Real Time Control

7.1 Conclusions With the advancement in the automation industry, the need to perform complex remote operations has grown significantly. Ever-increasing computational capabilities and advancements in the networking technology enabled researchers to develop NCSs to implement the control scheme of real-time control over networks. However, the introduction of network communications in the closed-loop system’s dynamics would inevitably produce additional uncertainties of time-delay and data-packet losses. They would come from the nondeterministic factors during the physical signal coding and processing and the data transmission process. Time sharing of the communication medium in an NCS also introduces a serious network scheduling problem since the network bandwidth is usually limited. These uncertainties could degrade the system performance and even cause system instability and should be analyzed and dealt with.

If the process is to be included in a real time control system it must be done accurately, reliably and rapidly, and with a minimum of field data. Substantial work has been directed towards developing methods to estimate the infiltration characteristics of soil from irrigation advance data. However, none of the existing methods are entirely suitable for use in real time control. The greatest limitation is that they are data intensive and or unreliable and provide soil infiltration properties after an irrigation event.

In this chapter a simple real-time control system for furrow irrigation is proposed that predicts the infiltration characteristic of the soil in real-time using data measured during an irrigation event, simulates the irrigation and determines the optimum time to cut-off for that irrigation. The basis of the system is a new method for estimating the soil infiltration characteristic under furrow irrigation, developed in chapter 6, that uses a model infiltration curve, and a scaling process to predict the infiltration characteristic for each furrow and each irrigation event. Using the new method, infiltration parameters were calculated for two different fields. The SIRMOD simulation model was then used to simulate irrigation performance under different model strategies which were framed to assess the feasibility of, and demonstrate the gains from, the real-time control strategy. The simulation results showed that the system is feasible. The scaled infiltration gave predictions of the irrigation performance comparable to the measured performance, clearly establishing the suitability of this method for use in real-time control. The results further indicated that under simple real-time control the irrigation performance for the two fields could be improved greatly with reductions in the total volume of water applied to the two fields of 20% and 60% respectively, indicating the scale of benefits that can be achieved in the irrigation sector by implementing simple real-time control.

4. Characteristic time intervals In order to judge the capacitance of a real-time control system and to compare the efficiency of its performance, the user and the programmer need information on time spans consumed in interrupt handling. For reasons of correct comparison, time intervals and related activities should be defined clear ly.

RCI was designed as a substrate for implementing RCCL (Robot Control C Library), a software package for doing robot control from UNIX [Lloyd, et al. 88, Hayward and Paul 86]. In RCCL, robot actions are requested from a UNIX process, and the trajectories to implement these actions are computed by a real-time control task, which communicates with the UNIX process using shared memory. The control task typically runs at 50 to 100 Hz., which is beyond the real-time capabilities of most current stock UNIX systems.

Aaron Pittenger Marquette University, 2012 One potential application for a smartphone-type device is a flight management and control computer for an unmanned aerial vehicle (UAV). The hardware employed in most smartphones and tablets has the capabilities necessary to fly an air vehicle without user interaction. The user can pre-program in a flight plan and the smartphone will do the rest. In the past, this real time control application has been done using many separate sensor packages and processors, but never on a single, stand-alone device. Also, capabilities such as the high definition camera present on most smartphones can take photographs and store them on the phone for retrieval later. This opens many potential markets for a device of this nature. Farmers that have large properties could use this to see if their fences are broken. The general public could use the application to take aerial views of their properties. Law enforcement could be an application for this project; to map out house fires or other potentially harmful situations before lives are put at stake.

electromechanical machines, machine components, and mechatronic vehicles. New software tools, integrated development environments, and systematic design methods are also introduced. The editors are extremely grateful to all the authors for their valuable contributions. The book begins with eight chapters related to modelling and control of electromechanical machines and machine components. Chapter 9 presents a nonlinear model for the control of a three-DOF helicopter. A helicopter model and a control method of the model are also presented and validated experimentally in Chapter 10. Chapter 11 introduces a planar laboratory testbed for the simulation of autonomous proximity manoeuvres of a uniquely control actuator configured spacecraft. Integrated methods of simulation and Real-Time control aiming at improving the efficiency of an iterative design process of control systems are presented in Chapter 12. Reliability analysis methods for an embedded Open Source Software (OSS) are discussed in Chapter 13. A new specification technique for the conceptual design of self-optimizing mechatronic systems is presented in Chapter 14.

switched off in this case. However, the time frame remains in effect. That is, the switch off cannot occur until the minimum nitrification time has been completed. 2.5.1.2 Time delay control (2-channel version) In the RTC module variant for two activations, the time frame (which ensures useful cyclical operation under all conditions) is responsible for aerating activation 1 and activation 2 with a time delay. Thus, in one tank there is nitrification and in the other denitrification, for the longest time frames possible. This reduces load peaks in power consumption.

Figure 3 - Observed and simulated recession, advance and infiltration for a level basin irrigation, considering a variation of ±20% in inflow rate. a particular[r]

Another m-file was written to load the results and plot the intake port air/fuel ratio versus simulation time (shown in Fig. 24). In the first run the fuel is injected right as the intake valve closes where it would remain in the port for nearly two revolutions before the valve reopens. During the throttle transient the air flow rate changes significantly during two revolutions of the crankshaft. This effect contributes a substantial portion of the air/fuel ratio error shown in the first run. In the second run (where SOItoIVC_deg=240) the fuel injection is completed at about the same time as the intake valve closing. This helps to minimize the transient air/fuel errors but does not allow the fuel as much time to vaporize in the intake port. The third and fourth runs show that when fuel is injected a significant time before the intake valve closes the transient air/fuel errors will again increase. To help minimize these transient air/fuel ratio errors, some injection strategies control the end of injection relative to intake valve closure rather than the start of injection.

1.3.1 The early THESIS approach The development of real-time systems, with implementation choices such as hardware interfaces, control algorithms and control software, could become a rather complex process. This is because all these components have influence on the dynamic behaviour of the system. THESIS is a structured methodology in which the dynamic properties of a system play an important role. The main idea of the THESIS project is to develop a system, which covers the complete design trajectory, from obtaining design requirements to generating code, for embedded real-time control systems. An objective of THESIS is the mechatronic design approach. In this approach system development is no longer done by separately developing parts that are integrated later, but the system is treated as a whole. A second objective of THESIS is verification and validation by gradual refinement of the model. The result is a functional description of the model. A third objective is the separate

Real-time control of these systems can be achieved using different methods. In this project, electromyographic (EMG) signals from the patient’s forearm are used. The controlled robotic systems are soft hand exoskeletons actuated with Shape-Memory Alloys (SMA) wires. The SMA wires are controlled with a microcontroller. The main objective of these exoskeletons is to help the patient with the movement of grasping an object and releasing it afterwards. Machine learning is used to detect the intention of the patient to grasp or release an object based on the patient’s EMG signals. Once one of these movements is detected, real-time communication with the microcontroller is achieved and the necessary SMA wires are activated. The system is developed in Matlab, and it involves signal acquisition, signal rectification, signal segmentation, feature extraction, dimensionality reduction, signal classification, and communication with the microcontroller. To differentiate between the movements of grasping and releasing an object, three different classifiers will be tested: Artificial Neural Networks (ANN), Support Vector Machine (SVM) and K-Nearest Neighbors (KNN). Their performance will be compared using a confusion matrix and the best one will be selected for the system’s algorithm.

All these approaches come with various transport and application protocols as well as programming interfaces, which are generally not compatible with each other. Ad- ditionally, there are other transport media beyond Eth- ernet 100Base-T approaching the real-time domain: Gi- gabit Ethernet, wireless media as IEEE 802.11 or Blue- tooth, and also promising trends like using FireWire for time-critical control and measuring tasks. While this di- versity of solutions can stimulate competition, it also in- terferes with the portability and extensibility of applica- tions both in research and industrial scenarios. Further- more, the question arises which solutions can guarantee long-term availability, especially when taking their spe-

5. CONCLUSION The Performance of TCP when operated along with UDP is compared and simulation results show that TCP suffers with UDP traffic. Simulation results also show that TFRC (RFC5348) can share bandwidth with TCP flow efficiently in wired environment. The specification of RFC 3448 poorly supported interactive multimedia applications where padding can be used to guarantee the required media rate for RTA applications. Where RFC5348 does not require padding, which consumes unnecessary network capacity. RFC 5348 also increases the sending rate compared to RFC 3448. The performance of RFC5348 works fine with VoIP and video conference applications during variable bit rate through bottleneck capacity. We therefore expect this new standard to further encourage the use of a standard-based congestion control for Real Time Applications.

For example, he knows which threads run on which node (because he is the one who placed them there). This is why EMERALDS does not provide any naming service. For example, to send a me[r]

As indicated previously, the level of understanding required of the programming tools influenced to some extent the quality of the resulting software package. The software package at this stage allows the user to view only motor current and pump speed and change the mode of the system, as well as starting/stopping and resetting a fault. Future works propose to complete the WEB server inter- face so that it has the ability to upload/download parameter information from and to the VSD application. In addition, the development of a monitoring mode which will constantly update values in real-time. It can be concluded that a very basic approximation of the aims and objectives of this project has in fact been achieved. In order for this system to be suitable for commercial purposes a number of additional refinements were identified as important future works.

5.6.4 RHS on a five DOF system considering specimen mass These tests are characterized in two aspects, five DOFs and a dynamic physical substructure. The structure model is schematically depicted in Figure 5.20, where k 0 = 200kN/m, m 0 = 900kg, k e ≈ 40kN/m, m e ≈ 298kg, causing the natural fre- quencies 0.68Hz, 1.97Hz, 3.11Hz, 3.99Hz and 4.55Hz. Figure 5.14 shows the test rig, in which a mass, two springs as well as a damper can be observed. However, the damper was disconnected in the tests due to its too strong behavior. To begin with, the proposed third-order method was attempted to be used. Unfortunately, vi- bration which might be induced by the force noise and delay compensation pushes us to discard it. Then the tests were conducted with the second order method. The time histories of desired displacements and simulated displacements are presented in Figure 5.21. These figures indicate that the test results are reliable. In addition, the frequency components of the displacement synchronization errors are illustrated in Figure 5.22, which reconfirms the effectiveness of the proposed method in terms of treatment to delay-varying systems and, to some extent, control errors.

TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they are sent. Being connection-oriented means that before transmitting data, the connection between the server and the client is opened. The data can be transferred in full duplex. When the transfer is completed, the connection is closed to free system resources. Handshaking signals are used for making and closing the connection. If time delay or data loss takes place, the client re-requests the packet to the server until the whole packet is completed. Although TCP is a reliable protocol for network communications, it is unsuitable for a client requiring a high sampling frequency such as Client 1. Due to various services like error checking and ensuring ordered data delivery, TCP has large overheads and may waste bandwidth. An additional time delay can be introduced to the system.

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Its induction is, however, impossible in the experiments, because of the currently available and used objects/medium combination. Apart from this, the phase control enabled me the utilization of a larger and more complicated four-sector electrode array. I conducted the experiments involving both of the arrays in order to demonstrate their manipulation capabilities and evaluate their performance. Surprisingly, the four-sector electrodes arrangement allows the manipulation even along arbitrary trajectories, which was not expected before. Next, I analyzed the system scalability with respect to the growing number of particles and electrodes and investigated a few methods dealing with the arising computational issues. No well working solution was however found. Further, I supplemented the system model by the mutual particle interactions and adapted the controller for taking them into account. Its function was then verified on simulations. Finally, I studied the sensitivity of the control algorithm to the position measurement uncertainties and I tested one of the possible approaches to the mini- mization of their effects. The modified optimization task was tested on a simplified simulation and the results seemed promising.