Foreign object detection system and method suitable for source resonator of wireless energy transfer system
A system and method to detect a foreign object proximate to a source resonator that is part of a wireless energy transfer system. The wireless energy transfer system may be one used to wirelessly charge the batteries of an electric vehicle. Data from a visible light camera and a multiple zone temperature sensor are combined or fused to determine whether a foreign object, such a metallic object or an animal, is in the vicinity of, or in close proximity to, a source resonator. The system controls an electric current provided to the source resonator based on whether a foreign object is detected to reduce or inhibit energy emitted by the source resonator. The visible light camera may be a monochrome or color camera and the temperature sensor may be an infrared camera or a thermopile array.
1. A system to detect a foreign object proximate to a source resonator, said system comprising:
a visible light camera mounted so as to have a camera field of view that includes the source resonator, and configured to output image data indicative of visible light intensity detected by pixels in the camera;
a multiple zone temperature sensor mounted so as to have a sensor field of view that includes the source resonator and is similar to the camera field of view, and configured to output thermal data indicative of a zone temperature for each of the multiple zones; and
a controller in communication with the visible light camera and the multiple zone temperature sensor and configured to
receive visible light image data from the camera;
determine an intensity map characterized as an array of intensity data cells;
designate an intensity object on an area of the intensity map;
receive the thermal data from the multiple zone temperature sensor;
determine a thermal map characterized as an array of thermal data cells;
designate a thermal object on an area of the thermal map;
detect the foreign object when the intensity object and the thermal object intersect; and
control an electric current provided to the source resonator when the foreign object is detected.
2. The system in accordance with claim 1 , wherein the camera is further configured
to output image data indicative of visible light color and wherein the controller is further configured to
determine a hue map characterized as an array of hue data cells;
designate a hue object on an area of the hue map; and
detect the foreign object when the hue object, the intensity object, and the thermal object intersect.
3. The system in accordance with claim 1 , wherein the camera is further configured
to output image data indicative of visible light color and wherein the controller is further configured to
determine a saturation map characterized as an array of saturation data cells;
designate a saturation object on an area of the saturation map; and
detect the foreign object when the saturation object, the intensity object, and the thermal object intersect.
4. The system in accordance with claim 1 , said system further comprising a warning indicator coupled to the controller effective to generate a warning signal when the foreign object is detected.
5. The system in accordance with claim 1 , wherein the visible light camera and the multiple zone temperature sensor are mounted on an underside of a vehicle.
6. The system in accordance with claim 5 , wherein the visible light camera and the multiple zone temperature sensor are mounted in close proximity to a capture resonator.
7. The system in accordance with claim 1 , wherein the camera has more than 100,000 pixels, and the multiple zone temperature sensor has fewer than 1000 zones.
8. A controller for a system configured to detect that a foreign object is proximate to a source resonator, said system comprising a visible light camera mounted so as to have a camera field of view that includes the source resonator, and configured to output image data indicative of visible light intensity detected by pixels in the camera, and a multiple zone temperature sensor mounted so as to have a sensor field of view that includes the source resonator and is similar to the camera field of view, and configured to output thermal data indicative of a zone temperature for each of the multiple zones, said controller configured to receive visible light image data from the camera;
determine an intensity map characterized as an array of intensity data cells;
designate an intensity object on an area of the intensity map;
receive the thermal data from the multiple zone temperature sensor;
determine a thermal map characterized as an array of thermal data cells;
designate a thermal object on an area of the thermal map;
detect the foreign object when the intensity object and the thermal object intersect; and
control an electric current provided to the source resonator when the foreign object is detected.