Zigbee Radio

Online Projection System (OPS) and Quality and Production Management (QPM)

What is OPS/QPM

Both the Online Projection System (OPS) and the Quality and Production Management (QPM) systems are KFC initiatives, similar to smart kitchen products, that assists store operators in maintaining an appropriate inventory of cooked food, ready to serve, so that customers do not have to wait for their orders. The computer system performs real-time monitoring of sales, product inventory, product "in process" (being cooked), etc., and consults a history of past sales data in order to project expected sales. Based on projected sales and current inventory, the system prompts the restaurant staff on how much product to cook and when.

Data Tracking

In order to track how much product is being cooked and placed into inventory, the OPS/QPM system communicates directly with the kitchen equipment via an inhouse ZigBee wireless network. It can directly query each fryer, for example, to discover its current operating status: off, on, melt mode, cook mode, currently cooking, etc. Also, the fryer reports the start and end of each cook cycle, as well as which product is being cooked. For some products, like strips, the control asks the user to specify precisely how many pieces are being cooked, and then passes that information on to the OPS/QPM computer. For other products, like various loads of bone-in chicken, the OPS/QPM system is pre-programmed to know how many pieces to expect for the various standard loads.

Communication Architecture

The Digi ZigBee radio is hard-wired to communicate with the fryer’s control board but uses wireless to interact with the operator’s network. To facilitate two way communication between the Digi radio and fryer, the Digi radio must be properly installed, powered on, and the fryers communication software enabled. In addition, to facilitate communication between the fryer and the virtual (network) environment (Smart Kitchen), the network must see the Digi radio and allow it to join the network to enable seamless two way communication.

Digi ZigBee Radio

Digi is the company that manufactures the radio, and whose name and logo is prominently displayed on the radio, while ZigBee is a wireless technology developed as an open global standard to address the unique needs of low-cost, low-power wireless M2M networks.

Digi Radio

The Velocity control board communicates directly with the Digi radio module. The radio modules are manufactured by Digi with firmware customized for Henny Penny, to support operator requirements. The radio module speaks the standard ZigBee protocol on the wireless side, and speaks RS-485 Modbus protocol on the hard-wired side to communicate with the fryer’s control board. The radio module basically asks the control for a status update about every 5 seconds, and we send a reply message back to the radio module with the requested information. The radio module then takes care of converting this information to the ZigBee wireless format and broadcasts it on to the ZigBee wireless network.

ZigBee Protocol

ZigBee is the name of a type of wireless communications technology and protocol, just as WiFi and BlueTooth are names for other types of wireless network technologies.

The advantage of a ZigBee network—particularly in a commercial kitchen where large panels of stainless steel may obstruct other technologies—is that ZigBee can form a wireless mesh network, where the various radios that have joined the network are able to forward messages from one device to another. If a piece of equipment is out of range or is blocked from communicating directly with some other piece of equipment at the other end of the building, the radio modules in between can receive and forward messages as needed. That is, if equipment A cannot talk directly to equipment C, but A can talk to B and B can talk to C, then A will send the message to B, and B will pass it on to C.

The ZigBee protocol operates in the 2.4 GHz range and is therefore approved for operation worldwide. The data rate in the 2.4 GHz band is about 250 kilobits a second, which is acceptable performance for in-store monitoring of equipment status.

Mesh Network

A mesh network is a network topology in which each node relays data for the network. All mesh nodes cooperate in the distribution of data in the network. Mesh networks can relay messages using either a flooding technique or a routing technique. The flooding technique releases the data packets on to the network without specific routing instructions. The routing technique is more sophisticated and requires a table of addresses, which is used to route the data packets from point to point.

Practical Application

In a Smart Kitchen application a ZigBee (wireless) signal can travel through ZigBee (wireless) enabled appliances regardless of which appliance the signal originates from. Each ZigBee (wireless) enabled appliance becomes a node on the network. Eventually the signal reaches a local or virtual (over the Internet) server which contains the Operator’s Smart Kitchen software. The upside is the signal from the Henny Penny fryer has many additional opportunities to reach the server successfully. The downside is if our signal is blocked by a structure (i.e. wall, distance, etc.) and is using another appliance (node) to reach the server, then we have an additional point of failure. As an example, if the signal is being routed through a refrigerator (node) and not directly connecting to the server, then the refrigerator becomes a point of failure.