Various user interface software packages were used to allow control over the test setup. These included supervisory control and data acquisition (SCADA) software, ECU programming software, high speed data acquisition software and a lambda measuring package. The various graphical user interfaces used can be seen in Appendix D.
5.6.1. Supervisory control and data acquisition
For the test setup Engine Test Automation (ETA) software was used as a SCADA interface, using RsLinx to communicate with the PLC. RsLogix was used to program the PLC. ETA enabled the engine to be controlled, parameters to be monitored, alarms and emergency shutoffs to be set, sensor to be calibrated, data to be logged and automated test sequences to be programmed. The user interface developed can be seen in Appendix D, Figure 80.
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The program had two main operating modes, torque control and throttle control. In both modes the speed set point had the highest priority as it was directly controlled by the drive system. With the drive activated, the engine would always run at the speed set-point. The dynamometer was able to motor the engine if the engine could not reach the speed set-point. In throttle control mode the user had control over the engine throttle position and engine speed. Depending on the throttle position, the dynamometer would either load or motor the engine to maintain the set engine speed. In torque control mode the user selected the torque set point and speed set point. ETA then used PID control to continuously adjust the throttle position to match the measured torque to the torque set point.
Throttle control mode was mainly used to start the engine and during engine warm-up periods. Torque control mode was used for most tests, including automated tests. The only tests ran in throttle control mode were the timing swing and fuel loop tests, as changes in torque had to be observed (see section 6.2). 5.6.2. High speed data acquisition software
The software package used in conjunction with the DAQ was National Instruments’ LabView. The program was used to capture, manipulate and store data. This was done in two parts: a main block diagram program and a user interface panel. The main program was compiled using a block diagram consisting of various interconnected functions. The diagram is shown in Appendix D.3. Figure 91. The program was a further development based on a program used by E. Grobbelaar (2017). The block diagram was then used to create a user interface panel, see Appendix D.2. Figure 81, showing the measured pressure traces for the given cycle.
With the program running, the DAQ read the data from the pressure transducers every 0.1° of crank shaft rotation. The Z-channel pulse of the shaft encoder was used as a reference point to start the program. As each thermodynamic cycle consisted of two crank rotations, two trigger pulses were observed for each cycle. To ensure that the correct pulse was used as the starting point, a “RESTART” button was programmed allowing the program to be restarted until the desired starting point was used.
With the correct starting trigger captured, the number of cycles to be logged could be specified and the logging process started by pressing the “LOG” button. After the logging procedure was completed, the user was prompted to specify the file to which the data should be stored.
5.6.3. ECU programming software
Together with the ECU, Perfect Power provided its own software package called LetRippII that served as a platform to set up and monitor the ECU (Perfect Power, [S.a.]). For details on the ECU setup and programming, refer to section 4. The software had three major functions namely; ECU programming, real time data
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display and data logging. An example of the interface used during testing can be found in Appendix D.1, Figure 82.
The LetRippII software was mainly used to program and set up the ECU. The software provided an easy to use graphical interface to set up and edit ECU maps and set points. With the software connected to the ECU, programming changes could be applied to the ECU while the engine was running, including switching between closed-loop and open-loop control. If required, the software provided a basic help function describing the function of general programming locations. The software also enabled live data to be viewed while connected to the ECU. These display values could be any of the input, output or active map values and could be logged as well. The logging function featured in the software logged all the channels of the ECU and had a set structure. None of the ECU logs were used for calculations as all the required measurements were obtained by separate systems.
5.6.4. Lambda data acquisition software
The Ecotrons lambda scanner used to capture the lambda measurements was supplied with its own graphical user interface, ALM GUI. The software package had a variety of features including sensor calibration, real time data display, data logging and data playback. Diagnostic tools were also available to indicate faulty sensors.
The software package was used to log the lambda measurements as well as give real time lambda measurements of the individual cylinders. This helped to monitor lambda compared the ECU measurement and indicated any lambda measurement differences between the two cylinders. These measurements were also used to adjust the injection trim of the two cylinders, enabling the lambda measurement for both cylinders to be similar. An illustration of the interface used during testing can be found in Appendix D.1, Figure 83.