1 1 / 1 / Due : Fri. Nov. 23 rd / Mon. Nov. 26

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1 ENGG*4420 Real Time System Design Due : Fri. Nov. 23 rd / Mon. Nov. 26 th 1 1

2 Today s Activities Lab 4 Introduction. Lab 3 Demos. Start work on Lab

3 Lab 4 Development Environment Host PC Target Quad-Core PC NI PCI-6229 DAQ LabVIEW 2009 Software Standard Module. Real-Time Development Module. Trace Execution Toolkit. 3 3

4 Lab 4 Requirements The goal of lab 4 is to implement a half-car vehicle suspension system model using the quarter-car suspension implemented in lab 2. The implementation is divided into two main components: RT Target PC: LQR control system. Host PC: Half-Car suspension system plant model. 4 4

5 Lab 4 Architecture 5 5

6 Half-Car Suspension Model 6 6

7 Host PC Implementation Road Disturbance Half-Car Suspension system Front Quarter-Car Suspension Rear Quarter-Car Suspension System States Damping Coefficients Communication and Synchronization Task DAQmx 7 7

8 Host PC Implementation Two quarter-car models representing the front and rear suspension systems. The models should use the parameters in Table 2.3. The front and rear sprung mass values are calculated using equations 2.18 and Road profile Generated using a time-delayed input. Assume that the rear suspension is 2 samples behind the front suspension. The ride quality of the half-car body must be calculated using equation 2.28 in the lab manual. 8 8

9 Real-Time Target PC Implementation 9 9

10 Real-Time Target PC Implementation Implement two separate LQR controllers using equation 2.14 from the manual. Each of the LQR controllers must execute on a dedicated CPU. The communication and synchronization task must have it s own dedicated CPU. Communication between the various tasks must be implemented using Real-Time FIFOs

11 Host/Target Communication You have the following channels available for use in your implementation: Host PC: 2 Analog Outputs 2 Analog Inputs 1 Digital Output Target PC: 2 Analog Outputs 2 Analog Inputs 1 Digital Input Note: You ll need to handle timing such that your transmissions are not delayed and data sets are not separated

12 Lab 4 Requirements/Steps Step 1: Check that your target computer and DAQ are available in NIMax (slide 22). Step 2: Set up your project file (slide 24). Step 3: On the Host PC implement the half-car suspension system by duplicating your quarter-car suspension model from Lab

13 Lab 4 Requirements/Steps Step 4: Review the DAQmx examples in LabVIEW. Step 5: Build the synchronization and communication process between the plant system and controller using the DAQmx interface. Communication must be implemented using the two connection blocks (DAQs). Task communication must be performed using queues on the host PC and Real-Time FIFOs on the RT target PC. Step 6: On the target PC implement two LQR controllers each occupying a dedicated CPU (one for each suspension system). Note that Math Script nodes CANNOT be used on the Target PC

14 Lab 4 Requirements/Steps Step 7: Test the correctness and performance of your design using: Expected system response. The Performance Profiler (slide 44). Real-Time System Manager (RTSM) (slide 46). The Real-Time Execution Trace Toolkit (RTETT) (slide 50). Step 8: Experiment with changing parameters such as: Loop priority, timing, processor allocation, and SubVI priority. Observe the behavior of your design using the RTSM and the RTETT

15 Lab 4 Demo Requirements The demo will include the examination of the following: Front Panel (graphs and controls). Model Response (both with and without semi- active control). Organization of host and target implementations. Communication and synchronization between the host and target. Understanding of LabVIEW implementation. Understanding of the Execution Trace Toolkit figures

16 Lab 4 Report Requirements 1. Introduction: Briefly describe the problem (i.e. what system are you implementing, why is control required, difference from implementation in lab 2, etc ). System Requirements. 2. Implementation: Equipment used. Short overview of the benefits of using the LV RTOS. Present your designed control strategy, discuss the number of cores used, and which tasks will be allocated on which core. Also, present your proposed communication method

17 Lab 4 Report Requirements 2. Implementation Cont.: Present a top-down implementation of your system, showing which major operations are being performed on the Host and Target PCs Theory presented in Lab 2 does not need to be documented in the Lab 4 report. Semi-Active Suspension LQR Theory Fully document your LabVIEW implementation with figures and code snippets where appropriate. Front Panel Block Diagram Script Nodes

18 Lab 4 Report Requirements 3. Simulation/Results: Document your system s performance for various configurations. Timing and CPU usage can be obtained using the performance analyzer, the RTSM and the RTETT. Experiment with changing the periods of the loops, processor allocation, and assigned VI and loop priorities. Use figures where appropriate to document the results (e.g. RTSM usage graph and VI/Thread execution graphs from the RTETT)

19 Lab 4 Report Requirements 3. Simulation/Results Cont.: Discuss any changes that need to be made to your design to obtain better system performance in terms of memory consumption, CPU performance, core allocation, etc. Discuss any difference in performance between your lab 2 and lab 4 implementations. Replace the Timed Loops in your lab 4 implementation with standard while loops and comment of any change in performance (use figures from the RTETT)

20 Lab 4 Report Requirements 3. Simulation/Results Cont.: Experiment with controlling your Timed Loops through both hardware and software timing. 4. Conclusion: Provide some brief concluding statements on the lab based upon your implementation and the observed effects of varying parameters. This section should be clear and concise

21 Deadlines and Marking Lab 4 is worth 12%. 6% for the report and 6% for the demo The Demo is due Nov. 23 rd /Nov. 26 th, 2012 in the Lab. The Report is due Nov. 23 rd /Nov. 26 th, 2012 in the Lab. Physical and Electronic copy. A signed group evaluation sheet must be submitted with the lab report. Do NOT include student numbers on the lab report

22 Target Configuration Open NI - Measurement and Automation (NIMax) on the host computer and expand the remote systems tab. Find your target PC. The target displays both its name and IP address when RT LabVIEW is running. Expand the Devices and Interfaces tab of your target PC. Check that the DAQ is detected and available. DO NOT TURN OFF YOUR TARGET PC!!! DUE TO NETWORK PERMISSIONS ADMINISTRATIVE ACCESS IS REQUIRED TO RECONFIGURE THE TARGETS!!

23 Target Configuration

24 Creating a LabVIEW RT Project Step 1: Create a Real-Time Project. Step 2: Select the Continuous communication architecture

25 Creating a LabVIEW RT Project Step 3: Add your configured target PC to your project. Step 4: New Vis and DAQ tasks may now be added to the Host and Target by right-clicking in the project window. Remember to save your project file and not just your VIs

26 Project Organization You can experiment with the organization of your project to find what you feel works best. Note that priorities can be set at the VI level (I.E. Time-Critical, Normal, etc..) and in timed loops running within a VI. Group similar tasks together. Start off making use of three cores and change the allocations later as you see fit

27 Useful Tools SubVIs: Used to build frequently used functions that can later be added to the main VI. Global and Shared Variables: Used to move data between loops and VIs. DAQmx channels and tasks for connected devices: Used to move data between the host and target PCs

28 Useful Tools

29 Creating SubVI SubVIs can be created as functions to be used in the main VI. These subvis can have their own priorities predefined (default priority is Normal ). To create your own VI: Build your function on the block diagram. Right click the VI icon on the top right corner of the block diagram. From here you can define the terminals the VI needs, and the shape of the icon. Drag your newly created subvi onto your main block diagram. Remember that by default the VIs are not set for reentrant execution

30 Creating SubVI Right click icon to get VI related options

31 VI Properties VI properties can be set by going to File VI Properties. You can set and enable debugging (active by default) and set priority to be normal or time-critical. Most needed options can be found under execution

32 Useful Structures - Communication In order to send and receive data, you ll need to setup NI-DAQmx tasks. To do this, right click on the desired PC (host or target) and go to New DAQmx task. Configuration is then performed in the same fashion as using a DAQ assistant. You can then drag the configured channel or task on to the block diagram

33 Useful Structures - Communication Right-clicking on the channel or task will give you the option to access the DAQmx pallet where you can find the blocks for both reading and writing. The configured channel/task can then be connected as shown below

34 Useful Structures Timed Loops Within a VI, timed loops can be placed. The loops can be configured to have different priorities, execution periods, and processor allocations. Double click the left terminal to get the configuration window

35 Useful Structures Timed Loops Useful Link:

36 Task/Loop Synchronization Synchronized measurements refer to measurements that start at the same time and share a single clock. Needed when measuring/sampling highly dynamic data where any phase mismatch is unacceptable. Two methods: Software Synchronization Hardware Synchronization

37 Task/Loop Synchronization Software Synchronization Allows for simple but not accurate synchronization between the various Timed Loops in the implementation. Global Timing source that is independent of the loop timing source

38 Task/Loop Synchronization Hardware Synchronization Highly accurate timing source. For best synchronization with the Timed Loop use the Control Loop From Task instance

39 Passing Data Between Threads Data should be passed between tasks and timed loops using one of the following methods: Global Variables Good Functional Global Variables Better RT FIFO VIs Best method

40 Global Variables (GVs) Shared resource can cause jitter Global variables may be written to many times before being read. Using GVs in time-critical tasks can compromise determinism. If one task accesses the variable, no other task can access it until the first task releases the variable. The second task will be forced to wait, therefore introducing jitter

41 Functional Global Variables (FGVs) Avoid shared resource problems by using FGVs. Can have several inputs and outputs. Allows for a skip if busy function. Functional global variables can be a lossy form of communication, if a VI overwrites the shift register data before another VI reads the data

42 Real-Time FIFO (RT-FIFO) Best method of communication. Ensures determinism of time-critical tasks. Uses fixed buffer size. An RT-FIFO can be a lossy communication method. When the FIFO gets full, the system starts to overwrite the old data

43 Performance Analysis LabVIEW Real-Time has several tools that can be used to evaluate the performance and response of your system. Performance Profiler Real-Time System Manager Real-Time Execution Trace Toolkit Note that your application needs to be running on the target for any performance metrics to be recorded

44 Performance Profiler Can be used to track the timing statistics of both main and sub VIs. The performance profiler can also be used to track the memory usage of a given part of the application. It can be opened by going to Tools Profile Performance and Memory

45 Performance Profiler

46 Real-Time System Manager (RTSM) The RTSM can be used to track the proportional CPU usage of each processor. It can also be used to start and stop top-level VIs during execution on the target to evaluate the effects on CPU load. The RTSM runs on the host computer and receives information from the target during operation

47 Real-Time System Manager (RTSM) The RTSM can be found under Tools Real-Time Module System Manager

48 RTSM Configuration In order to use the RTSM, you need to configure TCP/IP communication between the target and host computers. Under the properties of the target computer, make sure that TCP/IP is enabled in the VI Server menu. Add the host s IP address (this can be checked using ipconfig/all ) to the list of permitted machines in the Machine Access List of the VI Server menu

49 RTSM Configuration

50 Real-Time Execution Toolkit Use the Execution Trace Toolkit to capture the timing and execution data of VIs and thread events for your implementation. In LabVIEW select Tools Real-Time Execution Trace Toolkit. Before you use the toolkit to observe your application performance, go through the toolkit examples in Help Open Example Session in the RTETT window. For examples on how to use the toolkit see the context help of the toolkit Vis (search Execution Trace in the LabVIEW function pallet)

51 Real-Time Execution Toolkit

52 Real-Time Execution Toolkit