Self test for obstacle detection system

A method for detecting objects in the proximity of a movable vehicle, said method comprising the steps of:

• transmitting object detection signals from a transmitter;
• receiving said object detection signals as first reflected signals reflected from a ground surface on which said vehicle is supported, and receiving said object detection signals as second reflected signals reflected from an object in the proximity of said movable vehicle at a receiver;
• generating an alarm signal in response to receiving both said first reflected signals and said second reflected signals;
• and
• indicating an alarm condition in response to said alarm signal being generated.

A system for detecting the presence of objects in the proximity of a movable vehicle, said system comprising:

• transmitter means for transmitting object detection signals;
• receiver means for receiving said object detection signals as both first reflected signals reflected from a ground surface on which said vehicle is supported and as second reflected signals reflected from an object in the proximity of said movable vehicle;
• control means responsive to the reception of said first reflected signals from said ground surface for providing a first alarm signal indicative of the operability of said system;
• and
• alarm indication means responsive to the reception of said second reflected signals from said object for providing a second alarm signal indicative of the detection of said object proximate to said vehicle.

A method for detecting the presence of objects in the proximity of a movable vehicle, said method comprising the steps of:

• providing a transmitter and receiver on said vehicle;
• transmitting object detection signals from said transmitter;
• receiving said object detection signals at said receiver as both first reflected signals reflected from a ground surface on which said vehicle is supported and as second reflected signals reflected from an object in the proximity of said movable vehicle;
• providing a first alarm signal indicative of the operability of said transmitter and receiver in response to the reception of said first reflected signals from said ground surface;
• and
• providing a second alarm signal indicative of the detection of said object proximate to said vehicle in response to the reception of said second reflected signals from said object.

A system for detecting the presence of objects in the proximity of a movable vehicle, said system comprising:

• a transmitter for transmitting object detection signals;
• a receiver for receiving said object detection signals as first reflected signals reflected from a ground surface on which said vehicle is supported, and for receiving said object detection signal as second reflected signals reflected from an object in the proximity of said movable vehicle;
• a control circuit operable for varying the detection threshold at which said receiver responds to received reflected signals, said control circuit initially setting said detection threshold to a first level so that said receiver responds to said first reflected signals reflected from said ground surface, and in response to said receiver receiving said first reflected signals adjusting said detection threshold to a second level so that said receiver responds only to said second reflected signals reflected from said object in the proximity of said vehicle, said control circuit being responsive to said receiver receiving both said first reflected signals and said second reflected signals for generating an alarm signal;
• and
• an alarm indicator for indicating an alarm condition in response to receiving said alarm signal from said control circuit.