega <br><br>}}^2\\ -v<br><br><br><br>\mathrm{\omega <br><br>}\end{array}\right)+\left(\begin{array}{cc}\cos <br><br><br><br>\mathrm{\phi <br><br>}& -\sin <br><br><br><br>\mathrm{\phi <br><br>}\\ \sin <br><br><br><br>\mathrm{\phi <br><br>}& \cos <br><br><br><br>\mathrm{\phi <br><br>}\end{array}\right)<br><br>\left(\begin{array}{c}{s}_1\\ s_2\end{array}\right)$

where v is the velocity of the vehicle, ω

is the angular velocity of the vehicle, F is the force generated by the drive units (1, 2) on the ground, m is the mass of the vehicle, τ

is the torque generated by the drive units (1, 2), J is the moment of inertia, φ

the angle of the camera relative to the vehicle;

the force of the first and the second drive unit is calculated by the control unit as follows;

$\left(\begin{array}{c}{F}_1\\ F_2\end{array}\right)=\left(\begin{array}{cc}1/2& 1/b\\ 1/2& -1/b\end{array}\right)<br><br>\left(\begin{array}{c}F\\ \mathrm{\tau <br><br>}\end{array}\right)$

where F₁ is the force exerted on tracks/drive wheels of the first drive unit and F₂ is the force exerted on tracks/drive wheels of the second drive unit;

the angular velocity of the camera relative to the vehicle is calculated as follows;

k=s−

{dot over (θ

)}=s_ω

−

ω

where θ

is the orientation of the vehicle relative to an earth-fixed coordinate system;

the first and the second control signal (21, 22) contain information on force (F₁, F₂) of the respective drive units (1, 2);

the third control signal (24) contains information on angular velocity (k) of the camera (4) relative to the vehicle.

4. A method as claimed in claim 1, wherein the first and the second drive unit (1, 2) comprise tracks (6, 7).

5. A method as claimed in claim 1, wherein the first and the second drive unit each comprise one or more drive wheels.

6. A method as claimed in claim 1, wherein the vehicle (10) comprises a navigation sensor (3) that measures the movement of the vehicle and compares it with the control signals (20) of the operator and transmits correction signals to the control unit (5) to compensate for differences.

7. A method as claimed in claim 1, wherein the ratio L/b is greater than 1/3, where b is the distance between the drive units, L is the distance from the nominal centre of rotation (z) to the camera (4).

8. A method as claimed in claim 1, wherein the control unit makes the calculations in real time and the control signals are transmitted to the drive units and the camera in real time.

9. An unmanned ground vehicle comprising a first drive unit (1), a second drive unit (2) and a pan camera, characterised in that it comprises a control unit (5) which uses a method as claimed in claim 1.

10. An unmanned ground vehicle as claimed in claim 9, wherein the first and the second drive unit (1, 2) comprise tracks (6, 7).

11. An unmanned ground vehicle as claimed in claim 9, wherein the first and the second drive unit each comprise one or more drive wheels.

12. An unmanned ground vehicle as claimed in claim 9, wherein the vehicle (10) comprises a navigation sensor (3) that measures the movement of the vehicle and compares it with the control signals (20) of the operator and transmits correction signals to the control unit (5) to compensate for differences.

13. An unmanned ground vehicle as claimed in claim 9, wherein the ratio L/b is greater than 1/3, where b is the distance between the drive units, L is the distance from the nominal centre of rotation (z) to the camera (4).