Follower vehicle control system and method for forward and reverse convoy movement

1. A vehicle control system for causing a follower vehicle to follow a leader, comprising:

a tether system mounted to the follower vehicle, said tether system comprising:

a tether having an end adapted to be attached to the leader;

a length sensor operatively associated with said tether, said length sensor sensing a length of said tether extending between the follower vehicle and the leader; and

an angle sensor operatively associated with said tether, said angle sensor sensing an angle between said tether and the follower vehicle;

a path tracking system operatively associated with said tether system, said path tracking system determining a path traveled by the leader;

a path control system operatively associated with said path tracking system and the follower vehicle, said path control system causing the follower vehicle to follow the path traveled by the leader;

a spacing control system operatively associated with said path tracking system and the follower vehicle, said spacing control system causing the follower vehicle to maintain a predetermined spacing between the follower vehicle and the leader; and

a dead reckoning system operatively associated with the follower vehicle, said path tracking system, and said path control system, said dead reckoning system producing position and heading estimates of the follower vehicle.

2. The system of claim 1 , wherein said dead reckoning system comprises an odometer and a steering angle sensor.

3. The system of claim 1 , wherein said dead reckoning system comprises an odometer and a heading gyroscope.

4. A vehicle control system for causing a follower vehicle to follow a leader, comprising:

a tether system mounted to the follower vehicle, said tether system comprising:

a tether having an end adapted to be attached to the leader;

a length sensor operatively associated with said tether, said length sensor sensing a length of said tether extending between the follower vehicle and the leader; and

an angle sensor operatively associated with said tether, said angle sensor sensing an angle between said tether and the follower vehicle;

a path tracking system operatively associated with said tether system, said path tracking system determining a path traveled by the leader;

a path control system operatively associated with said path tracking system and the follower vehicle, said path control system causing the follower vehicle to follow the path traveled by the leader;

a spacing control system operatively associated with said path tracking system and the follower vehicle, said spacing control system causing the follower vehicle to maintain a predetermined spacing between the follower vehicle and the leader; and

a direction control system operatively associated with the follower vehicle and said tether system, said direction control system selecting between a forward travel direction and a reverse travel direction for the follower vehicle based on a change in length of said tether.

5. A vehicle control system for causing a follower vehicle to follow a leader, comprising:

a tether system mounted to the follower vehicle, said tether system comprising:

a tether having an end adapted to be attached to the leader;

a length sensor operatively associated with said tether, said length sensor sensing a length of said tether extending between the follower vehicle and the leader; and

an angle sensor operatively associated with said tether, said angle sensor sensing an angle between said tether and the follower vehicle,

a path tracking system operatively associated with said tether system, said path tracking system determining a path traveled by the leader;

a path control system operatively associated with said path tracking system and the follower vehicle, said path control system causing the follower vehicle to follow the path traveled by the leader;

a spacing control system operatively associated with said path tracking system and the follower vehicle, said spacing control system causing the follower vehicle to maintain a predetermined spacing between the follower vehicle and the leader; and

a damper operatively associated with said angle sensor.

6. A vehicle control system for causing a follower vehicle to follow a leader, comprising:

a tether mounted to the follower vehicle, said tether having an end adapted to be attached to the leader;

length sensing means operatively associated with said tether for sensing a length of said tether extending between the follower vehicle and the leader;

angle sensing means operatively associated with said tether for sensing an angle between said tether and the follower vehicle;

a path tracking system operatively associated with said length sensing means and said angle sensing means, said path tracking system determining a path traveled by the leader;

a path control system operatively associated with said path tracking system and the follower vehicle, said path control system causing the follower vehicle to follow the path traveled by the leader;

a spacing control system operatively associated with said path tracking system and the follower vehicle, said spacing control system causing the follower vehicle to maintain a predetermined spacing between the follower vehicle and the leader; and

a dead reckoning system operatively associated with the follower vehicle, said path tracking system, and said path control system, said dead reckoning system producing position and heading estimates of the follower vehicle.

7. A method for causing a follower vehicle to follow a leader, comprising:

connecting the follower vehicle to the leader with a tether;

measuring a length of the tether connecting the follower vehicle to the leader;

measuring an angle between the tether and the follower vehicle;

determining a position of the leader based on the measured length and the measured angle;

determining a path traveled by the leader based on a plurality of determined leader positions;

steering the follower vehicle so that the follower vehicle substantially follows the path traveled by the leader, wherein steering the follower vehicle comprises:

determining an actual position of the follower vehicle;

comparing the actual position of the follower vehicle with a desired position of the follower vehicle to determine an off-path error;

using the off-path error to calculate a desired curvature; and

using the desired curvature to produce a steering command for the follower vehicle; and

controlling a velocity of the follower vehicle so that the follower vehicle maintains a predetermined distance from the leader.

8. The method of claim 7 , wherein using the off-path error to calculate a desired curvature comprises:

establishing a look-ahead length;

using the look-ahead length to identify a look-ahead point on the path traveled by the leader; and

using the look-ahead point to determine the off-path error.

9. The method of claim 8 , wherein the look-ahead length is a function of the velocity of the follower vehicle.

10. A method for causing a follower vehicle to follow a leader, comprising:

connecting the follower vehicle to the leader with a tether

measuring a length of the tether connecting the follower vehicle to the leader;

measuring an angle between the tether and the follower vehicle;

determining a position of the leader based on the measured length and the measured angle;

determining a path traveled by the leader based on a plurality of determined leader positions;

steering the follower vehicle so that the follower vehicle substantially follows the path traveled by the leader; and

controlling a velocity of the follower vehicle so that the follower vehicle maintains a predetermined distance from the leader, wherein controlling the velocity of the follower vehicle comprises:

determining an actual length between the leader and the follower vehicle, the actual length being measured along the path traveled by the leader;

determining a desired length between the leader and the follower vehicle, the desired length being measured along the path traveled by the leader;

comparing the actual length and the desired length to determine a vehicle spacing error; and

using the vehicle spacing error to control the velocity of the follower vehicle.

11. A method for causing a follower vehicle to follow a leader, comprising:

connecting the follower vehicle to the leader with a tether;

measuring a length of the tether connecting the follower vehicle to the leader;

measuring an angle between the tether and the follower vehicle;

determining a position of the leader based on the measured length and the measured angle;

determining a path traveled by the leader based on a plurality of determined leader positions;

steering the follower vehicle so that the follower vehicle substantially follows the path traveled by the leader;

controlling a velocity of the follower vehicle so that the follower vehicle maintains a predetermined distance from the leader;

operating the follower vehicle in a reverse travel direction; and

steering the follower vehicle in the reverse travel direction to follow in reverse at least a portion of the path traveled by the leader.

12. A method for causing a follower vehicle to follow a leader, comprising:

connecting the follower vehicle to the leader with a tether;

measuring a length of the tether connecting the follower vehicle to the leader;

measuring an angle between the tether and the follower vehicle;

determining a position of the leader based on the measured length and the measured angle;

determining a path traveled by the leader based on a plurality of determined leader positions;

steering the follower vehicle so that the follower vehicle substantially follows the path traveled by the leader;

controlling a velocity of the follower vehicle so that the follower vehicle maintains a predetermined distance from the leader;

operating the follower vehicle in a reverse travel direction; and

steering the follower vehicle in the reverse travel direction based on the measured angle between the tether and the follower vehicle.

13. A method for causing a follower vehicle to follow a leader, comprising:

connecting the follower vehicle to the leader with a tether;

measuring a length of the tether connecting the follower vehicle to the leader;

measuring an angle between the tether and the follower vehicle;

determining a position of the leader based on the measured length and the measured angle;

determining a path traveled by the leader based on a plurality of determined leader positions;

steering the follower vehicle so that the follower vehicle substantially follows the path traveled by the leader;

controlling a velocity of the follower vehicle so that the follower vehicle maintains a predetermined distance from the leader; and

selecting to operate the follower vehicle in either a forward travel direction or a reverse travel direction for the follower vehicle based on a change in length of said tether.