Abstract: An obstacle detection system includes an acoustic piezoelectric transducer capable of radiating and receiving ultrasonic energy. During a BIT transmission period, a controller briefly enables a transmit circuit which provides an AC transmit signal that induces oscillatory motion in a piezoelectric element within the transducer. At the end of BIT transmission period the controller disables the transmit circuit and begins BIT receive period operation. Once the transmit circuit is disabled, the oscillatory motion of the piezoelectric element begins to dampen out causing the transducer to generate and provide a vibration generated signal which is input to a receive circuit which detects the presence of the vibration generated signal and provides received status signal indicative thereof. If the vibration generated signal is not present during this period, a system fault exists and the controller notifies the system user.

Abstract: A radar system which detects the presence of objects in the proximity of a movable vehicle includes a signal source which generates object detection signals, a first antenna which transmits the object detection signals and receives the object detection signals as reflected signals reflected from an object in the proximity of the movable vehicle. The first antenna is further operable for receiving non-reflected test signals. A second antenna is provided for transmitting test signals which correspond to a delayed portion of the object detection signal generated by the signal source. A control unit is responsive to the reception of the reflected signals for providing an indication of the detection of the object, and is responsive to the reception of the test signals for providing an indication of the operability of the system.

Abstract: An object detection system and method for detecting the presence of objects in the path of a vehicle, and in which includes a self test operation. The system includes a transmitter which transmits object detection signals and a receiver which receives reflections of the transmitted object detection signals. A controller is provided for adjusting the gain and signal threshold of the receiver so that the receiver initially is able to detect reflections from irregularities in the ground surface. Once the receiver receives a signal reflected from the ground surface, an indication is provided that the system is in a ready or operable state. Thereafter, the controller adjusts the receiver gain and signal detection threshold so that signals reflected from the ground surface are effectively ignored and only signals reflected from significant objects in the path of the vehicle are detected. An alarm signal is generated in response to the receiver receiving signals reflected from the object.

Abstract: A system and method for detecting the presence of objects in the path of the end portion of a movable vehicle are disclosed. A vehicle mounted transmitter transmits bursts of ultrasonic object detection signals. A receiver also mounted on the vehicle receives not only a direct signal from the transmitter, but also signals reflected from objects in the path of the movable vehicle. The transmitter and receiver are mounted on the end portion of the vehicle so that they constitute the foci of an elliptical path defining the loci of all points of signal reflection having the same total transit time of signal from the transmitter to a reflecting object and back to the receiver. The elliptical path of the loci of the closest detectable objects preferably encompasses substantially the entire end portion of the movable vehicle.