Patent Application
20080094193
A preferred embodiment of the invention is illustrated in
The CPU 10 is the central processing device of the invention. This embodiment uses an ATMega8 microprocessor with 1 kb memory.
The memory unit 20 is connected to the CPU 10 for storing digital data. In this embodiment, the memory unit 20 is the memory inside the ATMega8 microprocessor.
The ultrasonic transceiving module 30 is used to emit and receive ultrasonic waves. As shown in
Each of the sensor drivers 31 includes a transistor Q1˜Q4 and a transformer T1˜T4. The bases of the transistors Q1˜Q4 are connected to pins 13, 14, 16, 15 of the ATMega8 microprocessor, respectively. The pulse signal sent out by the CPU 10 is amplified by the transistors Q1˜Q4 and the transformers T1˜T4.
The ultrasonic sensors 321, 322, 323, 324 are connected to the CPU 10 via a sensor driver 31. In addition to using the pulse signal amplified by the transistors Q1˜Q4 and the transformers T1˜T4 to control and drive the ultrasonic sensors 321, 322, 323, 324 to send out ultrasonic waves, the ultrasonic sensors 321, 322, 323, 324 also receive ultrasonic waves reflected by the obstacles to generate a reflective signal.
The multiplexer 33 is connected to pin 9 and 10 of the ATMega8 microprocessor and the sensor drivers 31.
The signal amplifying module 40 is connected to pin 24 of the ATMega8 microprocessor and the multiplexer 33 of the ultrasonic transceiving module 30. Through the switch of the multiplexer 33, the reflected signals received by the ultrasonic sensors 321, 322, 323, 324 are sent to the signal amplifying module 40 for amplification before sending them to the CPU 10. In this embodiment, as shown in
The warning module 50 is connected to the CPU 10 for notifying the driver about any obstacle. As shown in
The disclosed method of automatically modifying the sensor scanning range of a car reversal radar is applied to the above-mentioned CPU 10. Its working principle is based upon the fact that the energy of the ultrasonic waves reflected by an obstacle is proportional to the size of the obstacle. The larger the obstacle is, the more ultrasonic energy it reflects. With reference to
First, four compensation values and a threshold distance are predetermined (step 100). Each compensation value corresponds to one of the ultrasonic sensors 321, 322, 323, 324. The threshold distance is set to be 60 cm according to a preferred embodiment of the invention.
After the car reversal radar starts, each of the ultrasonic sensors 321, 322, 323, 324 immediately sends out ultrasonic waves to detect an obstacle (step 101).
Each of the ultrasonic sensors 321, 322, 323, 324 receives the ultrasonic waves reflected by the obstacle to obtain several initial sensing results corresponding to the ultrasonic sensors 321, 322, 323, 324 (step 102).
The CPU 10 converts the initial sensing results into initial sensing values and stores them in the memory unit 20 (step 103).
Each of the ultrasonic sensors 321, 322, 323, 324 continues sending out ultrasonic waves for detecting obstacles and receiving ultrasonic waves reflected from the obstacles. Several subsequent sensing results of the ultrasonic sensors 321, 322, 323, 324 are thus obtained (step 104).
The CPU 10 converts the subsequent sensing results into subsequent sensing values and stores them in the memory unit 20 (step 105).
Afterwards, the subsequent sensing values of the ultrasonic sensors 321, 322, 323, 324 are compared with “initial sensing value+compensation value” (step 106) to determine is any of the subsequent sensing value greater than the sum of the initial sensing value and the corresponding compensation value. If not, then the radar determines that there is no obstacle within range (step 107). If so, then the radar determines that obstacles are detected within range (step 108).
Moreover, when an obstacle is detected, the actual distance between the obstacle and the ultrasonic sensors 321, 322, 323, 324 are computed using the speed of sound (340 m/s) and the interval between sending out the ultrasonic waves and receiving the reflected ultrasonic waves (step 109).
The computed actual distances between the obstacle and the ultrasonic sensors on both sides at the back of the vehicle are compared with the threshold distance (step 110). If the latter is larger than the former, then the CPU 10 drives the warning module 50 to send out a warning to the driver (step 111). Otherwise, the compensation value is increased (step 112), so that the sum “initial sensing value+compensation value” becomes larger. Therefore, a larger subsequent sensing value is required in order to be bigger than “initial sensing value+compensation value.” That is, the size of the obstacle has to be larger or it has to closer to the vehicle. Therefore, the sensitivity of the ultrasonic sensors 321, 322, 323, 324 can be considered as lowered.
The working principle of the disclosed car reversal radar is described as follows.
Before a car is backed, it should have a larger distance to any obstacle. Therefore, less ultrasonic waves are reflected by the obstacle, resulting in a smaller initial sensing value.
As the car is backed, its distance to the obstacle may become smaller. The solid angle subtended by the obstacle to the car tail becomes larger, reflecting more ultrasonic waves. Therefore, the subsequent sensing value may be larger than the initial sensing value recorded before backing the car. Possible errors are avoided by requiring that the subsequent sensing value has to be larger than the sum of the initial sensing value and the compensation value.
When the actual distance between the obstacle and the ultrasonic sensors on both sides, it means that the obstacle may be on an outer side of the car tail. In this case, the sensitivity of the car reversal radar can be reduced by increasing the compensation value to prevent incorrect actions.
In summary, the disclosed car reversal radar first records the initial surrounding condition before the car is backed. It then compares the surrounding condition while the car is being backed with the initial surrounding condition to determine whether any obstacle exists. Once both sides of the car tail are determined to have no nearby obstacle, the invention automatically modifies the scanning range of the ultrasonic sensors on both sides at the back of the vehicle to reduce the sensitivity. This prevents incorrect actions of the car reversal radar from misguiding the driver.
