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Model-Based Design for Embedded Systems- Part 20

Model-Based Design for Embedded Systems- P20: This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. | 166 Model-Based Design for Embedded Systems The Lund RBbot is a dual-drive unicycle robot. It is modeled as a third-order system 1 Px 2 R1 1 R2 2 cos 0 1 Py 2 R1 1 R2W2 sm 0 1 0 D R2 2 - R1 1 6.1 where the state consists of the x- and y-positions and the heading 0. Inputs to the system are the angular velocities rn1 and rn2 of the two wheels. The parameters Ri and R2 are the radii of the two wheels and D is the distance between the wheels. The top-level TrueTime model diagram is shown in Figure 6.14. The stationary sensor nodes are implemented as Simulink subsystems that internally contain a TrueTime kernel modeling the Tmote Sky mote and connections to the radio network and the ultrasound communication blocks. In order to reduce the wiring From and To blocks hidden inside the corresponding subsystems are used for the connections. The block handling the dynamic animation is not shown in Figure 6.14. The subsystem for the mobile robots is shown in Figure 6.15. The robot dynamics block contains the motor models and the robot dynamics model. The position of the robots and the status of the stationary sensor nodes i.e. whether or not they are operational are shown in a separate animation workspace see Figure 6.16 . The workspace shows one tunnel segment with sensor nodes out of which some are non-operational along the walls. Two robots are inside the tunnel together with two obstacles that the robots must avoid. FIGURE 6.14 The TrueTime model diagram. In order to reduce the use of wires From and To blocks hidden inside the corresponding subsystems are used to connect the stationary sensor nodes to the radio and ultrasound networks. TrueTime Simulation Tool for Performance Analysis 167 FIGURE 6.15 The Simulink model of the mobile robots. For the sake of clarity the obstacledetection sensors have been omitted. These should be connected to AVR Mega16-1. 6.6.6 Evaluation The implemented TrueTime model contains several simplifications. For example interrupt latencies are .