WCPS: Wireless Cyber-Physical Simulator

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Wireless Cyber-Physical Simulator (WCPS) is an open-source simulation environment for wireless control systems. By integrating Simulink and the TOSSIM wireless sensor simulator in a holistic simulation environment, WCPS accurately captures the dynamics of both the physical systems and the wireless sensor-actuator networks used for control. WCPS has been used for realistic case studies of wireless structural control systems for civil infrastructure, studying routing and control of cyber physical system, and incorporating emergency alarms in reliable wireless process control. The broad application of WCPS is to support cyber-physical systems research on large-scale wireless control systems through high-fidelity joint cyber and physical simulations. This site includes the code release, tutorial, and simulation examples for wireless structural control systems.

What's New

WCPS Architecture

Figure 1. WCPS Architecture

In the Fig.1, WCPS simulates the feedback control loop of the control system as follows. Sensor data is generated from plant models such as structures and water tanks. Through a cross-platform function call from Simulink, sensor data is injected to the corresponding wireless sensors in TOSSIM. Following the routes and transmission schedule calculated by the network manager module, TOSSIM simulates the end-to-end wireless communication of the sensor data packets from the sensors to the base station, and then return the packet delay and loss to the Interfacing Block in Simulink through the Python interface. The Packet Collector module extracts packet delivery information(the delay and loss)from the message pool. Sensor data and their loss and delay are provided to the Data Block, which can feed the sensor data to the controller at the right time based on the packet delay (if the packet is not lost). WCPS utilizes basic API (e.g., the dos, UNIX command) of MATLAB to do cross-platform function calls. In TOSSIM, we re-implement a printf method in TinyOS to send simulation results to the Interfacing Block.

User inputs to WCPS includes reference signals of the plants and wireless traces used as input to TOSSIM. The scheduler module calculates transmission schedules. Networking schedule is then deployed into the MAC layer code of wireless nodes and becomes effective after a TinyOS compilation. The TDMA MAC layer in WCPS is developed based on the MAC Layer Architecture (MLA) library and further adapted for TOSSIM under TinyOS 2.1.1. Received Signal Strength Indication( RSSI) and wireless noises traces are collected from real-world environments and provided to the wireless model used by TOSSIM for realistic wireless network simulations. The interfaces between the Simulink model and TOSSIM are encapsulated as two MATLAB embedded functions in Simulink: the Interfacing Block and the Data Block, as is shown in Fig.2. The Interfacing Block extracts delay and loss information from TOSSIM messages, and the Data Block decides what data will be used for discrete control during each sampling period. The federated architecture of WCPS provides great flexibilities to incorporate different structural models and implement alternative scheduling-control approaches.

Figure 2. Simulink Model

Environment Installation

  • Install TinyOS
WCPS is implemented and tested on MacOS X (snowleopard), Windows XP, and Windows 7. 
Current release of WCPS is under  TinyOS 2.1.1, which can be installed following the two methods.
  • Install Mac Layer Architecture(MLA)
The MAC Layer Architecture (MLA) provides a component-based architecture for MAC protocols in wireless sensor networks. MLA extends the Unified Power 
Management Architecture to provide the hardware-independent interfaces required by timing sensitive MAC protocols, and defines platform-independent 
reusable components that implement MAC layer logic on top of them. The MLA architecture can be used to develop a large number of platform-independent 
MAC implementations, with little or no further effort required to adapt these implementations to new hardware platforms. Our current implementation of MLA
is built on top of TinyOS 2.1.1. It currently supports platforms which use the CC2420 radio stack and has been tested on TelosB motes. In addition to providing
interfaces and components for building new MAC layer implementations, MLA includes implementations of five representative MAC layers. Specifically for WCPS, we 
adopt and further change the pure-TDMA MAC protocol for centralized data communication.
  • Install MATLAB and Simulink
  • If you already have MATLAB MATLAB 7.11.0.584 (2010b) or later version, skip this step. Otherwise, follow the tutorial here: install MATLAB
  • Install Python

If you already have Python 2.7.2 or later version installed, skip this step. Otherwise, follow the manual here: install Python 

Below is the installation guide of WCPS v3.0. 
For Mac OSX Users who would like to run WCPS on their own computer, please follow first instruction link below for a detailed installation and test procedures.
For OSX/Linux/UNIX/Windows users, please follow the second instruction link below for ruining Dockerized WCPS in a Docker container.

Download WCPS

Use WCPS

Wireless network plays a critical role in close-loop wireless control system. Sitting on top of WCPS, simulating a wireless TDMA network is as easy as collecting these NesC files below:

  • "Makefile" takes advantage of the fact that it's not necessary to recompile all the files not changed while specifying all necessary libraries.
  • "TestNetwork.h" defines necessary message structures for the wireless communication.
  • "TestNetworkAppC.nc" connects claimed application interfaces to interfaces that are defined in the hardware library.
  • "TestNetworkC.nc" implements send/receive functionality of a wireless node.
  • "tossim-call.py" configures TOSSIM network and does packet injection into the Tossim network.All above necessary files..
  • Re-implemented TOSSIM libraries for TDMA simulation.TDMA components for TOSSIM..
  • Wireless traces: Traces for 5-sensor wireless network in a building.

Put all the above files into the same folder, prompt a terminal (or a Cygwin window), and in the terminal run 

 Make micaz sim

If TinyOS and python is configured correctly, go ahead and run in the terminal: 

./tossim-call.py

Having collected aforementioned TinyOS files, a simplified example that uses key networking Interfacing Block and Data Block of WCPS is shown in Fig. 3.

Figure 3. A Simple Example that uses Interfacing and Data Block of WCPS.

This examples shows:

  • How input data in Simulink is injected to TOSSIM network;
  • How TOSSIM Interfacing Block runs as a Matlab Embedded function;
  • What type of data is output from the Interfacing Block;
  • How data usage strategies are applied to the data in the Data Block.
  • What type of data is eventually output from the Data Block and provided for future control use.

Source code for the example can be found here. To run this integrated example, simply download, unzip the source code, and run Run_delay_data_func.m in Matlab.

WCPS-RT

Figure 4. WCPS-RT Architecture

Given the complexity of wireless communication in physical environments, simulators cannot always capture the real-world behavior of WSANs. Network-in-the-loop simulations have been developed to address the limitation of wireless simulations by incorporating physical wireless networks.

To experiment with wireless control over real-world WSANs, we develop wireless cyber-physical simulator real-time (WCPS-RT). WCPS-RT integrates MATLAB/Simulink Desktop Real-time (SLDRT) and a 3-floor WSAN testbed. It captures realistic wireless dynamics that are hard to simulate accurately, and leverages simulation support for controllers and physical plants. The architecture of WCPS-RT is shown in Fig. 4.

SLDRT is used to simulate the physical part of the WNCS: physical plants, controllers, state observers, and physical disturbance. In practice, industrial plants usually operate continuously or at very high rates. However, the wireless communication and controller execute at a relatively low rate because of the communication and computation latencies. Therefore, SLDRT modules are operated at different rates in our design.

The 3-floor WSAN testbed is deployed on the 3rd to 5th floors of Jolley Hall at Washington University in St. Louis. It consists of 70 TelosB motes. Each mote is equipped with Chipcon CC2420 radio compliant with the IEEE 802.15.4 standard and a TI MSP430 microcontroller. 40 Raspberry Pis with a backplane network are used for the management of the WSAN.

The interfaces between SLDRT and WSAN are socket connections between the PCs that run SLDRT and the Pis, and serial connections between the Pis and the end nodes. In this way, the end nodes of the sensing and actuation flows can be any nodes in the testbed.


WCPS-EC

Figure 5. WCPS-EC Architecture

We built a real-time hybrid simulator, wireless cyber-physical simulator edge-computing (WCPS-EC), which integrates (1) Real controllers running on various computation platforms; (2) Real Wi-Fi network and Ethernet, or simulated network using TOSSIM; (3) Simulink Desktop Real-time (SLDRT), which simulates robotic arm in real-time.

The architecture of WCPS-EC is shown in Fig. 5. Compared with WCPS-RT, WCPS-EC includes immigrated controllers running on various computation platforms instead of controllers running in MATLAB/Simulink. In addition, WCPS-EC can reflect the impacts of real communication network and computation platform during run-time.

In WCPS-RT, the worst-case end-to-end latency is below one sampling period. Hence the actuation commands are set to have fixed latency of one sampling period. However, in multi-tier control systems, the E2E latency can be longer than one sampling period. In addition, we consider a more realistic control system setup with (1) clock-driven sensors that sample the plant outputs periodically every sampling period; (2) an event-driven controller which calculates the actuation commands as soon as the sensor data arrives; and (3) event-driven actuators, which means actuators can respond to updated actuation commands immediately.

Talks

Publication

Get Support

  • WCPS v3.0: Yehan Ma: yehan.ma@wustl.edu
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