From Design to Implementation with Simulink and LEGO NXT

The use of mobile robotics in teaching has the potential to be revolutionized by a) advances in low-cost, computationally powerful target hardware, and b) automatic code generation or 'rapid prototyping' tools which allow these devices to be programmed directly from high-level Matlab / Simulink-based designs. This paper describes progress on a National Science Foundation and MathWorks sponsored project aimed at bringing all these elements together for practical use and benefit in the classroom. The paper describes the Villanova University LEGO Real Time target (VU-LRT) which extends the MathWorks Real Time Workshop to enable target implementation on the LEGO MindStorms NXT brick. The VU-LRT blockset enables students to access the hardware capabilities of the 32-bit LEGO NXT brick from within Simulink environment, and to automatically generate and cross-compile the necessary code for real time autonomous implementation. The tool is similar to the existing ECRobot target, but the latter is constrained by its function call architecture and non-standard use of the Simulink Real-Time Workshop. The presented toolbox is much simpler to use. LEGO hardware I/O is represented in the Simulink design mode as blocks for accessing motors, encoders, pushbuttons , ultrasound sensors, light sensors and more. Blocks have also been developed to allow the LEGO target to communicate in real time with a host computer over USB or BlueTooth communications. An example system, consisting of a closed loop dc motor speed control system is discussed.