Servo - February 2012

DIGILENT DESIGN CONTEST • DIGILENT DESIGN CONTEST • DIGILENT DESIGN CONTEST • DIGILENT DESIGN CONTEST

FIGURE 4. Manual driving demonstration.

software, the smart shopping cart achieves manual cart driving, automatic following, an RFID electronic key, a voice shopping guide, and self-checkout. Following are brief descriptions about these features.

Manual Cart Driving

A game joystick is installed on the handle of cart so users can control movement style in all directions, including forward, backward, left, and right. The cart will automatically stop when sensors detect obstacles on any side. The cart’s running speed can be adjusted to ensure safety of operation. When customers feel tired during shopping, they can simply stand on the supermarket cart and switch it to driving mode.

way for the RS-232 IP core to be supported by the Xilinx Spartan 3E; we only need to call the IP core and change some serial port parameters to achieve any related functions, so operation is very simple. The supermarket scanner module uses a PS/2 keyboard interface on the FPGA. This is because the scanner output code signal is the same output signal as the number keys on the keyboard. The other module’s interfaces to the system use the Pmod interfaces on the FPGA. Pmod interfaces are reserved for additional sets of general-purpose input/output interfaces; these are flexible and can link directly to the FPGA chip pins.

Cart Functions

Through the development of the hardware and

Automatic Following

The smart shopping cart provides a new shopping experience: just release your hands and focus your attention on the products you need to buy; your supermarket cart will follow behind you. In case the smart cart is faced with different environments, it has been set up with infrared sensors and a camera for its following mode. The infrared following mode is simple to implement. The tracking effect is good and isn’t easily impacted by interference in the environment. One issue is that the infrared mode cannot distinguish between different people; the cart will follow any moving objects that appears in front of the cart. This error may occur unexpectedly, and is difficult to autocorrect. One way to avoid this problem is to join the camera mode with the infrared sensor mode. When using the image tracking algorithm and the wireless camera module, the smart cart will follow the initial target image during the following process. The algorithm distinguishes the target image to the rest of the environment, based on relevant physical characteristics. By using algorithms, the smart cart can automatically find the target image in the environment, achieve a track positioning, and adjust itself to the correct location. With a combination of the two tracking modes, the cart can achieve automatic tracking and automatic correction.