One embodiment relates to a computer-implemented method for multiple-keyword matching performed using a computer including at least a processor, data storage, and computer-readable instructions. The frame of the changing table is formed in an oval shape to eliminate any portion thereof that would be oriented generally parallel to the upper frame members of the play yard. Magnetic field sensors are specially positioned in relation to the disk-shaped member to accurately measure torque while providing improved RSU performance and reducing the detrimental effects of compassing.