Distance control system of vehicle

1. A distance control system of a vehicle, comprising:

a signal transmitter for transmitting wireless signals forward with respect to a distance-controlled vehicle;

a signal receiver for receiving the wireless signals reflected and returned from an object vehicle;

a relative velocity measuring unit for measuring the relative velocity of the object vehicle in relation to the distance-controlled vehicle based on the received wireless signals;

a vehicle-to-vehicle distance measuring unit for measuring a first vehicle-to-vehicle distance between the distance-controlled vehicle and the object vehicle; and

a vehicle-to-vehicle distance calculating unit for calculating a third vehicle-to-vehicle distance based on the first vehicle-to-vehicle distance and a second vehicle-to-vehicle distance calculated from the relative velocity.

2. The distance control system as claimed in claim 1 , wherein the relative velocity measuring unit measures the difference between the frequency of the returned and received signal and the frequency of the wireless signals at the time of transmitting them to calculate the relative velocity.

3. The distance control system as claimed in claim 1 , wherein the vehicle-to-vehicle distance calculating unit calculates the second vehicle-to-vehicle distance by integrating the relative velocity.

4. The distance control system as claimed in claim 1 , wherein the vehicle-to-vehicle distance calculating unit calculates the third vehicle-to-vehicle distance by using an equation,

R — 3 rd =R — 1 st *G+R — 2 nd *(1 −G ),

wherein R — 3 rd is the third vehicle distance, R — 1 st is the first vehicle-to-vehicle distance, R — 2 nd is the second vehicle-to-vehicle distance, G is a gain for the first vehicle-to-vehicle distance, and (1−G) is a gain for the second vehicle-to-vehicle distance.

5. The distance control system as claimed in claim 4 , wherein the sum of the gains for the first vehicle-to-vehicle distance and the second vehicle-to-vehicle distance is 1.

6. The distance control system as claimed in claim 4 , wherein if the second vehicle-to-vehicle distance is smaller than the first vehicle-to-vehicle distance, the vehicle-to-vehicle distance calculating unit reduces the gain for the first vehicle-to-vehicle distance and increases the gain for the second vehicle-to-vehicle distance, and if the second vehicle-to-vehicle distance is larger than the first vehicle-to-vehicle distance, the vehicle-to-vehicle distance calculating unit increases the gain for the first vehicle-to-vehicle distance, and reduces the gain for the second vehicle-to-vehicle distance.

7. The distance control system as claimed in claim 1 , wherein if the first vehicle-to-vehicle distance is equal to or smaller than a reference vehicle-to-vehicle distance, the vehicle-to-vehicle distance calculating unit calculates the third vehicle-to-vehicle distance based on the first vehicle-to-vehicle distance, and if the first vehicle-to-vehicle distance is larger than the reference vehicle-to-vehicle distance, the vehicle-to-vehicle distance calculating unit determines the first vehicle-to-vehicle distance as the third vehicle-to-vehicle distance.

8. A distance control method of a vehicle, comprising:

transmitting wireless signals forward with respect to a distance-controlled vehicle;

receiving the wireless signals reflected and returned from an object vehicle;

measuring the relative velocity of the object vehicle in relation to the distance-controlled vehicle based on the received wireless signals;

measuring a first vehicle-to-vehicle distance between the distance-controlled vehicle and the object vehicle; and

calculating a third vehicle-to-vehicle distance based on the first vehicle-to-vehicle distance and a second vehicle-to-vehicle distance calculated from the relative velocity.

9. The distance control method as claimed in claim 8 , wherein the third vehicle-to-vehicle distance is calculated using an equation,

R — 3 rd =R — 1 st *G+R — 2 nd *(1 −G ),

wherein R — 3 rd is the third vehicle distance, R — 1 st is the first vehicle-to-vehicle distance, R — 2 nd is the second vehicle-to-vehicle distance, G is a gain for the first vehicle-to-vehicle distance, and (1−G) is a gain for the second vehicle-to-vehicle distance.

10. The distance control method as claimed in claim 9 , wherein the gain for the first vehicle-to-vehicle distance is decreased and the gain for the second vehicle-to-vehicle distance is increased if the second vehicle-to-vehicle distance is smaller than the first vehicle-to-vehicle distance, and the gain for the first vehicle-to-vehicle distance is increased and the gain for the second vehicle-to-vehicle distance is decreased if the second vehicle-to-vehicle distance is larger than the first vehicle-to-vehicle distance.

11. The distance control method as claimed in claim 8 , wherein the third vehicle-to-vehicle distance is calculated based on the first vehicle-to-vehicle distance if the first vehicle-to-vehicle distance is equal to or smaller than a reference vehicle-to-vehicle distance, and the first vehicle-to-vehicle distance is determined as the third vehicle-to-vehicle distance if the first vehicle-to-vehicle distance is larger than the reference vehicle-to-vehicle distance.